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Author Topic:   Blue flame
Blackgold
Dirt Full Roller

Total posts: 71
posted November 19, 2004 12:28 PM  
We run a 355 in a bomber and it blows a blue flame most of the length of the straights. Lots on the right side and some on the left. Running about 11.5 compression, Double humps with the 1.94-1.5 valves on a MW #8 cam. Have to run the Roch 2 bbl and had it jetted at 70. Tried going up to 74 jets and it didn't seem to make any difference. Didn't notice the blue flame until we put on this carb. It has been redone for racing and has the stock 1 11/16 throttle bore and 1 3/8 venturi. Holley jets. Not for sure what else has been done other than smmothing up and rounding off some of the sharp bend inside. Engine seems to run a little warmer with this carb than it did with the stock big bore carb we had before. Seems to pull good and throttle response is good, just concerned as to why we have the bright blue flame. It's blue like the flame in a propane stove. Are we possibly running too rich. The plugs are just a tan to light gray tint. Thanks for any help.

andykmod
Dirt Freak

Total posts: 351
posted November 19, 2004 02:17 PM  
You said it runs warmer,Sounds lean to me.Add some jet also check to make sure your headers are not cracked or leaking up by the gaskets sucking in air.my2cents

donslink1
Dirt Freak

Total posts: 318
posted November 19, 2004 03:31 PM  
Andykmods two cents hit it right on the head I think. We where running a 69 - 70 jet in the stock car with stock everything. We ran 80 - 82 with dart heads and worked carb. It doesnt idle to good but it wont lean out on the straights. Andy, Didnt think you came on there anymore.

Blackgold
Dirt Full Roller

Total posts: 71
posted November 19, 2004 06:54 PM  
We had a guy at the track who thought we were running lean, so we went up to 74s and really couldn't tell any difference. Is it common to go up to the 80s with the Roch 2 bbl.? I've never gone larger than the 74s, even on my 406. We're topping out at 63-6500 rpm with the 355 and that's about where we need to be with the gearing we run.

andykmod
Dirt Freak

Total posts: 351
posted November 19, 2004 09:32 PM  
What ignition timing are you running,maybe to much timing for air-fuel mixture with the smaller bore carb?????????You said it has good throttle response is that off idle or under racing conditions.Donslink is right my carb never idled good and would loaded up while at idle.But had awsome throttle response under race conditions.

Blackgold
Dirt Full Roller

Total posts: 71
posted November 19, 2004 09:46 PM  
We're timed at34-36 degrees. It loads up a little at low rpm but seems OK at racing speeds from starts and restarts on up.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted November 19, 2004 10:17 PM  
My openwheel done that about two years ago. Ended up that the heads had a small crack in them causing an internal vaccum leak and therefore making the engine run lean.

So check for vaccumm leaks, see what your vac. gauge does at idle.

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