How to prevent lifters pumping up at rpm - Team Camaro Tech
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post #1 of 24 (permalink) Old Jan 23rd, 10, 02:14 AM Thread Starter
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AJ
 
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How to prevent lifters pumping up at rpm

Cam is a comp 286H-10 236 @.050" .490" lift 110lsa in an 10.8:1-11:1 .040" 327, cast crank, others forged, heads have 190cc runners 2.02/1.60, full rollers, switched from a team G to a performer rpm.
The cam specs say 2 something to 6,800rpm
When I do a wide open throttle run from about 2,200 or 3k up to 6,400 it just kind of "hangs" there (pedal to the floor) and the rpm start to drop a tad, I just recently noticed this. When I do the WOT run it is down a hill. I'm not positive they are pumping up, but there is no reason it shouldn't spin past that. It does the maybe 2 out of 5 times, maybe it's because of load, but it pulls hard even in 3rd gear. First gear is 2.54, rear is a 3.08 (I know, bad choice with the cam, but it's a driver)
It will spin to 7k without any problems, but every once in a while, it will do this, which catches my attention. It does break the tires loose, maybe by the time 6,400 comes around they are catching traction and holding the rpm's there?
Would overly tightened valves cause this? We did the cold settings per GM manual which is like a 1/4 turn, in the correct order, and we have adjusted them while running.
If I accelerate some what aggressively, it does not do this.
Other than this small issue, it runs really strong. Next cam I buy will be a solid, I thought taking a hydraulic cam past 6k or so was getting sketchy, but I figured comp would stand by their operating range...

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
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post #2 of 24 (permalink) Old Jan 23rd, 10, 06:20 AM
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Re: How to prevent lifters pumping up at rpm

What valve springs are you using?What is the seat and open pressure?

67 Plum Mist Met. 408 TH350 3.08 posi
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post #3 of 24 (permalink) Old Jan 23rd, 10, 06:48 AM
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Re: How to prevent lifters pumping up at rpm

Is this your cam?...http://www.compcams.com/Cam_Specs/Ca...x?csid=80&sb=2... 2200-6200 rpm.
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post #4 of 24 (permalink) Old Jan 23rd, 10, 07:54 AM
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Re: How to prevent lifters pumping up at rpm

Overly tightened adjustment will lose you rpm. I like to set zero plus 1/2 turn. If the motor is doing this down hill you might be running into the opposite problem of pump up-running out of oil to keep them pumped up as all the oil runs away from the pickup and the valves don't open as fully as they should. You have plenty of everything to run 7000 to 7500. I'm thinking you might benefit from a cam with more duration. That one could be a bit peaky.
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post #5 of 24 (permalink) Old Jan 23rd, 10, 08:03 AM
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Re: How to prevent lifters pumping up at rpm

My first thought was running out of fuel first and second gear and not in 3rd.

One of your last statements were," If I accelerate some what aggressively, it does not do this", So I am trying to understand what the differance on what you were saying in the first part of your question "When I do a wide open throttle run from about 2,200 or 3k up to 6,400 it just kind of "hangs" there (pedal to the floor) and the rpm start to drop a tad,"

An then you say you do this downhill? No load?

Other than going to anti pump up lifters, you decision is correct in going with solids on the next cam.
I try to keep my rpm down below 6500 but then , I run high spring pressures.

Hope this helps.

Don
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post #6 of 24 (permalink) Old Jan 23rd, 10, 02:58 PM Thread Starter
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Re: How to prevent lifters pumping up at rpm

I could probably call and the get spring rates, they came with the heads, I know you are supposed to use springs that match the cam, but I didn't, if they are really far off, I could get different springs and change them. Springs can take up to .550" lift and coil bind is at or around .600" so the lift shouldn't be a problem.

I thought summit's site said 6,800 rpm, maybe I was wrong.

If I do a WOT down the hill it will do the 6,400rpm hang, and not raise anymore, but begin to lower. If I do it on a flat road, i'm pretty sure it will spin to 7k, but don't do it that often because the place with the hill is really the only place I feel comfortable doing a WOT run.
If I ease the throttle up to 7k it will not do the rpm hang.

What cam should I step up to in the future? I thought that cam was pretty much as big as I could go for such a small motor, and too large of heads. I think the motor makes 6" of vac at best, no power brakes.

The only Mustang I'd ever own is a Fender.

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'14 5.0 Mustang
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post #7 of 24 (permalink) Old Jan 23rd, 10, 04:54 PM
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Re: How to prevent lifters pumping up at rpm

You also need to know that the springs went in a the correct installed height.You could buy some really good springs that need to go in at 1.750" and find out that your heads are .100" higher then that or more.Multiple valve job,longer then stock valves,heads machined for taller sprigs,there are plenty or reasons fo this.I have seem some petty big brand new 155" springs{thats big block territory} that dont make enough pessure to run 6500rpm.I would want at least 120 on the seat with stock weight valves to run that high.I would also look into a fuel pressure guae,even if yuo just borrow one to make sure everything is O.K.

Good luck.
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post #8 of 24 (permalink) Old Jan 23rd, 10, 05:11 PM
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Re: How to prevent lifters pumping up at rpm

John,
From your description of the problem it sounds more like a fuel issue to me. Will it spin up past 6400 ok in 2nd gear every time ? If so and the problem occurs in high gear only, then it has nothing to do with the lifters, they dont have a clue what gear you are in

Bill Koustenis
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1971 Chevelle "Heavy Chevy" original owner


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post #9 of 24 (permalink) Old Jan 23rd, 10, 07:06 PM
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Re: How to prevent lifters pumping up at rpm

I was thinking fuel too but the down hill thing doesn't seem to make sense does it?

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post #10 of 24 (permalink) Old Jan 23rd, 10, 07:32 PM
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Re: How to prevent lifters pumping up at rpm

I think it's a fuel issue too. Like Bill said, springs/things have no clue what gear you are in.

Does it do it on your down-hill blast if the tank is full?
What pump? Where? What size fuel line?

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post #11 of 24 (permalink) Old Jan 23rd, 10, 07:38 PM
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Re: How to prevent lifters pumping up at rpm

Have you checked the sock filter thingamabob in the tank? Could be some crap moves against it going down hill (I've never seen one, only know about it from the guys here)

Tim Smith
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post #12 of 24 (permalink) Old Jan 23rd, 10, 08:09 PM Thread Starter
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Re: How to prevent lifters pumping up at rpm

hmm lots of things to look into here.
carb is a 750 edelbrock, stock replacement fuel pump from the local ac/delco.
I mentioned the gearing because I thought maybe the motor couldn't pull the car(weight) and the high rear gear ratios, since the car will be moving faster with the help of the slope.
I have an autometer gauge to mount on the cowl, but it's an a/n type fitting and I run a steel 3/8 line with a rubber line to the carb.
When I shift into second it has no probs pulling to 5,500rpm still doing WOT, but I haven't taken it up past 5,500 or so in second since the car is already doing at or near 90-100mph. I have drum brakes, so I try to be as careful as possible, and the steering isn't so great.

Tank was boiled out at the radiator shop, latex or some kind of coating inside to prevent rust, brand new sending unit from year one(sock included).
When I do this I have a little over a 1/4 tank, or more, sometimes over 1/2 full.

My friend who is also on this board helped me with the new motor, and we even had our friend down the street who runs outlaw 10.5 in a '66 chevelle that does 8.11's check, and re check the valves when running.
Every time I have ever set valves per the GM book, next time I rotate the motor, the ones I just tightened are loose and can be moved by hand, so I re set them when it is their turn to be reset, and eventually we start it, and set them while running.

Thanks for the replies so far, sorry for the confusion the down hill blast is causing.

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
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post #13 of 24 (permalink) Old Jan 24th, 10, 01:36 PM
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Re: How to prevent lifters pumping up at rpm

Quote:
Originally Posted by ace's68 View Post
but I haven't taken it up past 5,500 or so in second since the car is already doing at or near 90-100mph..
So what gear has it been in when you are feeling it slack off at 6400 rpm ? What gear are you in when you say it will spin to 7000 rpm ok ?? Just confused by your description of when the problem is happening.

Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner


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post #14 of 24 (permalink) Old Jan 24th, 10, 01:50 PM Thread Starter
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Re: How to prevent lifters pumping up at rpm

Quote:
Originally Posted by BillK View Post
So what gear has it been in when you are feeling it slack off at 6400 rpm ? What gear are you in when you say it will spin to 7000 rpm ok ?? Just confused by your description of when the problem is happening.
First gear, when it's under WOT down the hill it won't rev any higher and the rpms seem to start dropping, and I shift out of that gear and usually just go back to driving normally.

It will spin to 7k if it's not a WOT run, and also to 7k every now and then under WOT, first gear. The car should be plenty light and have enough power to pull it past 6,400rpm, even with 3.08's.

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
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post #15 of 24 (permalink) Old Jan 24th, 10, 02:46 PM
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Re: How to prevent lifters pumping up at rpm

Quote:
Originally Posted by ace's68 View Post
It will spin to 7k if it's not a WOT run.
That right there points to a fuel problem. If it will rev up to 7000 when you are slowly increasing the rpms, but not at WOT, then the fuel pump is not supplying enough fuel to the carb to keep up at WOT which requires more fuel than an easy run up to 7k. You could probably prove this by raising the float level some in the carb so that there is more fuel in the bowl. I bet it will help, but it is not a long term fix because it affects running under other conditions.

A stock pump is probably not going to cut it.

Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner


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