My SB build...

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Captainkirk

Captainkirk

Old School Mopar Warrior
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Looking for input on my proposed 340 build...
I had it all figured out, see...then things changed.
Most of you who have read my resto thread know what I had, back in the day. This time around I was going to simply replicate it as close as I could and go from there. BUT...the heart and soul of that motor was the piston/cam combo. The pistons worked well with the cam because it the long duration and overlap allowed my to run a roughly 12:1 CR on leaded premium.
Those days are gone; I've accepted it. I'm also 4 decades from 18, and I no longer feel the urge to squeeze as many ponies from a small block as I can at the sacrifice of comfort and reliability.
Not that I don't want a wicked motor; just that I would like it to start in the winter if I choose.
Rusty Rad Rods thread about "Hot Rod Bliss" really got me to thinking about sticking close to the factory performance blueprints of years gone by, for reliability and factory developed and tested performance. After all who really needs sub-12 second performance/400+HP if you aren't planning on racing? The factory performance 340's were some of the best performing off-the-lot cars ever developed! With that in mind, here are the basics:
Chassis: 1972 Duster 340, standard weight and equipment
Gearing: choice between 3.55 or 3.91 8-3/4 limited slip (planning on the 3.91 at present)
Trans: A833 four speed with Competition Plus

The motor, so far, is going to be bored +30, Speed Pro L2316F forged pistons, 10:1 compression. I need a cam that will work well with this; thinking one of the factory purple grinds such as the '68 340 4 speed cam or equivalent.
Heads: have my choice of two sets:
*Original 1.88 J heads that have been mildly ported and cc'd to 67 cc's
*an untouched set of 2.02 X heads that are probably in need of a complete rebuild...I have not cc'd these or checked the cc volume
Ignition: planning on using the stock electronic distributor with the fast advance spring kit already installed and vacuum advance disabled (unless someone thinks this is a really bad idea; worked great back in the day)...looking for recommendations on which ignition box and coil to use if other than stock
Last time around I ran a Torker 340 with Holley 650 DP. I still have these, but this time around I would like to experiment with the original TQ, either on the stock factory spreadbore manifold, or the used AirGap I bought....hood clearance notwithstanding. The jury's still out on that one. Air Gap, spreadbore adapter plate and TQ make for one hell of a Dagwood sandwich!!!
Headers? Seems like Rusty is all over the Summit headers for fit and price. I will likely go that route.
Clutch? Open to suggestions.
Talk to me, guys.
 
like the direction you're heading, rustys post hit home for me also, im doing the wifes 72 340 duster, we want it to perform the way they did from the factory, but in a day two sort of way.i puthookers on her car, what a pain, hedmans on my demon were much more user friendly, summits probably would be too
 
The torker is terrible on these 340s use a stock dual plane or aftermarket. The j heads will work and the summit 232-242 112 cam works nicely on 340s from my personal experience.
 
run an air gap for a square bore then get a mechanical secondary quick fuel or aed carb.

use 4032 material pistons

run your quench/squish clearance between .043" and .034" with closer to .034" being better.
 
Captainkirk said:
Looking for input on my proposed 340 build...
I had it all figured out, see...then things changed.
Most of you who have read my resto thread know what I had, back in the day. This time around I was going to simply replicate it as close as I could and go from there. BUT...the heart and soul of that motor was the piston/cam combo. The pistons worked well with the cam because it the long duration and overlap allowed my to run a roughly 12:1 CR on leaded premium.
Those days are gone; I've accepted it. I'm also 4 decades from 18, and I no longer feel the urge to squeeze as many ponies from a small block as I can at the sacrifice of comfort and reliability.
Not that I don't want a wicked motor; just that I would like it to start in the winter if I choose.
Rusty Rad Rods thread about "Hot Rod Bliss" really got me to thinking about sticking close to the factory performance blueprints of years gone by, for reliability and factory developed and tested performance. After all who really needs sub-12 second performance/400+HP if you aren't planning on racing? The factory performance 340's were some of the best performing off-the-lot cars ever developed! With that in mind, here are the basics:
Chassis: 1972 Duster 340, standard weight and equipment
Gearing: choice between 3.55 or 3.91 8-3/4 limited slip (planning on the 3.91 at present)
Trans: A833 four speed with Competition Plus

The motor, so far, is going to be bored +30, Speed Pro L2316F forged pistons, 10:1 compression. I need a cam that will work well with this; thinking one of the factory purple grinds such as the '68 340 4 speed cam or equivalent.
Heads: have my choice of two sets:
*Original 1.88 J heads that have been mildly ported and cc'd to 67 cc's
*an untouched set of 2.02 X heads that are probably in need of a complete rebuild...I have not cc'd these or checked the cc volume
Ignition: planning on using the stock electronic distributor with the fast advance spring kit already installed and vacuum advance disabled (unless someone thinks this is a really bad idea; worked great back in the day)...looking for recommendations on which ignition box and coil to use if other than stock
Last time around I ran a Torker 340 with Holley 650 DP. I still have these, but this time around I would like to experiment with the original TQ, either on the stock factory spreadbore manifold, or the used AirGap I bought....hood clearance notwithstanding. The jury's still out on that one. Air Gap, spreadbore adapter plate and TQ make for one hell of a Dagwood sandwich!!!
Headers? Seems like Rusty is all over the Summit headers for fit and price. I will likely go that route.
Clutch? Open to suggestions.
Talk to me, guys.
Click to expand...
Not only are you four decades from 18, but also four decades from the way those factory engine combinations were designed for their time. Those combos aren't going to work well these days. You can make 350+ horsepower on pump premium, without the motor being cantankerous in any way. Here are a few suggestions, rooted in experience, and based on the info you have provided.

First, ditch the forged pistons, and the 10:1 CR. The forged pistons are unnecessary, noisy, heavy, and have zero benefit at your power goals. A hypereutectic piston is a much better choice. The CR is too high for a pump gas motor with a sane camshaft that you can actually use. The factory motors rarely, if ever, measured a true 10:1, and they had better fuel back then. Stay between 9:1 and 9.5:1, with the right cam profile, and you will be much happier.

Speaking of cams, the Lunati Voodoo 220/226 cam would be an excellent choice, or if you wanted to go a little bigger, a Comp XE268 would also work well. Of course there is also Hughes, but I would stay under 224 @ .050".

You don't want to bring in the distributor advance to quickly, or you will have detonation problems. You will need to limit the amount of mechanical advance so you can run about 15 degrees of initial advance, with about 34 total, all in by 3000 rpm.

On the heads, my vote would be for the 2.02 X heads, with some bowl work, but the 1.88 valve heads, properly ported, would work fine as well.

The air gap is a really decent manifold on the street, but I would stick with a square bore carb. The TQ can be made to work as well, but is a lot more work, IMO.

Headers, yes! Nuff said.

And finally, a set of 1.6 roller rockers, properly set up, would be a nice performance upgrade. Not a must, but definitely an improvement.

A combo like I described, in a 72 Duster, will be capable of 12 second ets, and be tame enough for a grandma to drive.
 
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I'd run the factory 71 , 72 or early 73 (no EGR) intake with a TQ. Since your J heads are all but done cc'd and all , I'd run them. Run a cam you can use good valve seals and single springs. Run the vacuum advance distributor and a Chrome box and be done. Unfortunately headers are probably cheaper than stock manifolds, but I hate headers for a street car. You know what you are doing, it is decision time. Good Luck.
 
Can someone provide a link to RRR's link HotRod Bliss?

I'll weigh in on the OP's build if he wants me to but I agree with just about everything B3RE said. J.Rob
 
Roller or hydraulic lifters? Definitely watching this because SOME day I'll be able to work on my car here in MI.
 
Louie70Dart said:
Roller or hydraulic lifters? Definitely watching this because SOME day I'll be able to work on my car here in MI.
Click to expand...
My suggestions were for hydraulic flat tappet cams, but a hydraulic roller would be even better, albeit a bit pricier.
 
B3RE said:
First, ditch the forged pistons, and the 10:1 CR. The forged pistons are unnecessary, noisy, heavy, and have zero benefit at your power goals. A hypereutectic piston is a much better choice. The CR is too high for a pump gas motor with a sane camshaft that you can actually use. The factory motors rarely, if ever, measured a true 10:1, and they had better fuel back then. Stay between 9:1 and 9.5:1, with the right cam profile, and you will be much happier.
Click to expand...

Well, that train already left the station. Pistons should be arriving this week.
I've never been a fan of the hypers, plenty of horror stories (some probably unfounded, yes) of KB's self-destructing even outside of the ring thing (using the PROPER ring clearance). There are many reported incidents of cracked skirts, etc that my machinist relayed to me when presenting the choices. I would sooner go with more weight and mass for the benefit of a good, solid forged piston.

B3RE said:
Speaking of cams, the Lunati Voodoo 220/226 cam would be an excellent choice, or if you wanted to go a little bigger, a Comp XE268 would also work well. Of course there is also Hughes, but I would stay under 224 @ .050".
Click to expand...
Not really familiar with these...do you have the complete specs by chance?

B3RE said:
You don't want to bring in the distributor advance to quickly, or you will have detonation problems. You will need to limit the amount of mechanical advance so you can run about 15 degrees of initial advance, with about 34 total, all in by 3000 rpm.
Click to expand...

Last build was using 34 total with Mr. Gasket spring kit, vacuum disabled

B3RE said:
On the heads, my vote would be for the 2.02 X heads, with some bowl work, but the 1.88 valve heads, properly ported, would work fine as well.
Click to expand...

Based on your compression comments, the 1.88 J's seem to be the best route as they are already cc'd to 67 cc's which drops the CR to roughly 9.75:1. Opening them up to 71cc's should drop it down to roughly 9.5

B3RE said:
The air gap is a really decent manifold on the street, but I would stick with a square bore carb. The TQ can be made to work as well, but is a lot more work, IMO.
Click to expand...
Agreed, the TQ looks like it will require a lot more engineering, and hood clearance may well be an issue. Either that, or look for a more TQ-friendly manifold.

B3RE said:
And finally, a set of 1.6 roller rockers, properly set up, would be a nice performance upgrade. Not a must, but definitely an improvement.
Click to expand...

Unless there is a really good reason, will probly stick with stock rockers. They've never done me wrong in the past, even with that old cam and 6500 RPM...

B3RE said:
A combo like I described, in a 72 Duster, will be capable of 12 second ets, and be tame enough for a grandma to drive.
Click to expand...

That's what I'm talking about...
 
66fs said:
I'd run the factory 71 , 72 or early 73 (no EGR) intake with a TQ. Since your J heads are all but done cc'd and all , I'd run them. Run a cam you can use good valve seals and single springs. Run the vacuum advance distributor and a Chrome box and be done. Unfortunately headers are probably cheaper than stock manifolds, but I hate headers for a street car. You know what you are doing, it is decision time. Good Luck.
Click to expand...
The factory cast intake, though heavy, is an excellent performer when linked with a TQ from my research. Just not sure if I can make myself do it...
 
Make yourself do it as in make the purchase? Move to a heavier older set up? Or tune it?

If your interested in a TQ intake and carb, let me know. At least hood clearance will not be an issue. And you can look stock and still run like stink. A tuning kit is not available. This makes it hard to use them.

A roller cam is really only over kill in price but the performance of the roller has the valves opening up and staying open longer. On your application, it would buy more torque. At near triple the price of a Hyd. cam, it is really not worth it IMO.

Cam specs can be found at the manufactures sites.

I myself am using the next size up from the Lunati cam. A Hyd. roller comp cam.
XE 274HR-10, 224 - 230 @.050 / .538-.534-110. The compression ratio is 9.3-1 w/Edelbrock heads for 87 swil.
TTI for exhaust. Weiand Stealth intake.

The move to roller rockers @ 1.6 buys back the lost lift from the bad angles of the pushrods and the horrible "Actual ratio" of the stock rockers.
 
Getting there .....

image.jpeg


The idea was to start off with factory era heads and intake. The head need to much $$$ at this point and were shelved for parts on hand. The wallet is to light to forge on with the plan.
 
rumblefish360 said:
Make yourself do it as in make the purchase? Move to a heavier older set up? Or tune it?
Click to expand...

"Make myself do it" as in run a cast-iron manifold! Yes, move back to the older heavier setup.
I still have the original carb and manifold from this engine.....
 
Getting some great advice from you all. Thanks!
Pretty much committed to the +.030 Speed Pro's at this point because I already bought them. As I mentioned, with the 67cc 1.88 J heads this will be pushing somewhere in the 9.75:1 static CR. Will any of the cam grinds recommended drop the dynamic down to a more reasonable 9-9.5:1 without any more machine work to those heads?
The cam grind will be the next big choice I will have to make. Don't want to make a mistake.
 
With you combo and a standard Felpro head gasket that is .051" thick, I come up with a static CR of 9.6. With the Lunati cam listed by B3RE, I come up with a dynamic CR of 7.85, assuming you install it straight up as ground (with the already 4 degrees of ground-in cam advance). That DCR should be quite safe for premium, and you may get by with less octane. The range of the low 8'sor high 7's is good; the lower, the less torque but also the less critical timing and jetting is in avoiding detonation. Just take the advice given in ignition timing and tune it with reasonable care, and IMHO it should be OK.

I have run higher SCR and DCR on the street with premium and had no issues on iron heads (Ford 351C); I was careful with ignition timing, and I towed and daily drove it for over 90k miles (while revving the snot out of it from time to time LOL!). (The large-ish bore clearances of the forged pistons eventually got the blowby too high to keep running it.)

BTW, the 351C head flows back in the day made me a junkie for good head flow LOL. So I would probably go for the J heads and shave them a bit and use thinner head gaskets to keep the SCR up in the 9.5-9.7 SCR range to keep torque up and torque band wide for the street, but if you are not revving at all, the 1.88's seem like they would be fine.

And I like the 1.6 ratio rockers but that is some cash; headers are a better investment, IMHO.

So is this just a street cruiser?
 
Ok, well, keeping up CR for a wide torque band will make street and cruiser use a lot of fun. IMHO, that is where it is worth the effort to play that balance between higher CR, smaller cam, and timing to push low RPM torque up as much as you can without getting into detonation. I think you are on a good track with the bottom end for a spunky street car; it'll smoke tires fine and dandy.

For the high RPM 'romps', that is where the larger heads would push the top RPM higher. So that is a decision for you; perhaps others can comment on how much the 2.02" intake extra flow would be worth vs. 1.88". I just learned 'back in the day' to go for a gob of flow from the get-go, and so pushed my son to go straight to Edelbrock Performer flow levels from the outset on his 340. Then I don't worry about reaching 350-400 or more HP, which will 'brown up' most folks' pants. LOL
 
I was 'told' by my engine builder a while back that "a street car will never see the benefits of the 2.02 over the 1.88, but will definitely see the torque benefit of the 1.88 over the 2.02".
Of course, he could be full of it, too...
What do you head guys say?
 
My 340 street car runs 66cc j heads, .040 felpro headgasket, 2316 pistons .018 above deck, XE262 hyd flat tappet on 93 octane. A 4 speed and 3.91 gear in a light A body is in your favor. Smooth the combustion chamber and put a good tune on the motor. A wideband will help to get a flat fuel curve.
 
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