I am installing the LT4 Hot Cam in my 87 L98 motor in my IROC. I have the cam, timing chain, timing cover, heads, lifters, rockers, push rods and headers all installed. The engine is in the car. My questions are:

1. When I set the valve lash, to set the lifter pre-load you spin the pushrod till there is resistance, right? And how do you feel the resistence, is it at the exact point where the top of the push rod touches the rocker? I need that part explained a little better.

2. The cam is a hydraluic roller cam, does it require any special break in periods? If not, with my new valve springs (good till .540" lift), new cam and new roller rockers how high can I wrap my engine, is 6000 RPM possible with out risking problems? Also, how long do I have to wait till I can go WOT and hold it there through 3 gears?

3. Would gutting my cat be benificial andhelp my car brethe better with the new, much more radical cam?

4. I was told to put in some cheap oil, like Valvolene 10W30, and run the car for a few hours then put in my good Mobil 1 Synthetic and new filter, does that sound like a good idea?

Thanks a lot guys!



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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

1. You tighten till you can't spin the pushrod with your fingers anymore and then go 1/4turn more. Make sure you're at the bottom of the cam lobe.

2. I don't think so. The break in period is 20 min. on flat tappet lifters. It's to wear the cam lobes smooth.

3. I wouldn't everyone i've ever seen didn't help that much and sounded like a$$.

4. Don't break in anything with synthetic oil because it won't get hot enough to break in the parts.

 

I'm send you a file on just how to adjust the lifter preload on your new cam.

The 'spinning the pushrod' method is seen often in mags and service manuals and it causes just the kinds of questions that you raised.

You only tighten the adjusting nut until you feel SLIGHT resistance. That's how you know you're at zero lash.

Problem is that what seems like "slight resistance" to one person isn't for another.

The best way is to use an up and down method to identify zero lash. When you can no longer move the pushrod up or down, you know that you are at zero.

Rollers don't require a break in period and only engine oil should be used on the cam's lobes and the lifter rollers. The moly lube is too thick can can clog the oil passages in the roller lifters. Flat tappet cams need the moly stuff though.

BTW, Valvoline 10-30 isn't cheap oil, if by cheap you mean inferior. Yes, it's 'cheaper' than Mobil 1, but it's top grade oil. Now some of that stuff you can buy in a five gallon bucket from WalMart, well that's another story.

As far as revving the engine, you'll need to know the power band of the camshaft; where it peaks. Revving well beyond the power peak isn't going to do you or your engine any good. Whether it'll go 6 depends on how tired your springs are; work up to that level in increments.

When you run out of cam or springs the engine will lay down on you, so you'll know.

Hope this helps and let me know how you make out.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

 

Dan,

Random Technologies makes a high flow CAT that would be a good upgrade for your exhaust. They are $150 thru JEGS or SUMMIT.
The GM CAT is a restriction at high RPM.

You can skip the Valvoline and go straight to synthetic oil with the new cam, since roller cams do not require any break-in.

The HOT cam offers a power curve that peaks around 5,200 - 5,600 depending on the heads you're using. An AFR head may flow to 6,000 with that cam. With L-98 heads, I'd shift it at 5,400 RPM. Any more than that actually slows you down because the peak power is already been seen and you're on the downhill side of the curve.

For accuracy's sake, the fastest way down the track involves finding the peak torque RPM of your vehicle. Shift gears at a point where the next gear drops the motor closest to peak torque without exceeding the redline in the previous gear.

This usually means you need to zing the motor past peak power in order to catch peak torque in the upshift. A happy medium is best found by trying different shift RPM's - experimentation. Try not to scatter the pup while you're improving ET's.

Good luck.
BOR

 

Thanks guys. And by "cheap" I just ment in-expensive not inferior, I know Valvolene is good oil. Thanks again.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!