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Type 3 small stroker build

Posted: Sat Oct 01, 2016 6:15 pm
by Thenoj
IMG_4178.JPG
.042 deck with no shims, CR of 11.3. Cam is C20 with 1.4:1 rockers. Heads are 044 castings, no port work and I think 40x35.5 valves with single high rev springs. I figure I'm going to add barrel shims to get the CR down a bit. I'd like to build this thing with the parts I have on hand but if a cam change would make this thing run on US 87 octane I could scrounge up a few bucks.


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Re: Type 3 small stroker build

Posted: Sat Oct 01, 2016 6:19 pm
by Thenoj
This is a street engine and the carbs are dual 40idf's.



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Re: Type 3 small stroker build

Posted: Sun Oct 02, 2016 7:02 am
by 66brm
Keep the tight deck and open the chambers up, can that cam run with 1.4s?

Re: Type 3 small stroker build

Posted: Sun Oct 02, 2016 1:02 pm
by Thenoj
Yeah, the C20 is supposed to work well with 1.4 rockers. If I could add 10cc's to the chambers, that would bring the CR down to about 9.5:1.


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Re: Type 3 small stroker build

Posted: Sun Oct 02, 2016 1:42 pm
by Marc
Take the piston deck up some - .042" is scary-tight for a 90.5 bore, and with a little more you'll still have good "quench".
I'd go with .055" and 55cc chambers (or .050" and 56cc), that'd give you 8.4:1 static and a chance of getting away with 87 (R+M)/2 gas.
Even better, mill a shallow flat dish in the piston top and remove less from the head. For example, a 2" dia dish .060" deep would add ~3cc unswept volume and still leave a >3/4" wide quench pad around the perimeter.

Re: Type 3 small stroker build

Posted: Tue Oct 04, 2016 3:23 pm
by Thenoj
Old configuration of this engine had 5.7 rods and .054 deck for 9.6:1 CR. As you can imagine, it ran hot.


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Re: Type 3 small stroker build

Posted: Mon Nov 07, 2016 7:55 am
by Thenoj
I was able to get the chambers up to 50cc and put a .020 shim under the barrel to get down to 8.8:1 static. The cam and long(ish) rods get the dynamic down to 7.9:1. The engine should be running this week.


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Re: Type 3 small stroker build

Posted: Tue Mar 28, 2017 9:43 am
by Thenoj
4K miles on this engine and it runs great except needs 89 to not ping. Not a terrible situation but missed my goal. Marc was probable spot on with .050" and 55cc but I wasn't comfortable removing any more material from the heads I had and I thought more deck would kill quench and cause other issues.

Re: Type 3 small stroker build

Posted: Mon Jan 01, 2018 1:13 am
by sidemarkers
hemi cut or flat chamber?

Re: Type 3 small stroker build

Posted: Sun Jan 14, 2018 7:37 pm
by Thenoj
I hand shaped the chambers mainly unshrouding the valves. Most of the flat area on the spark plug side is intact.