I'd say 154mph is realistic now.
And yes, the rod ratio and managing load (minimize rpm drop between gears) are part of the secret.
MONTE CARLO "COPO" Monte Carlo SS - Turbosaurus Build (Swinging Dick Racing's c*ck got bent... she bounced a little too high & hard, & came down awkwardly)
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I'd say 154mph is realistic now.
And yes, the rod ratio and managing load (minimize rpm drop between gears) are part of the secret.
That was so funny I had tears in my eyes. "I wanted to go fast cheap. You said build it right."
Now's there's a damn sloppy tax on 4.8s.
Do it Mike, let the lil 4.8 eat!
Do it Mike, let the lil 4.8 eat!
Tell me about it. I am going to start stockpiling Gen IVs as soon as financially possible.
I am currently in Mr. Mom mode (which comes to an end tonight). Thankfully, I can start focusing on getting this 4.hate together over the 21 days of vacation that start for me tomorrow evening. 😀 I'll start with a basic port-job on the 241s and reworking a used-stock oil pump MHM-style - then I am going to empty a shelf or two worth of parts into the little guy.
I think I am avoiding notching the frame and mini-tubbing it in fear of creating too much downtime before the spring.
Ported the oil pump yesterday. Then it was on to the heads today - 6 hours and 8 ports later the exhaust side is done. Opened the throat up to about 88% of the valve size. Intake side starts soon.
241s on a 4.8? Where's that gonna put your compression? Then again I have 799s on the wife's 5.3. My guess is around 9.0?
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706s are 61.5cc, 799s are 64cc, and 241s are 66cc. So yeah, the compression drop is pretty minor. It is important to remember that with the change in cam from stock, while the static compression may drop with the heads, the dynamic compression number may not given the specs of the aftermarket cam's overlap.
The big difference between this engine and other sloppy-type builds is an eye toward optimizing flow efficiency. Hence all the porting of the turbo, heads, manifolds, etc.
Interesting (albeit dated) article on how to influence head flow through porting (although I fully disagree with the discouraging of the reader from DIYing it, typical rich guy targeted marketing BS): https://www.hemmings.com/blog/article/lets-cheat/
Simply put, if you can maintain self-control you can find decent gains with some basic blending and radiusing. The reason I spent so much time cleaning up the exhaust side is because that is where this engine stands to benefit most, as cramming a bunch of air in is easy - evacuating it is more difficult. Also, you need to appreciate that the exhaust side cares less about flow numbers (typically measured in inches of Mercury (aka vacuum) and more about volume as those gases leave the cylinder at hypersonic speeds. Obviously exercising restraint is paramount because you can royally F-up the flow potential of the port.
When I get to the intake side, like I did with the 706s I did a while back, you can see where the engineers had to make a trade off in emissions vs performance with the swirl ramp. From initial review these 241s are much nicer production pieces in terms of casting accuracy - but they are also lower production volume "high-performance" parts specifically made for the LS1. By comparison the 706s were doorstop truck heads with some serious production compromises made (including the potential Castech cracking issue).
Simply put, if you can maintain self-control you can find decent gains with some basic blending and radiusing. The reason I spent so much time cleaning up the exhaust side is because that is where this engine stands to benefit most, as cramming a bunch of air in is easy - evacuating it is more difficult. Also, you need to appreciate that the exhaust side cares less about flow numbers (typically measured in inches of Mercury (aka vacuum) and more about volume as those gases leave the cylinder at hypersonic speeds. Obviously exercising restraint is paramount because you can royally F-up the flow potential of the port.
When I get to the intake side, like I did with the 706s I did a while back, you can see where the engineers had to make a trade off in emissions vs performance with the swirl ramp. From initial review these 241s are much nicer production pieces in terms of casting accuracy - but they are also lower production volume "high-performance" parts specifically made for the LS1. By comparison the 706s were doorstop truck heads with some serious production compromises made (including the potential Castech cracking issue).
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