77 E150
351W
4 bbl Holley

I have an original 351W that was rebuilt sometime in the past 20 K with a 4 bbl Holley carb 4500 series carb. I just bought the van a month ago. I dont have alot of history on it.

I just drove it 2K miles from texas to az and it did great. I got 13 MPG most the trip! Although I did burn alot of oil and I just pulled all the plugs to find that 1 and 4 are fouled with oil. The others are all fine. The repair manual I have just says that I have some "internal engine problem". Given that I do not have the hoist or space to pull the engine...Im curious just how much of an topend overhaul is possible. I am just curious if I can do some kind of topend over haul without pulling the engine out that could possibly remedy this.

Someone recommended that I use a product call "Restore" for to seal the rings.

Also, it just started backfiring in the intake when I punch the throttle in idle or in drive. If I keep the throttle at the same place, it will almost stall, backfire at the carb, then rev up as normal. I have rebuilt the carb last week.

The back firing all started when I installed a fuel regulator because discovered that the electric fuel pump was at 10 - 14 psi. Im wanting better MPG, not performance. I installed the only regulator autopart stores have on stock that goes up to a max of 5.5 psi. Thats when it started this backfire, stummble on accleration thing. I took it off since that was obviousely the cause only its continuing to still do it.

I realize that perhaps something got into the fuel line upon installation, but Im curious what you all think before I tear the carb back off again.

So basically,

fouled plugs on 1 and 4

and

intake backfireing on acceleration after install and uninstall of fuel regulator.

Im new here, I have searched alot of the site but find that there is almost too much information and most of it over my head.

Thanks for your help

 

Since you started to have this problem AFTER the carb rebuild I'd say it just needs the carb adjusted. There are two screws on the base plate of the carb. Try backing each one out 1/2 turn and see what happens.

 

I rebuilt the carb, then drove the 2K from texas to az. Installed the regulator, Then it started the backfiring thing. I did back out the air mixture screws and it seemed to help some, but it didnt solve the problem.

Would my "internal engine" problem, fouling on 1 and 4, whatever may be causeing that, also cause this backfire/stumble on heavy acceleration problem?

Newbie question I know... but that what I am.

 

Unless it ate a valve or ring on BOTH cylinders which is unlikely you have something else going on. Did you replace the bad plugs? Is the PCV system hooked up properly?