He's talking about the .500" down cylinder fill. That's the correct way to measure piston head volume.
Can I make this work on pump gas?
- Thread starter Freezerman
- Start date
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He's talking about the .500" down cylinder fill. That's the correct way to measure piston head volume.
Exactly right. Done it literally hundreds of times.
Freezerman
Well-Known Member
Thanks, it would go in my 72 dart. It has 3.23 gear right now, i will be getting a different converter. I do have electric fuel pump now.
OldmanRick
Well-Known Member
I admit I did speed read thru this thread, but that engine seems to be a rare build these days. As long as the cylinders are clean enough with a light hone, i'd keep it as is. What I mean is, with a good clean up, it would make a real nice bracket engine with a little more cam. I'd probably put it under the bench for now, or see if someone else wanted to use it for how it was built, and maybe find another engine for your needs/want's on the street.
Freezerman
Well-Known Member
It has the old 11.5 MP pistons in it with 340 x heads and I was told a crane 272 cam. Two cylinders have a few vertical scratches, the rest look good with no ridge on top.
Robbie2734
Lambcharger
Just one more vote for a thicker gasket from Cometech. It's not cheap but compared to new pistons and a rebalance it's the best option. The cost will be the gasket and maybe new pushrods. Then tune it for the lower compression ratio and have some fun! One more thing, FelPro makes a gasket that's .054 thick and inexpensive. I don't think it will be enough though.
Freezerman
Well-Known Member
I am looking at cometic .075 gaskets for 123$ at summit. Would I need to mess with the pushrods with them?
EL5DEMON340
Well-Known Member
The cosmetics need a special finish on both the deck and head so might be cheaper to just get some 9 to 1 pistons that will fit hone it and let it fly. Cheapest thing is probably go with the felpros that are .054 or whatever and to tell you the truth I would go with the old mopar 484 cam that has 244 @ .050 or even better the 509 that I think has around 248. @ .050. They have a lot of overlap and I'm guessing it will run fine on 93. The part that I don't like is the dome piston that may cause ping. This is not the type of engine that you want to start throwing a lot of money at with it being a 318 with outdated pistons and scratched cyl. Just mt two pennys
DaveBonds
Garage Trash
You may want to, but if I were you, no matter which head and gasket combo used, I would put it through a valve clearance test off of a solid or shimmed/ locked hydraulic, with some light springs on the #1 intake and exhaust. 1st and 3rd lobe of the cam from the front.
You're looking for clearances from the crank sweep starting at 15btdc to 5btdc and again from 5atdc to 15atdc.
You want .100" clearance between the valve and piston on the exhaust of over extending the rocker by hand until it touches, and .060" on the intake, min.
You may want to just set up some 308s or some J heads. 915s will get you there. Any stock J head with some dished valves should put you at around 71cc. If you tossed some of those Fel-pro gaskets on it that got you about .053" crush, you'd be within your range.
Another thing you may consider doing is polishing the chambers, if you're up for it. Get more CC and better detonation resistance at the same time, since you're not going for quench.
Another option that I haven't heard mentioned on the cheap is water injection.
E-85 does kill aluminum, but not for a long time. About the only thing that gets hammered by that stuff that I've actually seen in shorter time frames than longer are things like metering blocks. Most new carb bodies are set up for ethanol and have nickel plating or another coating inside the fuel bowls.
If you want to have the convenience of pump gas, you may consider rigging a water injection system to WOT or check throttle position on ping and set up a switch at that level.
If I were going after it, I'd try the Fel-Pro gaskets without spending tons on the Cometics, then cut and polish the crap out of those X head chambers. Maybe get some open faced valves and shoot for 71-72cc.
You're looking for clearances from the crank sweep starting at 15btdc to 5btdc and again from 5atdc to 15atdc.
You want .100" clearance between the valve and piston on the exhaust of over extending the rocker by hand until it touches, and .060" on the intake, min.
You may want to just set up some 308s or some J heads. 915s will get you there. Any stock J head with some dished valves should put you at around 71cc. If you tossed some of those Fel-pro gaskets on it that got you about .053" crush, you'd be within your range.
Another thing you may consider doing is polishing the chambers, if you're up for it. Get more CC and better detonation resistance at the same time, since you're not going for quench.
Another option that I haven't heard mentioned on the cheap is water injection.
E-85 does kill aluminum, but not for a long time. About the only thing that gets hammered by that stuff that I've actually seen in shorter time frames than longer are things like metering blocks. Most new carb bodies are set up for ethanol and have nickel plating or another coating inside the fuel bowls.
If you want to have the convenience of pump gas, you may consider rigging a water injection system to WOT or check throttle position on ping and set up a switch at that level.
If I were going after it, I'd try the Fel-Pro gaskets without spending tons on the Cometics, then cut and polish the crap out of those X head chambers. Maybe get some open faced valves and shoot for 71-72cc.
With iron heads and a small cam, that is too much compression for pump gas. E85 would remedy this issue....or swap out the pistons for something that gets you in the 9.8-9.5:1 range. If you had aluminum heads it would be closer to working, but you would probably still need a bigger cam to bleed off some of the pressure....just my 2 cents.
Freezerman
Well-Known Member
It is sounding like this might be more trouble than its worth. I am willing to try polishing up the heads, thicker gasket and new cam if it would work.
If I went to E85, will it eat out the gas tank? I already have fairly new carb so that should be OK.
If I swap out pistons then I need to rebalance correct? Then it gets into might as well rebuild.
If I went to E85, will it eat out the gas tank? I already have fairly new carb so that should be OK.
If I swap out pistons then I need to rebalance correct? Then it gets into might as well rebuild.
80fbody
Well-Known Member
Deleted
moper
Well-Known Member
No - he's right. It's actually easier to do it 1" down - or at least it is for me. But it's a simple adjustment to the formula.
I think I'd do what Cracked said - just add gasket to it or enlarge the chambers to get the ratios down.
I wouldn't be worried so much about the gas tank as I would everything else in the fuel system. Really need to make sure the fuel pump, lines, carb, etc are going to be tolerant to the ethanol and you need to make sure you have a robust enough of a fuel system to feed 30% more fuel. You'll want a good flowing fuel regulator too. It would definitely remedy your high CR problem, but I wouldn't go that route with a half a$$ed fuel system. I'm not saying your fuel system is not up to the job because I honestly don't know what you have, but just making a recommendation.
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