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Old 01-31-2015, 03:14 PM   #1
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Join Date: Jan 2007
Location: SoCal
Posts: 10
Default Interest in a high compression motor...E85 experiment

I have this 500, might be a 472 but should be a 500 in a 69 F250. The motor runs well but is tired to one degree or another. It has large chamber 902 heads IIRC. I was told it's a 1973 version so from what I've read it's 8:1, possibly lower with bad large distance from top of piston at TDC to the top of block...the name of that spec escapes me for the moment.

Ive got a lot of oil on plug threads etc. with a particularly bad #4 hole for oil intrusion... a problem which I helped cope with by using a special spark plug I just wrote about in another thread.

I would like to set up a motor to run on E85. I don't have any particular criteria other than from the reading Ive done it seems I should aim for 12:1-13:1 static compression to make this worthwhile. I will probably run iron heads and a carburetor.

If I am going to do the build I might as well aim for 400-500 hp. 500 hp has been my goal for a first performance Cad build. I also have a 472 in a 70 CDV, so this may not be the only one.

I have not decided what I want to do parts wise, but don't think I want to rev past 5000-5300 rpm or so...will probably go with entry level shaft rocker set up anyway.

What I would like to do is set up a short block that I can keep come what may, even if I decide to lower compression and go back to gasoline....just by changing the heads and end up with 9.5 or 10:1 or so, plus or minus if the chambers can be set up for the change.

So, part of my compression increase I think needs to come from switching to small chamber heads from large, which appears to be a net negative airflow wise....but I am not looking for huge power. Bigger valves in a small chamber head? Seems to work for some BBC heads that get shrouded by the small chamber....

I would probably run a cam aggressive enough to put me at best efficiency about 2500 rpm plus or minus range. I get about 65 mph at 2500 rpm in 3rd with Th400 and a 33 inch rear tire and 3.73 Dana 60. It hasn't so far but the truck may get used for some moderate towing....up to 6-7K lbs. or so, so probably ought to run well enough under load down to 2200 rpm or so. The torque converter will remain reasonably tight for various reasons...efficiency, low heat etc.

Looking for suggestions for an entry level build to get that compression and just make the motor survive making at least 400 hp...obviously not spinning fast, vs. a short block that will handle 500-600 hp if I choose to go aggressive enough with heads/cam at some point.

What do I do with rods/pistons? And iron cylinder heads? Probably should leave cast piston behind...or should I...if power output isn't very high even if compression is high and low risk of detonation etc with E85?

I've mulled over idea of custom stroke grinds for the crank some day but I think I will stick with stock 500 or 472 crank...guess I'll pick up a 500 crank if it turns out its a lets' assume stock 500 4.3 stroke and as minimal an overbore as possible. I'd like to keep it stock bore if it cleans up OK if using my motor but .010 to .030 over would be OK if needed to make things work.
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Old 02-18-2015, 10:05 PM   #2
Miklo II
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Join Date: Dec 2012
Posts: 16

Nice project. Ild like to "test the waters" of alternate fuel for the future. Methanol to be precise. Dead dino fuel wont last forever....
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