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Hi all - Welcome back for the second time this month!

I apologize for the inconvenience of the site being offline. The site was down for technical reasons, but it didn't help that I was of offline for two weeks (camping and travel). Once I got back, it took a while to get things sorted out. That's resolved, and the site is now back up. Huzzah!

Please take a minute and read the Site News thread I've posted in the General section, and feel free to comment. Thanks!


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Author Topic: 8.0:1 or 9.8:1 Mechanical Compression?  (Read 26 times)
Two cylinders
Posts: 133

dat ass tho. Lol

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« on: May 14, 2018, 04:13:57 AM »

Hi all! I need some Genius help. ( skip to the bottom for the question.)

Years ago in high school I rebuilt my '87 22RE-T. It was my introduction into the industry. Currently I am a much more knowledgeable and skilled technician. Unfortunately I don't know everything (Crazy right  Wink ), and i would love some expert advice.

I am in the process of building the motor. Current parts list includes

Stock block (currently being machined)
Stock crank (was able to polish journals, but keep stock diameter)
New "Stage 3" cylinder head. Extra port work and combustion chamber deburring/polishing done by yours truly (chambers now 1cc oversized, exact on all 4. I did not like all the hotspots left by LCE")
Pro Turbo camshaft and Valve train that came with the head. From LCE
I Changed the "stage 3" head valve springs to the dual spring set w/ titanium keepers (8500rpm springs, 110psi seat pressure and 210psi at .500")
Dual Timing chain conversion kit with included water and oil pump from LCE
Chromoly H-Beam connecting rods and CP lightweight high compression piston set from LCE
ARP Head studs and stock thickness gasket
55mil T3/T4 hybrid turbo charger. With a Bar/ Plate air to air cooler.
I think i got it all, maybe. All the misc stuff to go along of course.

Controller = Megasquirt PnP2 ECU
Stock engine harness, Cleaned, repaired and rewraped.

Ignition = Fast ignition waste coil conversion kit( If i remember correctly, its in the garage)

Now for my question.

I have not yet ordered the pistons mentioned above. LCE offers a few compression ratios. 8.0:1, 9.8:1, 10.5:1 and 12:1. See them all here =


Now I have not figured out which compression ratio I would like to go with. I figure obviously with the 8.0 pistons I could run higher boost levels, but with the 9.8 I would have better lower end torque.
I have not yet done the math to determine the effective compression of either set. Nor have I decided exactly what boost I should run. I will figure it all out soon, but I would like your guy's opinion.
Do you think the block/piston/rod/head combo could handle a 9.8:1 mechanical compression with say 10, 13 or 15psi of boost? or should I play it safe with the 8.0:1?

Some advice would be greatly appreciated. Feel free to ask anything if you have questions about the build. Pictures available also.

This truck is the reason I got into the automotive industry. Its part of why i am so successful at my young age. I have been patching everything i screwed up on it back in high school, and now its time to finally bite the bullet and fix it right. ( making some power will be nice too)

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