Alcohol SB Chevy combinations?

[killerpanda]

I'm trying to get a small block chevy motor together to run off a Hilborn injection w/alcohol. What compression, lift/duration on cam, cubic in. .... ect. Any advise to point me in the right direction would be of great help to me. This will be going into a 37 Ford gasser w/ a 4 speed and plan on detuning the motor so as to not work the motor as hard. Were looking to produce around 450hp. This should put us in our project high 11 sec. 1/4 mile runs.

Thanks,
Andy B

 

[ivymike]

your stated goals seem to be conflicting - you apparently want to increase BMEP while trying to "not work the motor as hard." If you're currently producing more than 450hp, you should be able to accomplish both, but I assume you're not.

 

[patprimmer]

What is the intended use or uses.

What parts do you already have.

Do you have to comply with any traffic authority or environmental authority rules.

Do you intend to race in a class with rules. If so how do they impact on engine selection.

I really don't like having to play 20 questions, so can you try to be precise, concise, thorough and clear.

Regards
Pat
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[killerpanda]

I beleive that I can produce the 1/4 mile time with a 400hp motor. So I'm hoping that with a motor that will produce 450 hp, I will in turn not have to wind the motor up to the higher rpms to produce the 400hp needed. I'm just looking for a good overall combination that will acheive this.

Thanks,
AndyB

 

[killerpanda]

No rules to say. This will not be a street driven vechile. This is a retored Gasser(drag car) to look and run the way it did in the 60's. We had a 10-1, 355 motor in it last weekend that lost a rod bolt. The rest should be self explanetory. So I'm in the process of building a new motor and wish to get a good combination together to work with alcohol. I'm preferring alcohol so that I can get away for the heat issues and I'm looking to go with a 383 stroker motor.

Hope this helps,
Andy B

 

[patprimmer]

A 383 in my opinion is the least favorite SBC combo.

If you want strength and durability use a 400 block and a 350 crank.

Are you using stock or aftermarket components.

Losing a rod bolt does not tell me a lot. What did it take out. What do you have left.

By definition, a gasser runs petrol, not alcohol.

If you decide to go MFI with alcohol, join hre.com

It will be the best $40 you ever spent if you want to learn about MFI, alky and drag racing.

You need to get your mind in order and give us a clear list of parts you have and exactly what you want to achieve and how much trouble you intend to go to. Alky changes everything, including how you think about tuning the engine and how you go about fuel storage and maintainance every time you use it

Regards
Pat
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[TDIMeister]

A well-tuned, naturally-aspirated streetable gasoline engine with 2V/cyl will have a BMEP at peak power in the order of about 10 bar and ~12 bar at peak torque. Your criteria of not wanting "to work the engine as hard" probably means you want to keep the revs and BMEPs down. 5500 RPM @ maximum power with redline about 6000 RPM seems reasonable along with the above-mentioned BMEP values.

With those assumptions as boundary conditions, I calculate a displacement of 7.3 liters, or 445 cu.in. Yeah, seems like a lot, certainly well into BB territory. Naturally, by optimizing the compression ratio and timing for alcohol-fuelling, you can increase the BMEP or conversely reduce the necessary displacement to achieve your horsepower goals, but don't be unrealistic; figure on maybe 15% at most.

Naturally, you can build an engine that gets much more than the ~1HP/CID displacement calculated above, but then that gets out of what I would define as a "not hard working engine." Cams should be mild, and ports should be well-shaped but certainly not oversized for the expected HP range, and use compact combustion chambers without excessive valve shrouding but properly placed to maximize charge motion. Static compression ratio can be around 12:1 as a starting point with flat-crowned pistons. A very high-energy ignition system would be necessary to reliably ignite alcohol/air mixtures. Keep in mind that stoichiometric AFR is ~9:1 for ethanol and only ~6.4:1 for methanol. Perform all cals at stoichiometric first before venturing out to even richer mixtures.

The lesson still holds, there's no substitute for cubic inches.

 

[patprimmer]

TDI

Are you saying that 6000 rpm is the same not working to hard with a 3.5" stroke and a 4.25" stroke.

You can do 427 SBC in this day and age, but they are not cheap.

NA SBC at about 400 CI regularly make over 800 hp in a Sprint Car. Is half that not working to hard.

I for one have some real problems with the term not working to hard as it is so subjective. Also there is zero indication of budget and current parts.

An old 283 with power pack heads and a small journal cast iron crank would be working hard at 7000 rpm and still only 300 HP

An Iron Eagle block with non twist forged 400 journal size, 4" stroke and 4.155" bore with SB2.2 heads,Eagle H beam 6" long rods and SRP forged pistons and 0.600" lift 280 deg at 0.050" cam, 14:1 CR moderate power magneto, methanol and stack injection would be loafing at 6000 rpm and 600 HP.

Regards
Pat
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[patprimmer]

Like I already asked several times. What do you have, what do you really want and how much time and money are you willing to invest.

1 hours running in competition is a VERY long life for a drag race engine that typically runs under load for about 10 second per event.

Regards
Pat
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[TDIMeister]

Are you saying that 6000 rpm is the same not working to hard with a 3.5" stroke and a 4.25" stroke.
I assume you mean 4.25" bore . Mean piston speed at 6000 RPM and 3.5" stroke (88.9 mm) is 17.78 m/s. At 5500 RPM, it's 16.3 m/s. Is that high? In the scheme of performance engines, not in the least.

NA SBC at about 400 CI regularly make over 800 hp in a Sprint Car. Is half that not working to hard.
To use your Sprint Car example (I know numbers from Cup racing engines from RET Magazine analyzed by Jake Kane in Issue 029); RPMs are around 9000 RPM with BMEPs of 14 bar at peak power. There, mean piston speed is 24.8 m/s. Now THAT's high. How do you want to halve the power figure? Halving the mean piston speed (peak power @ 4500 RPM)? Getting 14 bar BMEP will require a LOT of optimization and running low-friction parts and undersize bearings that will blow any sub-NASCAR budget away and compromise durability.

Note that I said with proper optimizations for alcohol operation, a 15% increase in BMEP over my initial assumption is feasible. To get 450 HP, a 15% reduction in displacement from my original 445 CID gives 387 CID. We can meet somewhere in between and say 400 CID. Why would your suggestion of a 434 CID engine with higher mean piston speed (20.32 m/s) and BMEP (12.59 bar) be "loafing", but you question above if I'm overdoing what I propose?

I agree, the term "not working too hard" is far too vague. And other than for the novelty of it, why do alcohol in the first place if an unstressed engine is the driving factor?

I think we agree far more than we disagree

 

[patprimmer]

My real point is there is not enough data.

I did mean 4.25 stroke. Obviously 6000 rpm with 4.25" stroke reaches piston speeds where first class components are required for long term durability, but at 3.5" even std cast pistons should have a long life.

The OP gives no clue as to what quality components he is prepared to pay for or already has or what he actually means by not working to hard. I don't know how you can even begin to put numbers on such poor data.

Regards
Pat
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[TDIMeister]

I misunderstood the tone of your post. I apologise.

 

[patprimmer]

No need to apologise. just wanted to clarify my meaning so we understood each other.

I am reluctant to play 20 questions with OPs who are to lazy or to incompetent to post a sensible easy to answer question however I will try to jolt them into fixing it in their reply.

I still don't see a post here where we can begin an analysis that might be useful and I see no point in doing it 20 times over in the hope that we eventually fluke an answer to the question never actually asked.

Regards
Pat
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