Zilla's rebuild (exhaust mod revealed, gauges going in.....) - Page 7 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 03-08-2007, 12:23 AM   #61
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Quote:
Originally Posted by J Wikoff
I ask because my dad'* 89 C/K2500 had a little worse scoring on one cylinder, just enough to just barely feel it. It didn't hold much compression... and it happened fairly quickly. At around 125k.


And how bout that LIM?
Can't feel this scoring, and compression is great. If it'* that good, I'm certainly not worried about it.

LIM? I'll have to hold the Stage1 LIM as a reserve in case I go too far with the Stage2. After that, it'* got your name on it if I don't need it.

I only have one spare non-walled LIM here, and I'm about to go after it with a vengeance.

BTW, further Exhaust Manifold porting won't be necessary. In looking at my heads, that'* where the effort will be concentrated. My exhaust mani'* flow MUCH better than my heads right now.
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Old 03-08-2007, 12:36 AM   #62
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Holy crap, its naked!
Everything looks REALLY good considering how much that engine has taken, power wise.
This build up has my attention, thats for sure
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Old 03-08-2007, 12:54 AM   #63
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unless i missed something your replacing the old style rocker arms (non-rollers) too?
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Old 03-08-2007, 01:16 AM   #64
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At most I think He'* going to the Roller Pivot( L67 didn't have them in 93 )

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Old 03-08-2007, 09:13 AM   #65
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Quote:
Originally Posted by jr's3800
At most I think He'* going to the Roller Pivot( L67 didn't have them in 93 )
that'* what I ment
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Old 03-08-2007, 09:51 AM   #66
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Quote:
Originally Posted by willwren
Stronger valve springs to fix the valve float at the top of 2nd gear that I've had for 3 years.
How do you know this is occurring? Curve flattens right out on the dyno? (just trying to learn lol)
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Old 03-08-2007, 11:39 AM   #67
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Quote:
Originally Posted by Logan
Quote:
Originally Posted by willwren
Stronger valve springs to fix the valve float at the top of 2nd gear that I've had for 3 years.
How do you know this is occurring? Curve flattens right out on the dyno? (just trying to learn lol)
I had the same issue on my 91... It was like hitting a brick wall in terms of power... And you know when you get there.. The new springs will give him the ability to rev a little further up the rev band if he wishes, but most importantly it will kill off the valve float

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Old 03-08-2007, 11:47 AM   #68
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Feels like you run out of fuel, but the scantool says you don't. Car falls flat at the upper rpm'*. Won't make more power, even though the rev'* go up and the fuel trims are correct.

Springs are just weak enough (even though they're 5lbs heavier than S2 springs) that when the came lobe turns and the lifter/pushrod drop, the spring can't close the valve quickly enough. This causes valve 'overlap' in a sense.

I've had valve float in varying amounts since I installed the Jet PCM 3 years ago or so. Only at the top of 2nd gear and 3rd gear. Much more noticable in 3rd though.

The interesting thing is that we found yet another commonality. Buick Grand Nationals have the same springs stock from the factory, and the same install (closed) height. John Wikoff, jr's3800 and I had already pretty much selected a stronger spring for the S1 L67 by calculations and measurements, then after we'd agreed on a spring, I discovered the commonality with the GN. I searched their forums and found out they use the same CompCams springs we'd selected for ours. Icing on the cake.

Alot of factors go into selecting valve springs. Spring rate, load at valve close, load at valve open (have to know your cam lift for this), etc. Overdoing your springs puts alot of wear and tear on the valvetrain and timing chain/gears.
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Old 03-09-2007, 08:41 AM   #69
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Back to it. Rear cylinder head is cleaned enough to strip the valvetrain. Front will be like that tomorrow sometime.

LIM (original ZM LIM) is clean, as are the valve covers. Change in plans......I'll be taking the ZM1 LIM to the next level, holding a spare in reserve, unmodified. This will save me porting time.

After further measurements and calcuations, Exhaust manifolds won't be going to stage 2. They already outflow the cylinder heads by a significant amount. I am going to re-calculate to be sure, though. My original porting seems more than sufficient to support the car another year, even after the head work.

With the SLE'* trans failing, time is the factor now.
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Old 03-09-2007, 08:59 AM   #70
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Quote:
Originally Posted by willwren
With the SLE'* trans failing, time is the factor now.
I bet... soooo what are you gonna do?
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