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Hey everyone, I've recently been rebuilding my 1995 f150. Pulled a stock 302 out of it with the 351 firing order, the motor I put in is a built up standard 302 pre 90s block. Has somewhere around 350hp and 375 ft/lbs of torque. The issue I am running into is eratic idle. Have the timing set to about 6 degrees before top dead center. It will run for a few minutes and die. I'm curious if there could be a vaccuum line not run to the right spot? I've replace quite a few parts, ie distributor and coil, pcm is new air intake is new. The motor I pulled out has a 50 Oz harmonic balancer weight and the stock flywheel. So when I converted the new motor to efi I swapped to the 50 Oz harmonic to the new engine. It had I belive 35 Oz harmonic balancer for that block style. Could the difference in weight cause the rough idle? Thanks hoping to find a little clarity.
If you mean rough as in, "The entire engine is shaking but seems to be running smoothly otherwise." then, yes, the wrong balancer will cause the engine to run roughly.
You would notice the roughness tighten up but not go away as you revved the engine.
If this is the problem. Fix it now. Don't run it that way or you can break the crank, etc.
A couple things; the 302 is externally balanced by the harmonic balancer and the flywheel or flex plate as the case may be. These 2 things have to be matched to the engine. Period.
I believe the balance weight changed back in about 1982. I think it went from 28 oz to 50.
The other thing is firing order, re injector firing. If the firing order of the engine changed, did you compensate for that in the injector firing order ?
But as seschenburg just said, fix the balance now. Don't even fire that motor up again until it has the proper h/b and f/w on it or you will turn it into a boat anchor.
How do I adjust for injector firing order? Also as far as the harmonic balancer and flexplate/flywheel balancing goes. If the crank was for the 28 ounce harmonic balancer what is the different weight for the flywheel? If I put the lighter flywheel in will it do anything to how the transmission operates? Or will it operate fine as long as I get the correct teeth on the sprocket? I'm trying to find a way around getting a whole new motor that has the same weighting as the one I pulled out if possible. Thanks for the great info so far it's much appreciated. Uploaded some pictures of what I've done to it in my profile.
The transmission doesn't care about the imbalance weight of the flywheel (the motor definitely does). You need to match the teeth so your starter will work.
If you have the correct weight on the f/w and the proper number of teeth (that's the catch because the earlier motor used a different starter) then the trans and motor will work fine. You may possibly have to get an aftermarket f/w to make the old motor match up to the newer starter and trans, if the motor is pre-82.
As for injectors, the 95 truck should have MAF, which fires 1 injector at a time - the one right beside the valve that is opening (92-93 speed density fired 4 at a time, 2 on each side and then the other 4). Speed density covered both firing orders, but was inefficient in comparison to MAF.
You will have 1 injector opening at a time, but not the right one.
I think the only way to fix the firing order issue is a custom computer (expensive) or repinning the wires at the plug that attaches to the computer.
I just had a thread in the last week or so about a truck I bought for parts that had that kind of thing going on (old style firing order in a 95 w/MAF). I forget who answered me on that, but they may know more about it.
Before you ask, somebody with a 460 conversion project going on bought that harness to
be able to put the 460 on MAF.
But apparently it doesn't really cost anything to repin the plug you just have to do the research and put your thinking cap on. Relocating colours to different locations. I think that requires concentration and patience - but not a lot of money.
Big thing to remember is that no matter what you want to do to your truck, somebody has done it before. And most likely written it all down and posted it on the internet somewhere. It's just going to take some research.
So let me see if I understand correctly when it comes to the imbalance weights of my motor. If the weight on the crankshaft is 28 Oz then I'd need to have 28 ozs on the harmonic balancer and the flywheel/flexplate for it to be properly "balanced"? I am no expert and am just trying to get this straight. You all are the best source of information
Just had a look at your album. Nice. Really nice job so far. Man, you've put a lot of work into that puppy. Should be a really pretty showpiece when it's done.
As far as your imbalance, I would sort of assume that you still have the original harmonic balancer on there that came on the motor ? That would mean just getting a matching weight flywheel or flexplate and you should be good. That link that seschenburg put up there is very good. If you still have questions - ask. We'll try to help you get it sorted properly.
11-22-2016, 03:11 PM
Idle eratic
