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472 sputters at WOT?? Help!

3K views 25 replies 10 participants last post by  bigblok86ranger 
#1 · (Edited)
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
 
#20 ·
Are you still only running 20 degrees total timing? It's never going to run right till you get the timing right. Set it at 30 total, with 76/84 jets, 4.5 primary power valve, plugged secondary power valve, and go from there.
 
#10 ·
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
 
#12 ·
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?
 
#18 ·
I ran my 86 gt with factory for cylinder radiator and cheepie electric fan and factory water pump in 110 weather and sitting in a traffic jam for over an hour never went over 195. So yes timing plays a very big role in engine temps.
 
#15 ·
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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#22 ·
Before you even attempt to set timing.make sure you find TDC with that adjustable timing pointer.If you don't,you will never know the correct timing. If you don't know how to find correct TDC,just ask and we will guide you through it. The correct timing will wake it up for sure.:)
 
#23 · (Edited)
ok everyone , i installed 78s and 84s set base timing at 12 and total was right around 30-31, it runs alot better and cooler to mention but im still having some sputter and i take my foot out of it beause right around the same time the secondaries open and it starts to sputter my oil pressure drop almost to zero! and it is consistant with rpm starts around 3200 and just drops. because of this i havent really been able to see how the motor runs above 3500- 4k. i am using a autometer electric gauge and sender on the back of the block 10-40 royal purple 6qts in a FMS swap pan. new oil pump w/ arp drive. the gauge is smooth and brand new when crusing under 3200 its ok, but even slowly depressing the accel pedal past that i see oil press flutter and drop???? any ideas??

oil pressure reads 75 cold , 30 warmed up and will raise up to 60-75 when accel up to 3200 and start to fall above that or drop to zero with a WOT
 
#24 ·
Ok. You probably have an electrical connection problem I'm guessing. Ground on the engine? Throttle linkage hitting the wiring harness? Alternator going haywire at a certain engine RPM? Wiring harness loose at the firewall connection? Broken wire that's moving? Have you got a rev limiter somewhere in the system? The fluctuating oil pressure indicates that you have a wiring problem with that, at least.
Check it out.
Rob
 
#26 ·
Hope that cures the problem, I had a similar oil pressure once and turned out my buddy has dropped my engine down a little to fast and caved the oil pan in. It sure didn't look like enough to do any harm but the oil pickup was to close the pan so I had to pound out the spot on the oil pan while it was off I welded some 1/4" feet on the pickup to prevent any further issues.
 
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