jim i know you kept us up to date with your single turbo set up.
i got 3 questions for you.
1. how much diffrent is the computer tuning on the twin set up as to your old single set up?
2. you may not have said, or i just don't remember you ever saying you floated the valves on the single set up, or what rpm if you did?
3. is your motor still the same as the single set up or did you make some internal changes for the twins?

 

motor is the same.

tuning... hmm. heck if i know. i am always playing with the tune. still learning.

i dont think i hit a wall floating the valves like we did last weekend but i dont think that has anything to do with the twins. with the single it wouldn't hold the boost up top so by the time it was up to 6000rpm the boost was droping to 20psi or less. now it holds the boost steady all the way up. from my recent research the valve springs i have are very weak for what i am trying to do.

 

You have 921's? Please say no

 

please explain your comment.

yes i have 921's. i have a long thread going on over on tech about valvetrain. i am puting some patriot golds in there today. they test a little higher seat and open presures than the 921's. i am also shiming them .060 more than the 921's were.

my 921's only tested at 112lbs of seat presure, the shimed patriots are testing at 142lbs. some guys over there are saying i should shoot for 180lbs of seat presure but i have other people telling me anything over about 145lb's is asking for trouble with the stock lifters. 30 extra lb's of seat presure should help me get a few more rpm and psi

here is the link to the valve train talk on tech https://ls1tech.com/forums/showthread.php?t=592828

 

I'm running 120lb seat pressure on my NA engine...so I would definately so to step up your valve springs.

Also, Parish, they was a thread other on tech that was talking about some new lifters that SPDC is starting to sell and are good for 7k+ rpms. SPDC were selling them for like $200. You might want to check them out.

 

I've ran 180lbs seat pressure with no problems( factory lifters). I'ts the big open pressure that kills the lifters. I bet it picks up big power over the whole curve even with the 142lbs.

 

Thanks Jim. My comment was all about the 921's I have on my motor... I thought I was almost done man!

 

Jim I read the other thread.

I'm no Mr. wizard on turbos.
To me you should have been making more back pressure on the exhaust valves with your single set up, both sides going in to one collector to power the turbo.
As to now with each turbo being powered by each side with a small crossover pipe to equalize pressure.

Your harden pushrods should be good to handle a higher spring pressure.
As to the stock lifters, I am not sure what the limit is on them.
The word stock on these gen 3 motors is proving to be high with the right tuning.
a set of arp rod and head bolts seam to be all you need to make it a performance motor
over stock.

from what i read, i would go with the golds set to 142 like your doing and see what happens
on the next dyno run.

 

jim any updates yet?

 

https://www.performancetrucks.net/fo...d.php?t=378012


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