I just finished building my car last month and have been driving relativly easy to break it in for about 1000 miles. I built it be a fast car that will only see the street maybe on the weekends. I have tuned and tuned this thing and cant get it running right. It is a 468 with 11:1 compression and afr heads. it has a solid isky cam with 264 duration @50 and 590 lift. It has a team g intake and a holley 850. The car is not way slow it still beats most cars that are here in town but it still doesnt seem right for the time and money that i put into the engine. The thing that has really confused me is that before i rebuilt the motor it had iron heads and a smaller cam in it. The carb ran perfect the plugs were a good brown color. I have read that when you increase the duration on cam that you must run richer jets to compensate. Well i have had to step 4 and 5 jet sizes leaner and it still runs incredibly rich almost fouling plugs. I thing that this carb problem maybe my problem with the overall performance. could there be somthing somewher else that is making it do this. If anybody has in idea it would be greatly appreciated.

Well for one, you are scaring me because i am building a 468 with AFR 305CC heads, solid cam, 11-1 compression, one thing is that the cam has a lot of duration and not that much lift, for comparison my cam is solid and has about 250 duration and 620 lift. Anyway i had an 850dp and everyone said those carbs don't run that great. I have bought a HP950 these carbs are supposed to be great! I read that the 850's only run good at WOT. If you can find a place that has an Air/Fuel ration guage/machine hook it up! Also i went and got my car with the current 400 pontiac motor rear wheel dynoed and they hooked up the A/F ratio. It turned out i was way too lean in the secondaries, and my primary squirter was much too big. Plus you would of never known it was too lean in the secondaries, the plugs looked rich. My advise is hook it up to the machine, my car now runs like an entirely different car!!!! Wayyyy better, i gained 12hp at the rear wheels just from changing the jetting(up 4 jet sizes).

What cam are you going to run. I called comp thinking i had already got the wrong cam and the cam they reccomended was huge 272 @50 on intake and 278 on exaust with 639 and 631 lift but i want to try to get this one running better first. I talked to a friend that has a Quick fuel 950 on his 502 and we are going to try that. and don't get me wrong it is still ok fast, it will probaly still get into the mid 12's but this is not what i had expected i was thinking more like low 11's

cody and others

how can an A/F meter tell whether its the primaries or secondaries that are too lean or too rich?

just trying to learn.

thanks

Your problem could be carb or ignition.

What is your ignition setup including initial & total advance, what rpm it tops out, etc. What plug, plug gap, etc.

What carb? What have you tuned on the carb? Any mods to the carb? power valve? curb idle adjustments? throttle blade air bleed holes? 4 corner idle? secondaried opened up slightly? transfer slots exposed?

Originally posted by Slowazzbu:
Your problem could be carb or ignition.

What is your ignition setup including initial & total advance, what rpm it tops out, etc. What plug, plug gap, etc.

What carb? What have you tuned on the carb? Any mods to the carb? power valve? curb idle adjustments? throttle blade air bleed holes? 4 corner idle? secondaried opened up slightly? transfer slots exposed? And carbs are simple compared to EFI. :rolleyes:

Rather than stab around in the dark how about sharing the rest of your combo (car weight,trans,rear gear etc) A motor will load up pretty quickly when subjected to low speed cruising with a long duration cam. I suspect that a combination of factors are at play here, timing,jetting and driving style.

Sometimes you got to let the beast eat.

The engine i already said but here are some details. The initial advance is 18 total advance is 38 in by 3300 rpm. It is an msd distributor and coil with a mallory digital box. I am running autolite 3924 plugs with .035 gap. it has a holley 850 double pumper carb. The mods i have made to the carb are i drilled 1/16 holes in the throttle plates to get the idle transfer slots back were they should be and the secondary idle slots are exposed the same length as they are wide. I changed the power valves to 3.5 because it has between 5.5 and 6 inches of vac at idle in gear. This change made no noticible difference in performance that i could tell. The rest of the car is as follows. It is 3580 with me in it and a full tank of gas. It has a turbo 400 trans with 4000 stall and t-brake. It has a 12 bolt with 4.56 gears, soon to be 4.11. it has ssm trac bars that is about it for the drivtrain and thanks for replys. I just talked to afr and they said that i should get a victor jr instead of my team g which has larger ports than my heads and this swithch would be worth 35-45 horsepower i dont know but i went ahead and ordered one because i did not want to enlarge the ports on the head to match the intake.

I think the Team G is most of your problem. I couldn't get one to work right on a 1600# dragster. Personally I would have gotten a good quality dual plane but the Victor Jr. is about the best single plane. You have an awful lot of camshaft even with the 4.56s it is going to give you low speed problems no matter what you do.

I agree with oger on the Team G, the Edelbrock is a better choice graemlins/thumbsup.gif . You should not have drilled the throttle blades :rolleyes: but quess it's too late now. I question the idle vacuum (6") I run a bigger cam and have 11" at idle. What are all the specs on that cam? It must have huge over-lap. The 4.11 is a good choice with your convertor and trans graemlins/hurray.gif

i had to drill the throttle blades because before i did the idle sdjustment screw was turned in all the which put it way past the transfer slot and even then it would barely idle with 4 inches of vacum. all of the cam specs are 310 advertised duration 264 @.05, .590 lift with 108 lobe seperation installed at 108 intake centline. it does have kind of alot of overlap with 94 degrees . What cam are you running My10SecSS?

I was running a (ovalport) Team-G on my 502,
then switched to a (oval) Dart & added a ram air,
the car picked up over 3mph with these 2 changes.
I'm guessing 10hp for the ram air, and 20hp for
the intake swap - the Dart is bigger/better.
So the intake will help you.

My cam is a Lunati 680/685 266/267@.050 110LSA installed with a 108ICL. I use a Holley strip dominator intake with 049 heads.

i just got through changing the springs on my mechanical advance and it is no longer running rich and i jetted back up a size. This is confusing because it still has the same advance just in 400 rpm earlier. I think i am going to wait until my new intake gets here and then mess with this thing some more. Thanks for everyones help I will probably need it again here soon.

I'm running a Ultradyne solid flat tappet, 288/296 with about 252/254 @ .050, 612/630 lift. I am using the vic. jr. also, how did you like your AFR's i like mine a lot, real quality pieces!

They seem to be of good quality but as far a performance i have been rather disappointed but i do realize i have alot of tuning and learning to go. One thing i don't like is the huge AFR logos on the front. Nobody here even runs big blocks and only a very few of the small blocks run Afr's. So everyone that sees my motor thinks my car should be in the low 10's or somthing. I do still like them. Didi you have to wait three months for yours?

Three months!!!!!!!!! i waited about 5 weeks. Tony is a real good guy. He really helped me out, actually i guess it is just my young minded side, but i really like the big AFR sign on the front of the head and the exhaust port, if i am paying a couple thousand for my heads i want to at least represent it. I was actually pleased that it said it big instead of really small like the small blocks! I think you have a lot of tuning to do and you are in the right direction, I still think your cam is kinda wacky, i would call tony at AFR and see what he thinks. You will be amazed at how much of a difference getting your car accurately tuned makes!! it will feel like a totally different car! let us know

I would strongly recommend opening your plug gaps up to around .048"-.052". A hot CD ignition likes and can easily jump big gaps, and will create more complete combustion.