Oxygenated fuel and cooler engine temps
08-07-2007, 12:29 PM
#1
Burning Brakes
Thread Starter
Oxygenated fuel and cooler engine temps
A couple of weeks ago, I had the 59 out for a drive with the outdoor temps hovering around 90 degrees. Our 59 was rebuilt back to the stock engine configuration, but with a 63 Vette aluminum intake and a Carter 3721 SB 4-barrel carb. I am also running a vac advance distributor with 12 degrees initial advance and all vac advance in by 3000 RPM. Dwell is 30 degrees with the stock coil. The cam is a stock hydraulic type for that engine and DeWitts aluminum radiator. The car runs cool with the Wells TU-5 temp sender sending a signal that keeps the temp gauge at around 180 degrees all of the time. This was verified with an IR gun.
When accelerating from a dead stop, my wife asked why the car was louder under acceleration, but not while cruising. A good question I couldn't answer. When we got home, I pulled a plug to check the tip for color on a hunch that maybe I was running too lean, thus causing the loud rasp from the off-road mufflers under acceleration. Reading the plug verified my hunch as the porcelain tip was white. Since I rebuilt the carb back to its stock configuration for use on the engine, I decided to play with some metering rods to fatten, err richen, the fuel delivery. WOW, what a wakeup!!! The engine responded immediately to the slimmer metering rods. I've left it for now as I have new metering jets on order from Jegs that I'm going to install and experiment with.
Our 62 has a 327 with 3721 SB, factory aluminum intake and the 097 cam with solid lifters. Similar timing as the 59, aluminum radiator and vac advance can. The car runs well, but it always ran somewhat hot, around 210 on the temp gauge. The IR gun verified it was running hot, but more around 200 degrees. Having messed with the metering rods on the 59 with positive results, I did the same experiment on the 62 and the results were dramatic. The engine felt like it had picked up more torque and smoother driveability. The temp gauge also responded by reading no higher than a tick over 180 degrees!!! I don't remember what size the main metering jets are in the Carter carb, but I will post to all when I finish this experiment.
I'm hoping that this experiment will help others who have to run oxygenated fuels (i.e. 10% ethanol added) which is causing our cars to run way too lean, and potentially causing some of the overheating issues. I don't pretend to have all of the answers, but richening up both carbs with slimmer metering rods, went a long way towards making the cars run better and cooler. I hope others will chime in if you've been down this path before me.
When accelerating from a dead stop, my wife asked why the car was louder under acceleration, but not while cruising. A good question I couldn't answer. When we got home, I pulled a plug to check the tip for color on a hunch that maybe I was running too lean, thus causing the loud rasp from the off-road mufflers under acceleration. Reading the plug verified my hunch as the porcelain tip was white. Since I rebuilt the carb back to its stock configuration for use on the engine, I decided to play with some metering rods to fatten, err richen, the fuel delivery. WOW, what a wakeup!!! The engine responded immediately to the slimmer metering rods. I've left it for now as I have new metering jets on order from Jegs that I'm going to install and experiment with.
Our 62 has a 327 with 3721 SB, factory aluminum intake and the 097 cam with solid lifters. Similar timing as the 59, aluminum radiator and vac advance can. The car runs well, but it always ran somewhat hot, around 210 on the temp gauge. The IR gun verified it was running hot, but more around 200 degrees. Having messed with the metering rods on the 59 with positive results, I did the same experiment on the 62 and the results were dramatic. The engine felt like it had picked up more torque and smoother driveability. The temp gauge also responded by reading no higher than a tick over 180 degrees!!! I don't remember what size the main metering jets are in the Carter carb, but I will post to all when I finish this experiment.
I'm hoping that this experiment will help others who have to run oxygenated fuels (i.e. 10% ethanol added) which is causing our cars to run way too lean, and potentially causing some of the overheating issues. I don't pretend to have all of the answers, but richening up both carbs with slimmer metering rods, went a long way towards making the cars run better and cooler. I hope others will chime in if you've been down this path before me.
08-14-2007, 08:47 PM
#2
Burning Brakes
Thread Starter
As an update to my original post, I have found that changing the jets and rods out in my AFB on the 62 from the original Carter #120-244 (.0995) jets to Edelbrock #1431 jets with a .107 size and using Edelbrock # 7347 metering rods is the trick with oxygenated fuel. I left the secondary jets alone with #120-176's in place. The changes to the primaries not only mellowed out the exhaust, but it made mid-range acceleration smooth and top end power wonderful. I've made the same change to our 59 with the stock 283 and I hope to check it out this weekend when it is cooler outside. Hope this helps. 
08-14-2007, 11:17 PM
#3
Melting Slicks
As an update to my original post, I have found that changing the jets and rods out in my AFB on the 62 from the original Carter #120-244 (.0995) jets to Edelbrock #1431 jets with a .107 size and using Edelbrock # 7347 metering rods is the trick with oxygenated fuel. I left the secondary jets alone with #120-176's in place. The changes to the primaries not only mellowed out the exhaust, but it made mid-range acceleration smooth and top end power wonderful. I've made the same change to our 59 with the stock 283 and I hope to check it out this weekend when it is cooler outside. Hope this helps.
Great Post. It is always nice to see that someone who had success when trying something on their car explained what they did, shared their results and explained what it did for them. Right now I don't have the problem you ran into. I can still get non-oxygenated fuel. But there are plenty of other states that you are not able to find it. In the future I may not be able to find non-oxygenated fuel and can go back on what your results showed. Thanks for posting.
Steve
08-16-2007, 07:20 AM
#4
Heel & Toe
Member Since: Sep 2004
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Here's some info I have found (with non-Vettes).
On my 911, I lost ponies on the dyno & went looking for "why". I have come to the conclusion it's the Ethanol vs. MTBE in the gas. IIRC, Ethanol is about 30% lower in energy capacity than gasoline. 10% Ethanol mix is 3% lower for that fuel.
I went from 204 wheel hp to 198 wheel hp in my example with the 911. Figuring starting with 240 crank hp & a 15% driveline loss, that's my 204.
240*.97 * .85 = 198.
Same thing happened with my Taurus SHO, down to 214 wheel hp from 221 wheel hp. 260 * .97 * .85 = 214.
Compensating with additional fuel is certainly a place to start.
Nice read, BTW.
On my 911, I lost ponies on the dyno & went looking for "why". I have come to the conclusion it's the Ethanol vs. MTBE in the gas. IIRC, Ethanol is about 30% lower in energy capacity than gasoline. 10% Ethanol mix is 3% lower for that fuel.
I went from 204 wheel hp to 198 wheel hp in my example with the 911. Figuring starting with 240 crank hp & a 15% driveline loss, that's my 204.
240*.97 * .85 = 198.
Same thing happened with my Taurus SHO, down to 214 wheel hp from 221 wheel hp. 260 * .97 * .85 = 214.
Compensating with additional fuel is certainly a place to start.
Nice read, BTW.
