My car sat for many years and only had occasional starts and short drives. This past year I used it more and experienced vapor lock. Only happened after I had driven maybe 20-30 minutes. I have read somewhere on this forum that the alcohol blended fuel boils at a lower temp causing these cars to be prone to vapor lock. So while I am working on it this winter it might be a good time to do what I can to prevent vapor lock. The fuel lines are away from the block and the fuel log is offset from the block. I can easily insulate those, but I suspect the fuel actually boils in the carbs. Has anyone used the spacer blocks sold to isolate the carbs from heat? What have your experiences been with vapor lock and what did you do to cure it? Thanks.
Charlie D
Charlie, this has been beat to death on every auto enthusiast forum since Gore invented the internet. Need to differentiate between vapor lock and flooding due to fuel bowl peculation. With a dual quad FE and tube headers, under hood heat in traffic is an issue. My solution was, 1/2" thick phenolic spacers, and a race fan. Fan is ridged designed to move a LOT of air. Type intended for use in short track, modified cars.
Quote from: vtgt500 on January 19, 2019, 09:28:19 AM
Charlie, this has been beat to death on every auto enthusiast forum since Gore invented the internet. Need to differentiate between vapor lock and flooding due to fuel bowl peculation. With a dual quad FE and tube headers, under hood heat in traffic is an issue. My solution was, 1/2" thick phenolic spacers, and a race fan. Fan is ridged designed to move a LOT of air. Type intended for use in short track, modified cars.
To add to this excellent observation -don't forget the fuel log . The fuel log is bolted to the intake . The tabs bolted to the intake help turn the fuel in the fuel log into a boiling pot.The tabs are a conduit for heat from the block. I had some success by cutting the tabs off of the fuel log (only do this to a repro fuel log) and allowing the two rubber fuel lines and the metal fuel line hold the fuel line. The suspended fuel log was perfectly secured using this method.. The fuel pump is another source of heating the fuel . In some extreme cases the mechanical fuelpump is by passed by means of a electric fuel pump mounted in another location typically the trunk.Another location can be where the fuel line passes through the engine compartment apron. The pump is employed to completely isolate the fuel line from the hot engine block. You may have to use some or all of these suggestions .
Quote from: Bob Gaines on January 19, 2019, 10:45:27 AM
Quote from: vtgt500 on January 19, 2019, 09:28:19 AM
Charlie, this has been beat to death on every auto enthusiast forum since Gore invented the internet. Need to differentiate between vapor lock and flooding due to fuel bowl peculation. With a dual quad FE and tube headers, under hood heat in traffic is an issue. My solution was, 1/2" thick phenolic spacers, and a race fan. Fan is ridged designed to move a LOT of air. Type intended for use in short track, modified cars.
To add to this excellent observation -don't forget the fuel log . The fuel log is bolted to the intake . The tabs bolted to the intake help turn the fuel in the fuel log into a boiling pot.The tabs are a conduit for heat from the block. I had some success by cutting the tabs off of the fuel log (only do this to a repro fuel log) and allowing the two rubber fuel lines and the metal fuel line hold the fuel line. The suspended fuel log was perfectly secured using this method.. The fuel pump is another source of heating the fuel . In some extreme cases the mechanical fuelpump is by passed by means of a electric fuel pump mounted in another location typically the trunk.Another location can be where the fuel line passes through the engine compartment apron. The pump is employed to completely isolate the fuel line from the hot engine block. You may have to use some or all of these suggestions .
You can tell a repro fuel log from a genuine version by the way the taps are secured to the log. Repro tabs are welded across the top of the tab as it touches the log. Original fuel logs have the tabs spot welded to the log. You will not see the weld line on the top of the tab but will see two spot weld marks on the back side of the tab where it rolls over at the top and connects to the log.
Quote from: charlie D on January 19, 2019, 08:51:50 AM
My car sat for many years and only had occasional starts and short drives. This past year I used it more and experienced vapor lock. Only happened after I had driven maybe 20-30 minutes. I have read somewhere on this forum that the alcohol blended fuel boils at a lower temp causing these cars to be prone to vapor lock. So while I am working on it this winter it might be a good time to do what I can to prevent vapor lock. The fuel lines are away from the block and the fuel log is offset from the block. I can easily insulate those, but I suspect the fuel actually boils in the carbs. Has anyone used the spacer blocks sold to isolate the carbs from heat? What have your experiences been with vapor lock and what did you do to cure it? Thanks.
Charlie D
Look at the Mr Gasket 3710 heat shield kit. I used the two smaller heat shields sandwiched between a gasket on my old 427 2X4 Tunnelport powered Cobra kit car. Had issues similar to yours in the hot, high humidity, stop and go traffic of the northeast. Once I put the heat shields in, all of those issues went away. It really is that simple a solution.
Bill S.
I had the same issue on my 289 Shelby GT 350. Died a couple times in traffic on a car show/cruise-in. After it cooled off, started right up. I didn't add an extra cooling fan, just a spacer and new gaskets between spacer and carb and manifold. Solved the problem. I even got stuck in freeway traffic on the way home from SAAC convention in Indy a couple years ago. Temp gauge kept going up, but never stalled out. My fuel line from inner fender well to carb is a rubber line (not original, obviously) that doesn't clamp to engine anywhere, so no direct engine heat to fuel line.
Also, look for alcohol -free gas in your area. We have Casey's General Store chain that sells no alcohol premium.
There is no need for an electric fan. I will try and put you a list of products by part number together. I bought the Canton 1/4" spacers for the carbs and the 1/8" spacers for the fuel log. It insulates it for the most part from the intake. I also have the heater hoses running in close proximity to the fuel log. I used a portion of insulation at the rear where it comes up from the firewall and sits against the fuel log. That cured the issue. The only other item I am running is the 406/427 Canister fuel filter. I am in the Dallas area and it is well over 100 here during the summer.
-Keith
Anyone blocking off the EGR passage In the manifold?
Yes. I used the Fel Pro 1246 S3. They have a metal shim core. They block the manifold crossover and the metal core will assure they aren't burnt through like paper gaskets.
-Keith
Quote from: 1967 eight barrel on January 20, 2019, 06:52:40 AM
Yes. I used the Fel Pro 1246 S3. They have a metal shim core. They block the manifold crossover and the metal core will assure they aren't burnt through like paper gaskets.
-Keith
I like to block them too but it absolutely eliminates the possibility of driving the car under about 30 degrees. The carbs will ice up. You can run the car in the driveway, etc., but don't take it for a long ride. It's done until it warms up again.
Holley Sniper EFI system is the ultimate solution if you want to drive your car a lot in the summer heat. It will cold start like your daily driver, no more flooding/fuel smell after hot shut off, and a perfect air/fuel ratio all of the time. Plugs will never foul again.
https://www.holley.com/products/fuel_systems/fuel_injection/sniper_efi/sniper_4bbl_tbi_kits/
Bill beat me to the heatshield, as I had this on both my 428SCJ and the FFR race car. Get everything off the manifold, and the heat shield helps. Yes, does not look stock, but if you can't drive it, then what fun is it?
Other easy fix is the fuel pump. I bet you still have an old original, and they do get tired, check balls in the check valves no longer fit well. Replace.
Ultimate fix is a hidden electric pump out back.
Quote from: shelbydoug on January 20, 2019, 09:17:28 AM
Quote from: 1967 eight barrel on January 20, 2019, 06:52:40 AM
Yes. I used the Fel Pro 1246 S3. They have a metal shim core. They block the manifold crossover and the metal core will assure they aren't burnt through like paper gaskets.
-Keith
I like to block them too but it absolutely eliminates the possibility of driving the car under about 30 degrees. The carbs will ice up. You can run the car in the driveway, etc., but don't take it for a long ride. It's done until it warms up again.
You're in Hell....... I mean New York. I just got out of Ithica. Too cold to close them off if you want to drive the vehicle fall to early spring. I froze my arse off.
Quote from: 1967 eight barrel on January 21, 2019, 12:25:22 AM
Quote from: shelbydoug on January 20, 2019, 09:17:28 AM
Quote from: 1967 eight barrel on January 20, 2019, 06:52:40 AM
Yes. I used the Fel Pro 1246 S3. They have a metal shim core. They block the manifold crossover and the metal core will assure they aren't burnt through like paper gaskets.
-Keith
I like to block them too but it absolutely eliminates the possibility of driving the car under about 30 degrees. The carbs will ice up. You can run the car in the driveway, etc., but don't take it for a long ride. It's done until it warms up again.
You're in Hell....... I mean New York. I just got out of Ithica. Too cold to close them off if you want to drive the vehicle fall to early spring. I froze my arse off.
Well, it won't overheat. 8)
Thanks, great conversation guys. I will be doing the carb spacers and isolate the fuel log as well. Seems as though that worked for Kieth in 100 degree Texas, so it should do me OK in 98 degree Maryland. Why didn't I think to check the mechanical fuel pump, good idea! I do have an electric fuel pump that I originally switched from the dash, but moved it to a micro switch on the carb linkage so it only kicks in at full throttle. Not much help in that configuration for vapor lock. I will move it back to the dash. Thought about changing the whole induction system, but even though I am not into strict restoration/preservation, to me the dual quads are part of the character of the 67 GT500. If I were to do anything there, it would be to save the original system for the next owner and install a more modern, maybe smaller CFM, dual quad set up.
Hey Keith, if you can find those part numbers, it would be a big help.
Thanks again to all,
Charlie D
Quote from: 69 GT350 Vert on January 20, 2019, 11:28:57 AM
Holley Sniper EFI system is the ultimate solution if you want to drive your car a lot in the summer heat. It will cold start like your daily driver, no more flooding/fuel smell after hot shut off, and a perfect air/fuel ratio all of the time. Plugs will never foul again.
https://www.holley.com/products/fuel_systems/fuel_injection/sniper_efi/sniper_4bbl_tbi_kits/
One item that seems was never dealt with well on the '67 GT500 in particular is isolating the carbs from the engine heat. What happens is when you shut off a hot engine, (a normal operating temperature) heat will rise out of the engine, through the intake manifold and into the carbs. What it can do is make the fuel in the bowls boil and peculate like in a coffee pot.
In severe cases this will push the fuel up and out of the vents and into the intake manifold. There's your flooding.
The intake, then the carbs will act as heat risers. Weber carbs are great for this but the fix is really simple. What you need is just an 1/8"thick asbestos carb gasket. If you can get phenolitic isolators that will work too. You are trying to reduce the heat sink effect into the carbs. You can't eliminate that.
This perculating scenario, also affects the floats and the inlet valves. The pressure on the floats due to the rising lift created by the boiling fuel can jamb the inlet valves closed. Right there, that's your "vapor lock". It is only temporary or even momentary. Fuel pressure will push them open eventually. Look no further for the vapor lock. That's it right there.
That's how you get "vapor lock" and engine flooding simultaneously.
Just isolate the carbs. That's generally enough and will stop fuel from leaking out of the throttle shafts also. That's all there is to it.
You might want to think about isolating the fuel log tabs from the intake manifold also with phenoletic flat washers.
FE's in Mustang's and Cougar chassis' are particularly susceptible to this phenomenon because of the close quarters of the engine to the chassis. Small blocks are probably about 95% less susceptible to it.
My Pontiac 389 with the Carter AFB on it was the only other car I can think of that had this problem. I was 16 and no one ever heard of this kind of an issue back then. I wish I knew this back then 'cause that engine caught fire as a result on a hot attempted restart.
I don't feel too bad about it though. Even Inglese had to learn this when he saw the gas running out of the hood scoop and down the front of the hood on his 427 Cobra from the Webers! Easy fix though...if there's no fire? Just isolate the carbs. ;D
I'll bet 'ya a nickle that this is the cause of 95% of carb fires? :o
Could a person find a asbestos gasket today?
Quote from: 2112 on January 21, 2019, 03:13:20 PM
Could a person find a asbestos gasket today?
I have them for the Weber carbs but that term is not used. I don't know what the substitute is but is likely of ceramic content like ceramic coatings on headers. A man made concoction no doubt superior and safer.
You want to search for "phenolitic gaskets". Coming from me, that's likely spelled wrong. ;)
Charlie: I bought them from Summit with the exception of the AMK kit. You have to change the carburetor studs too. I used the AMK kit nuts on the Edelbrock stud kit. The carburetor stud side is 5/16 NF thread and 7/16 nuts instead of the 1/2" nut that is supplied by Edelbrock.
1. 2 X Canton Spacer 85-154 .250 Phenolic .
2. 2 X Edelbrock stud kit 8024 1.750. (Put the nuts and the washers your hardware drawer.)
3. 4 X Fel Pro SFL1901 base gaskets. ( 2 per carburetor. Each side of the spacer)
4. AMK 3475 2X4 special nut and stud kit.
-Keith
Kieth, thanks for the part numbers.
You don't need to go crazy with the spacers. The thinnest one I can find for the Holley's so far is 1/4". Here's a picture of the Canton 85-154.
https://www.summitracing.com/parts/ctr-85-154
The 85-154 is .250. That's 1/4" I don't recommend anymore than that because of air cleaner variances and hood interference. It'll stop the fuel bowl boil.
-Keith
Quote from: 1967 eight barrel on January 22, 2019, 03:23:09 PM
The 85-154 is .250. That's 1/4" I don't recommend anymore than that because of air cleaner variances and hood interference. It'll stop the fuel bowl boil.
-Keith
I'd like to find thinner but so far no good. The ones for the Webers are basically thick gaskets and work fine.
I agree. Thicker then 1/4" and you are too close to the hood.
A few years ago I noticed that a Pro Stock racer that I knew was using plywood spacers. Apparently that is common place in drag racing now?
It's got a better thermal transfer rate then the polymers do.
Holley offers a heat isolating gasket. It's part # 20-130. It retails at around $9 each. It's black and 1/4" thick.
Phenolic is a rather generic term. Includes laminates made from paper, canvas, linen, and glass weaves bonded by a thermoset resin. All work well as a thermal insulator. However, the canvas and linen product have good strength, preferred machinability, and reasonably good fuel resistance. Wood or plywood is a foolish idea. Porous, warps, can not be machined flat enough for a reliable sealing surface, and it only used because it's cheap, and car hobbyist are generally pretty stupid.
Quote from: vtgt500 on January 25, 2019, 08:43:24 AM
Phenolic is a rather generic term. Includes laminates made from paper, canvas, linen, and glass weaves bonded by an epoxy resin. All work well as a thermal insulator. However, the canvas and linen product have good strength, preferred machinability, and reasonably good fuel resistance. Wood or plywood is a foolish idea. Porous, warps, can not be machined flat enough for a reliable sealing surface, and it only used because it's cheap, and car hobbyist are generally pretty stupid.
I've used both the fabric and the hard epoxy versions. Neither is a perfect beast but my preferences are for the black fabric one. I've broken corners off of the epoxy units. They tend to be a little fragile.
None are going to give you 100% heat isolation.
The original factory configuration provided for no heat isolation so anything you do is going to seem 100% better.
PROBABLY any car will benefit for using some sort of heat shield? I remember using the GM Z28 heat shield for a while as well on a single 4v application. That one tends to be more of cosmetic device and causes issues due to limiting access to the intake manifold itself. Those are an aluminum plate with a thick gasket on the top and bottom.
Holley sells a generic version, Holley 108-70
There are generic "epoxy" versions of them that I suspect are going to get broken sooner or later since that material doesn't bend well and cantilevers over the intake.
This is great information! I have yet to start my MR 427, but will apply what you guys mention in this thread.
Question - All else being the same (motor mount etc.,) does anyone know if the 427 w/MR intake is the same height as the factory 428 PI with dual quads?
Before buying the gaskets/spacers, I want to make sure the wing nuts holding the air lid do not punch through the hood!
Thanks
Ron
Pic with the 427 lid, but I plan to replace it with the cobra element.
The '67 Shelby GT500 C7ZX dual quad intake is a medium riser intake. I'd recommend that you measure the clearance by using a compressible material like play doh.
The C7ZX-9425A is a 427 MR intake. The air cleaner clears the hood with plenty to spare with the .250 spacers I used and recommend. No more hard hot start ups and it's not boiling over into the vents and dripping onto the butterflies. I am thinking about having the spacers machined to the profile of the carb base on the intake instead of leaving them in the Holley square bore base profile. It will make them less noticeable. I have a relatively "hot" motor. It is always under 200 degrees. So no issue with over heating. Another point of interest is the fact that I had no issue with the fuel percolating with VP racing fuel. When I started using the 50/50 mix with pump 93 and VP 110 the issue started. So I am an in agreement that it has everything to do with the alcohol in the pump fuels.
-Keith
Quote from: shelbydoug on January 24, 2019, 09:37:28 PM
Holley offers a heat isolating gasket. It's part # 20-130. It retails at around $9 each. It's black and 1/4" thick.
https://www.ebay.com/itm/Holley-Insulator-Base-Flange-Gasket-Also-Avenger-B-G-Demon-AED-QFT-Carbs/292540785836?epid=1017853711&hash=item441cca24ac:g:65kAAOSwRMRYTbWU
Yes,Holley has those. They are about .200 thick. They'll stick out like a sore thumb. It's why I elected not to use them. I looked at them over at Summit.
-Keith
Quote from: 69 GT350 Vert on January 20, 2019, 11:28:57 AM
Holley Sniper EFI system is the ultimate solution if you want to drive your car a lot in the summer heat. It will cold start like your daily driver, no more flooding/fuel smell after hot shut off, and a perfect air/fuel ratio all of the time. Plugs will never foul again.
https://www.holley.com/products/fuel_systems/fuel_injection/sniper_efi/sniper_4bbl_tbi_kits/
I like the idea of an efi but if it requires drilling into the body that is a non starter for me. Is there a way around drilling holes?
Quote from: 1967 eight barrel on January 27, 2019, 12:22:06 AM
Yes,Holley has those. They are about .200 thick. They'll stick out like a sore thumb. It's why I elected not to use them. I looked at them over at Summit.
-Keith
And a piece of orange plastic doesn't? The Holley gasket looks just like a thick carb gasket, which is what it is.
Anything that varies from original here is going to be noticed.
The real solution would be to have the throttle plate made of phenolic material like the Carter Thermoquads had.
The spacer is not orange on the sides, Just the gasket surfaces. The sides are milled and more of a light gray and tan color.
As for EFI, you would have to change the tank, run wiring for the injection harness through the firewall, modify the fuel lines. I am unwilling to start hacking a factory tach harness up. Not particularly practical for dual quad applications if you're trying to do a stealth installation. The '67 Shelby just loses the "wow" factor when you remove the dual carbs. A good tuner can get just as much out of them as FI as well. Finding a Holley Guru is getting more difficult all the time.
-Keith
Quote from: 1967 eight barrel on January 27, 2019, 05:22:26 PM
The spacer is not orange on the sides, Just the gasket surfaces. The sides are milled and more of a light gray and tan color.
As for EFI, you would have to change the tank, run wiring for the injection harness through the firewall, modify the fuel lines. I am unwilling to start hacking a factory tach harness up. Not particularly practical for dual quad applications if you're trying to do a stealth installation. The '67 Shelby just loses the "wow" factor when you remove the dual carbs. A good tuner can get just as much out of them as FI as well. Finding a Holley Guru is getting more difficult all the time.
-Keith
I vote black. Grey is a designer color.
67 GT500's need big ugly Holleys. Once you get over the leaks, the flooding, the paranoia, you'll love 'em. NOTHING is quite like a 2x4 set up. Just the sound of the WHOMP when the secondaries open is worth it.
I've got Webers on my Pantera but the 500 swindled me into another set of 2x4 Holley's on a Trans-Am manifold on my 68 GT350. I think I'm a sick puppy? :(
As far as EFI, in the case of the Weber IDA's Borla actually makes one that looks exactly like the carbs. No one has done that yet with a Holley carb. Maybe some day?
They look just like Weber 48 IDA's right?