Quote:
Originally Posted by unruhjonny
I seem to recall an article from several years ago where these engines were dyno'd and came out nearly nuts on their respective ratings.
I digress, I wanted to comment about something else entirely;
I noticed this:
now, before I say much else, could you tell me if this isn't a PSMCD eligible motor?
Because unless there has been another rule change, the rods alone should disqualify this motor...
Also iirc this engine should have had an advertised compression of 7.6:1, and if I am correct this would be a bump of more than a full point - which should again make it disqualify.
I have not read of any builds here that have the piston out of the hole, most are (if my memory serves me) about 0.020" down so that was interesting for me to read.
I normally read that with the piston down and the thicker fel-pro gasket, that engines like this often yield a marginal drop in compression;
granted the overbore helps kick it back up;
And in this example the reduced cc valve reliefs would help too - I cannot off hand recall the size of the cc valve reliefs in pistons from this period - can someone post this to help me out?
This is pretty cool to see the honest to goodness power that can be made from a very stock appearing motor.
You guys sure do some interesting engine builds!
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Jonny, The pistons "out-of-the-hole" were not by design or intended. The original block was zero-decked way back by the original owner (by George Delorean) in early 80's, so, that was what we had to work with. We could have ordered custom pistons with a raised pin height to compensate, but went with off-the-self pistons since they wouldn't be too far out of the hole.
We allow, and encourage, forged rods for Pontiacs (and 360 AMC's) since we've had cast rods going out of round a couple of dyno sessions. Formulajones did a great job of explaining that in an earlier post (thank you!). However, this W72 400 wasn't built for the PSMCDR and has RA exhaust manifolds since the car already had a nice exhaust system for RA manifolds on it. The car also has the 80's era H-O Racing sub-frame connectors and chrome roll bar that are staying in...so a mildly modified street TA not to mention it's neat having that history/legacy.
Dennis