Weber 40IDA question 914-6 race car

jhynesrockmtn · 01-02-2020, 04:23 PM

Hi, I am in the process of freshening a 914-6 tribute race car that has been sitting for quite some time and not stored properly. The motor as built by GD racing in San Bruno CA many years ago and has little time on it according to the mechanic who built the car and ran it in PCA solo a few times. The motor is a 2.4 liter and running Weber 40 IDA's. I pulled the carbs to go through them and they are sorely in need of cleaning and a rebuild kit.

The float chambers have an aluminum baffle that has been secured with some type of epoxy that was breaking down. I removed them to clean. Should I refit them or try running the car without? If I do put them back in what should I use to secure them that won't break down and gum up the carbs?

This will be a race car. I'm tempted to pull them and run them without and see how the car does but wanted to see if anyone has other thoughts.

stownsen914 · 01-02-2020, 07:26 PM

The baffles were a common mod for Webers to address fuel starvation due to sloshing in the float chambers during cornering. I haven't raced a 911 with Webers so can't comment on whether it's still considered important to have the baffles.

1QuickS · 01-02-2020, 07:49 PM

Baffle plates are required for a car that will generate 1G+ lateral acceleration in turns that have some duration. The main jets will starve for fuel on one bank so fuel starvation occurs when you transition from the turn & begin to accelerate. Difficult to thoroughly clean float bowls below the baffle plates. JB Weld epoxy is not fuel resistant enough. Dow Corning 731 is good, so is Devcon Titanium epoxy...both are expensive.

jmz · jmz's Garage

and the man has spoken, you have your answer.

jhynesrockmtn · 01-03-2020, 06:11 AM

Quote:

Originally Posted by 1QuickS

Baffle plates are required for a car that will generate 1G+ lateral acceleration in turns that have some duration. The main jets will starve for fuel on one bank so fuel starvation occurs when you transition from the turn & begin to accelerate. Difficult to thoroughly clean float bowls below the baffle plates. JB Weld epoxy is not fuel resistant enough. Dow Corning 731 is good, so is Devcon Titanium epoxy...both are expensive.

Thank you. I see Devcon putty when searching, no Dow 731. To your point about removing these for cleaning, if I use something like the Devcon will I ever get them out? Any recommendation on where to purchase?

stownsen914 · 01-03-2020, 10:55 AM

Do PMO carbs need the baffles in a racecar? That might explain an issue I've been having ...

Trackrash · Trackrash's Garage

FWIW. Yes, you need those baffles in Webers. IMO the ethanol in modern gas eats the epoxy. I had the same problem.

However, I found that the baffles work fine with out any epoxy. I cleaned out the gunk like you have and replaced the baffles with no sealant and have had good luck on the track and at auto crosses. My baffles are wedged in tightly enough to not move around on their own.

jhynesrockmtn · 01-03-2020, 11:35 AM

Quote:

Originally Posted by Trackrash

FWIW. Yes, you need those baffles in Webers. IMO the ethanol in modern gas eats the epoxy. I had the same problem.

However, I found that the baffles work fine with out any epoxy. I cleaned out the gunk like you have and replaced the baffles with no sealant and have had good luck on the track and at auto crosses. My baffles are wedged in tightly enough to not move around on their own.

This car will never see ethanol again so there is that. I'll see how tight they fit.

1QuickS · 01-03-2020, 10:20 PM

Ti epoxy is good with ethanol but typical metal-filled epoxies are not so good. I tested JB Weld, Devcon Plastic Steel epoxy & Ti epoxy and also conferred with Devcon tech engineer and the baffles on my car with the TI epoxy showed long term resistance to ethanol. Unfortunately the Devcon Ti epoxy is $140 per pound. The Dow Corning is not readily available and is more like a caulk that does not harden. Jerry Woods uses the Dow product for Weber baffles. Wedging is a good plan, I like the thought of that. Make the plates from 0.020" thick aluminum or similar and adjust until they fit tightly and must be deformed downward to install. This should keep them in place quite effectively. Start with cardboard to construct prototype plates and cut aluminum plates when satisfied. PMOs have a narrow passageway between the emulsion wells so fuel transfer is not as rapid as in Webers. They also pick up fuel from a more central location in the float bowl than the Webers.

Cleaning under the baffle plates might be adequate using carb cleaner with an extension tube. You can also remove the main jet carriers and squirt through there which will bounce off the underside of the baffle plates & spray down onto the floor of the float well.

McMaster-Carr is your friend for most things mechanical.