> Thanks, Jim, you are right. It came up because I was talking to 'my
> expert" about doing a dynometer tune. He has always been considered to
> be a real carb Guru around here and last year he purchased a very nice
> dyno. My car is pretty much 'sorted' as far as the carburetor goes but
> I thought it would make sense to go all the way and find out exactly
> what is going on. He will be able to run it at various speeds and set
> the carb based on actually HP and emissions testing.
>
> So anyway, he did mention the air cleaner issue. He suggested that even
> a 10" or smaller with more height might be better.
CarCraft did some work on a SB chevy and found no restriction or power
changes from a 14 x 6" cleaner down to a single 6 x 2". The difference is
how dirty it can get before it starts to matter. Sure it would be great to
have more clearance but considering how little air these engines need and
how much the carbs can flow I don't think you would ever see anything. IMO
the best thing you can do is to put a spacer under the carb to keep
everything cooler. Do some research, but I think phenolic resin is the most
insulating. You and I have the same filter base I think, and I have more
than 1" above it to my C bonnet. I personally would rather have a carb
spacer than a taller air cleaner.
I don't know the relationship between fuel temp and power, but inlet air
temp reduction of 20deg is worth 1% HP increase. You might also want to
make sure you are getting enough cool fresh air into the engine compartment
to help keep everything cool during driving. Obviously if you let too much
through you will start overheating, but some cool air is good.
>
> Another thing he mentioned (because of my questioning). My car is
> harder to start after sitting in the heat, say, 20 minutes after
> shutdown. I've always suspected it is the fuel is expanding (and
> boiling and vaporizing) because of the heat, causing the car to flood.
> His pretty much agreed with this, his comment was lengthy, but here are
> the highlights. 1) move to sea level (more atmospheric pressure) 2) use
> an insulator between the manifold and carb 3) use the middle grade fuel
> (has less alcohol and/or MTBE than regular or premium) 3) add a lead
> additive (density of fuel goes up) 4) add kerosene or #1 diesel (same as
> #3). He would of course check float levels, etc to eliminate those type
> things as the culprit but really was saying that's typical of a
> carbureted engine, with modern fuel, at 5000 feet, in the summer.
If we assume the problem is in the carb you already know how to fix it. The
percolation vents are visible with the cleaner removed. If the carb is
boiling over then you will see it bubbling out these vents. When mine hit
240 that first run it boiled after shutdown but has never done so since.
Another thing could be vaporlock in the lines themselves. It is probably
worth your time to insulate the lines in the engine compartment. If you
want some of that insulation I have been using, I can spare more than you
would need. Lastly, since I think you are running a charcoal canister, if
that is shot it will cause the problems you are experiencing but often
coupled with a hot idle problem.
Am I babbling?
>
> I'll keep ya posted!
Please do
>
> Larry
>
James
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