[Cliff R]

"And if you dont think that closed loop EFI and full timing control with a knock sensor does'nt contribute to that engines ability to live @ 10:1 CR,then your kidding yourself."

No "kidding" here, I've never once had the first problem tuning or getting an SBC in any configuration (carbs and mechanical/vacuum advance distributors included) to effectively manage pump fuel at 10 to 1 compression with iron heads, some up near 11 to 1. Being a Chevy has little if anything to do with it, aside from the fact that they used some very good combustion chamber designs in later years to make it even easier for us.

"I've also worked on a few of the gen II LT1's that did'nt have the EFI and timing control,these were converted to carbs and HEI's with the LT1 carb intakes for use in classic cars and such,and guess what happens when you do that,they're not nearly as easy to "manage" like that."

I'm interested to hear some specifics about this, specific cam choices, dyno testing, track testing, etc. Once again, my experience with the little Chevy engines dates back to the 1970's. I probably know every decent SBC head casting number by heart, and have no problem whatsoever setting them up for pump gas at relatively high compression ratios.

To be perfectly honest SC, you are pegging my BS meter pretty hard ranting about them in the last couple of threads.

Those engines are actually easier to run at higher compression ratios on pump fuel than a long stroke Pontiac engine with less efficient cylinder head designs (chamber shapes) and with much greater mass to the total combination of parts. The SBC's have an excellent design (like it or not), nearly endless parts selection for them, and cylinder heads and camshafts in just about any variety the builder would want, at bargain basement pricing.

We just finished one up a few weeks ago powering my best friends 1 ton work van (1998 Vortec 350). We increased the compression ratio with flat top pistons, reduced quench distance to just over .030", and it laughs at low octane fuel pulling several tons of tools and equipment around all the time.

We used the stock 906 Vortec heads, cast pistons, stock replacment roller camshaft, and all of the factory emission control equipment. We upgraded the fuel injection system with the latest design/conversion, otherwise it is stone stock everyplace.

The only problem he's having with it is taking a LONG time to reach operating temperature, as it's a tad more efficient than it was before the rebuild/modifications.

FWIW, we've extended our tuning efforts and to Big Block Chevy engines as well. They respond as good as any Pontiac engine with careful parts selection. We worked with a customer last summer who refused to dump his Chevelle's "flat" 454 intake manifold and Q-jet. He's seen my car run, and wanted the type of power and vehicle performance we see from our 455 Pontiac engines using all of his factory equipment on his very expensive restoration.

We made some recomendations for him, quench distance, optimum compression ratio, longer connecting rods, cylinder head mods, camshaft (hydraulic roller on a wide LSA), etc, etc. He carried his 454 off to the dyno, where they just about laughed him out of the shop attempting to use the flat intake and factory Q-jet on his engine. The laughing all stopped when it cranked out over 590 ft lbs of torque and carried just under 500hp out the back door!!

Our current project is a 496cid BBC with 11 to 1 compression and solid roller camshaft. We're setting it up to run pump fuel only, and after reading some of the nonesense I've seen here, will certainly let everyone know the outcome here in a few weeks when we get it in service. The engine it is replacing is a 454 with a set of modified (by us) peanut port "Truck" heads, 234/244/112 Crower cam, RPM intake, Q-jet, HEI distributor. That engine has been in service since we built it in 2001, and has over 50,000 miles on it in a 69 Chevelle, and over 1000 drag strip runs in full street trim (low 12's at 112mph). It has 3.73 gears and one of our 4L60 transmissions. The CR is over 10 to 1 and it manages pump fuel without the first issue anyplace.

Funny how the N/A internal combustion V-8 engine shows so many similiarities following a few basic guidelines for setting them up, no matter what brand they are........Cliff

[PONTIAC DUDE]

Originally Posted by Cliff R

Funny how the N/A internal combustion V-8 engine shows so many similarities following a few basic guidelines for setting them up, no matter what brand they are........Cliff

I have said that over & over since I got heavily back into Pontiacs in 1994.

All you have to be is open minded and be able to do common math with the ability of common sense. Each brand or engine group has it's quirks and/or deals that need to be addresses. I good automotive machinist can work on just about anything, but specializes in what he loves.

[screamingchief]

Originally Posted by Cliff R

"And if you dont think that closed loop EFI and full timing control with a knock sensor does'nt contribute to that engines ability to live @ 10:1 CR,then your kidding yourself."

No "kidding" here, I've never once had the first problem tuning or getting an SBC in any configuration (carbs and mechanical/vacuum advance distributors included) to effectively manage pump fuel at 10 to 1 compression with iron heads, some up near 11 to 1. Being a Chevy has little if anything to do with it, aside from the fact that they used some very good combustion chamber designs in later years to make it even easier for us.

"I've also worked on a few of the gen II LT1's that did'nt have the EFI and timing control,these were converted to carbs and HEI's with the LT1 carb intakes for use in classic cars and such,and guess what happens when you do that,they're not nearly as easy to "manage" like that."

I'm interested to hear some specifics about this, specific cam choices, dyno testing, track testing, etc. Once again, my experience with the little Chevy engines dates back to the 1970's. I probably know every decent SBC head casting number by heart, and have no problem whatsoever setting them up for pump gas at relatively high compression ratios.

To be perfectly honest SC, you are pegging my BS meter pretty hard ranting about them in the last couple of threads.

Those engines are actually easier to run at higher compression ratios on pump fuel than a long stroke Pontiac engine with less efficient cylinder head designs (chamber shapes) and with much greater mass to the total combination of parts. The SBC's have an excellent design (like it or not), nearly endless parts selection for them, and cylinder heads and camshafts in just about any variety the builder would want, at bargain basement pricing.

We just finished one up a few weeks ago powering my best friends 1 ton work van (1998 Vortec 350). We increased the compression ratio with flat top pistons, reduced quench distance to just over .030", and it laughs at low octane fuel pulling several tons of tools and equipment around all the time.

We used the stock 906 Vortec heads, cast pistons, stock replacment roller camshaft, and all of the factory emission control equipment. We upgraded the fuel injection system with the latest design/conversion, otherwise it is stone stock everyplace.

The only problem he's having with it is taking a LONG time to reach operating temperature, as it's a tad more efficient than it was before the rebuild/modifications.

FWIW, we've extended our tuning efforts and to Big Block Chevy engines as well. They respond as good as any Pontiac engine with careful parts selection. We worked with a customer last summer who refused to dump his Chevelle's "flat" 454 intake manifold and Q-jet. He's seen my car run, and wanted the type of power and vehicle performance we see from our 455 Pontiac engines using all of his factory equipment on his very expensive restoration.

We made some recomendations for him, quench distance, optimum compression ratio, longer connecting rods, cylinder head mods, camshaft (hydraulic roller on a wide LSA), etc, etc. He carried his 454 off to the dyno, where they just about laughed him out of the shop attempting to use the flat intake and factory Q-jet on his engine. The laughing all stopped when it cranked out over 590 ft lbs of torque and carried just under 500hp out the back door!!

Our current project is a 496cid BBC with 11 to 1 compression and solid roller camshaft. We're setting it up to run pump fuel only, and after reading some of the nonesense I've seen here, will certainly let everyone know the outcome here in a few weeks when we get it in service. The engine it is replacing is a 454 with a set of modified (by us) peanut port "Truck" heads, 234/244/112 Crower cam, RPM intake, Q-jet, HEI distributor. That engine has been in service since we built it in 2001, and has over 50,000 miles on it in a 69 Chevelle, and over 1000 drag strip runs in full street trim (low 12's at 112mph). It has 3.73 gears and one of our 4L60 transmissions. The CR is over 10 to 1 and it manages pump fuel without the first issue anyplace.

Funny how the N/A internal combustion V-8 engine shows so many similiarities following a few basic guidelines for setting them up, no matter what brand they are........Cliff

Sigh,not again.

You sure do like to take a fellas words and twist them all around to suit your whims & views,dont'cha.

I never once said there was a problem getting a SBC live on pump fuel @ 10:1.
(please feel free to point out where I have said such)

I just said to deny that more factors are involved in doing such beyond the influence that a reverse cooling system brings to that dynamic is more than a bit misguided.

You mentioned the modern SBC chamber design,and guess what,so did I,please go back and re-read my reply post to mechanic17,I already pointed out that very same feature as you are now pointing out here.

You mentioned how the shorter SBC stroke affects that deal,well guess what,please go back and re-read my reply to mechanic17 again,I already said that too!

Again,I NEVER said there was any major problems running a carb equipped SBC @ 10:1 anywhere in this thread,even the carb/HEI equipped genII LT1's.
(again,please feel free to point out where I have said such)

All I said was it takes careful parts selection,and the proper tuning,just like any other engine requires to do the same.

Which again is exactly what you're saying...

I really dont care if your BS meter is pegged Cliff,because to me that's as much a matter of your reading comprehension skills as it might be a matter of my writing composition skills.

You read into another fellas words only what you wanna read into them,and that I have absolutely no control over.

Often it seems to me that you dont care to hear anything from anyone that has a tendency to think for themselves,all you ever seem to want is a crowd @ your feet hanging on your every word.

I told you guys this was gonna turn into a p!ss!ng contest.

And surprise surprise,now it has.

Funny thing is,I have'nt once expressed an opinion pro or con on this whole compression ratio debate in this thread,I've intentionally stayed away from doing such purely because I knew where all that drama would wind up going sooner or later,as it always does in these sorta threads.

All that about the LT1 was about was the fact that I personally feel it's probably one of the more over-rated SBC engines out there,simple as that.

And the fact that there are far more reasons beyond that reverse cooling system that lets that engine operate @ 10:1 CR on pump fuels.



Have fun guys.

Bret P.