How to build a 13 second 340 Duster

I'm planning a restoration on a 73 Duster 340 4 spd for street use. The 340 will need a rebuild and I'd like to achieve a 13.0 1/4 mile time. It will likely weigh the typical factory 3300 lb or so. The rear tires will have to fit in the factory fenders. I expect to have to replace or re-arc the springs.

I'd really appreciate some input as to the most practical engine build up to get to 13 seconds or just under.The only ideas I have so far would be to up the compression but not so much I can't run pump gas, and add headers. Maybe I should enlarge the intake valves to X head size. What else? I know there's lots of ways to do it.

I'm hoping I'll have a great plan in place with info gathered here.

My old Dart ran 13.18 @ 108.....stock 68 short block, grooved main bearings w/hi-volume pump, MP .484/284 cam and lifters, used Comp Cams steel retainers and springs, Mr. Gasket hardened keepers, LD340 w/3310-2 750 vac sec. with black spring. MP electronic ignition with chrome box and stock coil, Hooker 5204 1-3/4" headers w/2-1/2" pipes, DynoMax Super Turbos w/turndowns. GOOD Hays street/strip gold pressure plate and disc (could sidestep that thing all day long!), 3.23 gear, 6" X 27" J.C.Penny AFX Foremost cheater slicks. Carter electric fuel pump w/regulator and -8 fuel line to regulator. Car pulled like crazy, best times with trans left in third. Things that would have improved car: Change secondary spring to lighter one, Redone the trans with cut sliders, checked or changed to adjustable valvetrain.....the valves setted in two spots and the guides were wiped out. The combo was a blast to drive anywhere. The carb also had the secondary metering plate changed to allow jet changes. Simple combo, hope this helps! Bob

Well, some depends on gearing and how well you can stick the tires and shift. My old '74 Barracuda was a 340 4sp (original 318/3sp) with 3.23 sure grip. The engine was a ring and bearing job on a '68 340, I ran a Comp Magnum 268H cam, matched springs, a '71 Thermoquad intake and carb, and 1 5/8 cheapo headers. I could run a 13.0 on Dunlop radials. With the NOS, it went 12.50s without using in in 1st, and spinning the same radials when it hit.

That was the 80s. With better machining and parts, you should be able to run 13.0 easy. I'd run KB243 hypereutectics set to 0 deck, stock rods, stock crank, file to fit rings, factory heads with either 1.88 or 2.02 intake valves (doesnt really matter to me), have a good 5 angle vlave job, replacing anything that is marginal. Static compression with a typical Fel Pro gasket comes out around 10:1 normally, depending on how big the cahmbers are. The valve job is the single most important thing you pay for. Make sure it's a good one, on good eqiupment. For a cam, an XE268 with matching springs. I'd keep the Thermoquad and intake. They are quite good. If you want to upgrade, the Edelbrock RPM airgap with an Edelbrock Thunder AVS would be my coice for it. In a Dart, that is enough for under 13.0 running a street friendly 3.55s of 3.91s, and with you using a tire that can stick.

I think a good stock rebuild paying attention to machineing and tuning should be able to get a 340 a body in to the low 13 if you have the suspension and chassis to get the power to the ground.

I`m with Adam on this one, just build the engine to 68-71 340 specs, perhaps a 3.55 gear, and cram as much slick as you can get in the wheelwell. If you can get it to hook up ,then 13.00 should be simple. My stock 68 Dart 340 A/T ran 13.80`s with street tires.

Thanks a lot guys, just the kind of "seat of the pants" info I was hoping for. I have good basic mechanical knowledge/skill as I worked as an aircraft mechanic years ago but I'm not up on all the performance parts/lingo.

abdywgn:
GOOD Hays street/strip gold pressure plate and disc (could sidestep that thing all day long!),
At present I don't have a tranny. I do have a bellhousing. I'll check into your clutch recommendation. I presume by sidestep you mean dropping the clutch.

Things that would have improved car: Change secondary spring to lighter one, Redone the trans with cut sliders, checked or changed to adjustable valvetrain.....the valves setted in two spots and the guides were wiped out.
I presume here you refer to the vac secondary, allowing it to open sooner. I have no idea about "cut sliders". Also not sure about the adjustable valvetrain.

moper:
Well, some depends on gearing and how well you can stick the tires and shift.
Understood. The goal is 13.0 with reasonable amateur driving skill.

With better machining and parts, you should be able to run 13.0 easy. I'd run KB243 hypereutectics set to 0 deck, stock rods, stock crank, file to fit rings, factory heads with either 1.88 or 2.02 intake valves (doesnt really matter to me), have a good 5 angle vlave job, replacing anything that is marginal. Static compression with a typical Fel Pro gasket comes out around 10:1 normally, depending on how big the cahmbers are.
Not sure about "better machining". Not sure how pistons are "set to 0 deck".
I presume the 10.5 comp 340 could breathe a little harder and make use of the slightly larger valves so it makes sense to me if I raise the compression and the heads are being rebuilt anyway to enlarge the valve. I wonder though if this would only help at high rpm (good for track time) and hurt low rpm performance (not so good on the street).
I'm guessing 10:1 is around the upper limit for todays's pump gas? Chamber size would be per factory J head.

AdamR and Longgone:
I'd like to do it with as many factory parts as possible, but would like to achieve the goal the first time around.
I'm guessing you assume header use, which would maybe bring a 340 built to 68-71 specs up from 275 to near 300 hp (can't imagine not letting it breathe). I recognise factory hp may be under-rated. Anyone seen dyno numbers for a factory 340?
Maybe one of those calculators could give an idea if 300 hp should move 3300 lb 1/4 mile in under 13.

Dusterb suggested Caltraks to get the power to the ground (by PM) and I like that idea.

Below is a pic of tire size and overall look I'm thinking of, likely less the scoop since I doubt I'd use a high rise. Not sure what size the tires actually are but I'm guessing he's around the max without moving springs/tubbing. I'd go wider on the front of course. I was thinking I'd need more like a 4.11 gear, but then there's abdywgn's idea of using only 3 gears. A friend suggested low gears and a 4 speed overdrive, 3 gears at the track, 4 for cruisin.

The input is much appreciated.

you'd be pushing it with 10:1 compression on todays fuel...unless you had a large enough cam to bleed it off it will probably detonate w/ 91 octane

The adjustable valvetrain might have helped with the valve problem (should have read the valves seated in two spots). I think the solution maybe to check pushrod length. The sliders are in the trans, remove every other tooth. Passon? sell these or Brewer? The suspension was 002/003 SS springs, adjustable snubber, and long parts store shocks. The front suspension was 6-cylinder torsion bars, no front sway bar and worn shocks. Good luck and don't trick yourself out trying to meet your goals. Bob

Good luck and don't trick yourself out trying to meet your goals. Bob


Totally agree. Keep it simple and you'll have a nice reliable ride that puts down a number. My 340 is .030" over with a true 10:1 compression, "J" heads with 2.02 valves, Hughes hydraulic cam,Edelbrock Performer RPM intake, 750 d.p. carb, 1 5/8" headers, 2 1/2" exhaust. I run an automatic with a TCI Streetfighter convertor and a "shift kit". I run a 3.91 gear, super stock springs, and MP 50/50 shocks. Front shocks are Comp Eng adjustables with stock torsion bars. This combo went 12.80's and was super reliable. I have since put on some Edelbrock heads, 1.7 roller rockers, and a 100 shot of nitrous. Best time to date is 11.41 @ 119 mph. Good luck and have fun, :thumbup:
Randy

Not sure about "better machining". Not sure how pistons are "set to 0 deck".
I presume the 10.5 comp 340 could breathe a little harder and make use of the slightly larger valves so it makes sense to me if I raise the compression and the heads are being rebuilt anyway to enlarge the valve. I wonder though if this would only help at high rpm (good for track time) and hurt low rpm performance (not so good on the street).
I'm guessing 10:1 is around the upper limit for todays's pump gas? Chamber size would be per factory J head.




What he means is, a shop can do a real performance enhancing rebuild, or they can do a basic rebuild. Things like boring, honing, and turning a crank and valve job are basic rebuilding things. Things like square decking, using top of the line equipment, align honing, cylinder honing using a torque plate, degreeing the camshaft, 5 angle cutter type valve jobs, ccing the heads and correcting valve train geometry..Those are the areas that a performance shop build up will get you. It costs more, but results in smoother, more powerful, and longer lasting engines. Square decking and setting the block's cylinder head surface exactly where the factory blueprint puts it, results in 0 deck with the right piston. The process also allows for any piston (or almost any...lol) to be set that way. As far as cylinder head theory, there are as many ideas as there are guys doing the work. Personally, I use the largest intake valve I can. Because at low lifts, the more curtain area you have, the better. But, I dont make huge ports, because that does seriously hurt low end power with short stock strokes. I like static ratios in the 10:1 area with iron heads and pump gas. With careful cam choice, you can go higher, but it's not really worth the hassle. The biggest thing is, by skimping what I consider the mandatory machining, You sacrifice a lot in the resulting power. So bigger cams, bigger heads, etc are all employed, when in reality, better quality work and more mild parts would have performed more than adequately had things been "right".

1972 Duster 340. .030 over, speed pro forged pistons, steel crank(stock), Hamburger windage tray and 8 qt pan(run 7 qts), stock balancer, stock rods, CR is a true 9.02 to 1, 915 'J' heads ported (254 cfm @ .550), Mopar solid 284/.528 camshaft, installed @ 110, actual lift with lash = .538 as installed with Harlin Sharp rockers 1.65 ratio, 5/16 Comp chrome moly pushrods, Edelbrock true roller time chain and gears, Holley strip Dominator single plain, Holley 4779 750 DP, 1" open phenolic spacer, crancase evacuation system (moroso), Hooker Super comps 1 3/4", 727 with 10" TCI 3500 (stalled 3200) in my car, 4.30 gears, stock suspension with the front half clamped and the rear section open, stock wheels, Indy street tires, six-pac scoop with air box sealed to hood,(worth .20), all steel body and full interior. Would run 11.70's everyday, Best was 11.61 @ 114.47, 7.50 @ 92 in 1/8, 1.66 60ft. Ok on the street but didn't pull hard untill 3500. Wanted more street manners so I changed cam to XE275HL, Manifold to RPM Air Gap, changed rockers to Crane 1.6 ductile iron, Carb to Holley 3310 750 Vacuum sec, and 3.91 gears. Now runs 12.25 @ 110.71, and 7.85 @ 87 in 1/8. with 1.77 60ft. And is so much easier to live with on street. really turn key now not much to do other than change oil. Just thought I would throw that out there. Terry.

Back in 1978 I built this 340 Dart Sport for my buddy. It was a 1970 340 I rebuilt to stock specs and did a nice 3 angle valve job with stock valves. No porting at all but I milled the heads to get a true 10.5 comp. I used all the stock valvetrain but added a MP .474-280 cam. It had 1-5/8 headers and I used the stock electronic dist and recurved it. Had a LD-318 intake with a 650 DP. Rear was an 8-1/4 with 4.10's and G/60 street tires as we did not have drag radials in the 70's. I also had a stock 904 and convertor from a 318 Dart. The car would spin the tires bad so I had to walk it out without spinning the tires and ran 13.49 @ 105. Yes thats 105 mph which is easy 12.80's on a good sticky tires. It was a basically stock 340 with the MP .474 cam and some bolt on's. 340's run hard and like was said a good basic mild 340 combo will tap the high 12's with a good fine tune using headers with the right convertor and gears. Good luck with your combo. Ron

Sanguine: you'd be pushing it with 10:1 compression on todays fuel...unless you had a large enough cam to bleed it off it will probably detonate w/ 91 octane

Dartin: My 340 is .030" over with a true 10:1 compression,

moper: I like static ratios in the 10:1 area with iron heads and pump gas.

383 man: Back in 1978 I built this 340 Dart Sport for my buddy. It was a 1970 340 I rebuilt to stock specs and did a nice 3 angle valve job with stock valves. No porting at all but I milled the heads to get a true 10.5 comp.

Thanks for providing more input. I've asked a question with lots of potential answers but I'm learning from the responses. It seems I might achieve the goal with a well built 68-70 factory spec 340, headers and the right drivetrain combo. One important question will be whether to build to the factory 10.5:1 compression ratio as it has to run on pump gas.

Moper, your reply helps clarify the machining issue. I've located a local machinist who apparently has extensive experience with race engines who should be able to do the job. I'll just have to see HOW expensive this will be (anyone have a rough idea what to expect?). I imagine this person will have a big influence on what I do but I'd like to be somewhat educated before I talk to him so this is helping. I've also ordered the Mopar performance secrets book.

Taking the advice to keep it simple, perhaps I can narrow this down a bit by asking, in addition to good machining and headers, is there an engine upgrade I would likely regret not doing during the rebuild?

On the comp I would shoot for no more then 10.0 on iron heads. If it is a good quench eng then you might get away up to 10.5 and still use 93 pump. But you will need to check it as alot of the Mopar engines were a bit lower then advertised comp. Most 440's rated at 10.0 were in the 9.0 to 9.5 area so definetly you will need to check and machine for the right comp. Ron

Like what Ron said...compression is a combination of factors. Piston part number has a very small part of that. Flat tops can be 8:1 or less, or 11.5:1, depnding on the rest of the pakcage, and the guy setting it up. So, when I say "10:1 is what I like", I'm referring to real calculated static compression ratio. Pisotns you see that say "10.5:1 with 72cc heads" are not. They are whatever they end up at, when the block is decked, and with whatever the head chamber size ends up at after grinding or replacing valves and doing a vlave job and cleanup cut on the heads, and with whatever head gasket your builder uses. I've seen many small blocks with the old school TRW "10.5:1 stock replacement forged pistons" that calculate to 9:1 when the rest is taken into account thru measurement. Again, it comes back to a complete rebuild with an eye on making solid dependable performance, or a rebuild. I've priced a couple small blocks this week, and depending on what you start with, around me, the costs were around $4000-6500. Depending on cubic inch and options. None of these are less than 400hp tho.

I've priced a couple small blocks this week, and depending on what you start with, around me, the costs were around $4000-6500. Depending on cubic inch and options. None of these are less than 400hp tho.

The $4000-6500 number is well above what I would anticipate putting into my engine. I like the idea of a well machined engine but it will depend on the price. Of course I'm not shooting for 400 hp and I assume that price includes a lot of performance parts, which I don't likely need to acheive my goal. I'll have to see what the local guy says, and also see if I can do the assembling myself or if the machinst wants to assemble. Dollars spent is not my absolute bottom line, but I do get satisfaction from being very cost effective.

I may be off base, but whats on my mind right now is heads. It's apparent a good head rebuild is important and of course will cost some. It seems head technology has advanced, perhaps more than anything else for a carburated engine. Someone mentioned the old heads lack the newer mixing design. I've also been reading about "quench" with respect to compressioin and avoidance of detonation. I wonder if the newer aftermarket heads are designed with advantages that would make it worthwhile to put the money I would spend on a head rebuild toward an aftermarket head of newer design.

Arlie

A set of Performer RPM heads probably wouldnt be much more then what it will cost to redo the stock heads. I would however have the Eddys checked out, especially guide clearance. I think the best thing for you to do however is come up with a price range and talk to a few shops. See what they can do for X amount of money. Edlebrocks will cost you $1200 before having them looked at and arent needed to run high 12s. But if your heads need $800 worth of valves, springs and machine work it may be worth spending.

I see that's the new price for a pair of these (around $630 apiece).
I'm guessing there is definite advantage to these over the stock J heads and if that's the case, I'd pay something extra over the price of rebuilding mine.

I'm not sure why you're saying have them checked since they're new.

I'd like to learn more about what the actual advantage would be. I understand an aluminim head allows for more compression without detonation (I think due to better heat transfer?) so this alone is significant. I could not find actual flow numbers for these or the stock heads but I'm guessing these may flow better since the ports are machined.

I assume I can use the stock intake and rocker arm setup so I'm not forced into buying more parts to go with them.

I wonder about durability.

I've had it in my head that I'd like to pick one upgrade from the stock setup where I can transfer rebuilding costs into the upgrade and this would seem to fit.

I appreciate the help I'm getting, and hope I'm not asking too many questions!

I see that's the new price for a pair of these (around $630 apiece).
I'm guessing there is definite advantage to these over the stock J heads and if that's the case, I'd pay something extra over the price of rebuilding mine.

They have a better combustion chamber, better ports,2.02 valves, are lighter and are 30 years newer for starters

I'm not sure why you're saying have them checked since they're new.

I have been told that the valve guide clearance is to tight and they will need to be honed.

I'd like to learn more about what the actual advantage would be. I understand an aluminim head allows for more compression without detonation (I think due to better heat transfer?) so this alone is significant. I could not find actual flow numbers for these or the stock heads but I'm guessing these may flow better since the ports are machined.

Yes the aluminum will dissipate heat faster allowing more compression to be used. I would keep it around 10.5:1 for pump gas. Check out http://www.shadydellspeedshop.com/index.htm for flow numbers

I assume I can use the stock intake and rocker arm setup so I'm not forced into buying more parts to go with them.

yes they use all stock parts

I wonder about durability.

I havent heard of any durability problems with them

I've had it in my head that I'd like to pick one upgrade from the stock setup where I can transfer rebuilding costs into the upgrade and this would seem to fit.

I appreciate the help I'm getting, and hope I'm not asking too many questions!


thats why were here

What the heck, I'll post some numbers.

From Edelbrock's web site:

#60179,
.100" 69/64
.200" 129/108
.300" 188/142
.400" 232/171
.500" 249/183
.600" 251/190

Here's #s according to http://www.shadydellspeedshop.com/index.htm
for a J head with intake opened up to 2.08".


FLOW #’s

LIFT------ASCAST---------PORTED
.100”----62.1/46.6---------62.1/51.8
.200”----112.1/99.4-------135.2/103.5
.300”----156.6/128.3-----198.7/135.2
.400”----193.2/137.3-----239.8/158.7
.450”----200.1/138.3-----253.9/169.7
.500”----200.1/139.7-----258.4/182.9
.550”----200.1/140.8-----264.9/186.3
.600”----200.8/141.5-----254.6/186.3

All #’s at 28” of Water
2.02”/1.60” MP Stainless valves

It would appear that the Eddy flows slightly better than a worked over J head. If I assume this is their level 4 porting, the cost for a complete rebuild including their required 5-angle valve job would be substantially more than
a new set of Eddies.

Then there's this quote from the Edelbrock spec page which I take to say that the flow numbers can't predict which head will perform better:


2. Bigger is not always better! A large port doesn’t always mean more power. This is especially true with street heads and in some cases, race heads. Velocity is just as important as flow. A smaller port volume generally equates to higher velocity for better street performance. The speed of the mixture determines how tightly the combustion chamber is packed. The more tightly packed the combustion chamber, the more pressure is developed when the mixture is ignited, pushing the piston with more force for more power. For example: A large port and a big flow number at 0.600" lift means low velocity (especially off-idle to 3500 rpm) and results in less throttle response. For the street, velocity is the key to overall performance.

3. Compare peak flow and low lift flow. Cylinder head buyers have a tendency to only consider peak flow numbers. It’s important to look at
all the flow numbers, from .100" to peak, in order to determine the performance level of a head.

4. Type of valve influences flow. The type of valves used will influence how well a port flows. A valve with an undercut stem is less of a restriction to flow and will allow a port to flow more, filling the cylinder better and producing more power.

5. Consider this fact for street applications. Generally, in a street application, the smaller the valve diameter, the better the velocity and flow will be with
the correctly sized port. This holds true for both the intake and the exhaust ports. When you can equal the flow of a larger port and larger valve with a smaller port and smaller valve, you have a much more efficient port, which will generally make more power and use less fuel.

I don't wish to initiate controversy so I won't quote these points but shadydell does indicate that Eddy heads have valve guides too tight, and head mating surfaces that need machining to seal. This is somewhat baffling to me (I'm guessing Edelbrock might disagree).

I'm kinda running with the head upgrade idea but am still open to ideas about what is the best upgrade (if any).

Arlie, those prices are for top quality work, and good parts. Things I change, that many dont include the harmonic balancer, the oil pump drive ($65 from MP...), the fuel pump eccentric, pushrods, and rockers. I change these because they are worn, in many cases, they'd be fine at stock levels. But what you are asking is 140% of a stock buildup. And failures cause more expense when you are supposed to be enjoying the new engine. The difference between stock and "racey" (which i refer to as quality parts) can be substantial, but in the quotes' cases, they are hydraulic cams, MP stamped rocker assemblies, etc. I want a new engine. I dont want a slightly freshened engine. In the cases where that is what's desired, I'd rather not rebuild it, and simply use bolt ons. But that lack of expense translates directly into lost performance and lost longevity. So, in truth, perhaps what you should be indicating, is your budget and current parts situation (do you own a suitable engine core?) before all else. Just for comparison, thru my shop, a completely stock parts engine (318 in this example) was $3300 out the door last year. Not much of a savings really, when the $4000 360 is 40% more powerful for $700.

As far as the "why correct brand new heads"... The whole reason for building a high performance engine is to make all the parts fit perfectly, and perform better than a factory job. Edelbrock heads are assembled at a factory, and suffer from the same issues associated with std employees. Guides are usually too tight (not all, but 3-5 out of 16), seats may be out of round (more rare, but 1-2 perset that are "out" more than .005"), and in a few cases, incorrect or incorrectly installed springs/retainers/locks all are reasons to spend the $200 over the cost to have them gone thru. As far as Ryan, if he is runnign Cometics or any other MLS design gasket, Edelbrock's surface finish is too rough for them to work propery, so they have to be milled for the right finish. Another example of snowballing when in a rebuild project. The "might as wells" will get you if you're not prepared.

I think I get most of what you're saying.

I didn't realize you actually are in the rebuilding business. I assumed you were talking about building your own stuff. If I were in the business I'd want to do it right and charge accordingly as well. I'm sure the equipment required does not come cheap.

As far as a budget goes, for me it's an evolving thing. I intend to figure out what a quality rebuild like what you refer to will cost locally and compare to one that's well done but without the extra machining, then decide which way makes most sense to me. I don't doubt the value of the high end rebuild but I doubt I'll spend $4000 plus just because I know I can have a lot of fun without investing that much.

Yes I have a core 340. As far as I know it's stock and was smoking. It turns over. Of course it's possible it's junk. If so I'm back to square one with what to use but there's something appealing to me about the 340 (likely because a friend had one in a Duster, and they are a purebred performance engine) so I might go looking for another if necessary. Also, one of the cars was a 340 car so it may add value to stay with that.

I'm a little fuzzy on what the 140% refers to. As for $700 for 40% power gain that's a no-brainer.

I'm sure you guys know your stuff about the Eddy heads. It's just a surprise to me that there would be such a quality control problem.

Thanks again for the input.

My job is a project manager for St paul Travelers. I build engines for me, and others, along with pretty much anything else on mopars only. I've driven $200 engines for years with no problems, and I know how to get results with any budget. There are always ways...lol. But your post was about a rebuild of your 340. I am simply trying to relate what a performance rebuilt 340 will, or IMO should cost. If you dotn need the work, or dont want to spend the money, the effects are you lose the goal you had inmind. Or at least you might. One of the cars I ran for 3 years, passed emmissions twice in CT, and had no trouble with was a ring and bearing 340 I bought for $300 in '88. A cam, valve springs, and some tuning work and I was running 13.2s easy, able to run in the 12s flogging it. Dut, would I do that even for myself anymore, no. To me, it's just not worth doing things more than once. My time, or anyones, is too valuable, and the expense is more than I want to pay. Not bashing, not criticizing, just pointing stuff out. Part of my job at Travelers is to look ahead, and make sure things are done once, and right, and on budget.

Back in 1970, I bought a new 340, 4-speed Duster (b-5/b-5, bench seat, manual steering/4-piston disk brakes, 3.55 suregrip). With just a re-curve on the dual point dist. and a little playing with the jets on the stock avs carb. I ran 13.80's and 13.90's with the factory E-70 polyglass tires.
A year later, when I put a 440 in the car, I was told, by my machinist, that my 340 was a six-pack motor with single 4 barrel intake on it.

Seems like it wouldn't take much more to get it to where you want it to run.

Hey Idaho, you're getting some damn good advice here, these guys are good. One thing more that may have been covered but I missed it, is the 340 you're going to use should be completely disassembled and inspected up the ying yang before you decide it's ultimate fate. Judging by you're threads you can easily do the tear down and cleaning yourself but then a good shop will be needed for the crack inspections of the block and rotating assembly. Just my 2 cents.

Moper: I hear ya. I'm not perceiving any bashing or criticism. I'll be talking
with the local machinists before deciding about building to better than
factory specs.

Demon seed: makes sense to me. It'll be fun to tear it apart. I plan to have
all the details worked out with a local expert before I dive into it.

Dustpan: this agrees with the comments of others. I don't know how much
difference drag radials make but I'm guessing it might be enough
that an engine done to factory specs might be close to my goal.

My idea right now is that it might make sense to put my head money into new aluminum heads. I particularly like the idea of being able to build to factory compression without being close to detonation with pump gas. I would of course have them "checked out" based on the advice given as this would not add greatly to the price.

Arlie

My son has Eddy RPM heads on his 9.5:1 comp. 360 in his 70 Dart. He's running a 780dp Holley on a RPM intake, not sure of cam specs. The subframes are tied and the rear springs are moved inboard with 3.55, 8 3/4 and a 4-speed. With 255 BFG TA's his best 1/4 is an extremely traction limited 12.90 at 112. Personally, I think the aluminum heads would be the way to go.

Here is a pic of my sons motor with the Eddy RPM heads.
http://www.southsidestreetcars.org/supergallery/albums/userpics/10047/dart_motor_small.jpg

Dustpan: thanks for the input. I see he also upgraded the valvetrain. Looks very cool, almost worthy of some transparent valvecovers!. :happy4:
Arlie

I'm guessing 10:1 is around the upper limit for todays's pump gas? Chamber size would be per factory J head.QUOTE]

[QUOTE]On the comp I would shoot for no more then 10.0 on iron heads. If it is a good quench eng then you might get away up to 10.5 and still use 93 pump

Been watching this with interest from afar

I know I have probaly said this before but what is the high rated fuel generally
available in the States?
The reason for this in Australia when we plan a decent build of street engine
we allow for 98 octane as this is available everywhere and it is surprising that you guys build for 93 at the most.
Just thought in the home of performance there would be good fuel.

Cheers

Benton

93 is the highest that is easily available. Theres a few places around me that have Sunoco brand 100 octane unleaded though.

i think there may bee diferences in how the octane is measured, cant remember the names of the diferent measuring but from what i can remeber our europen 99octane pumpgas is equal to american 94octane, dont know for sure on the australian way of measuring, gues someone else may know!

Adam i would love some of that 100octane measured the american way at my local gasstation ;)

More than octane around us in CT is the ethanol mix they run. It's currently 10% for the entire year, but in addition to that, between November and February, we also have other additives so the moose in Maine can breathe easier. There's too much involved witht he engine package IMO to base a buildup soley on static compression. I have 10.8:1 iron head engines out there running fine all year, and I have 9:1 iron head engines that tuning for this fuel is a headache. All depends on the assembly as a whole, not just piston and head material.

I had a 440 with low compression TRWs .080" in the holes) L2266s ? and a set a very milled heads that would not run on pump gas. I never measure the compression on it but thosepistons are rated at 8.5:1. With my milled heads and .022" gaskets I fiigured around 9.5:1 but it could have been higher. As soon as the motor got warm it would ping like there no tomorrow.

There's too much involved witht he engine package IMO to base a buildup soley on static compression. I have 10.8:1 iron head engines out there running fine all year, and I have 9:1 iron head engines that tuning for this fuel is a headache. All depends on the assembly as a whole, not just piston and head material.

This is an important issue for anyone planning an engine buildup which will involve compression in a range where detonation on pump gas could be an issue. If static compression does not provide a reliable guideline then it would be nice if someone could lay down the fundamental principles involved. Examples of a combo that works are nice, but understanding why is better.

Unless this has been well covered elsewhere on the forum, this would be a nice opportunity for those with the expertise to provide some clarification.

Arlie

I think it's been touched in a bunch of forums...lol. It's an evolving technology. Designing for high power on hot and fast burning (read as low octane) fuel. As far as my experience goes..designing an engine for pump gas isnt htat hard. designing a package that runs on the hairy edge of detonation while providing maximum power, when depending on the quality of "in the ground" fuel sources is. Basically, the smaller the space for combustion, and the more turbulence you can build in will yeild the most detonation resistance, regardless of octane. Factors that affect pinging and detonation are: head material, chamber design, finish, and size, piston dome design and finish, top ring placement on piston, valve type, finish, and size, spark plug type and heat range, valve seal quality, guide clearance, cylinder finish hone quality, camshaft's intake valve closing event timing, and intake type, design, and finish, and ignition type and curve setup. Alter any of those, and you can encourage, or discourage detonation and ping. In the perfect engine, you would see no deposits on the valves, chamber, or piston tops. If you see that in any form, you are giving up efficiency and power. But there are only so many ways to "fix" a design that is 50-60 years old. Over head 2 valve engines have been around that long. Look at a modern LS1 style chamber. it's very compact, wiht the spark plug pointed at the exh valve, and the exh valve area clearly defined next to the intake valve. On a Mopar, look a tthe MP Stage heads, or the Indy offerings. Those are newer designs. Still not "modern" IMO, but way beyond a set of 906s...lol. For best results, a dished piston, with the dish under the chamber which is also small and tight, will give the best resistance to detonation and power focussed on where it should be. Flat top thinking works, but you give up some efficiency again, for the benefit of better flame propogation. It's better than any raised dome design, but really, you dont want to have the flame have to travel all across the piston. You want it to burn very fast, in a small area, building maximum cylinder pressure just as the crank angle is at it's most vulnerable. It's a huge deal right now..How to keep high performance engines alive on pump fuel. And it's still under development. That's because regardless of fuel type, the physics and power production gains happen. That's why I say it's all about the complete design, and should be a huge consideration from the beginning of any buildup.

Thanks moper.

I did a little reading about this and posted some info but somehow it didn't get onto the forum.

Basically just some principles regarding actual operating compression. One significant one being the fact that less than atmospheric pressure is delivered to the intake valve, with everything between the atmosphere and the cylinder (air cleaner, carb, intake, valve train, valve train timing etc) playing a part in how much less than atmospheric pressure is delivered. Then there's the flow characteristics, such a swirl. Exhaust resistance will also effect overall flow so there's much more than the static compression ratio, piston and chamber design involved, as you have pointed out.

It seems actual operating compression is a hard thing to pin down. It also seems to me that it is the fundamental parameter determining power output through which essentially all performance enhancements have their effect.

Hmmm... lots to think about. I'm still thinking the aluminum head upgrade makes sense, assuming Edelbrock incorporates newer/better design.



A360: Here's the answer to the octane question:
(from this website: http://en.wikipedia.org/wiki/Octane_rating)

In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-95 (regular) in Europe.

Arlie

[QUOTE=Idaho]
It seems actual operating compression is a hard thing to pin down. It also seems to me that it is the fundamental parameter determining power output through which essentially all performance enhancements have their effect.




The problem that I see is, what most people have to measure the variables involved cannot do it accurately. Kind of like flowing a single port on a set of heads, instead all of them. And even flowing it without the intake and carb, and without the exh header. And even doing that, you still cannot duplicate the entire true environmet in an operating engine. You cant get the pulsing an engine creates, or the momentum the temperature of the gasses creates. The best one can do is come close by "assuming" certain "average" numbers. Like the .6 mach number, and assuming airflow behaves exactly like a fluid in a shaped conduit. The results confirm the ideas are on the right track. But you can't really (at least in my opinion) point a finger at tthe result and say the positive end is only because of the theory. There's too many things that have come about by some person just rolling the dice and finding a new solution.

Well said. I suppose the engine dyno before and after individual changes might allow one to indirectly infer operating compression effects. I guess manufacturers doing research might have some interesting data.

I'm hoping the mopar performance secrets book might give a little insight.

For me it's mainly satisfying curiosity as I don't plan to do much beyond a stock configuration, but learning a bit along the way is part of the fun.

Arlie

all this 340 and 13sec, is making me happy im getting a 340, bump for all the good info, o and btw i looked at the flow chart.....(im dumb) what am i looking at, what is good, what is bad, im confused. Are there any beginner flow chart how to's and cam selection sites?

The biggest detail is..read it all, and try to understand it all. Then we can apply it to your situation. If you have an engine that turns and the bores are good, you can do a quicky on it. A quickie for me these days is a crank kit (crank with bearings), a set of rings, and most other wear parts replaced. The fact is, iron heads will cost you $600-$100+ to get "right" and setup for performance work. So that's where the debate about Edelbrocks or others or factory iron comes in. Is the extra performance worth the extra $$ to you. If it's a real 340 car, there are some who will not like seeing eddys on it. In terms of power, it's fairly easy to make 350-375hp with nothing more than a valve job done on the right equipment and using decent parts. If that's what you want, it's cheaper. My biggest peice of advice is plan the engine as a whole, once. There are tons of good ideas here and elswhere. So it can get dizzying...lol. But if you formulate a plan that fits the budget, execute that plan properly..And the result will keep you happy. There's always room for more $$. You can cut costs with things like re-using the balancer, redoing the rods and crank, reusing main bolts if the main bores are OK, re-using rockers and shafts and tin work(oil pan, valve covers, etc)...those savings (providing the parts are good to begin with) will save a bundle. So keep reading..and keep asking.

This was a great thread so off to the achives it goes.

I`m with Adam on this one, just build the engine to 68-71 340 specs, perhaps a 3.55 gear, and cram as much slick as you can get in the wheelwell. If you can get it to hook up ,then 13.00 should be simple. My stock 68 Dart 340 A/T ran 13.80`s with street tires.

73 Duster weighs more than a 68 Dart. Difference of maybe 200-300 lbs? Strip some of the weight out too.

I have a 73 340 Duster. I am using a 360 with Eddy heads, hughes 230/236 hydraulic cam, eddy air gap, holley 750 dp, TTi headers. Has stock converter and 3.23 gears. Rear tires are only 225/60-14.

I have to roll into throttle to keep from spinning tires. Ran 14.011 @ 101.26 in Las Vegas. My MPH says the Duster should run low 13's or faster if the car was geared/tires.

73 340 block and cast crank, j heads (clean up the bowls) 2.02 valves, 484 cam , 273 rockers , LD340 intake , hipo ex manifolds , cheapo Kieth black pistons 10:1 (polish cumb. chambers-no hot spots) ,stock ign. (recurve dist.) , holley 650 DP (I think a good TQ would have been better) ,good machine work , 833 O.D w/ 4.10's , battery in trunk , Drive to minnesota from Idaho , run 12.90's and drive back!


My Previous Motor - nothing fancy , just attention to detail and a good tune