The Stovebolt Site Forums The Shop Area Engine Shop E85 fuel in a 235

I filled up my tank at the local Chevron station and ran the truck at 60 on the freeway for about 30 minutes and when I stopped at the off ramp the truck was not idling smooth at all. I re timed it and put new plugs and points in and no luck. It runs OK? After it accelerates but flattens out.
I checked the exhaust and it was white even after the carb was set by the book. Could it be the E85 or and additive they put in the gas.
I didn't replace the condenser yet.

Unless you rejet the carburetor a bunch richer, E85 will run lean enough to burn holes in the pistons, melt the ground electrodes off the spark plugs, burn valves, and do a lot of other really nasty things to the inside of your engine. If you stop after a few miles at highway speed and open the hood quickly, you'll probably see that the exhaust manifolds are running red hot. E85 is so much lighter weight than regular gasoline there's no way to flow enough of it through a carb jetted for gasoline to perform right.
Jerry

Why even run E85 in a early engine? Cheap gas works fine with compression ratio of 7-8 to 1, 87 octane is ok,If timing is right.

really??? with all the folks who complain about E10, you put E85 in and expected it to work?? huh

Bill

Jerry:

In light of what was said here is the conclusion that the best gas to put in the tank is regular and not high test? Of late I have been putting in high test gas from BJs, is the high test doing more harm then good? Thanks.

God bless

Dave

Even new engines have much different fuel systems (injectors, pump module, ECM calibrations and some method of calculating fuel alcohol content) from regular gasoline engines which can handle E15.
Everything at the pump in Oregon in E10, with the later added exception of preimum can be sold as E0!
Brings us to the second topic, higher than needed octane is a waste, IMHO. I run the 87 E10 but run it dry and add some straight gasoline before sets in.

I have been running high test in my 235 ever since I put the 848 head on it about 20 years ago. Spark knocks on regular. Runs great, no complaints, costs more but I get better gas mileage. And I do think they put less alky in it.

Kurt

I've read that in some places you have to use premium to get alcohol free gas. It's not that way around here....yet. Back on topic you couldn't beat me hard enough to make me put E85 in my '38. Nothing personal against the original poster but that is just NOT smart.

If the engine spark knocks on regular, the timing is adjusted too early. There is absolutely no reason to run premium gas in an engine with less than 9.5-10:1 compression, and the old stovebolts don't even come close unless there's been a lot of modifications done. Mid-grade gas, maybe, but even then, you're compensaating for a mistake in setting the timing. An engine with heavy carbon deposits in the combustion chamber might be more prone to spark knock, because the carbon is redcuing the combustion chamber volume and/or the glowing carbon is causing pre-igntion which leads to detonation.

In a long series of dyno tests, we found that even one degree of over-advanced timing robs as much power as 5 degrees of retard from the optimum power point. If you're going to make a timing advance mistake, err on the side of not enough, instead of too much!
Jerry

Jerry,

I'm not really sure what the compression ratio my 848 head is giving me, but it seems higher than stock. I got the head from an old time machine shop about 25 years ago. They had rebuilt it years before that and put it on the shelf. The story on it had been lost, and the new owner of the shop sold it to me cheap just to get it off the shelf. I remember looking at it and thinking "this does not look stock" but that may just have been because it was different from my'53 235 head.

However after I swapped out the stock '53 235 head for this one, There was a very noticable increase in power, and also a spark knock on regular gas.

I'll try a tank of mid-grade next time just for fun - just have always run high test.

Anyway, you could be right, but I am very comfortable with the timing, power and fuel economy of this engine.

Kurt

No problem, Kurt, whatever works for you is fine with me! You can guesstimate the compression ratio by looking at the pressure a compression tester gives- - - -one atmosphere of pressure is 14.7 pounds per square inch, so in an ideal world, a compression pressure of 147 pounds would indicate a 10:1 compression ratio. In reality, there are losses, so you could expect to see maybe 125-130 PSI or so from a 10:1 engine. If the compression pressure on the gauge is down around 110 PSI or less, the engine should run well on 87 octane regular if the timing is set right.

Also, in the real world, compression pressure is affected by cam timing and other factors. Really radical cams keep the intake valve open through part of the compression stroke, so the actual cylinder volume the piston is compressing is reduced. Very radical cam grinds require increased "compression" to get the cylinder pressure back to what a stock engine would have.
Jerry

well that's interesting because last time I checked the engine compression it was in the 120+ range. Huh. What do you think could have been done to that ol' head? Always been curious about it.

When I originally got it, I had a friend with a book of casting numbers who said it was a Corvette head. Another guy said he thought it was a 235 head set up to use with a 261 engine for racing. I think I read somewhere that the 848 head was the replacement head for a Corvette.

Anyway. It's hot.

Kurt

Kurt,

A "high-compression" "848" head might have a 8.25:1 compression ratio (1959-1960). Other things like cams and decking a head/block might increase the ratio, but most likely not higher than 9.0:1 to 9.5:1 (Jerry would know the possibilities, not I).

120+psi compression +/-10 psi over all cylinders is excellent compression (130 psi is shown for 1959/60 235s).

I have never used higher octane fuel in my 235/261 engines. I do not think that either one has a compression ration of over 8.0:1 (1960 261; and my 1954 235 has, at the most, 7.1:1). I adjust the timing on my 261 using the "ping" method.

It could have been milled quite a bit to reduce the volume of the combustion chamber. The intake valve-to-piston clearance can get pretty close on a milled head, and/or the milling takes away part of the valve seat area, so the intake valves have to be recessed back into the head after the milling job. Then the rocker arm stands need to be shimmed up the same distance the head was milled to get the right geometry back on the valve train, or shorter-than-standard pushrods have to be installed. Shimming the rocker stands is a better option. Sometimes a lash cap has to be added to the top of the exhaust valves to get them working right. Tinkering with a stovebolt head for racing can get into a LOT of work! We haven't even started talking about porting and polishing yet!
Jerry

Jerry,

Is there some reference mark I could measure to on this head whereby I could get an idea of how much it may have been milled without removing the head?

Thanks

Kurt

I can't think of one offhand, but I've got a couple of 848 heads stashed away, off the engine. I'll be glad to look for some type of reference point. Back when my high school shop students were building "claimer" small block V-8's for racers at the local NASCAR track, I used a sneaky procedure to turn low-compression 350 heads into much higher compression models by "angle-milling". We took .100" off the spark plug side of the head, and zero at the intake manifold side. It turned a 76CC combustion chamber into a 60CC, higher compression than the illegal "Camel Hump" heads the modified division was allowed to use. That modification, plus a bigger exhaust valve, made the heads real performers, and they still had the casting number for the 76 CC heads everybody was throwing away. The heads wouldn't pass a teardown, or even a close visual inspection, but they really turned those engines on!

The modification was obvious to anyone with more than three brain cells to rub together- - - -the thickness of the head casting near the spark plugs was noticeably thinner, nearly 1/8", but the tech inspectors never caught it! That says a lot about the guys they hired for the tech line, doesn't it?
Jerry

A 235 with an 848 head a lot closer to 7.8 than 8.25 compression.
Accurate cc's for an unmillled 848 head is 80,piston sits down in the bore at least .015 for standard bore.Compressed head gasket is around .055-.060,online compression ratio calculators do the math.

Vehicle manufacturers always underestimated compression to allow for production variables. ....The info I gave was from actual measurements taken off several 235 engines a friend was building.

I doubt if they underestimated compression, my guess is that they might have overestimated compression?

for car engines (in some years, truck 235s might have been different):
1958-63 rated at 8.5
1956-1957 rated at 8.0 (848 head introduced in 1956)
1955 rated at 7.5
1954 7.1 or 7.5 (manual or Powerglide)

Yes overestimated,my mistake on words.

Thanks for all the response. I was just curious about the additives the gas companies were adding to the fuel. I hear they cause hoses to deteriorate along with gaskets.
My engine is not running like it should even after timing ,new points condenser and plugs have been used. Next I will look at the carb and rebuild.
The engine idles rough and lopes at 500 rpm and on acceleration flattens out about 2100 rpm.
Frustration sets in after trying to make it run like it should. But try and try again.

So you're still running E85 and it's running rough or did you note the replies above, drain it and refill with real gas and it still runs bad?

If you have E85 in it that's one big reason why it's running poorly, the 85% alcohol.

Grigg

Paul, the only "additive" that can deteriorate older rubber is the ethanol itself, newer formulations of rubber are less affected

Bill