About Us

Brian Baker · 03-16-2002, 09:55 PM

I'm going with the valve springs (or a bad or broken valve spring) since all the electricals check ok.

If you want to look for vacuum leaks, here's an easy tip:

Get a portable propane bottle (a small one) and a nozzle and open the valve (BUT OF COURSE, DO NOT LIGHT IT - LOL !!!). Run it over areas around the intake manifold. If you have a leak, the propane will get sucked in, and engine rpm will increase slightly. Works better than carb cleaner.

Tom Vaught · 03-16-2002, 10:02 PM

I agree with Skip, Have seen it before Check the
cam installation! Tom V.

Mike S · 03-16-2002, 10:36 PM

Ross,
I just had the same problem on new rebuild but mine is rce engine. I mean exactly the way you explained it would run fine below 3000 rpm and above would do what you said. After checking everything a couple time. I took valvecovers off and had someone turn over the starter and looked at rockers. One intake didn't move as much as the others. Pulled cam out today and had 2 intake and 1 ex. lobe wiped(all on diffrent cylinders ofcourse). Hope this isn't your problem but it's a simple check. Let us know what you find in the end.
Mike S

74gto · 03-16-2002, 10:50 PM

Had the same problem you described. My problem ended up being the condessor. I belive it gets hooked up to negative side of coil. I think you said you had it on positive side? I think that is also what I did, and after I switched it to neg. side, car would rev. If you buy the points and condessor together, It's all in your dist. and gets hooked up to the negative side.

RossGN · 03-17-2002, 12:34 AM

One thing i have noticed is the starter will spin the engine easily with the throttle closed, but when you tap the throttle a couple of times, it really drags the starter down like the timing is advanced too far.

Tim Swain · 03-17-2002, 12:42 AM

Some timming chain crank sprockets have a 0 mark for strait up installation and a larger 0 on the tooth of the gear for linning up with the cam spocket timming mark. The correct timming mark can be hidden by the chain. To check. Move the motor to top dead center open hole no# 1 and see if the piston is at TDC.

David Holmberg · 03-17-2002, 12:43 AM

I still say it's a timing issue. Either the timing chain or in the dist.

Did you pull the dist to make sure it was at TDC? That would be the easier of the two to check.

Robert Williams · 03-17-2002, 04:44 PM

OK, while i was working at the BIG HOUSE today i got to thinking about your problem. As i said, it could be in the valve springs, and also a mega vacuum leak. That is a Super Duty motor. On the SD heads you have to put sealer on the rocker arm studs that are above the intake ports.Also the upper valve cover bolts. These studs and bolts extend into the high intake port on the SD heads. Also have the same problem on the Edelbrock heads. Check these out to see if they have sealer on them. If not put teflon tape or pipe dope on them to seal up the intake ports. Good Luck

RossGN · 03-17-2002, 06:53 PM

Ok...after my __th birthday party this evening, I will get my little propane bottle and flow a little gas into the RH valve cover....if it's sucking air through the studs, it should increase rpms a little, huh? That would be a nice B day present if it is the studs rather than something which requires cracking open the motor.

If it does turn out to be internal, then I'm going to suggest to Ccass that he hire a online therapist for emotional traumas such as this. [img]/infopop/emoticons/icon_frown.gif[/img]

Tim Swain · 03-17-2002, 09:08 PM

Have you removed number 1 spark plug to see if it's at top dead center yet?

LenCaverly · 03-17-2002, 10:10 PM

Check to make sure distributer feed wire or anything on the hot side of the points is not shorting out when the distributer advances this would act just as you said like a built in rev limiter.
Len

RAJ7395 · 03-17-2002, 10:32 PM

Get a voltmeter and check the coil terminal voltage. If you've got a loose connection/bad wire the coil voltage will be lower than 12v (or whatever your setup requires). The engine will run fine at low idle but as you increase speed the coil output will fall off as it doesn't have the voltage required to sustain the magnetic field. Just a thought..

76TA · 03-17-2002, 11:31 PM

Might seem silly but are you sure the distributer isn't installed 180 degrees off? Pulled that stunt on my old work truck after a timing chain replacement. It started and ran but it sounded similer to what you have going on. I thought I had #1 piston at the top of the commpression stroke but it was at the top of the exhaust stroke instead.

poks · 03-18-2002, 12:30 AM

this may sound dumb but i had the same problem. thought it was the valve springs and the a/f ratio and the ignition and everything. i bought a degree kit and checked my came. it was retarded. haha it was way off. i made some sort of mistake and it was off. i advanced it to where it was supposed to be and things ran a lot better. before it would run on and backfire through the exhaust and would not go above 3 grand. thats what i found to be the problem but don't listen to me cause my car is still slow,(14's) but im working on it. it was also real rough at idle. good luck

poks · 03-18-2002, 12:34 AM

oh my god....i just read my post and it said came instead of cam...so really don't listen to me...

David Holmberg · 03-18-2002, 12:37 AM

Poks, You can click on the pencil icon above your post and edit the old post. It can be a lifesaver... [img]/infopop/emoticons/icon_biggrin.gif[/img]

RossGN · 03-18-2002, 12:57 AM

Well.....my apologies for not checking this sooner. The #1 piston is at TDC about 30 degrees after the timing mark on the balancer passes the zero on the indicator.

I adjusted the timing to close to where the actual TDC mark should be and it runs a lot better. Is this an indicator that the builder missed the mark on the timing gear? Can I create a new timing mark and run it like this without any problems?

I put come clear cellophane over the valve cover hole and when you rev, it sucks in the cellophane a little bit, so I doubt the builder sealed the studs. I cant run it very long until tomorrow since the neighbors would shoot me for running at this late hour.

Brian Baker · 03-18-2002, 01:01 AM

DO NOT! I REPEAT, DO NOT PUMP PROPANE INTO YOUR VALVE COVER LOOKING FOR A VACUUM LEAK UNDER THE ROCKER STUDS !!! My god, man what are you thinking?! Blowing propane over an intake manifold in open atmosphere is different than blowing into a closed valve cover. Where will it go? If enough of it collects and something hot sets it off, bye bye valve cover and whatever flesh is in its path.

RossGN · 03-18-2002, 03:25 AM

Yeah, I know. Thought about that shortly after i posted. Cellophane did the trick.

rasilverbird · 03-18-2002, 09:49 AM

Find it yet? I'm betting cam installation. I've also put one in, and even after "double checking", learned that it was in wrong after the startup. Wasn't even close. It did the same thing, idled like hell, and wouldn't rev above 2500 or so, all the while spitting and farting like and angry camel.

Menu

About Us