Is this too much carb?

[team39763]

I have a 86 SWB with 4.56gears/posi, 3000stall.  It has a .040 over 350 with flat top forged pistons, pink rods, steel crank, ported 882 heads, 228/234 cam(512/526 lift), victor jr intake, longtube headers, electric fan, Accel cap and rotor kit with a super coil.  This motor came with a demon 850 on it already.  Everybody tells me that the carb is too big, but that I could make it work.  Right now all my plugs are wet fouled.  If I jetted this carb down, could I still get away with it?  Maybe add more fire(like a MSD 6AL).  This truck is not a daily driver, but will see some street time, but mostly it's used for racing.

[BILTUP]

I would think its abit large.  I run a modded holley 850DP on my pontiac 455 race/street car (12.22 @ 109) 3800#, soon to be 11's.

Jet it down and see what happens.

[VileZambonie]

You have decent engine combo with absolutely crap heads on it. Try a better cylinder head with that combo and you'll be amazed  

[team39763]

I'm gonna try a 750 soon, so we'll see how it runs with that.  Yeah, I know about the heads, but that's the best I could do with my limited income.  I'm hoping to get some trickflow heads when my budget allows.  

[stepside454]

How much RPM you seeing with that? Even if your buzzing it to 7000  RPMs, ( IM sure your not) that motor wouldnt need a whole lot more than a 700 CFM carb..725 tops.

[team39763]

I shift at 5500 right now because I'm not sure what all has been done to the motor as far as what cam and springs.  After my cam swap, I plan on shifting at 6700.  The truck will have a 4000 stall (and 4.56 gears) and a 6800 redline.

[stepside454]

I think Id use a mech sec. carb. maybe a 700 DP

[team39763]

A friend of mine is going to lend me a 750DP.  If that is still too much, another friend offered to let me borrow his 650.

[team39763]

And it runs better as far as racing goes, but driveability sucks.  Something is definately wrong.  The brake pedal is very very hard and I almost couldn't get the truck stopped.  It also dies in gear.  It took about 3 whole minutes to back it into my driveway(truck would stall, windows tinted too dark+no side mirrors, brakes barely worked + lots of objects to go around).  I think a vacume line may be loose/broke somewhere, but I'm sure I hooked up the only two that I touched.  What could be wrong?

[VileZambonie]

vacuum leak. Did you hook up the brake booster? Check the vacuum port at the back of the carb

[team39763]

I will check that tommarrow.  I decided to go with some vortec heads and a smaller[lift] cam.  So hopefully this combo will work out better.

[team39763]

I checked and there was brake fluid splattered on the fan, bottom radiator hose, and fuel pump.  I'm sure it wasn't fuel, water/coolant, or oil.  I'm thinking that one of the passenger side brake lines ruptured or something.  Could that cause a low vacume situation?

[SUX2BU99]

A ruptured brake line I don't think would affect the vacuum, but it certainly would affect how your brakes work. But then your pedal would be very spongy and soft. The hard pedal sounds like no vacuum to the booster, which means you have manual brakes. And if you have ever driven a truck with manual brakes you know where the term "stand on the brakes" comes from!

As for the vehicle performance, you mean that the 750 made it less streetable than the 850? That's strange.

[team39763]

The hose to the brake booster came unhooked and it was hard to see.  I got the idle set to around 750-800 and it sounds good.  I'm gonna wait until I get an exhaust put on it and then I'll run it on the back roads to see how it drives.  Thanks ya'll.