273 302 318 340 build

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Someone say "360 in cuda?"
Heard it but not sure "I'm going to put 360 in the cuda" yeah I think that is what I heard.
 
Then u know what to do. Put the 318 back together witha re-ring kit. Install in truck. 360 has a new home. Kim
This ...even a smooth idling low compression 360, can hit 13.99 @ 100 mph through the traps, using street able factory parts.
 
Thanks for the in depth advice and responses. Doing the 360 right now wont happen as its in my truck which I use every once in a while(swap meets, dump runs, renovations). Time wise, space wise it just makes sense to do "something" with the 318 I have on the engine stand. I dont want to change rear gears. TC possibly, (current stall unknown)but still trying to keep it low budget. Ill try and figure out what stall I currently have.
I mentioned it earlier, but what I want to use, here is what I currently have so no $$ outta pocket
My cam/lifters/timing chain from 273 (270S solid from comp)
Set of 302 heads
Factory 273 adjustable rockers
LD4B or LD340 (Im leaning to LD4B)
Stock 1985 318 sitting on engine stand awaiting......???

I called the machine shop(long time mopar guy). Cost to bore 318 out .030 is $240. Seems like a good deal? $50-60 to get it dunked. So $300. A set of hicomp 30 over pistons approx $200.
Machinist also said to possibly advance cam 4* to wake it up.
Suggestions on size of overbore I should go?
Hicomp piston suggestions?
Heres some from Summit that RustyRatRod suggested in his "hot rod bliss" thread. Seem like a good deal for $106??
https://www.summitracing.com/int/parts/slp-526ap/overview/make/dodge
Upgrade to Moly rings?
Thanks all
 
my 318 with 302 heads and 284/484 mp cam ran stronger with ld 340 compared to the ld4b which i finally sold, according to the butt dyno.
 
The 526's are the best you are going to do with stock type cast pistons. With a compression height of 1.741", the pistons are still going to be .080" in the hole; you just lose the eyebrows which helps CR a bit. With your McCord head gaskets, you are at 8.45/6.8 SCR/DCR, and with the 1121G's you are at 8.7/7.0 SCR/DCR. A little better.....

Going to KB167 pistons (advertised at $321 USD from Campbell Enterprises in VA), the pistons are now about .010"-.012" in the hole, and your SCR/DCR with the McCord head gaskets is 9.28/7.8, and is 9.55/8.0 with the 1121G head gaskets.

With the 1121G gaskets, you now have an effective quench gap, with the pistons about .038 to .040" from the heads' closed area. (You would have to carefully measure that gap but you are good at that.) With the McCord gaskets, the quench gap is going reach around .050" and will start becoming less effective at reducing the tendency to detonate.

The KB's are going to cure your weak low end torque problems... even with that cam that you have. Did you machinist have another hi-comp piston PN to suggest?

Moly rings for sure..... make life easy on yourself.

Does your machinist know that your cam already has 4 degrees of ground-in advance if installed dot-to-dot (assuming all the parts are machined accurately)? If you're stuck with the the lower comp pistons, then by all means do 2-4 degrees of added advance.
 
Thanks for the reply nm9.
I see the difference in the compressed height KB vs Sealed power. .065" difference equates to like you said approx .080 for the Sealed Power vs approx .015" for KB.
I know quality comes into it, but quite the price difference between the 2?
I have tried to search for "hi comp" pistons, but not a lot of choices that I have found.
$300 US equates to over $400 here, now add taxes shipping blah blah. Adds up quick and quickly eats into the savings of using my cam/lifters etc.
My machinist looked at the specs last week on the cam card for the 270S but didnt go over it thoroughly. So Im not sure if he knows whether its advanced 4* or not.
When I spoke to him on the phone today about the .030 over bore, hi comp pistons and 302 heads he mentioned to watch for detonation.
Am I correct with my math that .030" over bore equates to 0.7% increase in volume?.030/3.94 =0.0076
I asked the machinist bout pistons, but he couldnt suggest any. I will do some more digging.
The compression for KB with either of the head gaskets is pretty decent. Just dont like the price of them lol

Thanks again nm9!
The 526's are the best you are going to do with stock type cast pistons. With a compression height of 1.741", the pistons are still going to be .080" in the hole; you just lose the eyebrows which helps CR a bit. With your McCord head gaskets, you are at 8.45/6.8 SCR/DCR, and with the 1121G's you are at 8.7/7.0 SCR/DCR. A little better.....

Going to KB167 pistons (advertised at $321 USD from Campbell Enterprises in VA), the pistons are now about .010"-.012" in the hole, and your SCR/DCR with the McCord head gaskets is 9.28/7.8, and is 9.55/8.0 with the 1121G head gaskets.

With the 1121G gaskets, you now have an effective quench gap, with the pistons about .038 to .040" from the heads' closed area. (You would have to carefully measure that gap but you are good at that.) With the McCord gaskets, the quench gap is going reach around .050" and will start becoming less effective at reducing the tendency to detonate.

The KB's are going to cure your weak low end torque problems... even with that cam that you have. Did you machinist have another hi-comp piston PN to suggest?

Moly rings for sure..... make life easy on yourself.

Does your machinist know that your cam already has 4 degrees of ground-in advance if installed dot-to-dot (assuming all the parts are machined accurately)? If you're stuck with the the lower comp pistons, then by all means do 2-4 degrees of added advance.
 
You're very welcome; this is always a tough problem with the LA 318 and the 2BBL 273: finding a way to cure the low compression and resulting low RPM bog, when putting in even a moderately large cam. I am not aware of any magic bullet, higher compression pistons either. You could deck the dickens off the top of the block but that costs $$ too (plus new pushrods). The piston change is the direct and clean path to get there. And yes on the .7% volume displacement increase; that is down 'in the noise'. As for the price of the hi-comp pistons, I am sure that part of that is market demand.

Buuuutt... one more thing (there's ALWAYS 'one more thing' right? LOL) that just popped into my wee brain: the KB's are a lot lighter than the stock cast pistons so you will have to re-balance the crank assembly. So that adds even more cost to the piston change, which may put the nail in the coffin of the KB pistons for you. A cam change or other changes may indeed be the way to go.

One thing to ask your machinist about is how much is will cost to mill about .040" off of you heads and the right amount off of the intake faces of the heads. (May require new pushrods.) The objective would be to get the chamber volume down to around 58 cc's Then your SCR/DCR will be 8.9/7.3 , and 9.2/7.55 with the 1121G gaskets. The latter is starting to edge in on decent DCR territory. (BTW, all the numbers I have given you are with your 270 cam installed do-to-dot, with ICL at 106.)

And yes, your machinist is right to mention detonation. When you start to approach a DCR of 8, then you need to be more careful with tuning and ignition timing. But I suspect you wold be careful about that. (How is your high frequency hearing, BTW? That is your built-in knock detector.) You are kinda between a rock and a hard place with that cam; you're gonna have to push up the DCR if you want to get rid of the weak low RPM performance. So it is either fix the DCR or change the cam.

If you would like to work these numbers all yourself just to play around with combinations, I use the Pat Kelley calculator. You can put in the piston/bore/head data to get SCR and then put in your cam data and rod/stroke data to get DCR. Once you get the various numbers into your brain (or written down), it is a snap to run new numbers to see where you are with any changes in parts or milling. The Pat Kelley calculator seems to give a bit more conservative (higher) DCR numbers than some others.
 
Frustrating as I knew 273 piston costs/availability were up there. But 318 ones too? Damn.
I can see how the science involved in engine builds takes years to learn.
Would it be "worth it" to go with .030 over bore and stick with stock height pistons?
The $$ savings would "help" towards MAYBE picking a new cam lifters. BUT at the expense of still lower compression.
Thanks for the Pat Kelley calculator too, I will play with the numbers on their site.
What should I expect to pay for rebalancing rotating assembly?
Thanks!
You're very welcome; this is always a tough problem with the LA 318 and the 2BBL 273: finding a way to cure the low compression and resulting low RPM bog, when putting in even a moderately large cam. I am not aware of any magic bullet, higher compression pistons either. You could deck the dickens off the top of the block but that costs $$ too (plus new pushrods). The piston change is the direct and clean path to get there. And yes on the .7% volume displacement increase; that is down 'in the noise'. As for the price of the hi-comp pistons, I am sure that part of that is market demand.

Buuuutt... one more thing (there's ALWAYS 'one more thing' right? LOL) that just popped into my wee brain: the KB's are a lot lighter than the stock cast pistons so you will have to re-balance the crank assembly. So that adds even more cost to the piston change, which may put the nail in the coffin of the KB pistons for you. A cam change or other changes may indeed be the way to go.

One thing to ask your machinist about is how much is will cost to mill about .040" off of you heads and the right amount off of the intake faces of the heads. (May require new pushrods.) The objective would be to get the chamber volume down to around 58 cc's Then your SCR/DCR will be 8.9/7.3 , and 9.2/7.55 with the 1121G gaskets. The latter is starting to edge in on decent DCR territory. (BTW, all the numbers I have given you are with your 270 cam installed do-to-dot, with ICL at 106.)

And yes, your machinist is right to mention detonation. When you start to approach a DCR of 8, then you need to be more careful with tuning and ignition timing. But I suspect you wold be careful about that. (How is your high frequency hearing, BTW? That is your built-in knock detector.) You are kinda between a rock and a hard place with that cam; you're gonna have to push up the DCR if you want to get rid of the weak low RPM performance. So it is either fix the DCR or change the cam.

If you would like to work these numbers all yourself just to play around with combinations, I use the Pat Kelley calculator. You can put in the piston/bore/head data to get SCR and then put in your cam data and rod/stroke data to get DCR. Once you get the various numbers into your brain (or written down), it is a snap to run new numbers to see where you are with any changes in parts or milling. The Pat Kelley calculator seems to give a bit more conservative (higher) DCR numbers than some others.
 
If you go with the .030" over bore, or even the .060" overbore, it will not fix the low RPM bog that you have. You will get around 0.2 of a bump in SCR/DCR with .060" overbore.

IMHO, going to a larger bore will do one thing for you: You will start with good straight bores, with the proper piston-to-bore clearance, and a good ring seal will result. A good ring seal is one of the 2 fundamentals to good performance; the other being goo valve seal. I don't ever do an engine anymore without a re-bore; I've been down the road in my poor college days with reqowkring an engine with poor bores.

Balance is probably gonna be on the order of $250-300 complete. You can save some $$ by:
- Setting up a way to correctly weigh both small and big end weights of the rods and doing the rod balance yourself. That is a tedious process but it the larger part of a full balance job.
- Weigh the pistons, rings, and ring locks your self... easy.
- Take the weights that you have from the above steps and give those to the machinist to compute a bobweight and just balance the crank only. (Or, compute the bobweight yourself and give that to the machinist for balancing the crank; that is what I do; it is just some math.)
- If you can give the bobweight or bobweight info the machinist, that should cut the cost by more than half. I recently paid $95 for a crank balance this way. (But our local shop costs are lower than standard.)

A smaller cam is not going to lower you DCR, it is going to raise it... which is where you want to go. The general cam profile of the present cam is decently steep to help DCR, but the duration is just too long, and the resulting intake closing angle is just too late.

Looking at cam options, let's try the smaller Lunati VooDoo hydraulic cam with a 253 duration in stalled at an ICL of 106. With the 302 heads unmilled, the block not decked at all, 1121G head gasket, and the 526 Silvolite pistons (no eyebrows), you end up at 8.6/7.5 DCR with about the same lift that you have now. Change to the smallest Crane hydraulic (the H-248-2) at an ICL of 106, then you are at SCR/DCR of 8.6/7.6, with a lot less lift than you have, so your RPM range is going to shift 1000 RPM or more downward.

That 7.5/7.6 DCR range is about as high as you are gonna get with any sort of cam and the stockish cast pistons and thinnest head gasket and 64 cc chambers. Some head milling to get to a 60 cc chamber would get you up to the 7.8 DCR range with that smallest VooDoo cam (to maintain decent lift) and you are getting into pretty good DCR territory now. Low end torque will be pretty darned good now, as in easy to spin the tires with that 3.23 rear gear.

I think you will be pretty happy in the upper 7's DCR range; I'll guess that you are looking for a 'spirited, spunky' car that still has good driveability. 7.8 DCR will do that, and 7.5 DCR will be a whole lot better than where you are now. Keep an eye on not being too aggressive on the ignition timing. What fuel octane do you have up there?
 
Thanks again, you can probably tell Im trying to stay away from machine work as much as possible(if possible).
I was hoping for some bolt on/in upgrades to a 318.
Im thinking I may pull caps and inspect bearings. Leave pistons in if I can.
Choose a new cam/lifters(solid) and use timing chain/gears from my 273(comp cams dbl roller, 7000 miles). Use the 1121G head gasket.
We have 94 Octane up here.
This is turning into a head scratcher LOL(no offense). Some GREAT info here.

If you go with the .030" over bore, or even the .060" overbore, it will not fix the low RPM bog that you have. You will get around 0.2 of a bump in SCR/DCR with .060" overbore.

IMHO, going to a larger bore will do one thing for you: You will start with good straight bores, with the proper piston-to-bore clearance, and a good ring seal will result. A good ring seal is one of the 2 fundamentals to good performance; the other being goo valve seal. I don't ever do an engine anymore without a re-bore; I've been down the road in my poor college days with reqowkring an engine with poor bores.

Balance is probably gonna be on the order of $250-300 complete. You can save some $$ by:
- Setting up a way to correctly weigh both small and big end weights of the rods and doing the rod balance yourself. That is a tedious process but it the larger part of a full balance job.
- Weigh the pistons, rings, and ring locks your self... easy.
- Take the weights that you have from the above steps and give those to the machinist to compute a bobweight and just balance the crank only. (Or, compute the bobweight yourself and give that to the machinist for balancing the crank; that is what I do; it is just some math.)
- If you can give the bobweight or bobweight info the machinist, that should cut the cost by more than half. I recently paid $95 for a crank balance this way. (But our local shop costs are lower than standard.)

A smaller cam is not going to lower you DCR, it is going to raise it... which is where you want to go. The general cam profile of the present cam is decently steep to help DCR, but the duration is just too long, and the resulting intake closing angle is just too late.

Looking at cam options, let's try the smaller Lunati VooDoo hydraulic cam with a 253 duration in stalled at an ICL of 106. With the 302 heads unmilled, the block not decked at all, 1121G head gasket, and the 526 Silvolite pistons (no eyebrows), you end up at 8.6/7.5 DCR with about the same lift that you have now. Change to the smallest Crane hydraulic (the H-248-2) at an ICL of 106, then you are at SCR/DCR of 8.6/7.6, with a lot less lift than you have, so your RPM range is going to shift 1000 RPM or more downward.

That 7.5/7.6 DCR range is about as high as you are gonna get with any sort of cam and the stockish cast pistons and thinnest head gasket and 64 cc chambers. Some head milling to get to a 60 cc chamber would get you up to the 7.8 DCR range with that smallest VooDoo cam (to maintain decent lift) and you are getting into pretty good DCR territory now. Low end torque will be pretty darned good now, as in easy to spin the tires with that 3.23 rear gear.

I think you will be pretty happy in the upper 7's DCR range; I'll guess that you are looking for a 'spirited, spunky' car that still has good driveability. 7.8 DCR will do that, and 7.5 DCR will be a whole lot better than where you are now. Keep an eye on not being too aggressive on the ignition timing. What fuel octane do you have up there?
Thanks again!
 
Yep, it is an interesting problem with no cheap cure. BTW, let us know when you find a solid cam with less duration than where you are at now. That is going to be a real challenge. Racer Brown ST-2 is the smallest I have run across, with 260 duration that presumably will be down to 255 or less when lashed. With those stock 4 eyebrow pistons, and the 64 cc heads, .028" head gasket, and cam ICL at 106, you are at 8.1/6.95 for SCR/DCR.... you're not there yet IMHO.

Dang, if you would juuust mill those heads .040" to get to 58 cc chambers.... at least your DCR with this ST-2 cam would be at 7.3-7.4.

Looking for other solids.... No, I won't because I suspect I won't find any smaller. I wonder if Racer Brown would do any sort of custom solid for this problem. A lower duration hydraulic would sure make your problem a bit easier to solve. What is the fascination with a solid lifter cam? And of course, a roller would be even better; you can keep the lift and lower the duration. But that is $$$$ too.
 
I have been pulling your leg about the 360 but is there any chance that someone in your area would have a running 360 (4 barrel) for sale? Not a screaming flat out race engine but just a standard running 360 that's in good shape. First off you get the longer stroke of a 360 in which in turn comes low end torque (no low RPM bog there) Second by the time you spend the money (add all that up and set it on the left) on what you're trying to do you could have bought a running 360 (find a engine add that up and set it on the right and make a comparison) Maybe even come out with a bunch of money left in you pocket with about the same or even more HP/TQ.
Just imagine your 360 that's in your truck running/installed in you cuda. I bet it would put a smile on your face if you smashed it to the floor wouldn't it?
If for instance you find a 360 you could just clean it up, paint it, find the correct motor mounts, etc... and drop it in.
I'm just throwing this out there since the 318 build seems to be getting pretty damn expensive.
 
I knew you were razzin Marland. I hear ya tho, the 360 would be nice i If my 360 was a simple drop in. Getting harder to find up here, especially one that you can hear running.
Whichever route I go with 318 it may find a home in my halfton.
Yes so may numbers and $$ floating in my head I need to write this stuff down lol
I have been pulling your leg about the 360 but is there any chance that someone in your area would have a running 360 (4 barrel) for sale? Not a screaming flat out race engine but just a standard running 360 that's in good shape. First off you get the longer stroke of a 360 in which in turn comes low end torque (no low RPM bog there) Second by the time you spend the money (add all that up and set it on the left) on what you're trying to do you could have bought a running 360 (find a engine add that up and set it on the right and make a comparison) Maybe even come out with a bunch of money left in you pocket with about the same or even more HP/TQ.
Just imagine your 360 that's in your truck running/installed in you cuda. I bet it would put a smile on your face if you smashed it to the floor wouldn't it?
If for instance you find a 360 you could just clean it up, paint it, find the correct motor mounts, etc... and drop it in.
I'm just throwing this out there since the 318 build seems to be getting pretty damn expensive.
 
Well gonna keep the hunt up for another engine. The cam bearings are toast. approx $150-200 installed. I pulled a couple of main caps and the bearings are showing flaking by the seams where the halves join. Lots of meat left to them, just some flaking.
This block may just end up taking some floor space. The hunt continues
 
OK. You know, you can pull in your own cam bearings.... easy with some threaded rod and some wooden discs.
 
Well gonna keep the hunt up for another engine. The cam bearings are toast. approx $150-200 installed. I pulled a couple of main caps and the bearings are showing flaking by the seams where the halves join. Lots of meat left to them, just some flaking.
This block may just end up taking some floor space. The hunt continues
My 340 is still available!
 
I decent small solid cam is ava off the shelf. The isky E-4 I know its been beaten to death but its the smallest off the shelf smallblock mopar solid cam I know of.
 
Racer Brown has lots of small solids, some even close to original Commando / Charger 273's. Racer Brown solid cams have pretty fast rates. If you want, I can look in my stash. Nothing wrong with an Isky E-4.
 
Thanks guys. I did go buy another 318 shortblock. 70 318
030 over with TRW L2373 pistons. Ballpark down in hole is deep...0.140 but looks clean and steel crank. Piston height is 1.672. Factory 318 is 1.720 correct?
Also got a great deal on a rebuilt low mile 904 with TC.
Been super busy so not much progress other than buying stuff lol
I haven't chosen a cam yet. Ive borrowed a dial indicator tho so I can do some calculations. I may still run the 270S cam from the 273.
Savings of approx $400-500
Isky E-4 is close to Commando spec?
Thanks all hoping for more updates/info in the next week or 2.
Thanks
Steve
OK. You know, you can pull in your own cam bearings.... easy with some threaded rod and some wooden discs.

My 340 is still available!

I decent small solid cam is ava off the shelf. The isky E-4 I know its been beaten to death but its the smallest off the shelf smallblock mopar solid cam I know of.

Racer Brown has lots of small solids, some even close to original Commando / Charger 273's. Racer Brown solid cams have pretty fast rates. If you want, I can look in my stash. Nothing wrong with an Isky E-4.
 
The HP273 cam specs were 248/248° .415/.425 48° overlap.
The Isky E-4 cam specs are 260/260° .425/.425

A great replacement cam for the HP273. It runs better than it sounds. I need to video that!

 
Love that look n sound Mike!
Before I pull 273 ill post a video for comparison to the 318.
So milling heads question... if I get them milled amd using adjustable rockers will custom pushrods be required? Or will the factory adjustables have enuf adjustment in them to use?
Does the 1.5 rocker ratio come into play here?

Thanks!
The HP273 cam specs were 248/248° .415/.425 48° overlap.
The Isky E-4 cam specs are 260/260° .425/.425

A great replacement cam for the HP273. It runs better than it sounds. I need to video that!

 
Love that look n sound Mike!
Before I pull 273 ill post a video for comparison to the 318.
So milling heads question... if I get them milled amd using adjustable rockers will custom pushrods be required? Or will the factory adjustables have enuf adjustment in them to use?
Does the 1.5 rocker ratio come into play here?

Thanks!
It depends how much you mill. The biggest issue I found that requires new pushrods is replacement lifters. Aftermarket lifters often have different pushrod seat dimensions.
 
We ran factory ball/cup pushrods with the lifters that came with 270S.
I plan on cc'ing the heads when I get a chance.
Thanks again
It depends how much you mill. The biggest issue I found that requires new pushrods is replacement lifters. Aftermarket lifters often have different pushrod seat dimensions.
 
Some of the 318 truck engines had that low 1.672" piston compression height to push the compression ratio way down to avoid detonation when hauling big loads on bad gas.

TMM is right; the amount you mill off the heads will mostly determine the pushrod issue. With the adjustable rockers, I doubt you will have to worry over it if you don't go wild on milling.

If you used the 302 heads at 64 cc, .028" thick head gasket and those flat top TRW pistons, then your static CR will be 7.6. Install an E-4 cam at an ICL of 102 (6 degrees of cam advance, then the dynamic CR will be 6.6.... expect poorer than /6 torque at low RPM's.

Mill the heads with the above combination by about .040"-045" to get to 57 cc chambers and then you are at a SCR/DCR of 8.1/7.0 Not great for low rpm torque.

Then change to the cam to a Racer Brown or Crane 248 degree hydraulic and set the ICL to 104 (6 or 8 degrees cam advance), and the SCR/DCR is 8.1/7.2. Still not there; not as good as a stock 5.2L Magnum

These pistons 'in the hole' are putting your low end torque 'in the hole'. Keep the cam as small as you can stand if getting rid of the low end lack of torque is still the objective. The only thing helping will be the added cubes.
 
ant a 85 318 a bit higher compression than older 318s??? like 9.2 from factory? to work with factory quench 302 heads bout has to be right???
 
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