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5.0 EFI to Carb = vibration?

 
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Old 06-24-2008, 08:38 PM
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5.0 EFI to Carb = vibration?

Hi guys,
Here's what I did. I took a 5.0L out of a 1988 F-150 to put in my 92 Ranger. I bought and installed everything to run an old school carb setup. Here's my setup, Edelbrock performer intake and cam, I slightly ported and polished my stock heads, Pertronix HEI dizzy, I'm running a 600CFM 4 barrel Edelbrock performer carb. Full dual 2.5 inch exhaust. 0 emissions equipment... except PVC valve

Here's the problem, I get vibration at about 3000 RPM it also seems slugish. Keep in mind I haven't changed anything on the lower end, the flywheel and balancer are the same that originally came with the motor so I wouldn't expect it to be a balance issue. Any thoughts????

The motor mounts on the ranger are tired but I would expect the vibration to start lower and progressively worsen if they were the problem, right?

Hope someone can chime in with some helpfull thoughts.

thanx

Madmike33
 
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Old 06-24-2008, 09:02 PM
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What firing order do you have the plugs wired for?
 
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Old 06-25-2008, 08:26 AM
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I couldn't give you the cylinder order off the top of my head. I can tell you that it's the 5.0 firing order, not the 5.0 HO or the 351 order. Should be the right one.

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Old 06-25-2008, 09:21 AM
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Hmm.. have you done a compression check then? There's only so many thing it could be, either an imbalance or low pressure on 1 or more lungs.
 
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Old 06-25-2008, 03:07 PM
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What was the status of the donor truck from whence you took the engine? Maybe the balancer was damaged in a wreck?

You might have your drive shaft checked and balanced as well. Most speed specific vibrations are driveline related. Is it vibrating at 3000 rpm in all gears or at a certain speed? Could worn out engine mounts have altered the driveline angle?
 
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Old 06-26-2008, 12:07 AM
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Originally Posted by BaronVonAutomatc View Post
What was the status of the donor truck from whence you took the engine? Maybe the balancer was damaged in a wreck?

You might have your drive shaft checked and balanced as well. Most speed specific vibrations are driveline related. Is it vibrating at 3000 rpm in all gears or at a certain speed? Could worn out engine mounts have altered the driveline angle?
I was also suspecting maybe the balancer, the truck was fine when I got it, but I was thinking it's not impossible that the rubber in the balancer might be coming apart. Also I had new driveshafts made and balanced, the vibration is present even when I rev it in neutral, sitting still.
I was thinking today I would check see if my choke comes off completely when I push in the cable(manual choke) I thought maybe the roughness is too much fuel maybe, that is if the choke is always partly on... Just a thought.

Anyone else???

Madmike33
 
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Old 06-27-2008, 05:52 PM
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Giving this a bump: Got the same problem and was waiting to see if tranny was causing it. Just rebuilt tranny, new flywheel, torque converter. Will check the motor mounts and HB tomorrow. Like Madmike33, anymore suggestions?
 
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Old 06-28-2008, 12:04 AM
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I've gone back to thinking it's either motor mounts or HB. The motor runs great under 3000 RPM, and finally I've noticed that it hasn't lost any power above 3000 RPM. I've noticed that sitting still and reving it, the vibration is there but not as bad. When I'm driving it and reving it up past 3000 RPM it's definitely more noticeable. Like mentioned before it isn't the driveshafts cause they are new and freshly balanced. I might also take a closer look at the tranny mount.

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Old 06-28-2008, 08:09 AM
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My situation is just a little bit diff, but exact same problem. "77" Bronco w/ "86" 5.0 Stock was 28 oz. counterbalance for flexplate and HB. The 5.0 is 50oz. I'm just hoping the tranny guy used wrong flexplate. I did tell him, but you never know. Checking HB, and motor mounts this morning when my help gets here. Good luck, I'll keep watching for updates and let you know what I find.
 
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Old 06-28-2008, 08:45 AM
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Good luck GFW1985, I'll keep you posted on my end although I"m not quite sure when I'll have time to get back to wrenching on the truck.

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Old 06-30-2008, 08:44 AM
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did you replace the dizzy correctly? Off a tooth maybe?
 
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Old 06-30-2008, 09:35 AM
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Originally Posted by 12secondstang View Post
did you replace the dizzy correctly? Off a tooth maybe?
That's a good question, I don't think it's the case though. I went from scratch, TDC on #1 and I even pulled it out and re-did it cause I wasn't sure it was sitting right. Off a tooth, wouldn't it make it rough even in the lower RPM range?? It doesn't seem to be missing. I have to admit that timing did cross my mind, I was thinking that the Vacuum advance wasn't working right.. at first. Cause it seems to do it right about when Vacuum advance would kick in. Other thing if you're any good with Dizzy's The Pertronix unit come with a spring kit to play with Mechanical advance, would that change the baseline for the Vacuum???

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Old 06-30-2008, 12:18 PM
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A lot of vac cans have an adjustment.(mine do) Small allen wrench inserted into tube to adjust. You can take a vac gun and see how much it takes to operate and adjust from there. Only thing a cog off on dizzy will do is move your timing marks and you can compensate by moving plug wires 1 position.
Madmike33: Supplier told tranny guy same flywheel fit the "77" and the "86" which is wrong. "77" was 28oz counterbalance and the "86" 5.0 is a 50oz counterbalance. Might do your homework on your combination, could be a mismatch in parts.
 
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Old 06-30-2008, 07:40 PM
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Originally Posted by gfw1985 View Post
A lot of vac cans have an adjustment.(mine do) Small allen wrench inserted into tube to adjust. You can take a vac gun and see how much it takes to operate and adjust from there. Only thing a cog off on dizzy will do is move your timing marks and you can compensate by moving plug wires 1 position.
Madmike33: Supplier told tranny guy same flywheel fit the "77" and the "86" which is wrong. "77" was 28oz counterbalance and the "86" 5.0 is a 50oz counterbalance. Might do your homework on your combination, could be a mismatch in parts.
I'll check vacuum this week and I'll see if there's and adjustment, Thanx

Madmike33
 
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Old 07-05-2008, 04:01 PM
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is it sluggish below 2000? around 3000? or everywhere? I ask because that 1405 is a rich carb, I got a neighbor with a 396, bigger cam, ported heads, longtube headers, and 6al ignition. even with all of this, she runs rich until about 4500. We changed it out for a 750 tuned for fuel economy and it really wakened up. You dont even smell fuel when it warms up now.
 

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