Temp reached 210 and then detonation started???? - Team Camaro Tech
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post #1 of 14 (permalink) Old Jul 16th, 02, 03:32 PM Thread Starter
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Car ran great until today, car ran really hot today actually reaching 210 at a light. it has never run above 180 until i put that freakin smaller crank pulley on, I was hoping to squeeze alittle more horses out of it for the track tomorrow and reach the 12's. Anyways, the car reached 210 degrees and then it started to detonate while cruising and accelerating lightly around 2100-2500 rpms. Above 3000 it was fine, but that is because it was fully advance and dropped back down to 36 degrees. I run vacuum advance, so I came home and disconnected the vacuum advance and it ran better, no pinging. Could it just be the heat that made it ping and get hot or was it to much vacuum advance while cruising? It was hot out today above 90+. I currenlty have the timing set at 15 intial with 36 total all in by 3000 rpms. And run 92 octane gas. My motor is close to 10:1 compression. I also have tweeking the carb and have it running good with just a slight hesitation or surging while cruising up to speed slowly. When I get on it, it takes off great, just when I am lightly accelerating I can feel it is not as smooth as it should be. It has a 750 with 68 and 78 jets and 31 squirters all around. Thanks, Erik

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68 Camaro RS, Built 355, 274 Comp Cam, Sportsman II Heads 200 c.c. 2.02. Ported to Performer RPM Manifold and 1.75" Headers, 1.5 Roller Rockers, 650 Holley, Steel Crank, 12 Bolt posi with 4.11 Gears, TH350 tranny w/ shift kit.
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post #2 of 14 (permalink) Old Jul 17th, 02, 02:45 AM Thread Starter
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Also, my front plugs seemed to be really lean and white but the back plugs seemed fine. How exactly does weather effect normal everyday driving and plugs?? This car ran great when the weather was in the 80's then up in the 90's it ran like crap.

Later, Erik

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68 Camaro RS, Built 355, 274 Comp Cam, Sportsman II Heads 200 c.c. 2.02. Ported to Performer RPM Manifold and 1.75" Headers, 1.5 Roller Rockers, 650 Holley, Steel Crank, 12 Bolt posi with 4.11 Gears, TH350 tranny w/ shift kit.
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post #3 of 14 (permalink) Old Jul 17th, 02, 03:00 AM
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Put the bigger crank pulley back on. I am in no means an expert but I hope someone will offer advice regarding the jet spread. Maybe fatten up the primary. The first thing to do is get it back the way it was before the overheating started.

-Mark.
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post #4 of 14 (permalink) Old Jul 18th, 02, 11:59 AM
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smaller crank pulley = lower water pump and fan RPM

Not sure if this could be the problem... but thought I'd mention it...

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post #5 of 14 (permalink) Old Jul 19th, 02, 01:17 AM
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Underdrive pulleys seldom offer hp gains at all and screw up your electrical charging and water pumping. The results are dead batteries and overheating engines..a risk that I would think that you would not want to take. Don't believe all the marketing hype that these pundits brain wash you with.

Underdrives work well on circle track cars adn others that are constantly turning in excess of 7000 rpms. At those rpms, pumps often cavitate and consume more hp, but if reduced to stock speeds this makes them work that much better. If you are running a stock water pump, you could have changed to a high performance Stewart pump and saved more hp thru the part design than any by reducing speed. Stewarts will pump 30% more flow with only a 2 hp total take. So, I ask you...how much hp can you really save by reducing the speed? If you are worried about time slips, usually the rank amature does nothing to provide the right traction control for such. Work on launching....it will be a better area for less time.

Yep...the heat problem is definitely the problem. Hotter combustion temperatures means that the flamefront travels faster, meaning that the combustion timing is essentially advanced (by the flame fronts speed) and this causes pinging. By unhooking your advance in stop and go driving, you risk further heat build up.

As another poster lauded, put the original pulley back on. In fact, our line of brackets and pulleys (Concept ONE conversion kits) offer a few more hp over the stock set up and they OVERDRIVE THE COMPONENTS! The savings are all in the choice of components.

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post #6 of 14 (permalink) Old Jul 19th, 02, 02:32 AM Thread Starter
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I appreciate all the replys. I went ahead and put the regular pulley back on last night and took it for a ride. No problems at all. Constantly stayed at 180. I don't understand what you say about unhooking the vacuum advance will raise the temperature inside the combustion chambers. I have done alot of research on this board and the only disadvantage to not running vaumm advance is gas mileage. I'm sorry but it doesn't make sense to me. Thanks again, Erik Beckett

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68 Camaro RS, Built 355, 274 Comp Cam, Sportsman II Heads 200 c.c. 2.02. Ported to Performer RPM Manifold and 1.75" Headers, 1.5 Roller Rockers, 650 Holley, Steel Crank, 12 Bolt posi with 4.11 Gears, TH350 tranny w/ shift kit.
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post #7 of 14 (permalink) Old Jul 19th, 02, 10:43 AM
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Not having full vacuum advance at idle (timing retarded from where it should be at idle) increases exhaust gas temperature, which heats the coolant more, driving up temperature at idle; this was the factory design "ported spark" condition in the 60's with air-injection systems to ensure a good "afterburn" in the exhaust manifolds when the injected air hit the exhaust stream at idle, which was where emissions testing was done in those days.

Most of those "ported-spark" cars had factory base timing at 0 degrees (some were actually 2-4 degrees AFTER TDC), and had 30-34 degrees of centrifugal advance in the distributor to try and make up for it. Cars with full manifold vacuum on the distributor at idle had factory base timing set at 8-12 degrees, and their distributors had 20-26 degrees of centrifugal advance. Same WOT total timing for both, but the "ported spark" engines with air injection systems and retarded idle timing ran like crap at idle and part-throttle, and ran hot at idle.

Properly-matched vacuum advance can calibration (so it's fully-deployed at idle) with manifold vacuum makes for stable idle and a cooler engine at idle, better part-throttle driveability and throttle response, and improved fuel economy.

If you had a timing light rigged so you could see it cruising down the highway at 50-60mph with vacuum advance, you'd see 50-52 degrees advance at highway cruise; the lean cruise mixture takes longer to burn than a rich mixture, so the vacuum advance "lights the fire" sooner so maximum cylinder pressure is still reached just past TDC for peak fuel efficiency. When you accelerate, the mixture is instantly richer and takes less time to burn, so the vacuum advance drops off, retarding the timing slightly to accommodate the faster burn time, again maintaining peak fuel efficiency.

Without vacuum advance (just centrifugal), timing is only affected by rpm, not engine load (manifold vacuum), so optimum torque isn't reached and timing isn't optimized for engine load and mixture burn rate. Vacuum advance is useless on a race engine that is run at WOT all the time, but it's essential for a good-running street engine that has to run at idle and part-throttle too.

People that run fancy chrome-and-polished whizbang centrifugal-only distributors on a street engine have been suckered by the Summit/Jeg's race-car marketing hype, and are missing out on the joys of a really good-running street combination. Absolutely. Positively.

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post #8 of 14 (permalink) Old Jul 20th, 02, 02:46 AM
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JohnZ....you da man! Well said professor.

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STEVE JACK
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post #9 of 14 (permalink) Old May 29th, 05, 08:33 PM
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Re: Temp reached 210 and then detonation started????

Quote:
Originally Posted by JohnZ
Not having full vacuum advance at idle (timing retarded from where it should be at idle) increases exhaust gas temperature, which heats the coolant more, driving up temperature at idle; this was the factory design "ported spark" condition in the 60's with air-injection systems to ensure a good "afterburn" in the exhaust manifolds when the injected air hit the exhaust stream at idle, which was where emissions testing was done in those days.

Most of those "ported-spark" cars had factory base timing at 0 degrees (some were actually 2-4 degrees AFTER TDC), and had 30-34 degrees of centrifugal advance in the distributor to try and make up for it. Cars with full manifold vacuum on the distributor at idle had factory base timing set at 8-12 degrees, and their distributors had 20-26 degrees of centrifugal advance. Same WOT total timing for both, but the "ported spark" engines with air injection systems and retarded idle timing ran like crap at idle and part-throttle, and ran hot at idle.

Properly-matched vacuum advance can calibration (so it's fully-deployed at idle) with manifold vacuum makes for stable idle and a cooler engine at idle, better part-throttle driveability and throttle response, and improved fuel economy.

If you had a timing light rigged so you could see it cruising down the highway at 50-60mph with vacuum advance, you'd see 50-52 degrees advance at highway cruise; the lean cruise mixture takes longer to burn than a rich mixture, so the vacuum advance "lights the fire" sooner so maximum cylinder pressure is still reached just past TDC for peak fuel efficiency. When you accelerate, the mixture is instantly richer and takes less time to burn, so the vacuum advance drops off, retarding the timing slightly to accommodate the faster burn time, again maintaining peak fuel efficiency.

Without vacuum advance (just centrifugal), timing is only affected by rpm, not engine load (manifold vacuum), so optimum torque isn't reached and timing isn't optimized for engine load and mixture burn rate. Vacuum advance is useless on a race engine that is run at WOT all the time, but it's essential for a good-running street engine that has to run at idle and part-throttle too.

People that run fancy chrome-and-polished whizbang centrifugal-only distributors on a street engine have been suckered by the Summit/Jeg's race-car marketing hype, and are missing out on the joys of a really good-running street combination. Absolutely. Positively.

------------------
JohnZ
CRG
'69 Z28 Fathom Green
would the amount of vacuum available make a difference on these vacuum advance distributors you praise? I am just wondering, if a car has a RACE cam in it, shouldnt the parts follow suit?.........because my 396(.030 over) was a stock block, but the cam is a FAR, FAR ,FAR ,FAR cry from OE. 292magnum, 244 on the I/E with .550 lift and laying on a 110LSA.........would stock parts be a good selection????? just wondering PROF.

i consider my car streetable, but nothing like the 95 monte carlo, or 01 GMC pickup i drive....they are light years ahead....

i mean, a stock fuel pump runs out of gas, the stock carb just wont work well with that cam, the stock points setup is far from desirable when you spin to 6500, i had to have headers you know, i mean the race parts get that domino effect............i believe that last portion of your comment gave too little info to lump us all into being gullable, ignorant consumers....just my .02

should i throw my pro billet distributor in the trash, and go OE?

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post #10 of 14 (permalink) Old May 29th, 05, 08:45 PM
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Re: Temp reached 210 and then detonation started????

You still need vacaum advance if you will drive the car under part throttle, low load conditions. A race car is wide open, period. Max load, all the time. It has no need for vac advance. Under light load conditions, the burn is slower, therefore it has to start sooner, therefore every street car needs a properly tuned vac advance to give it the correct timing under part throttle, low load conditions.





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post #11 of 14 (permalink) Old May 29th, 05, 08:54 PM
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Re: Temp reached 210 and then detonation started????

so you are saying to throw all my msd stuff in the trash? not sure if i can do that sir....that would definately prove my insanity has peaked.....

the hesitations i can live with, if i am able to get MAX HP/TQ out of my
BBC......period...

is there any OTHER place than WOT in a 5 speed BBC? i have yet to find it

all jokes aside, i didnt put the ignition together on this car,,but what i am trying to do is, make it do the best i can with what i have....

damn i miss fuel injection, and engine management on a laptop...

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post #12 of 14 (permalink) Old May 30th, 05, 05:53 AM
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Re: Temp reached 210 and then detonation started????

well, heck, you're $2500 away from efi...pop a Holley system on there, hook up your laptop and never look back! Those commander 950's are a joy to tune, if I had the money to spare, my carb and mechanical distributor would be in the trash today.

If you're msd has no vacaum advance, and can't be retrofitted with one, you're gonna be stuck with less than perfect around town driveabiity...not the end of the world, as you say.





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post #13 of 14 (permalink) Old May 30th, 05, 09:13 AM
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Re: Temp reached 210 and then detonation started????

Quote:
Originally Posted by Erik Beckett
...I don't understand what you say about unhooking the vacuum advance will raise the temperature inside the combustion chambers. I have done alot of research on this board and the only disadvantage to not running vaumm advance is gas mileage. ...
Vacuum advance is not a gas milage trick. It is a way of maximizing engine power at low throttle openings, but preventing detonation / ping when a load is placed on the engine. Sure, there is probably a milage improvement by making the engine more efficient, but that insn't the primary purpose.

In general, a 4-stroke engine will run optimally with as much ignition advance as it can get without ping / detonation. Until electronic engine controls were introduced, mechanical and vacuum advance were the only ways a timing advance curve could be optimized.

Engines without vacuum advance will idle slower, run richer, have lower manifold vacuum, and reduced power off-idle.

Dave
========================
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post #14 of 14 (permalink) Old Jun 1st, 05, 05:47 AM
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Re: Temp reached 210 and then detonation started????

on a lighter note, a closer look at the 750 puddle dumper indicated the pump cams were installed backwards(once again, not my selection or install)...........now the hesitation is gone...

but now you folks have me scratching my head on vacuum advance.

with the amount the car is driven, i have to weigh the cost options.....

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