351C valve float

Hi,

I'm running a 351C 2v with edelbrock cam, lifters, manifold and 1806 carb (650 cfm), iron manifolds but dual exhaust . Factory valves, springs and keepers. Engine was rebuilt to 2v specs about 13 -14 years ago.

It's been sitting for a few years, but now that it's running, it seems to be floating the valves at about 4800 rpms. Rev'ing up at that rpm it starts to make a lot of smoke, no more power and sounds bad enough to get the foot up quick.

Have the valves taken a set? weakened over time? maybe it's not float but ...what?

I've read the factory valves should be dumped before they drop and new springs installed, but that's a lot of work in prime cruizing time! Any quicker fixes? Or is it time to bite the bullet (or just continue to keep a 4000 rpm red line)?

Thanks,
jb

Is the smoke gray or blue? Sounds to me like you may have an ignition problem causing a high rpm misfire and unburned fuel.

Sounds like weak springs but are you SURE that's it's not FUEL or ELECTRICAL?

Originally Posted by allenman85

Sounds like weak springs but are you SURE that's it's not FUEL or ELECTRICAL?

Grey / brown / black --- smoke hmmm can't honestly say as I didn't let it continue for long and didn't look! It was my assumption that it was springs, but...

How would I be able to tell? Springs, fuel or electrical?

Fuel pump puts out 8.5 psi at idle and it has a pertronix (first version) under the cap.

jb

Well, you really should replace the valves, springs, etc, because the factory valves are friction welded 2 piece valves, and are known to separate, it's not a really common occourance, but it can happen, and it's not pretty. When I built my Cleveland for street duty, I used Ferrea 5000 one piece stainless valves so I wouldn't risk it.

Just my $.02

The smoke sounds more like a fuel rich problem. The 8.5 psi is quite high (for most applications).
Sounds like we need to find a buddy in your area that understands cars. Where are you located?

Could be the lifters pumping up. 351C's are BAD about that. The lifters pump up, then the valves hit the pistons and bend pushrods and/or break the heads off the valves.

For 351C's, I like SOLID cams, 1-piece stainless valves, single groove retainers, and an adjustable valvetrain.

WAY too many 351C's have died from their crappy valves contacting the pistons.

Good Luck!

Originally Posted by allenman85

The smoke sounds more like a fuel rich problem. The 8.5 psi is quite high (for most applications).
Sounds like we need to find a buddy in your area that understands cars. Where are you located?

I'm in Western Wisconsin.

I used to understand cars, but as time goes by... Most of my a background is with windsor engines. I've heard of the issues with the Clevelands and just assumed it was float due to weak springs and have limited myself to a 4k redline. It would be nice to be able to zip up to 5500 on occasion, even with the cost of a tank of arab juice.

I've found and fixed a couple issues with the distributor, put a regulator on the fuel line, re-routed fuel line to keep the line cool, tweaked the edel carb for better economy. Haven't run it up again as I don't want to have any damage.

Some other threads list the MSD blaster coil (which I have) as being a possible issue too. Thoughts?

jb