318 compression test results

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There is no way I would put a cam in a street-engine ANY street-engine, with pressure numbers as low or uneven yours.
Furthermore; it has happened that, that when a high mileage engine is given a valve job and put back together, that the engine now burns oil, by virtue of the greater cylinder pressure and better vacuum signals, which now reveal/aggravate a pre-existing ring problem.. So now yur into it for so many dollars, but now have to do the rings. So after that it just snowballs into a full rebuild.
Furthermore, that #3 cylinder is scary. Something could be going on in there that an LD test may not reveal. Before I spend a nickle on that engine, I'd want to know what it is. IMO, this is the only cylinder that might benefit from an LD test. But how will you know if the pressure loss is due to; a blown head gasket into the valley, a wrist-pin gutter, poor rings, or the engine just swallowed a foreign object. I don't think you can, and I don't think a LD test will reveal anything useful, unless you have a burned valve. And since we already know that the heads need a rebuild, and the engine by the wet/dry test, needs rings as well, IDK, at this point I think an LD test is superfluous. As for me, I'd just yank that head and look.
 
The service manual lists a minimum cranking compression pressure. See what it is. I don't think you're that far under it if at all. Anything else is pure conjecture.
 
Also 10% difference from lowest to highest is the factory spec for variance in compression readings. You are within that spec. Now, whether you meet the minimum required cranking pressure in the service manual remains to be seen.
 
AJ/FormS said:
There is no way I would put a cam in a street-engine ANY street-engine, with pressure numbers as low or uneven yours.
Furthermore; it has happened that, that when a high mileage engine is given a valve job and put back together, that the engine now burns oil, by virtue of the greater cylinder pressure and better vacuum signals, which now reveal/aggravate a pre-existing ring problem.. So now yur into it for so many dollars, but now have to do the rings. So after that it just snowballs into a full rebuild.
Furthermore, that #3 cylinder is scary. Something could be going on in there that an LD test may not reveal. Before I spend a nickle on that engine, I'd want to know what it is. IMO, this is the only cylinder that might benefit from an LD test. But how will you know if the pressure loss is due to; a blown head gasket into the valley, a wrist-pin gutter, poor rings, or the engine just swallowed a foreign object. I don't think you can, and I don't think a LD test will reveal anything useful, unless you have a burned valve. And since we already know that the heads need a rebuild, and the engine by the wet/dry test, needs rings as well, IDK, at this point I think an LD test is superfluous. As for me, I'd just yank that head and look.
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Did you read the entire thread?
Most have said he needs guides and a valve job, then a small step up in camshaft.
That's all he needs.
 
16434262054046023808965028439318.jpg
 
I’d use a cam with less advertised duration and a tighter lsa than the 340 cam.

However, with the supply chain issues....... it might come down to what’s actually available.
 
Flyinbrian72duster said:
View attachment 1715860735
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There you go! You pass on both counts. I thought you did. I just wasn't sure. I do agree getting the heads redone sure won't hurt. Especially if you want to step the cam up, because you'll need to have the matching valve springs set up correctly and the best way for that is with the heads off. So you may as well get um right.
 
PRH said:
I’d use a cam with less advertised duration and a tighter lsa than the 340 cam.

However, with the supply chain issues....... it might come down to what’s actually available.
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Oregon Cam Grinders can regrind what he has. He already has the core. I think the old tried and true 204/214 grind would be perfect but on a 108 with maybe .450-460 lift.
 
Something along the lines of a Comp XE262.
Guide tops should get shortened, will need upgraded springs........ and I’d have the guides machined for modern seals while the heads are at the shop.

While the heads are being done, have them cut .030” off the decks.
 
I used Oregon Cams grind #226 268/278 adv, 208/220 @.050, 423/441 lift, except I had it ground on 108 LSA instead of 114. Their copy of the 340 automatic cam.
 
Except #3, I dont' think the compression is "terrible" for a untouched stock 318. Could be better, around 140 psi across the board. I'd pull the heads, buy new exhaust valves and have the seats touched, then have a valve job done on the intake side. check the guides. Problem i have is the '71 may not have hardened seats. IF that's the case, I wouldn't spend the time or efforts on them. I'd replace them.
 
I like the tried and true Melling/Elgin/whatever that's like 204/214 422/441 but instead of on a 112, do it on a 108.
 
38369 said:
I used Oregon Cams grind #226 268/278 adv, 208/220 @.050, 423/441 lift, except I had it ground on 108 LSA instead of 114. Their copy of the 340 automatic cam.
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THIS^^^^^^ right here is what you're looking for!
 
318willrun said:
Except #3, I dont' think the compression is "terrible" for a untouched stock 318. Could be better, around 140 psi across the board. I'd pull the heads, buy new exhaust valves and have the seats touched, then have a valve job done on the intake side. check the guides. Problem i have is the '71 may not have hardened seats. IF that's the case, I wouldn't spend the time or efforts on them. I'd replace them.
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So have a valve job done springs to match cam and hardened seats and what about
.30 of the deck to
 
Flyinbrian72duster said:
So have a valve job done springs to match cam and hardened seats and what about
.30 of the deck to
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Cutting the deck would be fine. Many will tell you that you have to cut the intake side as well, but I've never found that need. Me personally, I wouldn't do hardened seats and all to stock 318 heads. Too many out there with hardened seats already. 318 heads are next to free. Actually, you can buy remanufactured 318 heads from like o'reilly's for 265 each. Pick something like 1975 so you'll have hardened seats.
 
318willrun said:
Cutting the deck would be fine. Many will tell you that you have to cut the intake side as well, but I've never found that need. Me personally, I wouldn't do hardened seats and all to stock 318 heads. Too many out there with hardened seats already. 318 heads are next to free. Actually, you can buy remanufactured 318 heads from like o'reilly's for 265 each. Pick something like 1975 so you'll have hardened seats.
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Cool I like that option do you think it will be worth it for a gain
 
Flyinbrian72duster said:
Cool I like that option do you think it will be worth it for a gain
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well, heads are critically important to gas mileage, performance, and quick starts. On any engine! A guy can throw all the cams, headers, and 4bbls they want at a 318 but if the valves are leaking and some cylinders are down to dead (like 90 psi), it isn't going to do much.
 
318willrun said:
well, heads are critically important to gas mileage, performance, and quick starts. On any engine! A guy can throw all the cams, headers, and 4bbls they want at a 318 but if the valves are leaking and some cylinders are down to dead (like 90 psi), it isn't going to do much.
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I hear ya decisions decisions would you do it . Thanks for responding back to me and I've also been watching your you tube channel very cool.
 
Flyinbrian72duster said:
I hear ya decisions decisions would you do it . Thanks for responding back to me and I've also been watching your you tube channel very cool.
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I would certainly put fresh heads on it. Whether it be a different set that I would have redone, or remanufactured, but I'd certainly put fresh heads on it.
 
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