rebuild top end of 345

1

1hc72

Member
Ok guys I am rebuilding the top end of my 345. One of the freeze plugs failed and going to replace them all. Also she is burning oil at a pretty good rate as well, will I be able to tell if the oil is being burn thru rings or valve?
I will be replaceing the water pump while I have it apart, do I need to replace anything else while I am down that far??? I wil be ordering the gasket kit(heads and rest of motor)


I have the sevice manual for the tq specs. But just want to confirm a few things that are bugging me.
1. Does the dizzy have to come out to pull intake (1972 enginei am assuming original)
2. Do the lifters and pushrods for each cylinder have to be returned to same cyl and position?
3. Do I have to drain cooling system before I pull head?
4. When retotqing heads do I use the numbers from the manual?
5. Anything I need to be aware of when I pull heads??

Thanks guys I appreciate all the help.
 
1. No, but you're less likely to break things if you do.
2. Yes on the lifters
3. Yes
4. Yes
5. Tell us about your oil burning. Does it leak? Smoke on startup? Going down hills? Tell us if there is a ridge at the top of the cylinder after you pull the heads. How many miles on this engine?
 
No visible leaks. I see smoke when idling, ds pipe (true dual exhaust). Changed the oil, ran about 500 miles when I checked was down by about 2.5 qts.
Fa4 as engine milage no idea. I would assume 200k min
 
Well a puff of smoke at startup is valve guides, always smoking is probably rings. If the cylinders look good you might plan on doing the rings since you're right there anyway.
 
It's a constant smoking. Cant afford to do a full rebuild right now. I do have a 392 that I am going to rebuild.
 
Idk, oil pressure gauge don't work lol. But to replace rings don't I have to also replace the crank bearings? Far as I know I have to drop crank to drop pistons to replace rings right?
 
No pistons will not come out the bottom, that's why it's easy to do with the heads off. The oil pan comes off easy and you've got good access from below. Inspect and plastigauge the rod bearings and if still in spec reuse them. The cranks on these engines are forged with induction hardened journals so when I rebuilt my 345 the crank didn't need to be touched.

You will need to hone the bores for the new rings, make sure you cover the crank and clean well when you're done.
 
Just an fyi,
bearings, while seemingly simple, have their limitation.
When they are installed the ends crush a little each time they are installed and reinstalled. The ends butt on each other and press into the bearing housings. This is the preload force that keeps them in place and prevents them from spinning in the housing. On an engine that has run 200k miles they loose more of this preload simply from the mechanical and thermal cycling they encounter.

Simply based on the relatively low cost to benefit ratio, I do not recommend reinstalling rod of main bearings after a long hard life.

On note on installing, make sure the bearing shell backs and housing bores are super clean and void of all oils. Oil will inhibit the bearing from biting to the housings and holding best.

On the rods and caps, there are no alignment features to keep them from shifting side to side and becoming miss aligned before or during the tightening process. To control this shift, lay feeler gauges across the cap/rod parting line while tightening. Use the two thickest gauges you can slip in between the cap/rod sides and the crank.
 
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