I'm getting serious about my turbo 170 project. In fact I ordered a set of ductile iron top rings from Total Seal this morning.

I spoke with Mike Jeffrey yesterday evening about cylinder head work. The plan is Chevy 1.72" intake and 1.50" exhaust valves.

Since I went for ductile rings I'll go for custom forged pistons too. My thinking is that with stock rods, unmilled head and block (clean-up cuts as needed only), slightly enlarged and polished combustion chambers I can use stock compression distance. I want a cam with 224° duration at .050" lift and 114° lobe centers to reduce overlap. I've used Oregon Cam Grinding in the past, but the solid profiles they have in this duration range only have about .440" lift. I'd like more lift, but that's the breaks. They do have new 170 style cam cores that are thicker than the 225 cores so I'm going to spend the extra money for one of those. Has anyone built a 170 with similar sized valves and cam and did you need valve reliefs?

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Joshua

Well today I spoke with Doug Dutra about my engine plans including valve to piston clearance. He believes that with the wide lobe center and relatively short duration I'll be using that valve to piston clearance shouldn't be a problem.

I'm leaning (oh, bad pun) toward doing my own head work along with my regular machinist. It will save me a fair bit of money over the Mike Jeffrey built head, but if I don't get the performance I'm after I'll go for the good stuff.

I also put in a call to a trans builder that's a friend of a friend. We're friendly too. Anyhow he's going to look into good parts for the 904 including the possibility of a 998 or 999 core from which to grab higher clutch capacity drums and 4 pinion planetaries.

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Joshua

Sounds like a fun buildup, Josh. If you have the coin, Mike can make a durn good flowin' head. I have one of his on my Project V 225 and it has gone 14.90s with a pretty mild buildup (228@0.050" and 8.8:1 comp and 2bbl) and 3.00 rear gear.

Lou

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Home of Slant6-powered fun machines since 1988

That's starting to move pretty good. The 318 in the Zebra would push it to 14.60s with a 10° shorter cam and really bad exhaust manifolds.

I finally came to my senses and decided to put my Supra turbo 5 speed behind the slant instead of the 904. I have the LA to slant adapter, an aluminum flywheel, a car that's already set up for the juice clutch, etc, etc. The only worrry I have is for the 1st gear thrust washer. I'll just have to launch the car kind of easy and it will be fine. I had ideas of using the two step rev limiter in the Mallory ignition box and a little nitrous to make the launches interesting, but drag racing isn't really my thing anyway.

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Joshua