Tuning a 5.7 Hemi with a Carb HELP ***

Uncle Don

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Hi

Ive been running a dual quad 6.1 with the MSD box for 8 years.

I’d like to examine your timing curves, both RPM and MAP.

I have a suspicion your MAP curve is not set up correctly and is pulling timing from your RPM curve.

I’ve added a pic of my timing curve - note there is nothing below the 0deg mark.

View attachment 1312611


I have conflicting advice on this one. I did have my MAP sensor plugged in, and another guy with Hemi and a carb said it is not needed, and not used because it can't do anything to a carb'd engine? with no computer to add or subtract fuel etc.. and a post above says similar that on carb'd engines it messes with the adjustments on the carb?? so i am not sure here whats right or wrong.? i uhooked mine and it made zero difference in how it ran i can attest to that.
 

Uncle Don

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I am puzzled as to why you installed a modern motor and vintage fuel system. I have a 5.7 with a mild cam, Hemi 6, convertor, 2.94 gears, 4150 style intake and a bolt on EFI. My desire was a OE looking highway cruiser that is maintenance free. I have used the factory tune and am tickled. It will break the tires loose and it loves the Interstate.
thought it would be cool, and no one around had done it in my area 7-8 years ago. i wanted to be the first....well now hindsight 20/20 wish i would have left it EFI. but when i win the lottery and down the road i want same set up as you yes. thats my final plan. or yank this and put a 383 with 727 in it and leave the hood closed lol.
 

Thrashingcows

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Never done anything with the modern Hemi's but I have had the wrong combo of parts that sure affected performance.

After reading through all the comments and replies first is that air intake hood on your carb....that thing is super restrictive and should be replaced with a big wide air cleaner....I think engine/carb height might be an issue though but they do make low profile air cleaners.

What are the specs on the cam....what RPM does it start building torque? You need to take that into consideration with transmission torque converter stall and rear gearing. I swapped a bigger cam into a 383 years ago thinking it would build more HP and performance...well the motor turned into a bog machine, wouldn't get up and go until I got the RPM up over 4000..then it would take off like a rocket!

What year is the 904 and does it have part throttle kick down? Also make sure your kick down linkage is set up properly.
 

furyus

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If you backed off the throttle pressure adjustment, and didn't make sure it was set properly, you will have a burned up trans as a reward. Fix the cable, and sort out the drivability before trying to do burnouts. Maybe watch some YouTube videos on carb tuning.
 

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