My smog pump on my 91 F-150 351w EFI seized up and I plan on just having the serpretine belt bypass it just to get this beast on the road for now. Any one have experence doing this? Belt brand/part number?

Thanks for nay help,
Russell Mack

 

I did this with my old 300-6. I just took some wire, ran it around the belts and then measured it. You can cut maybe 1/2 inch off for the tensioner travel. Then you just go to Napa and ask for a belt that size. Usually they are just a little longer or shorter. Take the truck and a socket/breaker bar and swap it on in the parking lot and try it, that's what I did.

 

I bypassed the smog pump on my 5.8, but the belt I had to use to do it was always a bit too tight or it would immediately slip off under high rpm. The tight belt eventually came off too. The angle and pressure of the tensioner wasn't right with the smog pump bypassed. I have the smog pump dummied up for now but I may eventually change the tensioner.

 

I used the surestion of the previous post to yours. Instead of string I used a tape measure and came up with 89.5". I went to Pep Boys and asked for 92.5 inch belt, adding 3 inches. They came back with a 93" belt that fits just fine. It is a Dynaflex 923K6 6 ribbed belt. Cost $31.00 here in Michigan.

Russell Mack

 

That's good information, thanks for the measurement.

Are late smallblock fords the same length with A/C and without, basically, is there an idler pulley where the A/C is if you don't have it?

Another thing to consider if you can't get a shorter belt to work right is what I did on my old 4.9 F-150. I opened it up, broke everything out of it but the center shaft with the bearings, cleaned everything up really good, welded washers over the hose fittings and sealed up any other little holes, put some motor oil in it and bolted it back together sealed up with some RTV. There is no way that thing is ever going to sieze up. It's worked fine as an idler pulley for over a year now.

The important thing to know about taking the AIR system off, and I don't know if it applies to SBF's, is that if the air gets injected before the first O2 sensor (into heads) then the computer will expect it and it won't run right if you take it off. If it goes in after the O2 sensor it won't make a bit of difference. I know this was definitely true with the 4.9's.