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Heads/Cam Z Low Dyno/Not Taking Timing

 
Old 04-13-2019, 12:22 PM
  #21  
old motorhead
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Originally Posted by MURDEREDOUT View Post
Old Motörhead.
Glad you figured out your issue. I’m aware of the valvetrain set up on where it can affect power. Still wouldn’t affect how it only takes 19 degrees of timing advance. But I have a feeling it’s .030 milled vs the .010 milled and I’m not taking out the heads to measure and CC of the heads.

How much shorter push rods did you use or need? Did you feel or dyno the difference?
7.35". Haven't put it on a dyno since the swap. Before, there was no doubt about when it was time to shift. Power would go down pretty hard after 6200 rpm. Now, it keeps pulling right on through to 6800. First time I went WOT after the swap, the rev limiter caught me at 6800. I wasn't ready for that. The difference is very noticeable.
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Old 04-15-2019, 01:03 AM
  #22  
kojo
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Originally Posted by jayyyw View Post
What I told you on IG, Kojo.
haha yeah you did but I wasn't out to make crazy power, that's the disappointing thing for me/why I wouldn't switch heads just yet. Anything over 550+ would be bonus for me...there have been comparable/identical set ups that have made that with AHP heads just fine although I am not sure how their cars were with taking timing

Originally Posted by Millenium Z06 View Post
You've either got a cam timing issue, bad springs or it's in the heads; all this assuming the tuner is competent. I had Frankenstein heads and had the same issue.
meaning the ls7 not being able to take timing?


Originally Posted by old motorhead View Post
Well, mine now pulls clean to rev limit after the shorter push rods installed. Not saying that it's a slam dunk that that's your problem. It's easy to check the preload though. Pull a valve cover off and locate a cylinder that has a valve wide open. The other valve is on the base circle. Back the rocker arm bolt off on that one until you can just wiggle the push rod. Now, tighten it up to 22'lbs counting the turns it takes to get there. If it's a whole lot more than one turn, you could probably use a shorter push rod. If you don't have good control of the valve train, timing doesn't matter.

I know the purists will get their diques bent doing it like that. That will get you in the ballpark though. Get you an adjustable length pushrod, a dial indicator, a white smock, and a pocket protector full of pens if you'd rather....
what length were your previous push rods? what cam specs/heads?

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Old 04-15-2019, 07:18 AM
  #23  
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Originally Posted by kojo View Post
what length were your previous push rods? what cam specs/heads?
Previous push rods were 7.4". I had them laying around from a previous project, so I figured I'd try them before buying new. All the particulars are in this thread:

https://www.corvetteforum.com/forums...cam-build.html
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Old 04-16-2019, 10:08 AM
  #24  
nuke61
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Originally Posted by kojo View Post
The only change that was made was a BTR Stage 3 cam and length of pushrods.
As others have said, start here, since you said the car ran strong prior to these changes. The cam could be ground wrong, that's why you would want to degree it if you're certain the dots were lined up correctly. Check pushrod length, even if just only using the "old school" method of counting turns.

BTW, if you changed the cam you should have changed the springs and retainers. When you said it ran strong prior to the cam and pushrod change, what was "strong" and what cam was it running?

Last edited by nuke61; 04-16-2019 at 10:10 AM.
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