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Old 10-15-2004, 06:12 PM
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problems after cam swap

Hello,
Was hoping to get some help. Have a 73 monte carlo with a 350. Car ran great but wanted a little more power to motivate the beast. Swap included edelbrock performer intake, edelbrock cam, edelbrock carb. roller tip rockers. The car starts fine and idles fine. Put it in gear and it wants to stall and idles very rough. Also had no low end power but seems to run well once you wind it up. I was afraid I put the timing chain on a tooth off, opened it up and it looks fine. (edlelbrock 7800 lined up 0's). The timing is set at 12 btdc. I've moved the timing all over the place. I think it's a vacuum leak, however I sprayed it with carb cleaner and the engine didn't change. I don't hear one either. Only thing I can think is maybe put it in gear with the emergency brake on and spray the intake and carb????? Also have adjusted the mixture screws and makes no difference. Thanks in advance.

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Old 10-15-2004, 06:18 PM
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welcome...moved thread to "Engine" forum.


Sounds like a vacuum leak, or too radical profile on the cam. What are the cam specs.
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Old 10-15-2004, 06:31 PM
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Thanks for the quick responce. It an edelbrock 7102.

duration is 234 intake, 244 exhaust @.050
Lift is 488 intake, exhaust 510.
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Old 10-15-2004, 06:34 PM
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Fairly mild cam.........maybe the timing is out, cam timing that is.....I would check over the carb and intake 1st to make sure everthing is good.
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Old 10-15-2004, 06:38 PM
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Like I mentioned, I made sure the marks were lined up. Is there something else I may be missing as far as cam timing? I will double check for vacuum leaks and carb issues.

Thanks again!
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Old 10-15-2004, 06:41 PM
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Nope...if the marks were lined, all should be well.

Is it a new carb?
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Old 10-15-2004, 06:42 PM
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Yes, everthing I replaced is brand new out of the box.

Thanks.
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Old 10-15-2004, 07:22 PM
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Quote:
Originally posted by 1973monte
Thanks for the quick responce. It an edelbrock 7102.

duration is 234 intake, 244 exhaust @.050
Lift is 488 intake, exhaust 510.
Thats the Performer RPM cam, kind of pushing mild, 234/244@.050" lift with .488 intake lift/.510 exhaust lift, power band ends at 6500rpms.
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Old 10-15-2004, 08:47 PM
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Just because the timing marks are lined up doesn't always mean the cam isn't off by a degree or two. If I were you I would check the lobe center on the cam and see if it needs an adjustment key/bushing to correct it.
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Old 10-15-2004, 08:52 PM
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Quote:
Originally posted by Ghetto Jet
Thats the Performer RPM cam, kind of pushing mild, 234/244@.050" lift with .488 intake lift/.510 exhaust lift, power band ends at 6500rpms.
Not quite mild.



You said it could be a vacuum leak. A performance cam's overlap is a big vacuum leak.

If you have a low compression engine it could run pretty lumpy. Your's is a '73. Not a very good year for compression figures. If everything is stock I bet you are at 8 to 8.5:1.

I would bring the idle up until you can get it smooth. Re-check your distributor timing. The carb could also be an issue.
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Old 10-15-2004, 09:14 PM
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Quote:
Originally posted by lluciano77
Not quite mild.
I know, poncho said it was a fairly mild cam, I think he overcammed the engine. He should have picked something more suitable to the intake manifold he bought.
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Old 10-15-2004, 09:19 PM
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Quote:
Originally posted by Ghetto Jet
I know, poncho said it was a fairly mild cam, I think he overcammed the engine. He should have picked something more suitable to the intake manifold he bought.

By mild, I meant short duration, high lift, exhaust higher than intake....usually found on an RV or mileage cam. It does have quite a high lift.

I think the carb is not tuned properly for his setup.
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Old 10-15-2004, 09:34 PM
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if that's the durration you need a stall converter! No wonder it dies in gear!

K
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Old 10-16-2004, 05:02 AM
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I appreciate the posts. Yes, the engine is otherwise stock. 8:5:1 compression. I went to the speed shop and asked the guy to help me pick out a cam. I told him I didn't want a race car, just something to get the 4400 lb beast going a bit better. This is a matched edelbrock setup. I'll be pi$$ed if it's too much cam when he told me it would work with the stock compnents. It does sound very lumpy now . Also, a little note I left out. Like I said before the upgrades, the car ran fine. After installing the cam, it would backfire when you revved it up . It would backfire when the rpms were coming back down. I unhooked the airpump and it stopped, knowing a bad diverter valve can cause this. However, it was fine before.

Thanks for all the help.
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Old 10-16-2004, 05:22 AM
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Readjust the valves, sounds like you have a couple too tight, that will give all of the symptoms that you are decribing.
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