MG Motorsports Forum

I am going to ask this here because you racer-guys fab-up, I think, better stuff than we road car drivers do. (I have recently found myself in the middle of a long cup-holder thread on the other side because I forgot to uncheck the box )

I have a pretty modified engine, 1924cc 18GB, and the car has really told me that he doesn't like to be sitting still or before too long, a series of red lights, traffic jam, etc, I will begin to get really troublesome fuel delivery problems. Surging, RPMs falling away, general disgruntledness. I think that it's heat soak into the carbs and fuel lines. Running down the road, I have no issues and his peevishness goes away once I get enough air coming in the front to lower the engine compartment temps a bit. By the way, I have a good, new heat shield under the SU4s. Even has the cloth stuff intact. Just seems like there is nowhere for the heat to go in a sealed up engine compartment.

I have an e-fan on the radiator and my coolant temps never get bad on even the hottest days. I am looking for some thoughts on how to clear the heat out of the engine compartment, and off the carbs (and maybe the fuel lines) when the going gets slow.

I think I remember some people cutting vent holes in the wheel arches. Some have had louvers cut into the bonnet (I don't think so!). Some have insulated the fuel bowls with aluminum foil. Some have insulated the fuel lines. Air ducts in the valance? What do you think is the best method?

Thanks all!

D.

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Douglas Tourtelot
Seattle, WA

"Every education has a tuition"

For starters Doug, what cam, and what idle speed are you running? Oh, and what needle in your carbs at what jet height ?

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

One option, depending on what carbs and fuel pump you use, is to run a return line.

Hap- I have an early stock cam, my idle is around 900RPM, and AAX needles in my carbs. I am loath to upend driving performance to cure this problem (see my excellent dyno runs in a thread on the other side) so this may turn into a moot question.

What is a return line Greg?

D.

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Douglas Tourtelot
Seattle, WA

"Every education has a tuition"

maybe a bilge blower. http://mgaguru.com/mgtech/carbs/cb208b.htm

Just for fun, try leaning your fuel mixture up a tad and see if the issue lessens.

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

Which carbs, HIF or HS?

Hi Hap. I am really happy with my running tune. Easy cruise at 4k, AFR of 14. Goes nicely rich on WOT to about 12. Idles at 13. Almost perfectly straight line on hard acceleration at about 12 on he dyno 2k to red line. This is only a problem when the car is sitting still so maybe a simple pull of the choke will be enough.

Dave, I'm running HS4s.

I like the bilge blower idea, but I will have to puzzle out how to duct it on my car. I will look into that; perhaps a brake duct inlet cut into the valence and a length of corrugated pipe.

Thanks for all the ideas.

D.

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Douglas Tourtelot
Seattle, WA

"Every education has a tuition"

Does it do all this sitting still with the bonnet open?

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.

Hi Adrian. I am not sure, but it would be a good test. I just have to figure out how to check it. It will be a lot easier when the weather gets hotter but I will let you know.

D.

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Douglas Tourtelot
Seattle, WA

"Every education has a tuition"

We have overcome many Motor heating problems by managing airflow through the engine compartment. If you are running an electric radiator fan only, fit a factory plastic engine fan ; might move more air over the engine , past the transmission.




Good Luck,

NitroRich

Doug, you're running rich.
Stoich at idle, 13:1 at WOT is the goal.

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jeff@advanceddistributors.com

Hi Jeff-

This is certainly possible. I have had an on-going battle for as long as I have owned this car to make it lean enough at idle and still rich enough at speed. I have an AFR dial in the car so I am pretty aware of the car's tendencies. And in fact, I have been tuning a tad richer recently, a flat at a time, because it wants to run lean at highway speeds. I am up pretty close to the bridges on my HS4s, maybe .035, which seems high but I can't for the life of me reverse the trend and get a lean idle and a richer running tune. We are talking fine tune, I think. The range of the whole shebang probably sits between 12 and 15, but simply reversed from the way I'd like. I have been rolling needles and currently run AAX. I have a set of ADX needles which go very rich in the middle of the curve, and may install them hoping, perhaps to be able to tune my idle rich and still get 13 or so at cruise dropping to mid 12 on hard acceleration.

Now I am guessing that there is some other factor that is causing me AFRs in reverse of what I want, and that putting exotic needles in my carbs is probably not the "fix." But I have discussed that problem here on the forums, Motorsports and MGB, with my mechanic, with other mechanics, with some local racers, with Joe Curto and with my cat and I have heard nothing that points me in the correct direction.

So I am not sure where to go from here (Webers ?). If you have any thoughts on this, please feel free to post them here for all to see, or PM me if an extended conversation is in order. I know that there is a way, I just haven't found it yet.

Thanks for all you help in general (dizzy stuff) and for this in particular.

D.

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Douglas Tourtelot
Seattle, WA

"Every education has a tuition"

Take one ounce out of the spring tension on your air pistons. This will lean the entire rev range just a tad. Should give you 14:1 idle, 15:1 cruise and 13:1 WOT. (if I read your current fuel ratios correctly)

Adrian

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Home built Eaton M62 Supercharger with 8psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, custom ground high ratio "stock" rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.

Remember a 02 sensor is further down the exhaust trail and exhaust temp drops pretty rapidly as they travel the length of the exhaust system. I run my race engine at 1300 EGT at WOT, and then have O2 just beyond the header collector and with 1300 EGTs I see 12.5 on the 02 at WOT.

I always tell folks too much advanced timing and a lean fuel mixture may make for better numbers on the dyno in a 10 second pull, but in the long run it could cause you trouble.

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com