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Author Topic:   NEED HELP!
ryan
Dirt Forum Champ
Total posts: 776
posted June 29, 2005 08:31 PM  
At about 5800-6000 the motor stops pulling and doesn't want to run right Its always right at this rpm it isn't random.It doesn't do it in the shop just under load. Its hard to explain it, its not really a miss I guess you could say it starts sputtering It doesn't really feel like one cylinder going down, its enough to keep you from pulling anymore rpm . Anyways I can't track where its coming from so far I have tried rebuilding carb changed sec rods and hanger, tried differnt power piston spring, my spare carb, o5racers spare carb, different cap, rotor, coil, module, pickup coil on my hei, and also tried o5's hei. Changed fuel pump, checked fuel pressure, changed plugs, no change between running 12 volts and 18 volts, added another ground to the motor, changed intake gaskets and maybe a couple things I forgot. Valvesprings I have are crane 99893's or something like that, 5 nights old with recomended installed height. This is on a 11 to 1 355 bowtie heads performer intake qjet carb.
I'm going to check compression yet and go from there.

Any ideas?? I'm stumped.

[This message has been edited by ryan (edited June 29, 2005).]

racer17j
Dirt Forum Champ
Total posts: 5390
posted June 29, 2005 09:34 PM  
Change Cam or change the intake

leapinlizard
Dirt Freak

Total posts: 402
posted June 30, 2005 12:56 PM  
That intake wasn't designed for power over 6000. Neither was the carb.

ryan
Dirt Forum Champ
Total posts: 776
posted June 30, 2005 02:29 PM  
Same cam, heads, intake, carb as before this is a new problem on a proven combo. It may not be designed for power but thats what the rules say. It isn't what parts I'm running its some component failure. 17 It's a ultradyne copy 530/550 been running same grind for 3 yrs now. Lash hasn't changed either.

[This message has been edited by ryan (edited June 30, 2005).]

ss99
Dirt Maniac

Total posts: 120
posted June 30, 2005 02:37 PM  
Detonation due to running too lean or improper timing. Just a thought.

nine finger
Dirt Forum Racer

Total posts: 76
posted June 30, 2005 04:46 PM  
did the motor ever turn higher than 6000 when built? if it did you probably hurt the springs. what i mean is when the springs were new it would rev a little higher say 7000. the motor should rev higher regardless of intake.

o5racer
Dirt Freak

Total posts: 402
posted June 30, 2005 05:08 PM  
That intake is a spec intake at our track. I have one on my streetstock and most of the latemodels run them as well.
Nick

nine finger
Dirt Forum Racer

Total posts: 76
posted June 30, 2005 07:06 PM  
you better check your springs!!!! a mismatched spring can be destroyed rather quickly. it will act exactly like your describing.I have seen new springs loose there seat pressure in very short order. do you rev your engine on cold springs, very bad for them.

ryan
Dirt Forum Champ
Total posts: 776
posted June 30, 2005 07:22 PM  
I have a set of springs from last year I could try, not enough time to get new for this weekend now. Its never wound up cold. Its turned higher than 6000, a 2 weeks ago I took it down the road and pulled hard to 6500 until I let off. What do you mean by a mismatched spring?

SS99 Timing is fine in the shop with a proper mech. advance curve. I tried richer secondary rods and that didn't help either so whats making it lean out?
Keep em coming

waltonjr1
Dirt Forum Champ
Total posts: 516
posted June 30, 2005 07:33 PM  
Do you have a fuel pressure gauge in your car that you can watch at high rpm's? I had a fuel pump get weak and it would do this at around 6,000.


nine finger
Dirt Forum Racer

Total posts: 76
posted June 30, 2005 08:23 PM  
springs with the wrong rate for the cam. springs sound like they took a set. that is why it reved higher when brand new. if you have room you could shim them and gain your revs back for a little while. check for coil bind and if its not a problem put some (one under each spring) ......030 shims under each spring. should fix problem for weekend.then monday order some springs from comp cams.

nine finger
Dirt Forum Racer

Total posts: 76
posted June 30, 2005 08:47 PM  
what is your installed height on your heads. from spring seat to retainer. looked up your springs and they look pretty good for your application on paper. but paper dont make motors rev springs do. did you buy these springs new from an individual or from a store. also comp makes keepers to change installed height. would be a quick fix for the weekend.

ryan
Dirt Forum Champ
Total posts: 776
posted June 30, 2005 08:53 PM  
Walton- Been there done that pressure didn't drop from what it was regualted at.
Nine- unless the springs went sour that would be the only way. They are already shimmed for proper installed height. These are 1.46 dia springs by the way. We didn't have enough installed height earlier in the year and we broke a stud and rocker, so we had to put in .100 longer valves and and put in 15 thou shims to get it right. It ran perfect after it was put back together and ran good for a couple weeks until this happened. We are going to compression test it and if that shows up good we'll head towards the springs.

nine finger
Dirt Forum Racer

Total posts: 76
posted June 30, 2005 09:10 PM  
that is exactly how they do.couple weeks and they lose pressure. get your spring checker out. i will bet they wont have 100 lb. at 1.850 height. been around the block before and i would not be wasting time on another compression check.

nine finger
Dirt Forum Racer

Total posts: 76
posted June 30, 2005 09:36 PM  
you failed to mention you had put longer valves in it earlier.add that extra weight goin over the nose of the cam 6000 times a minute.im done beating a dead horse good luck

ryan
Dirt Forum Champ
Total posts: 776
posted July 01, 2005 02:36 PM  
I wasn't disagreeing with you I just wanted to rule out a dead cylinder before I messed around with valvesprings. They were bought brand new from one of the parts houses don't remember which midwest or speedway. I don't have a spring checker but I am searching for one that I can buy rent or borrow for this weekend. I can't remember the installed height(car is not here with me) but if I recall correctly it was a little under specs by only by a few thou.
btw 201-209 cylinder pressure

nine finger
Dirt Forum Racer

Total posts: 76
posted July 02, 2005 05:22 AM  
I have dragged dead cylinders past 7000.but you cannot make weak springs rev. please post your fix.

ryan
Dirt Forum Champ
Total posts: 776
posted July 02, 2005 08:10 AM  
Got a tester located will find out today.
Thanks.

ryan
Dirt Forum Champ
Total posts: 776
posted July 02, 2005 06:17 PM  
Valve springs are fine were checked in a digital bench tester. 120 lbs at 1.875" right what the springs say they are supposed to be at and mid 3's open. Thats what the cam calls for too. Put new plug wires on locked hei no help there either. This blows.

nine finger
Dirt Forum Racer

Total posts: 76
posted July 02, 2005 07:00 PM  
I dont think 10lb low would keep motor from revving.

nine finger
Dirt Forum Racer

Total posts: 76
posted July 02, 2005 07:24 PM  
did you check all 16 valve springs? fuel air compression spark springs should rev. has there been anythang that has changed humidity air temperature.

nine finger
Dirt Forum Racer

Total posts: 76
posted July 02, 2005 07:52 PM  
check fuel lines and pickup line could have been damaged racing. can you feed your carb from another source, this will allow you to flow test your pump at rpm. flow it into a clear container so you can see what it is doing at rpm. jack up rearend and load the motor against the brakes while watching fuel flow. springs & fuel flow act alot alike when trying to diagnose.

ryan
Dirt Forum Champ
Total posts: 776
posted July 02, 2005 10:44 PM  
Actually going out of the catalog we got them from thats what they were supposed to be. Yeah they were all checked. I'm going to dive back into the fuel system tommorrow. I'm about out of stuff to try. lol

merlinmech2
Dirt Maniac

Total posts: 131
posted July 04, 2005 07:06 AM  
Had a similar prob. Would run great for hot laps, would lose a couple hundred rpm for heat, by feature would lose 8-9 hundred rpm. Was a bad battery. Keep diggin', you'll find it.
Good luck.

ryan
Dirt Forum Champ
Total posts: 776
posted July 04, 2005 09:01 AM  
It runs like thiss all the time. If I keep digging any further I might as well lay down and have somebody kick some dirt over me. jk lol

[This message has been edited by ryan (edited July 04, 2005).]

ryan
Dirt Forum Champ
Total posts: 776
posted July 04, 2005 06:39 PM  
One thing I found out today going down the road was that if you gently roll into it up til 6000 its not as bad kinda like on a really dryslick track. Also I took it up the road and didn't let it get as warmed up as much as usual the 1st time and it didn't do it until the 3rd pull.
I was grasping at straws today and here's what we did.
First we bypassed all the wiring to the dash to eliminate switches(didn't work) we hooked up a digital voltmeter to make sure the volts weren't dropping(no problem there) we bypassed our fuel line back to the cell in case of sucking air somewhere(didn't work) Then after that here's what I did, I put in a stock module(which I had done before in a different distributor) and it didn't help. I come back and we decided to get rid of the vacumn sec. and go back to mechanical(which we had ran on a different carb) It worked great pulled hard to 6800 til I let off. So I get back and we decide to put it back to vac. second. to make sure thats what it was, changed it and it still worked right. So we took out that stock module and went back to our dyna mod and it still worked right. So we went from trying to get rid of it to trying to get it back. I'm glad that its fixed but it I'm doubtful that it will stay away for long.

[This message has been edited by ryan (edited July 04, 2005).]

o5racer
Dirt Freak

Total posts: 402
posted July 04, 2005 09:23 PM  
Reminds me of that dam old AMC that I started with 11 years ago. If we took it out on the road it ran perfect. Get to the track and it falls flat at 5200. misses stutters backfires, you name it. Get home and it runs great. I hate things that fix themself. They usually unfix them self at the most inconvienient time. Good luck. Keep me informed.
Nick

racing33A
Dirt Forum Racer

Total posts: 97
posted July 07, 2005 09:33 AM  
Ryan,
Did you ever figure out this problem? This my sound dumb, but would a wek or bad ground strap/s cause a problem like this. I have seen some weird things happen from bad grounds. Just a thought.
racing33A

ryan
Dirt Forum Champ
Total posts: 776
posted July 07, 2005 06:46 PM  
I guess its fixed for now I have'nt had it down the road since the 4th. We're kinda thinking ground as well even though we have a good ground to the battery, solid motor mounts and a ground off the engine. Hopefully its gone I'll post back if and when it comes back.

ryan
Dirt Forum Champ
Total posts: 776
posted July 10, 2005 08:42 AM  
Well it did it in hotlaps and the heat but not in the main, I'm guessing because it was dryer. I ran better though, it was more of a miss now and I turned 6500.

B.K.ENG45
Dirt Full Roller

Total posts: 31
posted July 17, 2005 07:31 PM  
WE HAD A GUY AT OUR TRACK HAVING SIMILAR A PROBLEM IT ENDED UP BEING THE AIR CLEANER. IT WAS GROUNDING OUT ON THE HEI.....QUICK FIX PUT A PIECE OF CARDBOARD BETWEEN AIR CLEANER AND HEI. GOOD LUCK, BRAD

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