Hi everyone - first post here, although I've been researching things on the forums for a while.
I'm 'refreshing' a 1970 F100 with a 360 and have a question regarding a head swap.

I'm doing my first 'rebuild', mainly to seal up some leaks and get a look inside. The engine ran well, but it had low compression on one cylinder. I tested compression both dry/wet, with no improvement, suggesting possible valve issues. I wanted to get familiar with the engine (first time I had one of these, and this is my first complete engine tear-down) and I was intending on taking the engine down to the block just to get familiar with the parts and freshen up what was needed (timing sprockets and chain, valve seals, etc) as I rebuild it. Once I got a good look at the heads I noticed that the cylinder with low compression had a sunken exhaust valve (all cylinders were a little sunken, but this one was visibly worse). The valves themselves look fine, as do the pushrods, lifters, etc. I am not interested in doing a whole engine overhaul, as I would ideally like to eventually find a 390 to put in.

I have a second 360 that is in decent shape (also out of an F100), with the same heads as my running engine (C8AE-H, if that matters) so I hope to swap one of the heads from the spare. Just wondering what else I should switch over - I'll obviously take the valves but should I also take the pushrods? I expect it would be best to leave the original lifters in the motor, and not take those from the spare?

I'm new to this, so any tips would be appreciated.

thanks

 

Have hardened valve seats installed in the heads. Todays unleaded gas doesn't cushion the seats.

 

Seconded.

The sunken exhaust valve could have taken up all the lash in the lifter, bottoming it out, so that the valve never really fully closed anymore or at the very least had almost no spring pressure so it would float at very low RPMs.

Keep the existing lifters, and make sure they stay on the cam lobes they came from. Don't mix the order. If you're going to swap a head, do both. Get those C8AE-H heads gone over by a machine shop. if they are runnable, just run 'em until you can do a set of heads "the right way" - as in, replace springs, get hardened exhaust seats, check/install guides (no knurling), etc.

If you're just going to run the C8AE-H heads with no machinist looking at them, do this: pour a small amount of VERY light machine oil into the port and make sure the valve and seat do not leak. Sit the head on it's side, with the intake ports facing up, and pour in a small amount of oil. Sit it back down on the cylinder side and let it sit for a few minutes, then check. Do the same for the exhaust side. If any do leak, well, take it to a machinist and at the very least get the valves lapped unless you're up for the job yourself.

 

Thanks guys - this all makes sense.

I leak tested the valve seats as suggested, and didn't see any obvious leaks - I'll check again later to be sure. So - I guess it looks like the heads aren't in too bad of condition. I'll plan to swap both heads as suggested, and I'll keep the existing lifters, and make sure they stay on the cam lobes they came from (thankfully I didn't mix the order when I removed them, so I know where they go). For now, I'll plan to run the stock heads without having a machine shop look at them (hardly worth investing much in stock heads, I'm told).

Hopefully this gets me running (it should, since both engines ran fairly well before I tore them apart), until such a time I can rebuild the other block into something worth investing in (hardened valve seats, springs, etc).

 

Let us know how it goes

 

Oh, and hey! WELCOME to FTE!

 

thanks again.
I'll be sure to post an update, but it will be a while before everything is back in the truck and ready to fire up.

 

Don't worry about finding a 390. The 360/390 share the same block. What you need is the rods, pistons and crank to convert a 360 to a 390. Or buy a stroker kit and build a 445. The top it with new aftermarket heads instead of pouring that same money into stock 50 year old heads.