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Tracking shows the LT4 retainers will be here tomorrow, in the meantime I decided to do some research and discovered I am half an idiot amongst other things.
When doing my vise test for coil bind height I forgot to take into account the installed height of the springs.
The LT4 springs use a retainer that gives them a taller installed height.
OEM L98 springs have an installed height of 1.70 inches, while the LT4 springs have an installed height of 1.78 inches.
So the math goes like this, Installed height minus coil bind height minus a 0.060 safety margin.
L98 spring is 1.70 - 1.15 - 0.060 = maximum lift of 0.490
LT4 spring is 1.78 - 1.172 - 0.060 = maximum lift of 0.548
Since the ZZ4 Cam has a maximum lift of 0.510...…. herein lies my problem. The coil bind is squeezing all of the preload out of my lifters and they are chattering.
I've gotten started replacing the springs and I'll be damned if I didn't have a few bent pushrods!! I was actually expecting that would be the case.
I have a hard time throwing anything away and have a tub of used valvetrain components left over from my previous L98 rebuild that went into my S-10.
I'll sort out the bent pushrods, pretty sure they are all on the exhaust side. Just so everyone knows, I priced out brand new pushrods and there is no way in hell that is happening at $19 apiece. The used pushrods, once they are cleaned up will do just fine!!
Any theory why the pushrods were bent? could there have been (god forbid) piston / valve interference? something else? And $19 each (not a typo?) is ridiculous.
Good ole' fashioned stupidity sprinkled with a lack of patience and knowledge was a major contribution...…… exhaust valve spring coil bind was the mechanical cause though.
Finished up installing the springs and got everything bolted back together, the cam install is finally complete!!!
Runs great and sounds great!! No funny noises, seems no irreparable damage was done.
While I don't think I picked up a bunch of HP, it does feel different..... a little more peppy so to speak. There is still a set of full length headers in the future, previous posters to the thread say they make quite a difference.
I have been researching roller rockers as well, I think I am going to drop the coin for a set of 1.5 GM Performance roller rockers. Maybe 1.6 on the intake side and 1.5 on the exhaust side.... not real sure yet. Arizona Speed and Marine Runners will follow eventually and I am considering purchasing another stock lower intake and plenum to do some port and polish work to, therefore I will have a bolt on ready setup and I don't have to be impatient.... again!!
Took it for a short drive after I topped off all the fluids, came home and rechecked all the fluids and then hit the road top down for about 45 minutes before coming back home. A fun mix of freeway driving followed by some winding backroads. I missed my C4 while it was down..... been stuck driving the Jetta.
Thx for sharing your experience here. Very helpful to others doing cam swaps and what it really takes.
I think that ZZ4 cam is a great idea for a upgrade w/o any bad affects. It really fits a niche between a stock cam and the LT4 Hot Cam. Like you mention adding 1.6 rockers to the intakes will add more torque.
The ZZ4 cam is advanced already 3 degrees more than the LT4 Hot Cam which should help the lower RPM power. So the ZZ4 cam intake valve closes at 64 degrees while the LT4 Hot Cam intake valve closes at 65 degrees making the ZZ4 trap a little more compression too. Something you want with low stock compression. That and the longer exhaust duration will help a restrictive stock exh sys. I really expect the ZZ4 cam to be a better daily driver than the Hot Cam.
The hot cam is hotter no misunderstanding there but the ZZ4 cam has it's niche and using 1.6 rockers on the intake can reduce the difference in performance between them.
Something I noticed on my power run this morning, it seems as though the engine pulls just a bit longer in the top end.
IIRC, it would only pull to about 4700 at WOT, now it is pulling to 4900 at WOT before it shifts. There's certainly not a lot of power way the hell up there, just something to note.
07-09-2019, 02:49 PM
I probably should have caught that as well...
