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Discussion Starter · #1 ·
I changed my carb from a Holley to an Edelbrock on the Chevy 350 in my CJ7. I also cut the exhaust on one side when I installed my new tranny. I went driving the other day and the CJ would bog and almost die at 2500 RPM under load. When parked everything sounds fine, smooth reving through the band (approx 3000 RPM), idle is good, running pretty good (certainly not rich).

Any ideas? Could the cut muffler have any impact? It was a dual exhaust and 1 side is intact the other side is cut about 6 inches after the collector.

Mark F

1986 CJ7, Chevy 350, D44/D30, more to come shortly
 
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Discussion Starter · #2 ·
From what I know, yes, the cut exhaust could affect the engine under a load.
Engines rely on backpressure from the exhaust system to run properly. If this pressure is unbalanced due to one tail pipe being shorter than the other than the engine will be thrown off when under a load.



'79 CJ-5
 

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It's the carb. Somethings wrong with it,or it needs tuning. IMHO a drastic change in reduced backpressure will not impact the tuning of a carb so badly that it bogs at 2500 rpm. Sure, changes in backpressure affect mixture, and can require jetting changes, but not that severely that the motor barely runs as you describe. Did you overhaul and set up the new carb (if it wasn't new).


84 CJ7, 258, HEI, M/C 2100 carb, 5 inch lift, RS9000's, 33x12.5 BFG M/T's, 4.56's and Detroit softlocker, full cage & belts, Xenon flares, Dana 44 rear, GM dual diaphragm brake booster
 
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Discussion Starter · #4 ·
Thanks for the replies, I'll fill in the blanks. The CJ ran fine last winter when I bought it and then the tranny went. I bought it with the Holley and I knew the choke was locked open. After the tranny went I decide to switch to a 700r4. To get it in, I had to cut the passanger side exhaust. After installing the tranny the holley was still on there. I test drove it around a bit, but I was scared to push it. I didn't drive it much as it still needed much work (ie exhaust, holes in the floor etc). Then my buddy mentioned he had a Edelbrock that he took off his 350 a few months prior that ran great and shouldn't need any adjustment. I took off the holley but the edelbrock on and now I noticed the bogging. The holley ran rich, had no high idle, a broken electric choke that was pinned open. The edelbrock, seems perfect in park, exhaust seems right on, high idle, electric choke that works, etc. I supposed I can swap back the Holley and see maybe that will be this weekends project if I can get it started (see my other post on welded with battery connected and now it won't start).

Thanks again for the input.

1986 CJ7, Chevy 350, D44/D30, more to come shortly
 

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I'm not sure if you are using the same air filter as you were before, but check it. I did a carb swap and had to "adapt" a smaller air filter to work.. Before too long, the smaller air filter had so much gunk on it that the engine bogged down when trying to accelerate..

Mark
83 CJ-7 and 76 CJ-7 with stuff
 
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Discussion Starter · #6 ·
I am using the same air filter. It is a 14" generic kind with an adapter plate on the bottom which does seem to fit the Edelbrock well. I don't think that's it.

1986 CJ7, Chevy 350, D44/D30, more to come shortly
 
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Discussion Starter · #7 ·
BTT - Anyone with any new ideas?

I'll be hopefully getting the exhaust done tomorrow so that will help rule that out
 

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how about all your vacuum lines? are they hooked up properly, in good condition, What about your vacuum advance? I'm not familiar with Chevy 350, just trying to think about things that could be different or done when swapping the two carbs. What's the CFM difference if any. I know that at times my holley 650cfm sems like a little too much on my 304.

Brent
 
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Discussion Starter · #9 ·
I think I might have gone from a 650CFM to a 700CFM.

The hoses are all new, I will try to check the edelbrock website to check on the hoses. I was on the phone with the party that donated the carb to and went over the hose connections with him. I'll double check the website though.
 

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Couple thoughts...

Air filters clog up over time. They seem to be especially good at it right after any work that involves grinding or sanding. Just because it fits well doesn't mean it isn't clogged. Have you tried running without the air cleaner just to make sure that's not the problem or part of it?

Have you checked your plugs to see if you are running lean or rich? For testing under-load conditions, you have to put the engine in the situation you want to know about and then shut it down fairly quickly. Plugs change color/condition very quickly. Another option here is to hook up a digital volt meter to your O2 sensor (if you have one), run it in the cab and duplicate the conditions. Here is a current thread about what the readings will tell you.

Could it be the point at which the secondaries are starting to open? If secondaries are opening too soon they will send all kinds of air into the plenum before the engine is ready, causing exactly the kind of bogging you are talking about. Have you tried changing secondary springs?

Not enough information to make any other guesses about mix or jetting. O2 readings would go a long way for that.
 
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Discussion Starter · #11 ·
I guess it was the muffler, I got a custom muffler installed (lousy job) and the bogging is gone.

Now I have new issues, tranny temp way too high, hopefully just a bad guage.

Crossover from the exhaust is resting on the D30 yoke, one nice bump and there goes my exhaust. I need a lift pronto.

Thanks
Mark F
 
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Discussion Starter · #12 ·
Simplicity is a bliss.

Time for Dual exhaust. down and back with cheap mufflers. Glasspacks makes 350s (and 305s and 302s 351s, 304s, 360s, and 401s) sound really mean. Of course your neighbors will Love you too.

Jesse
 
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Discussion Starter · #13 ·
Re: Simplicity is a bliss.

I had a dual, I went with a y crossover. 1 muffler and eventually 1 cat. Also the exit pipes aren't an issue with big tires.
 
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