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T-Series HIF4 Carbs, maniflow intake manifold, etc.

mgtildth

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I posted previously that I wasn't real happy with the fuel economy on my '72 GT. Yesterday I removed the #6 rich needles and put in the stock needle. I got great great mileage yesterday on a 60+ mile run. Car won't start now until the choke is pulled out. My problem is I get some pretty good popping coming out the exhaust when I take my foot off the pedal at high rpm's. I wondering if I'm too lean at high rpm? I may need to ditch the maniflow intake manifold and put the stock one back on. I will let the people on the list know in case anyone is interested in the maniflow. Cheers, N
 
Good to hear. I don't think the backfiring would be carb related tho', maybe ignition.

Let me know about the maniflow. I would be interested. Maybe I could trade you my stock intake as part of the deal.

mgupnorth@yahoo.com
 
What I think is happening is that the mixture is not rich enough at higher rpm's. When I pull the choke out on the freeway the popping stops. What I'm thinking about doing is getting a the Weber 38 DGES also called the "Outlaw" and getting a different cam. If that's the case I'll be selling the carbs, maniflow and K & N's. The HIF's are in good shape, but with #6 needles I don't think it ever ran properly. The car would fire right up in the morning with no choke. As you know HIF's had a fixed needle, they weren't supposed to be swaped out. I bought a conversion kit from Joe Curto that enables you to swap needles. The guy who did the work on swapping the needles did'nt do it correctly. The brass insert that goes into the piston was not flush with the hole in the piston. I don't know if this had anything to do with the car being rich upon start up. I would think that it would make it lean, being the needle would be deeper into the jet?? I'd really like to get a hotter cam, possibly keep the HIF4's and get correct needles. I will keep you informed. Cheers, N /ubbthreads/images/graemlins/nopity.gif
 
[ QUOTE ]
My problem is I get some pretty good popping coming out the exhaust when I take my foot off the pedal at high rpm's.

[/ QUOTE ]
This sort of popping is quite often related to air leaks in the exhaust system.
D
 
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