472 sputters at WOT?? Help!

[92stango]

hey everyone , just got my fox back on the road but having a issue at WOT the engine sputters and oil pressure guage needle starts to fluctuate rapidly but smooths out as soon as i just start to cruise, i believe it starts right as the secondaries open, could i been leaning out? this will also happen in P just reving the engine. a little info on combo, 460 .060 over, flattops, h beams, d3 heads, weind stealth, fms roller rockers, hooker headers,comp xe-284 cam and BG mighty demon 850 mech sec. around 10-1 i bought the carb off a guy that had it on a SBF so i dont know if he rejetted it for his application , but what jets should i start with as a base line for a bbf?? any carb adjustment tips>? thanks

[crittersf1]

What's your advance doing?

[92stango]

i have a msd billit dizzy and 6Al box, base is set at 0 and it locks out about 20. as i rev up to 4k. also it has silver advance springs

[A70Maverick]

Set base at 12-14 and try it with 32-34 total. Jets in carb without a power valve in secondary around 80-84ish to start I would think...

[92stango]

ok update i pulled the jets and the primaries had 85s and the secondaries had 93s. primaries have power valve. is this about right for this set up ? or will i need to start changing them out ?

[White Lightning]

Originally Posted by 92stango

ok update i pulled the jets and the primaries had 85s and the secondaries had 93s. primaries have power valve. is this about right for this set up ? or will i need to start changing them out ?

See post #4
Rob

[92stango]

i will be doing just as a70 recomended, i was just curious about the primary jetting as well since im in there, based on how this engine is responding is it a lack of timing and to much fuel? sorry for the newb questions!! first carbed big block

[White Lightning]

Originally Posted by 92stango

i will be doing just as a70 recomended, i was just curious about the primary jetting as well since im in there, based on how this engine is responding is it a lack of timing and to much fuel? sorry for the newb questions!! first carbed big block

Yes and yes. The primary's should be in the high 70's and the secondaries with a power valve should be there or in the low 80's IIRC. Is this a square bore double pumper?
Rob

[92stango]

yea Rob it is a square bore double pumper, with a power valve in the primaries but NO power valve in the secondaries

[White Lightning]

Originally Posted by 92stango

yea Rob it is a square bore double pumper, with a power valve in the primaries but NO power valve in the secondaries

OK, then my recommendation would be to start with 78's in the primary's and 82's in the secondaries. Set your timing as recommended, adjust your idle speed down to about 850 or so, adjust the idle mixture screws for best idle and best manifold vacuum then set the idle speed back up to about 850 in drive if you're using a stock converter and an automatic, or where ever the car just creeps forward in drive when you take your foot off the brake. Make a note on your manifold vacuum. Pull the primary bowl off and the number of the power valve should be 1/2 of your vacuum reading. Start off with clean plugs and warm up the engine to operating temp. Shut it off and pull the plugs and read them. You're looking for a nice golden brown color. If it seems to run good take it out and drive it and note any drivabilty problems and read the plugs again.
Rob

[bigblok86ranger]

Honestly surprised you don't have over heating issues with 0 initial and 20 degrees total!

[92stango]

thanks rob for the advice i will start with the jets you and A70 recomended as well as the advance in timing ill check the power valve as well! and big block ranger i have noticed the car running hot, with a huge 3 core alum rad and 160 tstat , markviii fan its touching 210+ cruising in 80 degree temps, not enough advance will cause it to run hott?

[92stango]

i am also using a FMS timing pointer which seems to be adjustable , you can loosen the scrws and move it , possibly i have it set wrong ill turn the motor over to tdc #1 and check to see if it is off!

[68xr7cat]

Having the ign. retarded will delay the burning of the A/F and it will be still burning going out the exhaust port. Instead of the heat going into making pressure to push the piston down and do work, it will go into the cooling system and exhaust.

[Dman64]

I run 205 to 210 and I have a brand new fan clutch, factory fan and super camper special rad which has been re-cored, I do run a180* stat which is a high flow unit. I don't think that temp is too hot.


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