383 engine build, how to lower the compression?

Hi,

Thanks for stopping by the site. I have forwarded your post to Ryan specifically to help answer your questions.

Take care and good luck with the build.

Joe

Hey there!

Thank you so much for watching the 383 series! So for lowering the compression ratio you either need a bigger combustion chamber in the heads or bigger dished pistons.

To decide on which to do check out this awesome compression calculator from Summit Racing https://www.summitracing.com/popup/calcsandtools/compression-calculator?srsltid=AfmBOor9OVeILCrtBhOANTvZvfXQiMxU7D7B85aI_YPnNPpKLJ2HGuih

If you use the same cylinder heads I am using, you can put these pistons in and get 9:1 which could run on 87 pretty easily and have good power still. https://www.summitracing.com/parts/uem-kb101-030/make/chevrolet

Just double check the wrist pin size and the cylinder bore!

For a camshaft something like this would be a good bet for a truck 4x4 application https://www.summitracing.com/parts/sum-1102/make/chevrolet

I have uploaded the calculator to show what it would look like with this combo.

Also here are the heads I plan on using, we have not gotten to this part on the build. https://www.summitracing.com/parts/SUM-162112

Good luck on your build, let me know how it goes!

If you have any other questions, please let me know and thank you for using 2CarPros!

Best,
Ryan

It would change the wrist pin height and affect the total volume of the cylinder a bit. My apologies. These should be everything right https://www.summitracing.com/parts/uem-kb121ktm-030/make/chevrolet but again check the wrist pin diameter. With these your compression ratio should be high 8's which is still solid for a street truck.

Best,
Ryan

Very cool! No problem!

Yeah, the camshaft I linked should be pretty good for your application. As far as the rings go the ones, I'm using are gas ported which are pretty high performance and pretty pricey. So, you could get away with this https://www.summitracing.com/parts/hsn-2m139030/make/chevrolet and be perfect. I'm also assuming your bore is 4.030 as I did with the pistons.

I get that! But if you make a mistake, remember, it is just an engine and it can be fixed.

Best,
Ryan

Rollers are really cool; they are just more expensive and complicated. But there is no risk of flattening the camshaft lobes out.

Check this one out https://www.summitracing.com/parts/hrs-180235-12/make/chevrolet

But I would call and ask if it will clear 383 stroker and what distributor gear to use.

Best,
Ryan

No problem at all, I am more than happy to answer any and all questions. Apologies for my late reply, I was out of the office until now.

So, lifters are surprisingly complicated to make, you should always go with a big-name brand that has the engineering prowess to back it up. Also, you want a hydraulic lifter, so it keeps it lash automatically. Solid lifters require you to reset the lash every 1000 miles or so. Not worth it in a street application in my opinion.

https://www.summitracing.com/parts/hrs-91160/make/chevrolet

Those above would be my bet, but you need to check the total height vs a stock lifter. You might get more total lift out of them so you would need a shorter pushrod to accommodate.

The stock lifter seat height is 2 inches, and these are 2.618 so you would need pushrods that are 0.618 inches shorter to compensate.

Thank you for using 2CarPros!

Best,
Ryan

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