Alcohol to Gas?

[johnnymac46]

Im building a 68 camaro, I have a guy who wants to trade a 383 for my old 70chev truck. It ran 527 on a dyno but i was on alcohol. My question is if i switch back to gas am i going to need to completely rebuild the engine or can i run it if the compression with allow me to run pump gas? I dont have any details on the engine yet, Ill be calling the shop that built it tomorrow to get more info. Im just lookin for a little bit of help on the matter. Thanks

[HRBS]

To convert to gas (pump or race) all you'll need is to swap out the carburetor. Alcohol carbs are set up very differently and use much larger jetting, venturis, power valve set ups, accelerator pumps etc. When running methonal you use more than 2 times the amount of fuel. Hense the larger items listed.
As far as the internals.... they wont know the difference one way or another so they wont have to change unless you are trying to achieve a lower compression to run pump gas. In that case you'll have to know what it is to start. Chances are its probably higher than pump gas yields.
Hope this helps.

[ma73z]

I think as long as your compression is low enough you should be able to run gas with a carb change and tune,but I'm no expert.

[deuce_454]

typically an alcohol motor runs in the 15:1+ compression range.. the cam is accordingly big and the carb is jetted for alky

you would need a new set of pistons, a cam and a re-jet you could also swap to a set fo heads with larger chambers, but 8 pistion would eb cheaper, and you could keep the heads that must have some nice port work in them to run 500+ hp.

then you would need gaskets, an oil pump, and timimg chain (you dont need to, but i like to change the pump when ever i have an engine appart) and im pretty sure you will want to change the intake to match the cam... and lastly the carb might be a POS so figure a ned deamon...

all in all it would take a couple of grand to redo to run gas, if you do it right.

another option would be to just run E85 and not touch a thing but the jetting

[johnnymac46]

so i talked to the previous owner of the engine and this is what i got
the engine was used in a car running circle track.
383 stroker
dart sportsman heads
12.1 hypertech dome pistons
13.1 compression
350 4bolt main .40 over
400 crank and rods
msd distributor

he wasnt sure of the cam, he said it ran 527 on the dyno running alcohol.

he said if it should run premium gas and that the HP should only drop about 10hp is there any truth to the loss of HP or is he just blowin smoke?

anythoughts he wants to trade for my truck that im asking $2750?

[HRBS]

Sounds about right.
Although I would argue that 11.5:1 would be borderline for 93-94 octane.
You could run a thicker head gasket. That might help drop the compression a little. I think a simple carb change would do it for you.

[deuce_454]

thats a load of .. dung.. i very much doubt you could run a 13:1 compression motor with an alcohol cam (it has very high dynamic compression since methanol si 120 octane)

you will most likely run into detonation and loose all 527 horsepower to an engine faliure...

with a change of cam, carb and intake you could propably get it running on premium and booster.... but it will be a radical engine, 13:1 CR is a strip only/mostly engine..

but if you want a 383 with a stock 400 crank in a .40 over block and sportsman heads are your fancy, buy it..

besides.. how many passes does he have on it?


otherwise check your other options... www.racingjunk.com and a bunch of others

[Taman]

Why not mix 50/50 with 108 race gas. Give you 100 octane. 12:1 should run on that. May have to back off the timing a few degrees. Are your heads aluminum? If so, you can get away with 11.5:1. to figure out the mix for a required octane use:
(octane A*number of gallons)+(octaneB*number of gallons)/total number of gallons. So if you need 100 octane and using 10 gallons of 93 and 5 amount of 108:
Octane of mix =(10*93)+(108*5)/ 10+5
=930+540/15
= 1470/15
Octane=98

[johnnymac46]

he said he ran dirt track about 20 nights on it, i believe they are iron heads

[MarkM66]

Keep your truck. If you need to sell it to buy an appropriate engine, do that.

This engine is not what you need. JMO.