Percolating?
Thread Starter
Melting Slicks
Joined: Apr 2003
Posts: 2,823
Likes: 484
From: Florida
Percolating?
It's mid 90's out and I took the Vette out for a spin since it's been weeks since the last drive. It's usually hard to restart in this weather after sitting a SHORT while. I pulled 1/2 into the garage to set up some ramps, maybe 10 minutes, try to restart. I occasionally get a "detonation" sound when starting even when cold, it did that and then the usual "HOT" crank fine, no fire unless I pump the pedal. It starts up and I move into place. I pulled off the air cleaner cover to see if any gas comes out of the accelerator nozzles. I give the linkage a slight tap and they start sputtering out gas like it's got air in it and powered by an electric pump! I dried the area off and watched it a bit. You could tell it was still dripping out some gas occasionally. I've thought about making some aluminum shields for the bases of the 2300's since there's little/no room for phenolic spacers.
And about the starting detonating sound, anyone think that's what it is? I've got an MSD6 and gapped the plugs maybe 45 thousands. Maybe it's arcing somewhere and I need to back off on the gap? I've got 5 and 7 well separated. Thanks
And about the starting detonating sound, anyone think that's what it is? I've got an MSD6 and gapped the plugs maybe 45 thousands. Maybe it's arcing somewhere and I need to back off on the gap? I've got 5 and 7 well separated. Thanks
Le Mans Master
Joined: Mar 1999
Posts: 5,398
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From: Itasca IL
I find any Holley needs a little throttle angle to introduce air on hot start after hot soaking for even a minute. Even my old Caddies with Q-jets need it on hot days. After Abt 30 secs or so they are fine. I consider it normal operation. If u find phenolic spacers for a tripower I'd be interested too.
Team Owner
Joined: Aug 2007
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Army
Thread Starter
Melting Slicks
Joined: Apr 2003
Posts: 2,823
Likes: 484
From: Florida
I've seen 3/4" or 1" spacers for 2300's but that's too thick. http://www.holley.com/17-72.asp
Did they help? Where did you get you 1/4" or so material? I can get 1/4" paper or linen micarta or fiberglass/phenolic material from www.texasknife.com. I think I could fit a 1/4" spacer under the hood.
Thanks
Thanks
Le Mans Master
Joined: Jan 2005
Posts: 8,226
Likes: 2
From: Lake Wylie SC
Any time any part of the fuel delivery system reaches 140 degrees percolation becomes a given. Metal lines and metal fittings in regards to fuel temperature only serve to make things worse and should be covered with a heat resistant material
Electric fuel pumps can cause additional problems in this area because they will keep as large a supply of fuel as the system can hold right in the area where all the heat is produced. If the fuel is not being used fast enough it will continue to gain heat while it is sitting still.
Fuel systems that are designed to be able to move a lot of fuel also have return lines so that the fuel not being used is returned to the fuel tank.
Installing such a line in a C2 would be a lot of work and it should enter the tank at the top and then travel to the bottom before the fuel is dispersed back into the tank.
Doug
Electric fuel pumps can cause additional problems in this area because they will keep as large a supply of fuel as the system can hold right in the area where all the heat is produced. If the fuel is not being used fast enough it will continue to gain heat while it is sitting still.
Fuel systems that are designed to be able to move a lot of fuel also have return lines so that the fuel not being used is returned to the fuel tank.
Installing such a line in a C2 would be a lot of work and it should enter the tank at the top and then travel to the bottom before the fuel is dispersed back into the tank.
Doug
Melting Slicks
Joined: Apr 2008
Posts: 2,703
Likes: 167
From: Western Washington
Intermediate
Joined: Sep 2008
Posts: 43
Likes: 7
By the way you describe the way the fuel is coming out of the nozzles I would also check the carburetor bowl vent and make sure they are open. If fuel is boiling in the bowl with no vent, vapor pressure could build up and force fuel out the nozzles resulting in a over rich fuel condition.
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Army
I ordered 1/4" phenolic from McMaster: http://www.mcmaster.com/
Part Number: 85315K164 Grade XX Garolite Sheet Black, 1/4" Thick, 24" X 24"
It was about $35...could of got away with a smaller piece but I knew I would have to make a couple of 'throw away' prototypes before I got it right!!! 1/4" is plenty as phenolic has excellent heat dispersion properties...
These custom heat spacers lowered my carb bowl temperature dramatically.....I don't have 'before' I/R temp gun readings but the carb bowls are around 147 degrees now....way below percolation temp.
I also used some fiber washers under the carb to manifold nuts to reduce heat transfer still more..
I did NOT have to alter my stock height for carbs/intake...just took 1/2" or so off my air cleaner studs...
Part Number: 85315K164 Grade XX Garolite Sheet Black, 1/4" Thick, 24" X 24"
It was about $35...could of got away with a smaller piece but I knew I would have to make a couple of 'throw away' prototypes before I got it right!!! 1/4" is plenty as phenolic has excellent heat dispersion properties...
These custom heat spacers lowered my carb bowl temperature dramatically.....I don't have 'before' I/R temp gun readings but the carb bowls are around 147 degrees now....way below percolation temp.
I also used some fiber washers under the carb to manifold nuts to reduce heat transfer still more..
I did NOT have to alter my stock height for carbs/intake...just took 1/2" or so off my air cleaner studs...
Last edited by Frankie the Fink; Jul 13, 2009 at 01:40 PM.
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
that "detonation" sound you are getting when cold is too much initial timing .....check for a stuck or inoperative advance weights or faulty springs in the dizzy.....what is your initial timing?....good luck....
Thread Starter
Melting Slicks
Joined: Apr 2003
Posts: 2,823
Likes: 484
From: Florida
By the way you describe the way the fuel is coming out of the nozzles I would also check the carburetor bowl vent and make sure they are open. If fuel is boiling in the bowl with no vent, vapor pressure could build up and force fuel out the nozzles resulting in a over rich fuel condition.
I ordered 1/4" phenolic from McMaster: http://www.mcmaster.com/
Part Number: 85315K164 [FONT=Arial,Helvetica,Sans-serif][SIZE=2][COLOR=#333333][COLOR=#333333][FONT=Arial]Grade XX Garolite Sheet Black, 1/4" Thick, 24" X 24"
Part Number: 85315K164 [FONT=Arial,Helvetica,Sans-serif][SIZE=2][COLOR=#333333][COLOR=#333333][FONT=Arial]Grade XX Garolite Sheet Black, 1/4" Thick, 24" X 24"
I reworked my springs last year after determining the original heavy ones were limiting the centrifugal advance. Just as I did that the water pump went out then the gas tank needed replacing... and now I can't find all my notes. I need to verify which springs and all the timing specs now that it's running. I don't think it's too advanced since it doesn't hesitate even when warm. But I'll recheck it all. Thanks for the ideas.
Last edited by 6T7L71CPE; Jul 13, 2009 at 06:52 PM.
