homebuilt

I just had my Camaro on the dyno with a new engine and the power quickly hit a wall around 6,200 RPM. It was breaking up and the power dropped substantially when we tried to test up to 6,800 RPM. I am using the stock lifters and I suspect that I having a lifter pump-up problem. I would like to obtain some advice on how to resolve this issue. Here are more details about my build up:

- Patriot Gold valve springs (150 lbs seat, 390 lbs open)
- Meldon HV/HP pump (62-65 psi @ idle, 70 psi cruising, I don't know what it was hitting at higher RPM)
- Royal Purple 10w40 XPR
- 0.605 / 0.613 lift
- Stock lifters
- Boost was only about 8-9 lbs
- Bearing clearances are 0.0025"

MeentSS02

iTrader: (11)

That's a shitload of oil pressure at idle (unless that's a cold value), but I wouldn't think that would cause the problem. What kinda lifter preload do you have?

homebuilt

The oil pressures I mentioned were warm. I can clearly see that the high pressure spring is overkill. I will change it out at the end of this season.

I didn't set the preload my self. I'm going to check to see what how much preload I have before setting them to ½ turn down from zero. From what I understand, the high oil pressure still isn't enough to win against the spring force multiplied though the rockers. Maybe my springs still aren't quiet enough. I wasn’t running much boost but that pressure is also acting on the valves.

homebuilt

I checked the lifter preload on one bank and found they were set to about 3/4 of a turn. I set them all to 1/2 turn. I am not convinced this was the cause of my issue. Can anyone shine some light on the subject?

vettenuts

iTrader: (4)

You need an adjustable pushrod to check preload. With that cam and boost, do you know if the valve springs are up to task? Got a dyno sheet?

7420NW7TH

iTrader: (8)

You should go ahead and upgrade your lifters to comp lifters or crane. Stock lifters aint going to cut it spinning up to 6800 rpm. just my opinion. One more question: have you milled the heads or anything that would require different length push rods? To me it sounds like you valve train geometry might be off. I don't think the oil pressure is a problem. I run a solid 60 psi and have no problems spinning up to 6800 rpm.

Shawn MacAnanny

iTrader: (12)

Sounds like valve float to me.

homebuilt

Thank you for your replies. The block was decked and I have custom length pushrods and adjustable rockers. Since we had the trouble on the dyno, I didn't ask Kirk for a print out. At about 5 lbs of boost, I saw about 460-470 rwhp (Mustang Dyno). I had about 475 rwhp using the stock engine @ about 9 lbs of boost so I wasn't too excited yet. Kirk doesn’t' have any timing in it yet (only 13 degrees total).

I agree, the oil pressure isn't the problem.

The springs are meeting the forces that were recommended by Comp Cams but it appears they are a little light based on the results.

My last question is regarding the benefit of switching to different lifters. I believe if the lifters are pumping up, they are just doing job and taking up the slack due to some valve float. How would aftermarket lifters be different? Do they limit the oil flow in more than stock? Maybe this is a Band-Aid too. I will probably do this upgrade this winter but I would like to understand the benefit.

warp_6

iTrader: (2)

I had comp adj. shaft mount rockers in mine with the patriot gold springs, comp "R" lifters. I had valve float at 6200, tried various pre load setting 1/8 turn up to I think I went a full turn at one point. No help. Switched lifters to Lunati, again various pre loads no help. Put the stk rocker's back in. All good, I've bounced the limiter once or twice 7100 , but usually I shift at 6500-6700.

homebuilt

Thank you. That is reinforcing my thinking. The lifters shouldn't be pumping up beyond the no lash point. I think the valve float causes slack and the lifters simply do their job and take it up. Do you think the lighter valve train mass you had with the stock rockers is what ultimately fixed the problem? Is the rocker ratio the same between stock and the shaft mounted rockers you had?

I am looking into stronger springs, perhaps a dual PSI spring.

vettenuts

iTrader: (4)

You either need to remove mass or add spring. PSI makes a good light beehive, not sure on your application though if they would work, but they would remove a lot of mass.

warp_6

iTrader: (2)

I do think it was the valve train mass. They were stk ratio 1.7. The wipe pattern was set correctly also. In hind sight the angle of the push rod where it met the rocker didn't look right to me, but with the wipe set and correct push rod lenght I don't know how I could have improved it. What type of rocker are you running?

homebuilt

They are Comp Cams Pro magnums.

warp_6

iTrader: (2)

Same ones $900 learning experience.

warp_6

iTrader: (2)

Be carefull with those I eyelashed a couple pistons.

homebuilt

What should I be concerned with regarding my Comp Rockers rockers?

For my valve float problem, I found that Patriot carries an Xtreme spring that is just a bit stronger. If I reuse the 0.030 shims I should increase my spring forces to 167 seat and 422 open (up from 150 and 390).

What I don't know yet is how much spring force I should have??? I followed what Comp Cams recommended previously and that didn't work out so well.

homebuilt

Can anyone help me with determining how much spring force I should have? I received my Patriot Performance Xtreme springs. I am going to take them to be checked. If I knew exactly what force I needed I could have him determine how much they would need to be shimmed.

I estimate that they would have 167 seat and 422 open with the current 0.030" shims (VS 150 seat 390 open currently).

GuitsBoy

iTrader: (4)

What cam is it? That spring should be plenty of pressure for most lobes, especially if its in the low 600 lift range.

Are you sure its not tune related? Maybe youre blowing out the spark? Maybe youre maxxing out the MAF?

Those valvetrain components should very easily stay in control past 6200.

Grimes

iTrader: (3)

how is your fuel pressure looking at WOT?

homebuilt

All good questions, thank you.

The cam is a custom grind from Comp Cams. The grind is using the "K" lobes. The specs are 238/246 @ 0.050 0.605/0.613.

The MAF is pegged for sure. Kirk is operating in open loop mode. Someday I hope to get the funds for a Big Stuff computer and better sensors. Kirk is sure the problem isn't tuning related. The power loss is very abrupt and significant.

My fuel pressure is steady at 62 psi.

I do have pretty high oil pressure (approx 80 psi @ WOT) and stock lifters. Based on all of the other posts and other threads the consensus seams to be that they are not the cause of lifter pump up.