Hemi tuning issues

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hemifish69

Dain bramaged Hemi freak
Joined
Oct 25, 2005
Messages
163
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3
Location
Saint Louis
I have to admit, I'm not a master tuner, I'm lucky this obscenly expensive motor is holding together. I'm starting to wonder what I will find out when I finally get some sticky tires on it if the money situation ever loosens up. For example: I wanted this thing to survive on crap gas, so it's only got 9.5:1 compression. Too low? or ok? 850 demon carb, Is it too small? I know the 750 holley was, it had no power, and ran out of pedal above 3500 rpm. cam is a crane 520 lift and 292 duration, I degreed it to the cam card at 106. So it's 4 degrees advanced from straight up. Hydraulic lifters, mild bowl porting bronze guides, 2.25 primaries on the headers, 4" collectors. Seems that the engine wont run smooth unless it's under load, just tooling down the street, there's a slight instability I can feel in the seat of my pants until I mash it or go up a hill. and if it's any help, there is no hesitation when you mash it, but it smells slightly rich. Not enough backpressure? Probably the biggest unknown is the famous $35 intake. Vintage hemi piece that somebody took and made from dual inline fours to a single carb. Milled out EVERYTHING into one big rectangular hole, and capped with a steel plate. The indy cyl head rep said that was the thing to do back in the day. It will go eventually, But no money for that. That's probably the biggest reason for the slight instability at part power, uneven distribution. I really want to make another top plate for a six pack setup.Too many unknowns, A dyno run with an exhaust gas analyzation is probably the only way to go. One note though, riding shotgun while a friend of mine thrashed it, I almost got my hand pinched where the vent window meets the roof. Even with thickwall tubing subframe connectors and non grabby tires, this thing flexes! :-({|=ps it's a std bore 2001 block with eagle h-beam rods and a 4.15 stroker crank. This thing is so far from ever being able to get on a track. I got it this far, but I have no idea where to go from here.
 
Where to go? the parts store..get areal intkae..It's not even worth a dyno trip with that thing. I dont think your carb choice or compression is of for that cam..I dont think I would have advanced it tho. Demons can be a handful to tune..Always err to the lean side is all I can say really..The rest you need to work out after the intake is changed.
 
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