!985 302 Holley 600 being held back

[Kyresearcher]

Hello, I am new here and hope you guys can help me out with some troubleshooting on my 1985 F150 bullnose 302 4bbl holley 600.

Engine ran great, only a 3 speed auto tranny, but in 3rd on the hwy, I could give it about an 8th more pedal and it would slightly push me into me seat, pick up power was great.

One day I drove it to work, ran great. normal running temp is at 190 degrees.

As I was leaving work, I started it and noticed instantly that the idle was very rough, let it warm for a few mins and put it into drive to leave, as soon as it went into drive, it died.

After playing around a bit, I managed to hold the gas a bit and keep it running to get it home, at red lights or stop signs I had to hold the break and gas to keep it from dying out.

Got it home and started troubleshooting it, checked for vacuum leaks and found none, plugs wires were fine, cleaned points and checked cap, all seemed fine.

So starting simple I changed the plugs wires and cap, still nothing...

Pulled the carb and rebuilt it. problem got even worse....

Decided to buy new carb, but before I did, I replaced the timing chain, and both gears, fuel pump, tps..still nothing..


Bought NEW Holley 600 and had garage install it and check the timing.

They said the timing was out a tiny bit so they adjusted it.

Once the new carb was installed, the engine started up a bit rough, but gets smooth within 5 seconds and stays smooth, engine warms in about 6 mins and temp is reaching 210 degrees, once engine is warm, the choke opens and the idle lowers and sounds pretty good.

Put it in reverse, and it seems like something is holding it back. I give it a bit of gas slowly and it sputters a bit and tries to die. I put it straight back into park and it smooths back out and idles perfect.

Drove it down the road after playing foot power with gas and break, and noticed that it took a bit to get to 45 mph, and once there, it seems to backfire from exhaust, and even if I put my pedal to the floor, the engine does not rev at all to increase speed.

Coming to stop signs and red lights, it does just fine, dont want to die or sputter at all, give it a bit of gas to take off and it again sputters a bit and then moves on, but still something holding it back.

On way home, I was going downhill and noticed that I could take my foot off the gas, and the truck would slow down like I was using the break.

Didnt notice any burning break smells after parking it at home.

Thought the cat converter may be clogged causing the overheating, loss of power and backfiring due to the back-pressure.

While the engine was running I walked around the truck, I noticed the exhaust was louder on the passenger side than driver side, not louder than it should be, but the driver side seemed to be more muffled.

So I got under the truck and banged on the cats a bit, not to hard just enough to try to break any clogs loose, nothing, so then I decided that I was going to get new exhaust soon anyways and I used a grinder and cut the pipes about halfway through just between the cat and the manifold.

Started it up and it made no difference.

Now I am not sure where to go from here, but first I am going to check the drums on the back wheels and see if maybe the 8 months of setting may have caused them to seize? never heard of it but I dont know. I know last winter I replaced the entire gut systems on both back drums, so locking up dont seems right, but I am going to try.

Do any of you guys know of any other place to check? would the back breaks being locked cause the backfiring?

Kyresearcher ** 1985 Ford F150 Bullnose 302 Holley 600 3 speed.

[fastEdsel]

Sounds like a timing chain problem to me.

[fordman]

Ywo things came to my mind. Maybe 3. The timing is off. The carb linkage may be adjusted wrong. And is a 600 too much for a 302.

[tnlprt]

Sounds like a lean mixture issue

I would check for vacuum leaks

A 600 is not to big for 302 CI

[Kyresearcher]

The carb that was on it was a 600, and it ran perfect up till this problem, I have owned it for about 8 years and never had a problem, granted plugs wires and regular maintenance here and there, but this truck being a 3 speed had a lot of get up ang go, and it all stopped at once, so the 600 Holley was only put on in replacement of the one that was already there.

Lean does sound right.......it just dont have the "get up" it had before, and at 45 mph, it dont matter how much gas I give it after that, then engine does not rev up at all past that point. could a lean mixture cause it to slow down really fast after letting go of the gas pedal?


I was even told a 650 would be a good fit for my truck, but it was perfect for me at 600 so thats why I went with it

[cep62]

It's time to check the basics .
Do a compression test.
Check your fuel pump for volume . Maybe a pluged filter or bad pump.
Hook up a vacuum gauge when its running.

[Grease Monkey]

I would lean toward timing related issue......... but, I would definitely be doing a compression check. Could be blown head gasket, or burnt/broke valve.