Muffler size in relation to performance

[junkyardjeff]

I got a 77 f150 with a 460 that just did not run like a big block,it had carb issues and I am making progress with it but a muffler went bad and noticed it had 2 small turbo mufflers on it.  Is it possible the mufflers are too small and could be part of the problem of it not running like it should,I got a 66 f250 with a 460 and had duals put on and it has mufflers that are about twice the size and it runs better then the 77.  Now I know the motor in the 66 is fresher and possibly has a RV cam but the 77 runs like a smallblock so I was wondering how much too small of mufflers would affect a motor,it will be getting a muffler of the same size for now but the motor will be going in another vehicle when I am done with it.

[kb426]

There was a period that Ford retarded the cam timing to pass emissions. You may have the retarded gears as well as other problems. If the mufflers are 2" or bigger, you probably have something else going on. I had several of those 460 trucks but I don't remember what size pipe was on them. If you hit the throttle at low speed and not much happens, it's probably not the exhaust unless you have a restriction in the system somewhere. For what it's worth, I bought a new 1974 460 3/4 ton and it ran real nice. I had a 1977 that wasn't as good and a 1978 that was a dog in comparison. I changed the timing gears in the 78 and it made a little difference. In retrospect, the 74 was good and the others were dogs.

[UGLY OLDS]

Make sure you don't have laminated exhaust pipes with the inner pipe collasped....   Easy to find with a vacume guage ......



Bob....

[junkyardjeff]

I now dont think its the exhaust as it has 2 1/2 pipes,its more likely the retarded cam timing which will be dealt with later.  The problem is I drove the 460 that was rebuilt first and expect every other 460 to be the same and its not that way.

[wayne petty]

jeff i think i pm'ed you the part numbers for the straight up gear set..

a 78 400M has it.. pick up applications...

so you can just get the crank gear for that app....  i know i have a brand new standard chain  and cam gear... for my 76...  i used the crank sprocket out of it as i could not get the straight up one individually  when i needed it..

if you really want to wake it up... swap the cam also..   not an RV cam..

i was really looking at one of the ford motorsports -460 cams... but PAW never had it in stock...  even though they said they had it ordered..

[junkyardjeff]

I got the PM and I am not going to do anything to this motor untill I put it in another vehicle,I was hoping it would be something simple as the exhaust but the pipes are large enough and its just a low compression smog motor.  If the timing chain goes out or I get bored with nothing to do then it will get the straight up gear,its running better with the carb change to use it as a beater and driving one thats been tweeked a little sure makes driving a stock motor a litlt.e boring.