Hey guys, I have a carbureted 460 that lacks power and backfires. It has a fresh rebuild, punched .010 new cam, lifters, timing chain and gears, 3 angle valve job, polished crank, brand new holley carb, pertronix flame thrower3 distributor and coil, I have checked the ignition timing, checked to make sure the cam and crank are lined up [ by the dots on the timing gears ] and checked the positive stop rockers are in place and I made sure the firing order was right. Is it possible that the marks are off on the timing gears? It acted the same with the Dura Spark ignition and a different holley that was new also. I'm looking for ideas. Thanks

 

I guess I should mention this is a 77 F250 4x4 that it's in. The 460 came out of a 77 F150 2wd. I deleted all of the Dura Spark stuff and ran the positive from the battery through a Bosch relay to the distributor, the distributor housing has been grounded to the battery also.

 

What timing set do you have?
What cam?

It sure sounds like the valve timing is off.

That said, a single backfire with a pre '92 Holley will blow the Powervalve.
Is it running really rich and clears up at higher rpm's?

 

I can't remember what the exact duration is on the cam. It is a mild crane cam and timing set though, everything should match up since it all came together as a complete engine kit that the shop that did the machine work sells. Both holleys have been purchased within the last 6 months and have the power valve blow out protection circuit. I was going to pull the timing cover and put in a gear drive timing set if we get some warmer weather.
It runs crappy all the time from idle all the way to higher rpm. The dimples on the current timing set line up the way they should, do you think the marks could be in the wrong spot on the gears? Or maybe the dowel hole in the cam is in the wrong spot? I'm hoping not to spend too much more on the engine though. Thanks

 

If you have a "straight up" timing set everything should be good!
I certainly would not spend the time or the $ to install a gear drive unless you just like the loud obnoxious whine.

Figure out what cam you have and check that number online to see if others report any problems.
Call the machine shop who did the work and ask them, they should have a record...

Crane has had issues in the past where cams were ground 'off time', but they won't admit it.
You say "a mild cam", I'm not sure what you are expecting.

 

The cam isn't much over stock, this will be a daily driver and pull trailers occasionally.
Thanks for the info on crane, maybe I should degree the cam. Hopefully I can get something figured out so I can drive it soon.

 

IDK
The Crane info was back before they went bankrupt. (it's been awhile)
Are you running Crane springs too?

I've found the cheap Summit 3500 cam and the factory cam do pretty good when installed straight up instead of 8* retarded.

 

Okay, I talked to the machine shop and got the cam number, I went on cranes sight and found all of the specs and no reported problems so I'm going to pull the valve covers and check the degrees when the valves open and see if they are opening at the correct time.
They are new ford springs

 

Is it possible the cam wiped a lobe or two during break-in?

 

I just run a compression check, every cylinder is good so I'm going to pull the valve covers and check the all of the valves with a dial indicator, four of the eight plugs are fouled (cylinders 3,4,5,8)

 

If compression is good, valves are opening and seating correctly.
I don't know what you expect to find from checking lift.

It might make more sense if one 'plane' was fouling.

Are you sure you have the cylinders numbered correctly?
It's not a Chevy.

firewall
4===8
3===7
2===6
1===5
--fan--

 

Thanks, I do know how fords are numbered Yes they are sealing so what I want to check is to see if the exhaust valves are opening correctly and all the way, if they aren't opening all the way they might backfire a little and possibly load up and foul the plugs. Plugs1,2,6,7 are perfectly clean (first and second on the right bank and second and third on left bank)

 

I replaced the bad plugs for the 5th time, now it runs beautiful what are the odds that I get 16 bad spark plugs?

 

Were these Autolite plugs?

 

Yeah they were Autolite. I have never had problems with brand new plugs before now. I put NGK plugs in it.