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#41
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here are pictures of my plugs
Also did a compression test on warm engine. All 8 were from 175 to 185 |
#42
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TTT
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#43
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Plugs look like they are a coupe heat ranges too hot. (Strap burnt nearly down to the base). Hard to tell color sometimes from a photo and not natural sun light, but looks like it is running fairly lean. Too hot of plug will effect the color also.
Sorry for the family health issues. Last edited by Jay S; 12-06-2022 at 10:12 AM. |
The Following User Says Thank You to Jay S For This Useful Post: | ||
#44
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X2 Jay , What"s the spark plug part number?
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Carburetor building & modification services Servicing the Pontiac community over 25 years |
#45
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I have used thicker Cometic gaskets up to.120 in the past . Was way easier to do that than getting different heads to lower compression .
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2008KRE Q16 Winner 2014 atco raceway doorslammer winner 86 grand am tube car 8.95 @152 455 eheads solid flat tappet cam Hoffman Racing building and racing Pontiacs for 35 years |
#46
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They are Delco R43S plugs.
Thanks guys |
#47
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43 is a cold plug , need to richen it up & that will help you greatly
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#48
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IMHO, the plug is saying it would like to be colder. I run 43s up to about 10:1, a 43 can be run with higher compression than that depending on how the engine is set up. We run often run colder plugs than 43s above 10:1. In this case, the strap is saying the 43 is running hot. I would switch to these, https://butlerperformance.com/i-2445...html%3Fq%3DNGK
Then also move up a couple jet sizes on the middle carb to richen it up some too. |
#49
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Dave, do you know the current jetting in your trips?
I think you could jet up a bit in center carb. Again this is a good example of tuning where everything needs to be known. A wideband O2 sensor is a good tool to confirm what's going on air/fuel wise in all aspects of operation. Also, before you put the car away and pull parts off I would suggest 4 cans of seafoam aggressively down the center carb. I.lke to stall it out at end of 3rd can & let sit 15 to 20 mins then proceed with last can. Your pistons & combustion chambers look like your plugs so cleaning up that area will make it run better especially good if your going to nail down the tune Seeing your set up is not stock you may benefit from adding a ported source in your center carb for vacuum advance. I usally add that source in on non stock combos.
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Carburetor building & modification services Servicing the Pontiac community over 25 years Last edited by shaker455; 12-07-2022 at 07:48 AM. |
#50
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Can anyone speak to the cost of the machined chamber modification?
I wonder if the loss of compression but the increase of flow and timing would offset each other? |
#51
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If some of the change in cranking compression from the 150-155 range in summer of 2020 (mentioned earlier in the thread) to the more recent 175-185 this fall came from carbon build up. The seafoam should really help.
FWIW..Dropping the spark plug heat range will help a bit, but will have a pretty limited effect since a 43 is already fairly cold. If your not using a wide band O2 sensor and judging jetting from only reading spark plugs the colder plug will make the jetting change more obvious. As hot as the plug are burning now it is not going to be very easy to read plugs and make jetting changes. I doubt the AFR is very far off, as is, as hot as the plugs are burning now, just reading the current plugs, you will probably shoot right past the optimal AFR and make it too way to rich. The wide band O2 would help a lot for jetting change info. I don’t think modifying the chamber to drop the compression will result in any gains in flow or power on a stock head. |
#52
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Quote:
The earlier number were with a cold engine the later number are with a warm engine. The posted cam card has adv duration as 290 and calls for a 106 ICL. This means an IVC of 71 degrees ABDC. With that and a true 10:1 CR I calculate around 185 psi cranking compression. Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#53
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Stan, I came up with similar numbers you did. I think the compression is a fair amount higher than 10:1, and the actual intake closing is in the mid to upper 70s. With the miles on the engine I doubt the ICL is at 106 anymore.
150 seemed really low on the earlier check, the 175-185 is more what I would expect. 30 or more change seems like a big change just going from a cold to hot engine? I don’t recall seeing that much difference on anything I have checked? |
#54
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I always recall the highest pumping numbers. If the earlier pump test a few years ago was cold (which I overlooked), and the last one was hot. I don’t think much info to be learn from the differences. Maybe would have to take another current test cold now to learn much?
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#55
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Jay,
Those numbers were with a true symmetrical cam. If that was one of Harold's cam it would have another 4 or so degrees on the IVC still in a 106 ICL which would be about 10.4:1 @ 185 psi. Now who knows where the ICL was placed when built and where it is now. Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#56
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I am still trying to get all the things done that was suggested. It's getting too cold here for me. Next few days are really cold. I bought a piston stop tool to get my exact TDC . I am soooo glad I checked before using it. I was skeptical about using it because it looked like the threaded part that goes in the cylinder seemed to wide. I got a milkshake straw (same diameter) and when I used that , the valve crushed it in more than half the thickness.
Don't think I will get to the car until after Xmas. Thanks again EV1. for your help. I am learning more about this as I go. I think I will be graduating from shade tree mechanics soon.(LOL) shaker455 is helping me thru texting. Great guy I will keep you posted. |
#57
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Quote:
Yeah, Jeff’s a good guy. He should be able to figure this thing out from a distance. |
#58
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I finally was able to get the car out today. Here are todays plug pics. Compression test.
My timing at idle (800rpm) is 11*. Timing all in @ 2800-3000 rpms was 32* I sent this info to shaker455 by text I hope all you guys have a great New Year, Dave |
#59
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Quote:
OOOPs forgot the pics. |
#60
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[QUOTE=dhcarguy;6397425]Having problems with pics.
OOOPs forgot the pics.[/QUOT try again. |
Reply |
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