Need some help dipping into the 11's

[sobiecam]

Alright guys I know we aren't working on an a body here but I trust you guys a lot more than I would a truck owners group!

What we're working with here is a 1987 Dodge D150 short bed, regular cab, it has run 12.01 for us before and usually runs a 12.1 and then drops to 12.3 or so for following passes in a day. The engine is a 416" (360 based) stroker with an Indy 360-1 top end on it and a mechanical roller cam, it has a Demon carb and large tube tti headers. So far traction doesn't feel like an issue and we were all convinced that the truck was as fast as it was going to get.... that was until we saw this picture of the truck launching at the Mopar Nationals last year:

If you look closely there enough the truck has dark smoke coming from the tailpipes, and the exhaust is open during this run so the majority of the exhaust is coming out of the cutouts under the truck. My thought is that being a heavier vehicle is that the truck doesn't really need a mechanical secondary carb on it but rather a vacuum secondary, but my hard-headed uncle wants no part of putting another carb on it.

Is there a way to tune out the smoke with maybe smaller jets or tuning on the secondary end of the carb with accelerator pump cams or squirters?

 

[Matts440]

Yes the black smoke is usually a rich condition, so yes try smaller jets, do you know the size accelerator pump is now 30 or 50cc? Keep to the mechanical especially for racing. There's also the power valve that ypu can change as well. Just start with small changes, how are ypur spark plugs reading? You want a light brown on them if its black then need to jet down. What size demon is on it?

 

[flyfish]

Some helpful info would be:

Do you have the incrementals from a time slip with 60', MPH at 1/8 and 1/4 (that would be REALLY helpful)?
How much does your truck weigh?
What gear?
What compression?
What cam?
What converter?
What jets are in the carb now (and what size is it)?

How much carb tuning have you done with the combo?

A vacuum secondary carb WILL slow you down more than likely....


If you need help tuning it you could bring it out to Lucas Oil Raceway on a Wednesday night test and tune and I could help you out if you like....assuming I'm not tied up with running kids to sports and such. There is also a race on August 17...sounds like you would fit in Sportsman quite well...Always nice to see other Mopars out there.

 

[moper]

I can;t see the picture on this PC.
So I'm clear - the engine now has what size Demon? What style (vacuum or mechanical secondaries)?
Soot may not mean anything bad.

 

[crackedback]

If you want it to run 12-20-12.50, put a vacuum secondary carb on it.

Borrow or spend a couple dollars on an A/F gauge that has data logging. You could be miles off on the tune up

 

[sobiecam]

Hey flyfish, I remember running one night when you were there a year or two back, I had my Mopar Express Dodge Dakota out, we haven't had anything track worthy down in Indy since the fall of 2012 or so but the plan is to leave this truck in Indy to make it out to the T&T's to get some seat time!


Anyways the truck weighs in at I'd guess 3400ish lbs, we've never scaled it.
Has a 4.56 gear in the rear, 850cfm mechanical secondary demon with the factory, I'd guess it's a 3k stall with 11 or 11.5:1 compression ratio, and I don't have the cam specs on me right now but it is a fairly radical mechanical roller, here are some time slip numbers:

Slip 1:
--R/T: .011
--60': 1.755
--330': 4.995
--1/8: 7.731
--MPH: 89.74
--1000: 10.090
--1/4: 12.095 @ 112.23


Slip 2:
--R/T: .114
--60': 1.671
--330': (unreadable)
--1/8: 7.731
--MPH: 88.38
--1000: 10.121
--1/4: 12.147 @ 110.89


Despite the truck being done for several years now I don't have tons of seat time in it nor have we got enough track time with it to predict it's times yet and neither my uncle, my dad, nor myself have done much tuning on it since we got it together in 2008

 

[70aarcuda]

"The engine is a 416" (360 based) stroker with an Indy 360-1 top end on it and a mechanical roller cam, it has a Demon carb and large tube tti headers."

that thing ought to be flying.....sure about the weight?

and 10 inch converter.....????

 

[Mopar Miller]

with that kind of reaction time you could win a lot of races, get it jetted right, race it and win some money who cares if it is a 12.09 or 11.99. We have raced at the US nationals, the air there is tricky to figure out. It seams like you should always run faster than you do. good luck.

 

[flyfish]

I agree with 70aarcuda, that thing should be hauling. I would start by making sure your timing is set in the right ball park (34° ish), then jet for best MPH. More converter would be a step in the right direction as well (without knowing cam specs I can't say for sure, but your 3k stall is probably way too tight).....but seeing that you can do 112 in the 1/4 tells me that you should be able to get a 11.9x as is.

 

[moparlover]

Your Horsepower computed from your vehicle weight of 3400 pounds and MPH of 89 is 191.95. assuming 30% drivetrain loss your getting 260HP at the flywheel

a 416 11:1 should be waaaaaay more

i've never heard great things about demon carbs... get yourself a 750HP holley and dont look back

mech secondaries are gonna get you better slips when racing

i doubt the cam being out of degree could be that much of a loss. what do you have the valve lash set to?

 

[RustyRatRod]

I think you're off on the truck's weight. A lot. Also, from the launch picture, you've got a long way to go before you extend the front shocks all the way. A lot more travel to be had there, so there's a good bit more in it for sure. Your estimate is in B body territory. That's a full frame truck you have there. I believe you'll find it is over 4K. I could be wrong. It's happened before. lol

 

[bOb shingler]

black smoke at the hit is to big a squirter. down size them 2 steps or so. your hotrod truck should weigh in around 4500lbs. the big change I recommend is an 8" 5000+ stall convertor to get the bad boy out of the gate. also if you change the carb put an 850dp holley on it.

 

[Dart Sport 360]

Ours is 3750 without driver with a BB and fiberglass hood and bumper. Not a lot else done to lighten it, no inner fenders and no heater....

I agree with keeping the double pumper. It just needs some tuning.... Also remember these suckers push a lot of air so your MPH are usually a couple MPH slower then what your combo would have in a car.

DON'T let anyone tell you a truck cant hook up on a small tire!

 

[moper]

I woudl agree the convertor is a mismatch but... The curb weight is around 3600lbs. Using that figure you're only making around 450hp. Should be another 100-150 more in there... Ever have the engine on a dyno or do a leak down on it?

 

[sledger46]

If you are having your ETs change from round to round and you are having 60ft times ranging from 1.67 to 1.75 then you have a traction issue. I agree with a 112 MPH trap speed being more then enough to produce a 11.99 time slip. You are going to have to get the 60 foot down to mid-high 1.5x to get an 11.

If your power is maxed out, then get a GOOD converter 8"-9.5".


If you don't think the power is maxed out then you need to start at the beginning and tweak the timing until you get it perfect, then play with the carb to maximize MPH. (and then get a GOOD converter match to your engine combination)