[oldman]

I'm putting in the cam, Pray's cam based on a TSP core with 32% fuel lobe... can somebody show me where I check the clearance to the pump and B) do I need to check the clearance. I think I need the lash cap.

2) is this the new cam bolt:
Chevrolet Performance – VVT Camshaft Sprocket Bolt (12588151)
$39.97

In GM parts direct and they don't list it? Strange.

Vengence for sure is offering a completely locked sprocket, is that worthwhile instead of fooling around with the VVT limiter?

OH and I'm putting the cam in without as in NOT dropping the pan... at least that is the plan.

[SC88]

What HPFP? From what I remember you do not use the lash cap on the LT4 fuel setups.

[BlackbeastSS2]

My experience with GM Performance cam install.

Cam bolt GM
Part number 12681018

Front end of car was removed for install.


You will need a cam phaser limiter.
GPI – Gen 5 LT VVT Phaser Limiter Kits

[tireslayer0331]

For the lash cap sizing I found this guide a while ago.
https://www.corvetteforum.com/forums...learances.html

Hope it helps!

[oldman]

Originally Posted by tireslayer0331

For the lash cap sizing I found this guide a while ago.
https://www.corvetteforum.com/forums...learances.html

Hope it helps!

Thanks I read it all and the link threads from there. IMO. I don't know why I need to measure the preload, but I do need to measure max lift with no gasket. For the most part it would seem the pumps have enough stroke. I'll pickup a .060 and an .080 cap.

[oldman]

I got off the phone with Texas Speed, they are local, they say I need a lash cap only with the 32 lobe AND the LT1 HPFP. No cap needed with the lt4 pump. I'll have to look more into this. I'm picking up their spring kit and lash cap. I may or maynot go with the LT4 pump, now that I'm still working on the engine.

[parish8]

You really should check your preload and make sure the pump doesn’t bottom out and get the right lash cap. I think you will need the .060 one.

On my car. 32% fuel lobe, no lash cap, lt4 pump, there was no preload. To me this suggests you are giving up stroke.

With the .080 lash cap it had preload but bottomed at the top of the stroke.

With the .060(or so, I just sanded down the .080). It had preload and did not bottom out.

[oldman]

Originally Posted by parish8

You really should check your preload and make sure the pump doesn’t bottom out and get the right lash cap. I think you will need the .060 one.

On my car. 32% fuel lobe, no lash cap, lt4 pump, there was no preload. To me this suggests you are giving up stroke.

With the .080 lash cap it had preload but bottomed at the top of the stroke.

With the .060(or so, I just sanded down the .080). It had preload and did not bottom out.

Thanks, sage advice, so it your seem that the Lt4 has more extension? IE may have some preload with the smaller base circle lobe 32%? and that there is no way the LT1 pump will have preload with the 32%. I was all set next year for cam, and LT4 HPFP, this year I have a second kid going to college.... so money is tight.

[parish8]

on my car the lt4 pump without a lash cap did not have any preload and would be missing out on some stroke without a lash cap.

if your short on funds just do the lt1 pump for now. probably needs the .080 lash cap but i would still check it. you can always swap that out later to an lt4 pump and figure out the perfect lash cap for that pump then.

[oldman]

good news and bad news. I can't take the chain off from the cam. Even after loosening the pump. I had to drop the pan. Good news It was super easy dropping the pan. I unbolted the engine mounts (1 bolt on either side). Stacked some washers / nuts let engine down... drop pan.. I did loosen all 8 cradle mounts, don't know if that gave me any more room... I have BMR mounts. So once again did not take anything off like headers etc, just stuff attached to the pan. Loosen two bolts jack engine, put nuts / washers on so the mount will not drop down. Pan off, I could use the electric gun on all up facing bolts too.. well not the one under the electric steering so that added 60 seconds.

[oldman]

OK, checking the preload without gasket I'm at least .047 too much (gasket is .010) with an .080 lash cap. Do yourselves a favor and get a LS7 valve lash cap GM part number: 12596509 at .060 and save yourselves a whole lot of grinding. No way the lash cap that comes with the cam is gonna work, the only thing it will do is destroy the pump. Even then that LS7 is probably too thick!

So don't change cam lobe and use the cam grinders lash cap cause they are on DRUGS. I did some checking around and the base circle is about .050 to .055 smaller meaning the cap should be MAX of .055 why do vendors just toss in a .080 cap? It makes no sense, and if you call the vendor they will say just run the cap we NEVER have had issues. Right, just go over to the Vette forum and check the guys with cam and lash cap. I can see if this was two years ago and the cam vendors did not know. But now? package an .080 cap that WILL fail the pump? Makes no sense. Off the soap box.

[oldman]

Also can somebody post the stroke of the LT1 pump vs the LT4 and maybe even the Ligenfelter 12mm bore pump...

[oldman]

evil deed is done. I took .055 off leaving .025 shim.
Preload with no gasket is about .007, gasket is about .010 uncompressed. This should mean that the pump plunger is all the way out when on the lowest part of the lobe.

full stroke is actually pretty hard to check because you are pushing on a loaded spring. I checked it with and without the gasket with finger tight bolts. So this should mean at a minimum I have .007 before plunger smashed through the top of the housing... probably a lot more.

I could find my second .080 and see how much interference with the standard cap and my pump at the top of the lobe. I did check with the initial .080 just for eyeball and it would seem that I had .020 or there about with no gasket. Meaning that if I put the cap on and try to run it I would be looking at about .013 of plunger hitting the top of the pump 3x on each rotation of the cam... No wonder the blots fail after a time. I can see the bolts flexing .013 for 1000 miles, but after that.....snap.

So you have all be told, the cam grinders .080 cap is a failure waiting to happen. .55 should have been included by default. Sure the vendor will say "the thicker one can be sanded down"... right or you could just included a cap that would work for 99.9% of your customers.... If you had a mechanic put a big fuel lobe in, I'd check the clearance.

[oldman]

so here are the specs, LT1 an LT4 pump have the same stroke .240. The compcam's lobe is 32% and it comes from out to .295. The LT1 pump has a .365 max stroke.

So you can see the factory has .125 play, if everything is set to factory specs the 32% lobe should give .070 play. The comp fuel lobe has a base circle of .050 to .055 smaller than the factory (smallest part). but wait, the factory fuel lobe is .005 to .020 smaller than the journal diameter (biggest part). Basically the after market cam is leaving the tallest part alone (so you can install it), and cutting away the base circle. The .080 cap is adding to the tallest part of the lobe (any cam), going from my instance I would say .060 LS7 lash cap (for the valve) would be the smartest starting point. and the .080 cap is just so you can blow your shiznet off the valley cover... that's why the cam grinders put one in every kit.