drex

iTrader: (1)

i have a holley 4150hp 650cfm 4 corner idle on a 350 with a 4 speed muncie and a strip dominator intake... i have had this carb off now 100 times... now i have 70 and 76 in the jets and 28 32 in the squirts...and the green snappy cam on the primary(which feels great) and the large brown cam on the secondary... and i adjusted the secondary butterflies so they just started opening from being totally closed and left it... it runs great when cruising and gently leaning into the gas, but if you **** stomp it she goes blah-ah-ah-ah.... am i dumping too much in the secondaries? what should i start with(jet and squirt wise)

327_TPI_77_Maro

iTrader: (8)

Even the stock jetting should run fine w/ that carb. Might not be optimized for every last HP, but it should not lay down like that.

drex

iTrader: (1)

the carb is off many cars and all the stock jets and squirts have been played with...im not even sure what the carb is really... its a 4 corner idle with no choke(wasnt milled off by someone) it has been honed/smoothed down every barrel and the bottoms of the venturis are ground sharp...was told its a 650 that flows 700...it was given to me by a 11 second mustang owner... i figure its a hp cause of the no choke and 4 corner but stock holley jets on there site says 70 and 70 for the jets and 28 and 29 squirts... i just took it all apart again and put in 67 and 76 and 28 32 squirts and its getting much better, no bog when i stomp it... now feels like i have great bottom end torque but not really too much top end pull...should i go smaller still? i could do 67 and 70? i have a few jets 66,67,70,76,78 and a few squirts 28,32,33,37

327_TPI_77_Maro

iTrader: (8)

If stock was 70/70, it sounds like going leaner may have been in the right direction. Worth a shot

xpndbl3

iTrader: (5)

read your plugs, they will tell you which way to go, or hit the track and jet for highest mph.

F-BIRD'88

If there are two power valves you can use even jetting front and back.
If there is only a primary power valve then there should be a 6 to 8 jet size spread front to back.
If the venturris and venturrii boosters have been played with the jetting will not be the same as stock. Do the primary first. Go down down down untill the car will not drive on the primarys. this is the "lean limit"... then go up again until drivability just returns. (motor fully warmed up) This is very near the best jet point for cruising fuel mileage. Its still probabily leaner that 14.7:1 AFR (cruise) . go up in pri jetting until it no longer gets faster at WOT. Stop and go back 2 jet sizes primary.
Then work on the secondaries. Go down first to find the lean limit at heavy throttle. Then back up adding jet until it needs no more fuel. watch for detonation and spark knock at WOT as you go lean on the secondary jetting.
it is easier to first find the lean misfire limit and work up to max power jetting than to start from a unknown rich point and try to find the best power point.
The lean limit point will be very very obvious. cause the car will bock, spit detonate or ping or otherwise let you know in certain terms.
now you know for sure where you are. You're too lean. Now go back up in jetting until it don;t want any more fuel.
The best primary jet for cruising will be some where richer than the lean limit primary jet point.
( 16:1 to 18:1 AFR) probabily within 4-6 jet sizes up/down of 70. the best cruise AFR is a mid to high 15:1 ratio for fuel mileage.
If the best power primary jet is much richer than the best cruise jet, the power valve channel restriction needs to be modified and or the air bleed needs to be tweeked.

The best power jet for the secondaries will likley be between 76 and 84. depending on what they did to the venturrii.

Ignore how the car launches when evaluating the jetting. thats all timing, squirters. Jetting is while cruising at above 2500rpm and while into the throttle up to WOT. go easy on the spark advance while experimenting with jetting.
when ya get the jetting right put the spark advance back in.

Make sure the motor is fully warmed up to evaluate a jet change effect.
A cold manifold will always bog.

A holley strip dominator manifold is a pure racing manifold. its is not happy below 3500rpm reguardless of how you fiddle with the jets. but has a big top end. evaluate all your jetting changes at above 3000rpm and higher.
make sure the manifold is not cold. Warm up the motor by driving it first, then evaluate the jetting change.
You'd be much much better off with a performer rpm manifold.
what cam are u using? If you have a big *** rough idle cam with low manifold vacuum at idle (bigger than 240@.050) then lock out the distributor timing and set the timing at 32 36deg at idle. use 32deg while playing the jetting game.
when ya get it right again go to max power timing. 34-37deg.

drex

iTrader: (1)

the carb only has one power valve...

the cam is a comp xs274s-10 .501 .510 duration at.050 236 242... ls 110 and its solid with lash at .016

and i have a performer rpm but figured the strip dominator air gap was better. will it be better with the rpm?

the car is running great and it has alot of tire spinning torque down low but doesnt pull hard up top...

Codename 47

iTrader: (4)

I know this may be a dumb thing to ask, but you do have the floats set right?

327_TPI_77_Maro

iTrader: (8)

Yes. Running more lash effectively reduces the cam's total lift at the valve. I don't know how much you can change the power band, and frankly I would just run the recommended specs. Don't change too many things at once or you'll chase your tail. That is a very strong cam, that thing should rip.

F-BIRD'88

put the rpm manifold on. The strip dominator is a high rpm racing manifold
4000rpm and up. Wants a high compression motor with a big 250+deg@.050 cam and a high gear ratio.

The rpm manifold is the right manifold to combine with you XS274 cam.

drex

iTrader: (1)

floats are just slightly pouring out the holes.... and it just now its starting to rip... it feels great off idle and idles fine but its when i go from quarter pedal to wot it feels like it has no "pin you back in your seat" pull... should i put the rpm back on?

drex

iTrader: (1)

ill try it...love this site, ive learned alot

F-BIRD'88

Discribe the fuel system from tank to carb on your car.
if its "stock" you're likely starving the motor for fuel at high rpm. No amount of jetting will correct it.

drex

iTrader: (1)

well i have the stock tank with stock lines but i removed the manual stock pump on the engine and got a holley blue electric with a mallory regulator with a guage and return...i always read at least 5 psi... i think i will lean out the secondary jets tomorrow and try it
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and there is still the bog when i stomp it...

five7kid

iTrader: (14)

5 psi under all conditions, including full power?

You need to remove the stock electric in-tank pump as well.

Not that it would cause it to bog when you first nail it, but it won't feed it properly.

drex

iTrader: (1)

i had a carbed 5.0 stock not tpi so i had a manual pump on the engine which i removed.. no in tank

five7kid

iTrader: (14)

'87 carb'd had a mechanical on the engine and an electrical in the tank.

drex

iTrader: (1)

are you sure... i always thought different and even while it was stock never heard it or never saw any wires?

Codename 47

iTrader: (4)

I have an 86 Z28 that originally came with an LG4. Do I also have an electrical in the tank? I thought I didn't.

five7kid

iTrader: (14)

Yes.
It might have been bad the whole time you've had the car. Not unusual.

'87 was the only year that had the in-tank electric in carb'd cars from the factory. '86 could have it as a dealer-installed vapor lock cure kit. My donor car didn't.

Codename 47

iTrader: (4)

Thanks.

battyice

Try disconnecting the secondary linkage, at least then you can narrow the problem down. If the problem goes away you know to look the secondaries. If it doesn't make any difference, look at the primaries.

Do you have the list number for the carb? If you do, we can give you the stock jetting information. Depending on which model 650DP you have, it could call for either a 67 or a 71 in the primaries.

One more thing, can you have a friend watch your car while you "stomp it"? Have them see if it smokes black or not.

drex

iTrader: (1)

i cant find numbers on the carb except the main body says p-32... and i will look for the rich smoke but by dropping jet sizes in the primary to 67 it is way more snappy and tire smokey... i will drop down the secondaries from 76 to 70 and see... i dont have that many jets to fool with

and if i do have a in tank pump ill cut a hole in my hatch to get to it, but can i just remove it or do i have to retro-fit something in there to suck gas?

five7kid

iTrader: (14)

See the sticky in the top section of the forum about fabricating a carb pick-up from an existing in-tank electric pump pick-up.

I don't even want to think about hacking a hole in your car to get to the pump, when all you have to do is drop the tank to do it right.