I have the gm ht383. The car seems lazy no matter what I do. I have a 650 Holley dp that's been tuned. Timing is 12 initial 33 total all in by 2500 rpm. Just think the motor is choking with my 2055 headers. There is no cat and I have a three inch gale banks exhaust. Is it possible the exhaust is holding back the motor?
Rear is 3:73 gears and turbo 350 tranny with 2 k stall

 

idk for sure,but sounds like u may need more carb. Perhaps a 750 double pumper. Where does it seem lazy? down low? with a small exhaust a car will have lots of low end torque but may suffer up higher in the rpms. It wont feel lazy off the line,thats for sure.

 

Definitely down low. Won't spin the tires. Also when I get on it the car goes but a slow pace. I read something on watching the vacuum gauge to see if the exhaust is not breathing correctly. Anyone know this theory?

 

if you had a smaller diameter exhaust on there it would obliterate the tires down low, so it's definitely not your exhaust. You have a 3" inch exhaust anyway. That is huge. Probably about right for your 383 anyway. Sounds like something else. Sounds like your distributor is off a tooth and/ or your timing is still incorrect.

 

The headers and exhaust are fine and the carb is okay for lower speeds (under 5000)...it's gotta be something else. Make sure the timing is really correct and the advance is really working. That setup should eat tires.

 

There is something about the headers flange being only 1.9 inches. You can however make it bigger but thats the part I haven't done yet. It seems my hole is oval shaped when its all together.

 

Out the box the small 1.9" diameter collector is gonna limit power since MOST combinations will want atleast a 2.5" collector and some hotter hp combinations at higher rpms will need 3".

Hooker 2055 likely can be opened up to about 2.25" or so and still leave room to seal. Thats about as far as I went with mine. Not sure how much more you could get before running out of ball flange to seal to the y pipe cup.

Either way, you should beable to roast tires fairly easily if you have a good converter and decent gears out back.

My LS1 car wouldnt spin tires from a dead stop throttle stomp and its 330whp. Didnt have torque come in til about 3000 rpm. Then you really start to fell the pull and it may start spinning tire at that point. Maybe you have a similar situation. With torque converter tho, it gets up quick and will roast tires easily since it puts me in the powerband at 3200 rpm.

 

what does that size have to do with his lack of low end power? if anything a smaller diameter exhaust components will provide MORE LOW END torque. He said he cant even spin tires. It is likely timing related. It sounds like it is not advancing.

 

Thanks everyone. I will recheck the timing. Glad to hear the exhaust is not the issue. I have the msd dist with vacuum advance. Plugged up the va and checked the timing. I am 11 initial and 32 total. My msd has the blue bushing which gives 21 cent. Total comes in at 2600. Two blue med springs. I thought they were the lighter ones till I checked them micrometer. I still have the two lighter ones. Should I try those? I have vortec heads so I can't have too much total. Well that is what I am told
Love the help. Please keep the advise coming

 

let me guess,your using an msd ignition box too right?

 

Yes I am. But don't think that is the issue. I will try the one medium and one lightest spring and if on my way will try the two lightest. I am also thinking of opening some of the collector. Does my combo seem good and am getting close?

 

Read somewhere that the 2460 can handle 5-600 without choking. They gave up something like an average of 4 hp over the RPM range compared to a set of higher flowing LT's.

You can prob wake up the timing a bit on initial as long as your starter can handle it and bring it up to 34-36 final. Have to know more about the motor to be sure. All in a 2600 is fine, I wouldn't change that. Don't touch the springs. You probably need more inital.

 

This what he is talking about.

This is what your collector looks like on those headers, that piece of tubing sticking in the collector is 1 3/4".

 

Thanks BlackMagic and Dyno Don. I can try to increase initial to see if the car responds more or less - then limit the vacuum advance to not increase total timing. (with the HT's Vortec Heads I don't want too much)

I can mark where the flange is sealing now and grind some metal away to see about increasing some air flow.

Funny thing is I have a set of 2460, but the Ypipe was choking the car. So I got a set of 2055's to mate to the HT383. Something is hurting the overall power....just need to tweak....that is where the fun is right?

 

WTF? And this is considered one of the better off the shelf shorty header/y-pipe combos?

 

what are the specs on the cam? Maybe the motor needs a larger converter? Still shouldn't feel that lazy though. What fuel pump are you using?

 

HT383 TECH SPECS:
Part Number: 12499101
Engine type: Chevy small-block V-8
Displacement (cu in): 383
Bore x stroke (in): 4.00 x 3.80
Block (P/N 88962516): Cast iron with 4-bolt main caps
Crankshaft (P/N 12489436): Forged steel
Connecting rods (P/N 12497624): Heavy-duty PM steel
Pistons (P/N 12499103): Hypereutectic aluminum
Camshaft type (P/N 14097395): Hydraulic roller
Camshaft lift (in): .431 intake / .451 exhaust
Camshaft duration (@.050 in): 196'c1 intake / 206'c1 exhaust
Cylinder heads (P/N 12558060): Vortec iron; 64cc chambers
Valve size (in): 1.94 intake / 1.50 exhaust
Compression ratio: 9.1:1
Rocker Arms (P/N 10089648): Stamped steel
Rocker arm ratio: 1.5:1
Water pump (P/N 88894341): Cast iron
Recommended fuel: 87 octane
Ignition timing: 32'c1 total @ 4000 rpm with vacuum advance disconnected
Maximum rpm: 5000

For a fuel pump, I am using a Carter High Volume Mechanical. I may need a larger converter, running a TCI Saturday Night Special now.

 

Wow, that's ridiculous...I'm almost tempted to swap out mine for the 2460s since I can fabricate the 2055 y pipe to mate with them.