FrontEngineDragsters.Org Forum
Technical => Matt Shaff's Engine Shop => Topic started by: old28 on October 03, 2014, 05:37:32 PM
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I am currently running a Chevy 194" generation 3 7 main motor in my vintage dragster. It has standard 3.563 + 0.040 cast pistons. I am looking for a replacement 3.623 (.060 over) forged piston to use in a build up on the motor. Current HP & CR is around 125/8.5, new build will be close to 200HP @ 6200 RPM and a CR around 9.5 - 10.0.
Does anyone make a forged piston for this motor? Have found 230/250/292 stuff, but no 194 forged piston.
Would I be OK with good Speed Pro cast units?
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Hi old28, I'm big inline-six fan and intimate with Chevy I-6's. Just curious, why sticking with 194", instead of 250"? It would be easier and cheaper to reach your HP goals.
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ricardo1967 -- Mainly because I started a few years ago with this motor and had a goal to make it the quickest SDRA Dragster with the smallest inch motor that is currently running. I know it would be easy to build a 250/292 motor with .80-1.0 HP to cubic inch ratio but after building my own motors for the past 40 years I am looking forward to the up's and down's of this build.
With most all parts from 194/230/250 interchangeable the pistons are the only real problem, have not been able to find any .060 over forged FT units out there.
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old28 – neat idea making fewer inches working harder “smarter.” Here’s piston idea for you to consider, a friend did this in his fh engine successfully.
Look at early Porsche pistons (forged too). Here’s ebay link to 2.2L used pistons, they are 84mm and too small for your bore. 92mm pistons converts to 3-5/8 inches, which I think is the 2.7L early Porsche engine. Porsche (and maybe VW) has pistons on either side too, 94mm, 95mm, etc. Find some and compare to your pistons, you never know. DF
http://www.ebay.com/itm/Porsche-911S-OEM-Mahle-Cylinders-And-Pistons-2-2/321541402406?_trksid=p2045573.c100033.m2042&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D24901%26meid%3D3d2499572df74c5ea7027634a0b06dc0%26pid%3D100033%26prg%3D10502%26rk%3D1%26rkt%3D4%26sd%3D321541402406
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old28 - I do understand your perspective. Best luck with your build and keep us posted.
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denverflatheader -- Thanks for the information, I will check it out. Got to be something out there with the 3.623 bore and the same CH for the pin.
I still may have to go with cast pistons, I think they would work fine with 92 pump gas, 9.5 CR, 6200 RPM max. Really don't want to go with custom forged pistons at $700+ a set.
ricardo1967 -- Thanks for the good word, it will all come togeather in time.
HAS ANYONE USED CAST PISTONS IN THE RANGE I HAVE LISTED< PLEASE LET ME KNOW.
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Yes, I have definitely used cast pistons on Chevy I-6 in this HP/RPM range. That's what I'd do in your case. Heck, I have friends with turbo 250's, with cast pistons, but you gotta be careful with the tuning there.
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ricardo1967 -- That's good to hear, I really don't have a problem with them in the 9.5CR, 190-195 HP & 6200RPM range. Make sure skirt side clearance is correct and keep the tuneup a little on the fat side.
Dolmetsch has talked to me before and has run slant 6 motor with cast pistons with no trouble, just got to be smart on the tune up.
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If I have to go with cast pistons is there a brand that stands out as being a little higher quality?
They have to be Chevy 62-64 194" .060 over bore that works out to 3.623" with a flat top & compression height at 1.779", standard .927 pins.
Lots of 230/250/292 pistons out there, not a lot for the 194" motor.