Matt87GTA

The 1/2 and 1/2 method is where you do half of the rockers at #1 TDC and the other half at #6 TDC.... I was just asking to see if you did it that way or individually by watching the valvetrain and just turning it over slowly and doing them one at a time. I always do the 1/2 and 1/2 method and it seems to work out quite well.....

I guess I don't see from that description how those lifters would be any different from the stock ones as far as pumping up at high RPM.... I think the only way to avoid this stuff is to run solids or hydraulics with just about zero preload..... Or run a monster valvespring but that will wipe out most lifters so maybe those Pro Magnums are just capable of handling a higher valvespring rate without being beaten senseless......

What's up 11s? How's your setup working out? I ended up doing alright on the PROM tuning on mine... Using the wideband to tune part throttle around town and not relying on VE Master to do all of the work was the ticket. Well that and finding a damn O2 sensor that would actually bring my BLMs inline with a 14.7 air fuel ratio for part throttle/cruise stuff.... I got it to cruise around in the high 14s to low 15s air fuel ratio and WOT was interesting but I got it dialed in fairly well after about 8 iterations on the dyno.... Those PE settings I had with my modified TPI setup were so far off from matching what this Miniram'd setup wanted it was ridiculous.... Anyways, I bet mine would even get decent mileage if I could ever stay out of the throttle for more than a mile...lol.

IRACE87

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IMO,just go solid. You can't really rev hydraulic lifters high.

My problem right now is that I spent some money on a rev kit that works with OEM style lifters and I don't know any company that makes solid lifters that works with GM alignment bars (so I can still use my rev kit).

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The 1/2 and 1/2 method is where you do half of the rockers at #1 TDC and the other half at #6 TDC....

I went individually.

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I guess I don't see from that description how those lifters would be any different from the stock ones as far as pumping up at high RPM.... I think the only way to avoid this stuff is to run solids or hydraulics with just about zero preload..... Or run a monster valvespring but that will wipe out most lifters so maybe those Pro Magnums are just capable of handling a higher valvespring rate without being beaten senseless......

I will try to get some answers from compcams about this. Something else on there site about those lifters is that the Pro Magnum lifters must be installed on an engine with adjustable rocker arms and preloaded to .002''-.004'' ????
Why is that I don't know.....yet

PAT

laiky

i would suggest that you do ask comp about their lifters but do not take there tech's word. In my experience they really suck. I would talk to a place that actually builds engines that rev. you might want to try something like writing into chp or hotrod. maybe LPE or bill mitchell, more performance etc.

i also wish i had bought a solid roller!

11sORbust

You might be able to use the oem style lifter as solid, just put metal check ***** in to replace the springs. I'm sure someone has done it before, you should check that out.

What is the open/closed pressure of the AFR springs? NOW, what does your cam card say is required for spring pressure? That is very important and it seems you overlooked that.

You might get xxx more rpms but hydraulic lifter are not good past 6000rpms. Might get them to rev past 6k but it's not the best. I think you cant rev past 6X00rpms because of valve float. No preload adjustments will make that go away.

When I was 18yrs old, I seen something that was very sick. Some dude put a solid cam/matching springs, good carb and headers on a bone stock LG4/305. It would rev to like 7500rpms in the blink of an eye. I don't think it was very fast BUT that sob revved to the moon!!

11sORbust

It's going quite well. Right now I've been going through little things like the s/a correction just fine tuning. The monster cam took some time but I tamed it. Cold start,idle and part throttle is very good. WOT is great! It's hard to keep my foot out of it. Long second gear peels are fun as hell. Or holding second untill 50mph,stab the gas and break traction. Man, it's fun!

Last time I ran 13.1 with the track temp of 120*f(ambient at 93*+).I didn't even get a good start. Next time to the track I'll be shooting for 12.7. Someday I'll get rid of the junk '71 heads

laiky

the problem with hyd rollers is that the lifters are heavy, removing the springs will not help.


here's a question: How does the LS1 in the ZO6 rev to 6500-7000 rpm? it uses hydraulic rollers.

IRACE87

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i would suggest that you do ask comp about their lifters

I sent some emails today and hopefully will get some answers soon.

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You might be able to use the oem style lifter as solid,

Hmmm.. I won't try this on this engine for sure...

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What is the open/closed pressure of the AFR springs? NOW, what does your cam card say is required for spring pressure? That is very important and it seems you overlooked that.

I upgraded to AFR springs # 8015 that is part of kit # 8032. Pressure of the springs is 150lbs/350-355 lbs (not sure about the last #gonna have to call someone about this). Cam card don't say anything about spring pressure but the engine builder that helped me out said it was good.

Here is a quote from AFR site..
Anyway I went with what the AFR tech told me at the time. Maybe with even higher pring pressure it could help.

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here's a question: How does the LS1 in the ZO6 rev to 6500-7000 rpm? it uses hydraulic rollers.

I'm wondering if the design of there lifter is the same.

PAT

11sORbust

ls1 valvetrain is lighter

laiky

what is lighter? it has hyd rollers, pushrods and needle bearing rockers??

11sORbust

it's totally redesigned. Even the valve stems are smaller....

IRACE87

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it's totally redesigned. Even the valve stems are smaller....

From what I know they use the same roller lifter that goes in our engines. On compcams site the 850 and 875 lifters are listed for '87 to present, and LS1. I know that the design of the valves, springs and rockers is different.

GM offer 2 different lifter, # 5234890 This lifter can be used with production and high-performance hydraulic roller camshafts. And # 17120735 These second design lifters are used in late model 350 HO engines and use a higher checkball spring preload.

My guess is that they are probably the same design or similar to what compcams sells.

I still need to change my lifters.

PAT

JP84Z430HP

Interesting, they both come up as the same price.....Must not be anything different other than the spring!

JP

IRACE87

Made some phone call and got different answers to what may be happening to my engine.
When we talk about lifters pumping up, what is actually happening is that at high rpm when the valve is on its closing cycle the lifter will go downward on the cam lobe but the rest of the valvetrain won't follow right away. So at this moment the lifter will get charge with oil to compensate for the gap and on the next cycle will keep the valve open longer since the bleed rate of the lifter is not fast enough.

What may be happening is that even if I have the proper opening and closing pressure on my spring for my cam 150lbs/355lbs. The energy stored and frequency at wich it operates may not be suited for my combo. So a spring with 165lbs/335lbs (more stored energy) pressure may work best with my combo even if I have less open pressure.

So I may need to change my springs to solve my problem and a higher rate spring may not be the answer.

On the other hand a lifter with a faster bleed rate would probably solve the problem as well.

The thing is that I couldn't get a straight answer from compcams as to what is different between there 850 and 875 lifters. (I felt like I was talking to there janitor on the tech line).

So in the end I will have to make a choice, either try new springs, new lifters or solid roller.

PAT

P.S. Moderator feel free to move the thread since it doesn't have anything to do with DIY PROM anymore.

11sORbust

valve float, I called it

IRACE87

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valve float, I called it

Exactly but that is the only time the lifter will actualy pump up from what I've been told. So it can only make matter worst.

Anyway I get I kind of conflicted idea about this and the only thing that is for sure is that my problem is in my valvetrain.



PAT

11sORbust

Just go solid.....

laiky

there really isn't a reason not to go solid, i fell for all the valve lash BS. I reality i would b surprised if you needed to adjust your lash every year or 3 depending on how much you drive.

11sORbust

hell yeah:rockon: