'68 302 compression ratio...

I swapped some '65 289 closed chamber heads (not hi-po, have round pushrod holes and setup for rail rockers) casting number C5AE onto my '68 302, which
originally had the lower compression open chamber 302 heads. I didn't realize this engine had the low compression heads on it. How much will my compression ratio increase with the new heads? Do you think I'll need to run 93 octane (ran 89 with the old heads)? I noticed on the 302 the pistons come flush with the deck where IIRC on my 289 there were slightly in the hole. Guess that's from the slightly longer stroke.
Anyway, the old heads looked pretty beat, particularly on the cylinder with low compression. Before I took the heads off I did the dollar bill to the exhaust test and it flapped back and forth with the pulses of the engine and then was sucked in. I was told that meant leaky exhaust valves. I didn't get everything back together tonight, I stopped when it started getting dark and the skeeters were getting bad. Gotta finish mounting my accessories and then I'll do a compression test to be sure all is well.
I'm expecting a decent increase in power between the closed chamber heads, new aluminum intake, and Holley carb (585 CFM I believe). Man was that aluminum intake a back saver after putting the heads on... Anyway, I was just wondering how much the closed chamber heads will affect compression ratio.
Cory
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The 1968 302 2V was rated by Ford as having 9.5:1 CR. Using the earlier heads will raise that up to around 10.6:1. It's gonna want premium gas.
Cory Dunkle wrote:

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Tom
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Thanks. I got it all together and of course it isn't working right (I either have the worst luck or am just plain stupid). First I had the distributor off one tooth. Then I had big vacuum leaks in a couple spots, fixed after a quick run to the parts store to get the _right_ gaskets (oops). Now the car idles fairly well, and sounds pretty good, but smokes. It's alright at idle and lighter throttle but if I step on it it will blow smoke out of the oil filler hole. My first thought was blow-by, but the car never did this before the head and intake swap. It's got 97,000 miles and I can still see parts of the cross hatch pattern of all the cylinders.
It was blowing _lots_ of smoke out the oil fill cap when I had the wrong spacer gasket on there. Fixing the vacuum leaks I could find greatly reduced that. So maybe I've still got some vacuum leaks? Perhaps the intake manifold is leaking somewhere? Any suggestions?
I took it for a couple quick spin around the block yesterday when I was testing and trying to get rid of the smoking, and it seemed to ping pretty easily before I retarded the timing. The timing is a hefty bit more retarded than it was with the old heads. It doesn't diesel though. I can probably keep running 89, but I think for the upgrade to be worth it 93 will be in order.
Well if it's not one thing it's always another. I think Today I'll re-torque the heads and intake to be sure they are all on there good and then spray around the carb and vacuum connections for leaks. If you've got any other ideas they are quite welcome.
Cory

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Thomas Moats wrote:

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Tom
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increase
a
be
Well I spent some time with it yesterday and minimized the blowing of oil a good bit. I went for a couple quick drives around the block and got the timing retarded to a bit before it would ping (it wasn't taking much advance with 89 octane gas that's in it). It seemed to be running pretty good, and sounded good so I decided to go for a spin across town and take a faster road back. Drove great through town, nice and peppy performance. A couple times I really stomped on it and there was a bit of smoke from under the hood, but not tons. I was running with just a ghetto rigged open element cleaner I had around, not the stock that had the connection from the oil fill cap, so I figured that would help with the smoke.
Anyway, I got on the faster road and accelerated to 55, the car felt fast and smooth. I was surprised how much power it had compared to it's old anemic self. A few seconds later it went kaput. The engine started surging a little, I pulled off to a side street and it stalled when I started turning. I looked it over and saw the point gap looked too small and the rotor was dirty. I re-gapped the points and cleaned up the rotor. I looked for vacuum leaks and plugged up a questionable line. Started it and it ran a little better but did the same thing, rough running, misfiring and wouldn't idle. So, I must have broke something, and it's not the distributor. I have excessively low compression on one cylinder, and slightly low on a couple. That's all definitely worn rings as the heads have only a couple thousand miles on them at most. I have a feeling that when I put these higher compression heads on the engine I cured one problem but made another one worse. I didn't realize the car had open chamber heads, after all, my '67 289 had closed chamber heads and ran on 87 octane, this had open chamber and ran 89. I don't think it's that bad cylinder or any of the low ones that's making it run so bad and miss like that though. It's definitely missing on more than one cylinder, so there's something else wrong with it too. Maybe I'll investigate that a bit. I almost wonder if the 89 octane is part of the problem, but then if it was it wouldn't have ran so good with no pinging or anything and then died. I'd imagine there would have been audible death throes.
I think at this point I have no logical option except to either rebuild the bottom end or buy a short block. So I think I'll be shopping around for a good engine shop (anyone know one in South Jersey?). The thing that really peeves me about this, even more than this happening at the least practical time (financially, that is) is that in all likelihood if my uncle had just taken good care of the car when he drove it for 6 years this would likely not have happened. He ran 87 octane in it so you could hear it knocking and pinging constantly, and it dieseled whenever he turned it off. Whenever I saw the car it barely had any oil in it, and it ran like crap. He would always make fun of me and tell me he didn't need to go fast and the car ran just fine, that I was just obsessed with speed. Fact of the matter is that the car was destroying itself, and being quick is a characteristic of a healthy engine. Apparently he didn't want to stop fast either because it had no front brakes and the back brakes leaked. I won't even go into any more detail about his abusing that car, but his saving a couple bucks a week on gas is now costing me at least $1000. I doubt he even saved half that on gas. To top it off he just gave away his shitty assed Mitsubishi that he knew I wanted. I mean really, what ever happened to family? So now, one week before school starts back up I have no working car and it's gonna cost me a hefty bit of money to fix. Perfect timing, eh?
Sorry, just venting my frustrations. At least on the positive side I'll have a virtually brand new engine after this is all said and done. I guess when you figure that the car was free it's not so bad. It's just a bad time, especially after I spent so much time and money fixing the rest of the car which my uncle neglected. Oh well, I guess shit happens.
Cory
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Cory, believe me if the motor is pouring smoke out of the bonnet under acceleration,...the thing is knackered. That blow-by is made up of exhaust gases and unburnt fuel-air. The exhaust part heats up the piston as it blows past and eventually the piston collapses (not literally, but shrinks due to overheating losing any gas-seal left).
You need to at least re-ring it and possibly replace pistons if they mic-up undersize due wear-punsment.
Jason
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blows
to
mic-up
I'm thinking a short block is probably my best option right now. I'm not going to screw around with re-ringing, as that is just asking for trouble, in my opinion. This engine was abused to no end for 6 years by my uncle, so if I'm going through the trouble to re-ring it I may as well take the whole thing out and do it properly, with machine work where needed. I don't really have the time to do it myself at the moment, so a short block is my best option. It's just a matter of getting the old engine out and the new one in... I suppose I can probably rent an engine lift for the day from somewhere.
Cory
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exhaust
so
whole
really
Depends on your money situation.Older tech low reving motors will get by with a re-ring and rod bearings as long as the pistons have not suffered due excessive breathing (bby). If good V8s are cheap then that is a better way though as long as they are water-tight and have decent oil-pressure. Floor hoists on wheels are good to use. They give greater manouvrability when juggling the donk out.
Jason
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