aveduf

Thanks for all the replies!

It runs and it backfires intermittently through the intake at the same time. I'm pretty sure that cylinder #1 is on compression. I checked by taking the spark plug out on cyl #1, gently inserting a clean dull screwdriver, and slowly turning the crank. I made sure it was at its maximum height.

Well up until now, I've assumed it was an HO and I used the 13726548 firing order without much success. So if I wanted to test for a Non-HO engine, should I simply try the other 15426378 firing order and see if that works?

Or will that not work because of the computer?


Thanks again guys, great input!

my77stang

its the puter that is screwing you over. if you still have the old motor, i'd buy a top end gasket set and go ahead and swap the cams. (this is a good time to drop something slightly larger in there, a B series will work with stock components as long as your not winding the hell outta it and floating valves

67mustang302

From what I understand the HO computer also uses the timing of the exhaust pulses on the O2 sensors to adjust mixture in certain cylinders, so just switching the plug wires and injector wires may not work, could cause AFR problems(don't quote me on this). This is yet one more reason why I like carburetion, simplicity(don't get me wrong though, EFI does have some strong points).

aveduf

Yeh well I didn't really blow the old engine, turns out the block has a nice crack in it hehe (don't ask...)

So in the end, if I want to know if the 1988 engine is really an HO, what are my options? By switching the firing order, it seems to me I have to assume a bunch of other things. I'll give it a try later and see what happens, but I'd like to have a better way of finding this out.

I'm trying to eliminate potential candidates to the backfiring problem and I thought figuring out what engine I put in there would be easy. Always good to know after the fact...

Thanks guys.

87ttopGT420

first things first did you remove the motor from the Bird or did somebody do it for you bacause if your not 100% sure if its even a HO then well haha you suck should have gotten a motor from a better source

LTnone

Hold the phone... you're not still using that block, are you?

Musclerestorer

Is it possible that HO's having the throttle body on passenger side & non HO on driver???

aveduf

haha there's no way I'm still using the old block. The engine from the Tbird is already setup in my mustang. Anyways, I'm pretty sure it's HO, I'm getting it checked by a mechanic who knows what he's doing. hehe thanks for the feedback guys. I'll let you know what happens.

frdmstng1986GT

ok..to end this right now.. the 5.0 in a 88 t-bird is a Non-HO motor... they didnt put the HO in the t-bird till 90 (might be 89). the old style t-bird on the fox chassis never had a 5.0HO stock. Only the MN12 chassis did.do the 15426378 and it will run better, but then it still wont run right because the computer is firring the wrong cylinders at the wrong time.you are gonna have to swap the cam from youre old motor to make it run correctly...but watch out.. the non-ho car 5.0's had e6 heads with flat top pistons so piston to valve clearence problems may show up..

To answer that. No. if the upper intake says "5.0EFI" instead of "5.0HO" then it isa non-ho motor.

86GT 93LX

edit", oh crap, i fogot the cam, yeah sorry, u need the old cam, or the valves wont open in ho order. so u got some work to do but no biggie"

yup, so if u havent already figured it out, u need to switch the plug wire around to ho firing order. non ho and ho are almost the same but have diff firing order. the ecu tells the injector when to open but ur not in ho firing order . its really easy and it will run fine as soon as u change it to ho firing order, there will be no issues. the order is 1-3-7-2-6-5-4-8 for HO and its counter clockwise starting from the 1 mark on the dizzy cap. with the hood up #1 cylinder is on ur left, on the right it starts with #5 in the front.

non ho and 4.2l (80-83) is 1-5-4-2-6-3-7-8
so u have 4 cylinders that wont fire at the right time!!! if its set to non ho. if it dont say ho on the plate and it just says EFI its non HO, this i promise u. i dont care what anyone says about what a t bird came with. it might not be from a t bird to start, prolly a lincoln motor. hope u got it or get it after reading this. good luck