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Old 11-28-2004, 03:32 PM   #16
mrl
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Re: Compression Ratio for Pump Gas

Volvord:

I have visited your website in the past(which is very nice by the way) because I have always been interested in engine swaps. I have an LT-1 clone which I've had for years collecting dust and rust and finally decided to rebuild it and stick it into something. Last year, a neighbor was having a moving sale and I bought his(mine now) 1962 Pontiac StratoChief(similar to a Catalina/Bonneville, but it is a Canadian version, Eh!). It will be the LT-1's new home in the near future. My question is if one adds toluene to 93 octane fuel to get up to 98 octane as you mention, what would then be the maximum safe compression ratio using either iron or aluminum heads?

Marty
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Old 11-28-2004, 04:27 PM   #17
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Your swap sound like a nice one, and in a very cool car eh (I am Canadian).
Also thanks for your comments on my website.

To answer your question there is no black and while answer. Let me explain, octane rating actually reduces the flashpoint of the fuel so preignition does not take place, but items other than static compression ratio have an infuence on detonation, these being dynamic compression ratio, combustion chamber design, quench area, air/fuel ratio, etc.

As a rough guide take a look at http://www.dunegoon.org/compression.html this is an interesting calculator although I really don't know how accurate it is.
Another intersting article http://www.faqs.org/faqs/autos/gasol...section-1.html

Hope this helps
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Old 11-28-2004, 05:08 PM   #18
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Re: Compression Ratio for Pump Gas

Volvord,

Thanks for the quick reply! I guess I was incomplete in my first message: although one could not get a 350 in a 1962 Stratochief, one could get one with a SBC, a 283, so this is not really a true "swap". Thus my next point: I also have a 283 SBC(which was in the Stratochief) that I want to swap into one of the following vehicles:
Chev S-10, probably the easiest of the three;
Volvo 240 or 740;
and this last one seems interesting BMW318 or 325, preferably the 325 since it must have beefier springs for the 6 inline.
I also thought of a 300ZX but don't have enough $$$$ for a decent Z.

I actually prefer Ford over GM then Mopar in third. My third project will be to swap in a 351 Clevor(Windsor block with 2V Cleveland heads) into a Ranger. I beleive the hardest parts to buy for this one will be headers.

Any Comments?
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Old 12-01-2004, 01:17 PM   #19
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Re: Compression Ratio for Pump Gas

So, MRL, is the StratoChief a Canadian Pontiac? Those were the only ones of the era that came with Chevy engines. Seems like an awfully lot of car for such a small engine. I don't believe I've ever seen a StratoChief. Interesting concept. Any pics available?

This 437. You said it was a 455, but destroked. Does that mean it's Pontiac 455 with a 421/428 crank in it? Which cylinder heads do you have? (casting number is on the center exhaust ports)

For a lot of great information on the Injun Engine (traditional Pontiac V8), get Jim Hand's book "How to Build Max-performance Pontiac V8s". It's only been out a few months, and is loaded with CURRENT information on building street Pontiacs. You can get it at Performance Years or Ames Performance, as well as many book stores. SA Designs is the publisher.

For a Pontiac with iron heads, 9.5 is the limit for 93 octane.

Yes, aluminum heads can run higher compression on the same octane. As others have said, it's due to the heat "sinking" capability of aluminum. But, what hasn't been said, is that all other factors being equal, an engine with aluminum heads MUST run higher compression, to make the same power. This is also due to the heat sinking. Extracting the heat from the combustion makes the process less efficient.

The comments on AV gas are right on the money, as well. While it does raise the ocatne level a bit, it's not well suited for automotive applications. Between constant/low RPM operation, and high altitude, it's better for the aircraft. The popular method of raising octane, that actually works, is to blend 93 with racing fuel. 3 parts 110, 7 parts 93, will roughly equal olden times 100.
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Old 12-01-2004, 04:41 PM   #20
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Re: Re: Compression Ratio for Pump Gas

A Stratochief is basically a Catalina/Bonneville but it's the base model. I believe the closest U.S. counterpart was called a Starchief, according to the owners manual I got from ebay. Yes, in my opinion also, it's a big car for a 283, but what's worse is that you could actually buy them with a 6 inline! That's why I am sticking in a 350 LT-1 clone. I think the 283 will do well in an S-10, since the vehicle is alot lighter(I figure about 500 lbs. min). Unfortunately, I don't have any good photos right now since my car is stripped down(I have to redo the body). As for the rest of your message re. the Pontiac engine, I think you have me confused for someone else.

Thanks for the info.
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Old 12-02-2004, 01:10 PM   #21
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Re: Compression Ratio for Pump Gas

Nope. I was addressing the original question from blue... I got sidetracked when I heard a Pontiac thing I hadn't heard of before (always interested in new Pontiac stuff, even if it's old).
MRL, might I suggest, rather than a run-of-the-mill small block, a 383. The stroked small block will make near "big block" torque numbers, something seriously needed in such a large car.
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Old 12-02-2004, 04:29 PM   #22
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Re: Re: Compression Ratio for Pump Gas

That's a really good idea. I actually thought of going with a big block but did not feel like changing the front springs and stuff. Plus I already have the small block.
What would be required to do that, a 400 crank? Do I have to change my pistons and rods? By the way, my block is bored .040 over. The 400 crank has bigger dia. main and rod journals, no? What effect will that have on compression ratio, I can go upto 93 octane in my area.
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Old 12-03-2004, 08:46 AM   #23
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Re: Compression Ratio for Pump Gas

MRL, if this car is a pleasure cruiser, and not intended for competition, I would suggest the Eagle "street/strip" rotating assembly. It comes with crank, rods, pistons, rod and main bearings, and rings. The competition versions are a LOT more money. You have a choice of pistons to arrive at the desired compression ratio.
There's some significant clearancing needed in the crankcase, to allow for the increased stroke and resulting rod interference. Most competent automotive machinists have been through the process.
You can e-mail me direct for more specific information. I can point you to the right stuff.

cvms@cstone.net
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Old 02-22-2005, 05:53 PM   #24
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Re: Compression Ratio for Pump Gas

where do you buy that from?
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Old 02-22-2005, 09:25 PM   #25
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Re: Compression Ratio for Pump Gas

I got a 383 kit from www.northernautoparts.com they are great to deal with.
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Old 02-27-2005, 10:19 PM   #26
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Re: Compression Ratio for Pump Gas

so whats really the safest way to raise octane. Out here in cali the premium is 91 octane.

thanx
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Old 02-28-2005, 07:25 AM   #27
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Re: Re: Compression Ratio for Pump Gas

Quote:
Originally Posted by daveid
so whats really the safest way to raise octane. Out here in cali the premium is 91 octane.

thanx
Torco Race Fuels makes an octane booster. 6 quarts for 75 bucks to your door. One quart
Raises 92 octane 20 gallons to 97
Raises 92 octane 10 gallons to 104
Raises 92 octane 5 gallons to 107
They make a unleaded and a leaded formula
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