Hot Rod Forum banner

1 - 20 of 25 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #1
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.
 

·
Administrator
Joined
·
18,438 Posts
welcome...moved thread to "Engine" forum.


Sounds like a vacuum leak, or too radical profile on the cam. What are the cam specs.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #3
Thanks for the quick responce. It an edelbrock 7102.

duration is 234 intake, 244 exhaust @.050
Lift is 488 intake, exhaust 510.
 

·
Administrator
Joined
·
18,438 Posts
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.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #5
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!
 

·
current hot rod: CTS-V
Joined
·
1,821 Posts
1973monte said:
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.
 

·
Registered
Joined
·
168 Posts
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.
 

·
Banned
Joined
·
3,532 Posts
Ghetto Jet said:
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.
 

·
current hot rod: CTS-V
Joined
·
1,821 Posts
lluciano77 said:
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.
 

·
Administrator
Joined
·
18,438 Posts
Ghetto Jet said:
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.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #14
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 :p. 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.
 

·
Almost an old guy...
Joined
·
180 Posts
Readjust the valves, sounds like you have a couple too tight, that will give all of the symptoms that you are decribing.
 

·
Registered
Joined
·
137 Posts
To much duration on the cam and it killed your low end torque.Your car also weighs a lot thats why its a turd out of the whole.Like Killer said your going to need more stall to run that cam.
 

·
Registered
Joined
·
1,443 Posts
1973monte said:
Thanks for the quick responce. It an edelbrock 7102.

duration is 234 intake, 244 exhaust @.050
Lift is 488 intake, exhaust 510.
Ummm.. who said this was a mild cam? Maybe for drag racing it is mild.

You should be looking for something around 204-214 duration, nothing above or you run into idling problems and loose all your low end. This cam you have has WAY too much duration for street use. You also can NOT run an engine like this (8.5:1) with a cam like that. You need somewhere around 9.5:1 or higher for it to be useable. Also as I have just read, you also need a higher stall converter.

If this block is "stock" as in the factory stock balancing job, you will kill your bottom end(ie crank, bearings) with this setup if that is the case. Too much high end use for a factory balancing job.

in fact the more I read, this is one big mis-match. You want top end performance, get a single plane intake, higher stall converter, keep the cam, get a balancing job done on the crank/rods/pistons, replace the pistons or heads for higher compression.

If you want your low end back, then you only need to ditch the cam and get a good dual plane manifold, that edlebrock you have is a dual plane right?
 

·
Registered
Joined
·
3,441 Posts
I hate to say it, but you have a classic bad combination of parts. That cam needs 9.5:1 or better to work well. You also need a looser than stock convertor or it will be a a gutless wonder off of idle until it revs up a bit.

One thing I see right away is that the timing is way to slow. With that low compression and that much cam, you can likely run around 20 degrees initial. You will need to recurve the distributor to limit total advance or you will have way too much in the high RPM. My turbo engine has about the same compression as yours and a little larger cam but with higher lsa. Similiar cylinder pressure at idle none the less. I run 22 degrees initial with 36 total. It cranks over perfectly and idles very well in gear with my 10" convertor. It is also very responsive off boost while cruising. I think you can make it work, but more compression would make a good bit of difference.

Chris
 

·
current hot rod: CTS-V
Joined
·
1,821 Posts
1973monte said:
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.
Actually it's not matched, your cam is matched with the Performer rpm manifold, power band 1500-6500 rpms, you got the Performer manifold idle-5500. To be matched you would need to be running the Performer RPM heads also. If you want this car to run good with just swapping the cam, you should take the Performer RPM cam out and put the Performer cam in. Besides the Performer cam, there are also other mild cams that would work well.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #20
Yes, I believe I got dupped :pain: I'm going to call the Monday, I have an email into edelbrock tech support. Hopefully they'll say it's too big. I'll see if he'll admit his mistake. I doubt it however. Thing is, I was doubting my work and chasing my tail to get this thing running right. Next time I'll research myself and not trust someone else to pick my components.


Thanks
 
1 - 20 of 25 Posts
Top