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Question about 383 pistons

Edelbrock E Street heads are available in a 75 CC version with a more modern chamber design, and are about $1,100. You will have most or all of that in a set of 516's with bigger valves and even bowl port work done by a pro.

The last 383 I did was .030", flat tops with no valve reliefs, .020" in the hole, 516 heads milled .010" with the 1.74" exhaust valve added, (nail head style which reduced chamber volume), and with a Fel-Pro gasket, it was still under 10-1 compression.

I think you would notice a fair difference if you could raise your compression. I would not want to tear into a fresh bottom end either, and a milled set of small chamber heads with a thin gasket is about your only choice.

Good luck, nice car by the way. :)
Yea I’ve learned a lot since putting the engine together. Next time i’ll be more aware of details and know exactly what pistons and other parts i’m putting together.
 
Yea I’ve learned a lot since putting the engine together. Next time i’ll be more aware of details and know exactly what pistons and other parts i’m putting together.

Heard that story to many times... It would be nice if more machinists felt like their job was to provide guidance instead of just throwing the first part in the catalog at a build...
 
I have these pistons (link below) in a 383 decked .020... they live .003 out of the hole, hopefully that gives you an idea of where you would be if you ran them. I have 915 heads and the car runs fantastic on 93 octane using a felpro .039 gasket. If you did choose to get back in it and run these pistons with a .020 shim gasket and factory deck height i would think you would have around a .037ish quench (based solely off my blocks dimensions) I'm not sure how much power would gain but you will certainly feel it 'assuming' the headflow is EXACTLY the same. However, i believe you will like that combo a lot more than the .060 down the hole w/open chamber setup, but before you take it apart try to run it at the track and or put it on a dyno so you and the rest of us can see the results of this popular debate!
https://www.summitracing.com/parts/slp-l2315nf30/overview/make/chrysler

D6FB938E-EB80-4A8F-B369-9B706EF5ECC5.jpeg
 
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Heard that story to many times... It would be nice if more machinists felt like their job was to provide guidance instead of just throwing the first part in the catalog at a build...
yea i thought the same thing after i found out which pistons i actually had in the engine. Spent $3000 at machine shop. Wanted to do the best job I could do on the engine. Rebuilt the rods, line bored the block surfaced heads and deck, bored and honed cylinders new valves. Really disappointed finding out it has less than 8:1 comp ratio. I should have done more homework
 
I have these pistons (link below) in a 383 decked .020... they live .003 out of the hole, hopefully that gives you an idea of where you would be if you ran them. I have 915 heads and the car runs fantastic on 93 octane using a felpro .039 gasket. If you did choose to get back in it and run these pistons with a .020 shim gasket and factory deck height i would think you would have around a .037ish quench (based solely off my blocks dimensions) I'm not sure how much power would gain but you will certainly feel it 'assuming' the headflow is EXACTLY the same. However, i believe you will like that combo a lot more than the .060 down the hole w/open chamber setup, but before you take it apart try to run it at the track and or put it on a dyno so you and the rest of us can see the results of this popular debate!
https://www.summitracing.com/parts/slp-l2315nf30/overview/make/chrysler

View attachment 854958
I was looking at those pistons the other night on the Summit website. Usually order from them. those would put me pretty close to even with the deck. I would also be interested on how she does at the track. I may take her up to Bandemere on test and tune night see what she’ll run. Probably be next spring.
 
I was looking at those pistons the other night on the Summit website. Usually order from them. those would put me pretty close to even with the deck. I would also be interested on how she does at the track. I may take her up to Bandemere on test and tune night see what she’ll run. Probably be next spring.

Mine have been running in my motor since 2012, 30,000+ miles. I shift it around 5700 and it sees that alot. I've got no complaints with them, i wish there where more options on the market but i can vouch for these.
 
I have these pistons (link below) in a 383 decked .020... they live .003 out of the hole, hopefully that gives you an idea of where you would be if you ran them. I have 915 heads and the car runs fantastic on 93 octane using a felpro .039 gasket. If you did choose to get back in it and run these pistons with a .020 shim gasket and factory deck height i would think you would have around a .037ish quench (based solely off my blocks dimensions) I'm not sure how much power would gain but you will certainly feel it 'assuming' the headflow is EXACTLY the same. However, i believe you will like that combo a lot more than the .060 down the hole w/open chamber setup, but before you take it apart try to run it at the track and or put it on a dyno so you and the rest of us can see the results of this popular debate!
https://www.summitracing.com/parts/slp-l2315nf30/overview/make/chrysler

View attachment 854958

I've looked at those before, thing is with the C/H & a flat top the piston to valve clearance is marginal at best... Have you checked to see what kind of clearance you actually have?
 
Mine have been running in my motor since 2012, 30,000+ miles. I shift it around 5700 and it sees that alot. I've got no complaints with them, i wish there where more options on the market but i can vouch for these.
I've looked at those before, thing is with the C/H & a flat top the piston to valve clearance is marginal at best... Have you checked to see what kind of clearance you actually have?
I haven’t. How would you check, with clay?
 
I haven’t. How would you check, with clay?

The question is actually directed at Austin Griggs... All you or I can do is theoretical clearance & I'm guessing I could get a more accurate number.... So I defer to Austin who should have actual measured numbers....
 
I haven’t. How would you check, with clay?
With my old cam there was a mile of room, but when swapping to a cam with more duration my brother put his borescope to use. I was going to advance the cam to buy up some clearance but after seeing the room I still had I just lined it up dot to dot. This is using a 1.74 valve with a 234 @ .050 duration.
 
This is just as the exhaust valve is about to close completely and the piston is getting right to the top. I can get you the video if it would help you. We didn’t pull the heads to do the cam swap so as far as measurements... this will have to do however this is AS close as the valve ever gets to the piston.

C7E1B990-04B4-457F-BFE8-F6255F2E5BA0.jpeg
 
You should probably use a set of light springs & a dial indicator... Start at 10 BTDC & check every 2 degrees... You want .100 for the exhaust & .080 for the intake...

If your piston is proud of the deck then that composition gasket is likely your saving grace....
 
This is just as the exhaust valve is about to close completely and the piston is getting right to the top. I can get you the video if it would help you. We didn’t pull the heads to do the cam swap so as far as measurements... this will have to do however this is AS close as the valve ever gets to the piston.

View attachment 854974

Actually it looks ok.. Me being me, I would probably still measure it but you have more room than I expected...
 
Actually it looks ok.. Me being me, I would probably still measure it but you have more room than I expected...
I was damn near losing sleep over this issue, because the cam was being changed from 208 to 234 and I had to have the car race ready in very little time. Once we actually put it to the test I felt silly for even worrying about it. It runs great, super strong, and isn’t even close. I’ll get a good measurement when I put my 1.81 valve heads on it. (This photo is a couple frames later Piston not all they way up, but close)

9C3A72B1-F003-4819-9CFE-434D02D89758.jpeg
 
To OP, did you actually measure the -.060 deck? Or that an approximation? As you have become aware actual measurement is what counts. What is the intended use/application? Raising the CR may not gain you enough power to justify the cost if you're not into it for competition. If you go for the 516's, do the "pocket porting" first & put in the bigger valves. I've done several sets of 516's that made good power with the porting, it's worth a LOT more than a CR increase for what you've got.
 
Without replacing pistons, close chambered heads is the way to go. You have a 66, do you know if those are the stock heads with the car or what # they are? They could already be the 516's! If they are, your better off drilling out for the larger exhaust valve and do a good port job on them and get them to breath. By the time your done if you don't DIY it, the coin you spend on those you could get these and be done! Good Luck

http://store.440source.com/Stealth-Aluminum-Cylinder-Head-COMPLETE-SINGLE-HEAD/productinfo/200-1055/
 
I got my numbers wrong off memory... it’s 230 not 234... the lift is .534 so it screwed with my memory... haha but here are the cam cards Comp is the new one, Hughes is the old one.

CC0AF9ED-2AF2-4098-B90F-CBF39454DF07.jpeg 8209040A-5C58-4934-9946-31E8321B7E08.jpeg
 
unfortunately, once you build a motor with the wrong pistons, there is no easy, simple or cheap fix. I think the best bang for the buck would be to get the 75 cc Eddy head, mill them to reduce the chamber more, and use the 0.020 shim gasket. I usually cut an additional 0.060" off of the intake side above what I cut from the block side of the head. Then run the paper gaskets on the intake.

As an alternative, I'd probably try to find some 915s. In the end, they'll cost more than the Eddys to get to the same performance level.
 
The intake is [email protected]. I'd worry more about head flow and combustion chamber shape than compression and quench at this stage. A good pair of used aluminum eddys is probably close to the cost of fixing up old stuff. Not worth it to swap pistons either. Advance the cam another 2-4 degrees and let it rip.
Doug
 
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