warped head. should i fix???

[clutchdust]

the machine shop i use (they do better machine work than follow instructions!) did all the machinework on the L26 motor i picked up before checking the head. i was pretty clear i wanted the head checked before doing anythign else. so the verdict? the head is warped .024"! just great. the guy says that if i can put the cam in the head and spin it without binding, they could take that .024" off without a problem.

now i do have another complete L24 motor in my '73 sitting out in a field about 80 miles from here.

so should i drive out and get the other head, which i don't know if that one is even straight, or should i just go ahead and shave this head?

advantages to the L26 head:

1) it's here

2) shaving will bump compression a little, not a bad thing

3) um, it's here

4) the L24 head is unknown condition, it may be warped too

possible disadvantages:

1) uneven CR, probably not enough to even measure

2) possible chain tension issues (input?)

i'm open to anyone else who has experience with such. man, if was only .005-.010", it wouldn't even be a queston. but .024"? that's a bunch. kind of makes me sketchy.

[hd240z]

I'm no expert, but I'd say mill the L26 head and use it because it is "here". :squareeye The 73 head should be the same as your L26 as far as specs go, if both are original. Generally it is a good idea to mill any used head just to be sure it is true. Some others here on the forum are more knowledgeable and can comment on the specifics of your questions.

Good Luck

[sblake01]

You could also use a 2mm gasket to compensate for the cut. That would also bring you c.r. back to somewhere close to stock. .024" is roughly 4 times the acceptable out of flat measurement. That will raise your c.r. a little more than you think. There shouldn't be any chain tension issues as the tensioner itself will compensate.

[DaveN]

Listen to your mechanic. When the head warps the cam bearings are usually pulled out of alignment. Running with it that way will fatigue and break the camshaft. Trying to slide the cam in and spin it is an alignment test. If it passes you're OK, just shave the gasket surface and go. If it fails the test go get the other head. The warped head needs to have new cam bearing blocks fabricated and align bored after they're bolted on.

[ZSaint]

I would go ahead with the head milling. (Keep what you have: good seats, guides, valves, etc) Just make certain your camshaft spins fairly freely after the head is installed. This will raise your compression ratio and advance the camshft timing a bit. Both items will enhance your engine's performance! (Moves power band up a bit) Did you overheat your engine? What caused it to warp?

[sblake01]

Your are correct, DaveN. I sometimes get ahead of myself. I'm more proficient at doing than explaining. My suggestion of course assumes that the cam bearings pass the alignment test.

[clutchdust]

well, this afternoon i bolted the cam towers and cam back in. it doesn't spin freely but i can spin it by hand.

as for the origins of this engine, i have no idea. a guy on craigslist posted it and the tranny for free.

now my machinist did say he wasn't real impressed by the brass valve seats and suggested i change them to steel. so he is giving me $90 for the machining but he hasn't quoted the valve seats yet.

based on what you guys are saying so far i may very well do that.

[clutchdust]

...The warped head needs to have new cam bearing blocks fabricated and align bored after they're bolted on.

this is so much more than what i have in mind for this motor. if it's going to take all that, i'll just check the other one instead.

besides, can't i just have .xxx" milled from the center cap and progress out until it spins more freely?

[ZSaint]

I have run these heads after milling. The cam is usually tight but it will work. If you are comfortable wih the brass seats, go for it. I ran some pretty good cams with a "bend" in the head and they never failed. (.620 lift!) I say go for it. I bet it runs like a champ!

[Curtis240Z]

You should at least change out the brass seats as they are for leaded gas. Brass seats are too soft for unleaded gas.

[clutchdust]

my machinist says he can tell from looking at them that the seats have already been recessed.

so here's the latest. tonight i sat down with the head and did some checking. the cam can turn by hand but i would certainly call it "tight".

logic (at least mine) tells me that if the head is warped .024" and you can actually see it, bowed in the middle, that the cam towers might be similarly out of alignment.

short version, with either the 1&2 or 4&5 tower bolts loose and the others tight, the cam spins pretty freely. i have motor alignment shims at my disposal (for work) and tighening down a couple of .003" under the 1&2 cam towers seems to free it up a bit. i can't seem to find a sweet spot where it's free even when the towers are tight but i'd feel much better if i got the towers milled too.

i need to do some more tinkering but i think that ~.003" off the towers on either end should make it about as good as this head is going to get. i'll ask my machinist if he wants to take a stab at it.