battz86

I'm running a 406 with a speed demon 750 v.sec, performer rpm, AFR 210 heads, Crane gold rockers, and a lunati cam with 249 / 254 and 543 / 552. The afr was way high, so carb tuning, changing the jets is in order, but this combo for some reason is just not making any power at all. At one time I had the smaller AFR's with an unknown cam and a holley carb and the car ran low 12's all day with street tires and horrible 60' times. If any one has a similar set-up I'd be curious in what you have to compare or if any one has any suggestions on the cam and carb. Thanks

ross

What comp ratio and cam secs at .050? Also lob sep on cam. Gear, conv size and weight of car and driver will also be helpfull.

jbenge

iTrader: (2)

More info would be helpful like ross said, all your parts need to match up well to perform. Maybe your secondaries aren't opening all the way or the right time? With that cam I would suggest using a mech. secondary carb, a 750DP or 850DP would be a good choice. I've never been a big fan of vacuum secondary carbs for drag strip use. Also check your timing, make sure you have around 36 degrees total timing. Assuming you have around 10:1 compression and a healthy engine your combo should run very well if tuned well. Hopefully its a tuning issue and not a mismatch of parts causing the poor performance.

IHI

iTrader: (1)

I see the problem highlighted

Get yourself a Deom or Holley 750-950 cfm carb mechanical secondaries and then hold onto youor friggin hats boyz, your goin for a ride

battz86

The specs I wrote down are at .50 it has a 106 lobe sep, stock 3:23 and a 3,000 stall. The car has a fiberglass hood w/ aluminum heads all else stock, assuming it way's around 3,400, and I'm 190. It has 10:1 comp. drives fina and doesn't smoke or burn oil. Will perform a comp. check, can't hurt. Timing is @36. Will double check tha carb to see if it's opening. By the way like you said I've heard about problems on demon carbs so maybe your right. I'll try a holley and get a mechanical carb. Buy the way it's not a roller cam. Do you guys suggest going roller? Thanks in adance for all the help and suggestions..

battz86

Also, just looked @ Hooley's set -up. How about the Holley 4150 strret hp mech sec double pumper?

IHI

iTrader: (1)

oops double post, sorry

mw66nova

iTrader: (13)

for this motor i would suggest maybe the new proform carb. it's about $500 through jegs and comes with a pro-form main body, billet throttle blade plate and billet metering blocks. everything on this monster is adjustable. it's just like the quickfuel carbs, but a little cheaper. i think it's suppost to flow like 800+cfm. again a mechanical secondary carb is a must on a go fast motor.

IHI

iTrader: (1)

I'm a firm believer in solid roller for "toy" cars. No worries on break in, super easy to set lash and when used with a girdle and proper lash setting technique lash adjustiments are few and far between. The ability for the lobes to hold the valves open longer to suck in and exhaust more air is a great way to increase hp/tq.

If it's in your budget to upgrade to a roller, then it's really a no brainer. But solid flat tappets are also capable of producing great hp as well...just the roller do it a lil better is all with less worries about grinding lobes flat.

battz86

Definatly going to look into it, and I think I am going to going to go the roller route. Seems, when I put that cam in the car changed dramastically. Thanks for the input, and what specific roller cam would you guy's suggest for this set-up? Something thats I can still drive it once in a while on the street?

IHI

iTrader: (1)

FWIW, a buddy is building a 406 with the same heads we run and is using the car in much the same format. Oddly he called Comp and then called Bullet and their cam specs were almost spot on the one I run. I'm more than happy with perfromance, it's not a valvetrain killer (same components for 2yr including springs), able to run my pwr brakes with a vacuum can, and absolutely daily driver mild in stop and go or interstate. So take a peek at the sig for an idea of where you want to be at, easily over 550hp, 550+tq, pump ggas freindly and able to push your docile street car into the 10's ever pass if it's under 3500lbs.

ross

I would go with a 750 dp hp carb change the rear gear for a 3.73 and a little more conv 3500-4000 would work better. What kind of exhaust system do you have?Also do you have trap speed and et for this combo?

battz86

IHI and everyone thanks for the great info and help. I'm goint to look into all those suggestions. I'm using Hooker super com. headers and a borla muffler. With the smaller heads and an unknown cam, with edelbrock headers and a holley 750 vac. sec stock suspension and stock gears on street tires the car ran 12.20's with horrible 60' @ 110-115. Now, with the hooker headers bigger heads and cam and the demon carb, the car runs horrible. Haven't been to the track with it, but seat of the pants, it's MUCH tamer for some reason.. But I'm going to use some of your sugestions and hope for the best. Thanks

IHI

iTrader: (1)

Aside from the terrible choice of using a VS for a "fast" car, the other problem I see going back over the posts is lack of compression and a larger duration cam. The fact your at 10:1 static I'm assuming; general rule of thumb is you lose one point of compression when using aluminum heads due to ability to disapate heat quickly, and I've seen first hand another racer that left everyting the same and took off his dart iron eagles and slapped on a similar runner/cc sized set or dart aluminum heads and slowed down-no other changes but heads. So assuming this factor since your not retaining heat and the fact you have alot of duration=valve overlap your losing even more compression, this is not a good combination

"Hypothetically" with your old cam at 10:1 static compression dynamic might have been 9.0:1 - 9.5:1 with overlap. Now with the larger cam and same compression it's possible you've dropped down to 8:1. Numbers are not meant to be accurate, but mearly an example of what's happening. But obviously mismatched with good alumie heads, large cam and low compression. Would be no different than building a motor to perform with 64cc heads, then slapping on some old azzed smogger large cc heads...you lose alot of compression and performacne that way. This is why much higher compression is needed with alrger duration camshafts since valve overlap gets longer and more compression is lost.

battz86

Just called cam company and there asking what the height is from cup to retainer or head to retainer and said it should be 60 or 80. I have AFR heads and tried to call them but all busy. I have no clue what this is, any one have an idea. thanks

85SILVERBULLET

it sounds like a lack of: compression, rear gear, stall, and velocity in the heads. i would think that the main problem is the heads. i am not saying that you have bad heads because afr makes some of the best in the buisness but with the larger intake ports you have slowed the velocity and decreased air flow and as we all know decreased air flow is decreased power. change the rear gear, spin the motor a little higher and you will be able to utilize the larger ports. also with these larger heads you should be able to make better gains with n20/forced induction. just my 2 cents