Use of 110 Octane Leaded in 327

[Joe L.]

Re: How about that Jack Podell additive?

clem-----

The lead additive that Jack Podell sells is not "straight" tetraethyl lead----it's a little tetraethyl lead diluted in a whole bunch of kerosene. When mixed as directed in gasoline, I think that it produces a final mixture with about 0.1g of lead per gallon. Of course, using more of it will increase the grams/gallon.

You are correct in that tetraethyl lead is EXTREMELY toxic. Skin exposure to the concentrated product can be fatal since it's readily absorbed through the skin. It would never be sold to the general public in concentrated form. Even laboratories are restricted in purchasing this chemical as well as other organo-metallics with similar toxicity.

[Clem Z.]

Re: How about that Jack Podell additive?

back before racing gas was sold we got TEL from gulf research labs to make sunoco 260 to even higher octane because we were running 14:1 CR in the drag engines. it came in a round metal can with a metal "hex" shaped cap that you needed a wrench to remove. we used rubber gloves to mix the TEL because the guys at gulf told us to do this and also not to breath the fumes.i remember the first time i picked up a can of TEL i could not believe how much it weighed.

[Theodore K.]

Re: How about that Jack Podell additive?

I have been running the Jack Podell additive in my 57 for several years now. I use av gas when I store it but otherwise Jack's additive. I mix with 91 octane premium unleaded. I use about 6-8 Oz per tank. It pretty much suppresses my ping problem and the Engine idles okay.Not so with 104 Octane booster. Stuff works well. It is a diluted mixture and safe to handle within reason.

I am satisfied with it. Av gas is better if you have access.
Ted

[Clem Z.]

CR vs power

a 304 HP engine with 8.5:1 CR will make about 317 HP calculated with a CR of 10.0:1.. peak torque with go from 372 to 387. so do not get carried away with higher CR

[Clem Z.]

free HP calculater

go to www.virtualengine2000.com for a engine power calculator download.

[Chas Kingston]

Re: 100 octane LL avgas

I believe that the usual formulations were in cc/gal, not grams/gal. If my ancient memory serves me correctly, premium was 3 cc/gal; regular was 1 cc/gal. The first cc/gal gives the most boost, more lead had only marginal effect. So, if you add avgas to unleaded premium, you are getting that big boost from that first cc/gal.

Again, I haven't looked into this sort of thing for 30 years, and the memory might be faulty.

Ol' Geezer

[Joe C.]

"Charge" Composition

Why does NOx injection increase power output? What about water injection? Water injection is still used , I believe, to increase power in aircraft applications. What about nitromethane?

Assuming that an engine will not detonate, then what is the best way to achieve optimum BMEP, with fuel as the variable.

[Clare Carpenter]

Re: 9.5 vs 11.25 in a 327/340 Desk Top Dyno Run

Duke, I don't care about running regular gas BUT I also don't want to be tethered to off road fuels or have to run a retarded ignition curve if I had a higher CR. I guess I could mix fuel if I had too but in the event I want to take a trip that requires refueling on the road, I would want to be able to run it on unleaded premium without detonation.

When I had this engine built I specified a 9.5:1 CR, or at least I believe I did, and the heads were CC'd. My engine builder has since retired and I have no way to contact him. I wasn't given the CC volume but I know the combustion chambers were made equal. The reason I asked for a 9.5:1 CR was because I wanted to run it on pump premium. I will have all meaurements taken while swapping to the LT-1 cam and I'll have to make a decision whether to swap pistons too at the same time.

Assuming I have a true 9.5:1 CR and will run the LT-1 cam. Would regular fuel be okay and the extra octane of premium just overkill?

If I were to raise the CR. What do you think the maximum CR might be to run an aggressive ignition curve on pump premium? What might be gained in HP and torque over staying with 9.5:1? I guess the most important question would be, how would you characterize a comparison of actual driving between the two combinations? I've been stalling on making a decision but if I'm going to do it, it's getting close to now or never.

One last question: Why did Chevy design the '71-'72 LT-1 to run on unleaded regular instead of unleaded premium?

[Dennis C.]

Re: CR vs power

Again, with 9.5 to 1, I can drive from the State of Washington to Virginia and back and never worry about any of the above. On average, I can still pass most anything on the road... Best, Dennis

[Duke W.]

Re: 9.5 vs 11.25 in a 327/340 Desk Top Dyno Run

Lot's of questions.

I'll answer the last one first. GM management decreed that ALL GM cars would run on 91 RON (equivalent to today's 87 PON) unleaded fuel in 1971. No exceptions! It was their way of being both "green" and preparing the fuel industry for the introduction of catalytic converters, which had to run on unleaded fuel to keep them from being poisoned. The LT-1 compression ratio was dropped from 11:1 to 9:1 and gross horsepower dropped from 370 to 330, an 11 percent reduction. Most other engines dropped to 8.5. As with previous high compression engine versions, the LT-1 could take a bit more because of the lower dynamic CR due to valve overlap.

I'm not sure if it's worth taking the whole engine apart to install new pistons. If you have a true 9.5:1 CR with the LT-1 cam it should be able to take an aggressive advance curve with premium, or run on mid-grade or even regular with less a less aggressive advance curve.

If you were building from scratch I would recommend a true 10.5 CR, and it should run well with reasonable timing on premium. The difference in the torque/power curve between 9.5 and 10.5 will be about 5 percent across the range.

Once you have the measurements get back to us. Compressed head gasket thickness can make a big difference, so you might be able to select one that is thin and raise the CR half a point relative to a .040" composition gasket.

The thin shim gaskets that GM used in production can fail to seal properly unless everything is dead flat and squeaky clean, but it's an option to consider. That's why most rebuilder use composition gaskets. They're more forgiving of surface defects. With freshly machined surfaced the steel shim gaskets rarely caused problems.

Once it's back together I'll want to hear your impressions of the LT-1 cam versus the Duntov cam being replaced.

Duke

[Clare Carpenter]

A couple of questions for Dennis-Thanks

Dennis, which engine are you running? What changes, cam, etc., if any, have you made except for the CR? Did your engine get built for a true 9.5:1 CR? What fuel do you typically use? What rear end ratio and transmission are you running? MPG? Thank you.

[Clem Z.]

matching the engine components

if you want max power with lower CR you need a cam that builds cylinder pressure. this will also cause you to need premium fuel. using cams designed for higher CR in a engine with a lower CR will result in a lazy feeling engine because as duke posted you will be bleeding off cylinder pressure. any time you use regular grade fuel you are giving away power if the engine is fitted with the correct matching components to develop max power. the newer FI corvette engine will run on regular grade fuel BUT the computer retireds the timing and reduces the HP output.

[Dick W.]

Re: CR vs power

With or without the Nitrous?

[Clare Carpenter]

Is no lead regular "greener" than no lead premium

When GM went the no-lead route as corporate policy couldn't they have specified an unleaded premium for the high performance engines and kept a slightly higher CR?

I'm trying to remember if there was even an unleaded premium available when no lead was first introduced. Maybe that's why GM lowered the CR to 9.5 on the LT-1, no higher octane fuels in an unleaded mix? I do remember that leaded regular was still available at the pump long after leaded premiums were gone.

[Warren F.]

Re: matching the engine components

Clem:

Your post was very interesting to me. I have the '71 LS6 engine, it seems to be a strong running engine, however when I ran a few gallons of racing fuel in it, it seemed to be a little bit livelier.

It too is similar to the LT-1 dilemma having dropped compression ratio of 11.25 to 1 in the '70 configuration to 9.0 to 1 in the '71 format(although completely different combustion chamber design & head material).

All the period "car buff" magazines stated that Duntov reduced the compression of this engine by the open chamber design head, AS WELL as a thicker head gasket. Do you know if this is true? Would using a thinner head gasket bring the power up some.