My motor swap is done and I am having some troubles. We installed an 86 model 302 in my 74 Mav. Everything from bearings to bolts is brand new, problem is it is idleing at about 1000 rpms and it will not drop. Motor will shake the fillings out of your teeth and we cannot smooth it out. Everyone that has looked at the car believes the problem is in the distributor. I put an HEI unit in and wired it through a 20/30 amp relay. Rotating the distributor does nothing for the timing and pulling the plug wires one at a time shows no change in engine operation. I would really hate to throw in the towel and take it to a shop but I have already run out of money and ideas, any advice from anyone would be grealty appreciated. Thanks, John
Rotating the distributor HAS to change the timing unless you have a computer controlled engine management system. As far as the idle goes, make sure the secondaries are closed, and then adjust the idle. Are you using the right firing order for the cam?
I agree with Paul, check firing order. If its a 5.0 HO roller engine, it should be 1-3-7-2-6-5-4-8. Is your timing light saying that turning the dist has no effect on timing, or are you assuming that based on how the engine runs?
I used the correct firing order,1542etc, its an HO block but it is not a roller setup, the timing light confirms that the engine is not intime, I cant get any readings from the balancer. One problem with the distributor is that the huge Chevy style cap hits on the heater hose inlet neck and I cant turn it past that point, I am curious if anyone has successfully used this style of distributor.
Sounds like you have issues with the balancer and flywheel balance weights. They are different on late 302s vs early. That will cause your shake.
Double check your fire order. We put a 86' 302 HO motor in my mav. & had a problem just like yours. It was the fire order, we went with a 302 fire order, it needs to be a Winsor order 1372658. We could crank that dist. all day and it didn't help. Good Luck!!!
For the distributor, sounds like you need to move your plug wires over one terminal all the way around the cap, in the direction you need the distributor to move. That will 'reset' your distributor to manifold clearance. What harmonic balancer and flexplate/flywheel did you use?
Also, your idle speed could be due to yet another issue... Vacuum leak. Get it timed, make sure you have the right flexplate, then work with your idle speed.
Sorta on topic...This is how I got my new motor so cheap. Some guy bought it, slapped it in his old truck, and never could get it to run right. I guessed (correctly) that he had it wired to the wrong firing order, and after he gave up, I got it for $200 (with ZERO miles on it, fresh rebuild). So, pull the valve covers off and make sure the cam is opening valves in the order you think it should be opening, and hopefully, it is an easy fix like swapping a couple of plug wires around. Keep in mind that it isn't the year or block that determines the firing order, but the cam.
In the begining I thought maybe it was a balancing issue. I used a 50oz balancer and flexplate. But I have been told the balance is fine. I already tryed the plug wire trick in both directions. The cam I am using is a mild Crane (363901), I watched the rockers with the covers off and made sure of my firing order. The thing thats getting me is that I can pull 2 or 3 plugwires and the engine doesnt respond to it. So I am sure it is either out of time or there is a problem with my distributor. One bit of information that could be useful in solving this dilemma is that the engine is advanced 4 degrees at the crank, could this be a varible in my difficult equasion?
Its a long shot, but I heard this from a smart dude on another forum. Maybe not related, but I never knew it before reading this, so maybe it can prevent future problems if its not part of the current one. "Why I was asking the firing order may very well have something to do with that. Next question- Are your #7 and #8 plug wires running next to each other? If they are, they likely cross-fired, and that's what could have blown the head gasket. This is a fairly commonly overlooked gotcha with Ford engines. Most people don't know that the factory always routed the driver side wires 5-7-6-8 rather than the logical 5-6-7-8, to isolate the #7 and #8 wires from each other. These two wires paralleling each other all the way to the rear of the engine can cause crossfiring, lighting off the #8 cylinder 90 degrees too soon, and that can take out the head gasket"
Hmmm, thats an interesting tip, I am gonna reinstall the distributor this week and I'll be sure to try that out. Thanks for the replies so far you guys.
just want to confirm youre running the correct flexplate and balance for the engine. did you order a new 157T 50oz flexplate for your application? the reason i ask is because they never built one factory and if someone told u that it was a factory 50oz and it bolted to a C4 then they're wrong. as for the firing, your delima might be caused by advancing the timing 4* like u stated u done. i cant confirm it because ive always installed my gears "straight up" with 0* of timing so that i have know i wont have any variables that im not used to
I thought the early fox mustangs that came with c-4 trannys had the 157 tooth 50oz flywheels. I just recently got rid of one. At least I belive it was a factory piece. I used to play around with the adjustable crank sprocket on my 86 gt. It never affected my spark timing.
