As long as you aren't going to lug it at low RPM and high load, I'd run 25-28 initial. I always run that much with a big cam and EFI systems. Just hope it cranks ok which isn't a problem with EFI.

 

If the only problem is idle quality, the right vacuum canister hooked to manifold vacuum should help a bunch. A B28 can (NAPA VC1810) will fully deploy at 8" vacuum and give 12º more advance. Another option is an adjustable canister that can be set to suit your particular needs.

 

I am already using a Crane adjustable vacuum can and with the limiter plate set so I get 10 degrees total vacuum advance. I tried more, and with the previous cam it surged during cruise,so I put in the limit of 10 degrees.(which does pull in at my current 10" vacuum at idle.

I've never run a 254 @ .050 cam before,and with the single plane intake am not sure what to expect to get for an idle. The holes in the plates and lower PV helped alot with the stinky rich idle,but the idle speed is still higher than I'd like.

 

What springs do you have in your mechanical advance? If you have the lightest, you may have to use one light, and one medium. I had to. With both light springs, the mechanical would raise my rpm to 1150, and in gear it is 750. I put in a medium spring, and now it idles at 950, and in gear at 750. Having both light springs in would kick in mechanical advance at 800 rpm as stated, and raise the rpm level in park.

 

Are you using ported or manifold vacuum? Sounds like manifold from what I read?

 

back of primary idle stop screw until it just touches and then open about 1/2 a turn,this will position your throttle blades to the approx correct position in relationship to the transition slots.

lock out your mechanical and vacuum advance in the distributor set total timing to 36° with your 10" torque convertor you drivability will be good

At this point seat idle fuel feeds gently,then back out to 1&1/2 turns on both sides.

Start the car and warm it up to running temp, if the idle is too low use feeler gages underneath the REAR throttle blade stop to determine how much to adjust the stop to your desired idle speed.
(since you have holes in the throttle blades this may not be necessary to a great extent).
PM me for any questions if necessary.

 

I am using stiff springs in the distributer,and full manifold vacuum for the advance as well.In the past I did use the "set the transfer slot,and tweak the secondaries" technique,but with no success.I'm not sure what to expect as an idle speed,as you all know the dyno charts we see in the rags all start at 3000 rpms or higher.

I'd like to hear from some of you that run 400 small blocks,or 396 big blocks with cams in this 254@.050 range for a comparison on setup.I realize it is fairly large for a street driver,but somebody besides me has got to be running on the edge.

This setup is good for 7000 rpms and overall I like the throttle response. Trans is still out,so I can't say how it'll run on the street now,but last year I pulled 7000 in second,and it took a week to get rid of the grin on my face.

 

I had similar problems with my 454 and a 25?* cam. I'm sure a small block is going to be worse but Wildman and 1968HotRod have given some good advice. When you get the trans back in I would check your timing in gear (don't trust your emergency brake, get someone to hold down the brake pedal) to make sure the distributor isn't malfunctioning. Also, I had to back out the idle mixture screws almost 3 full turns to get mine to idle in gear and there's still room for improvement. Right now I'm at 20* initial and 38* total. I'm going to lock out the timing at 38* and see if that helps the idle.

 

I hope to start on the tranny soon,and maybe the converter load in gear will tame the idle a bit.The pivit pins in the distributer are loose,slightly and may be giving me some timing error,but I've been from 12-20 ish initial and the idle has not settled down lower than 11-1200 rpms.Could be the nature of the beast.

Oh yea,the idle mix screws are out around 3 turns now,not much effect watching the vacuum when adjusting,except the engine will stall if I turn them in all the way.

 

i had similar problems with my cam in my 406, but it is only 246@.050. i tried the same things that you did other than drilling the throttle blades and what i ended up doing was buying an MSD Digital E-curve dist, locked the timing at 36* and the dist has a built in 20* start retard. i absolutely love it, always consistant at idle now, starts easy, never have to worry about weights, springs, or plastic bushings. solved all the vacuum and idle problems. it's a bit pricey though. i think i gave $350 for mine, plus the price of a coil as well since i had an HEI to start with.

 

RUN 18 to maybe 20 deg max btdc initial timing,then have the mech advance recurved to give an additional 20 deg advance max for a 38 deg total. Then get a vac adv which adds approx 10-12 deg max (not 15-20deg like most stockers) that's fully activated at 2 or more inches of vac less then your lowest idle vacuum.

Getting the timing dialed in to these specs is a decent startign point to dialing in most but wild 8 second ground pounders.

Now you will be able to dial in the carb better after getting the timming squared away .

Scott

 

I have run bigger cams than what you have and as long as the converter is a loose 10" its rarely a problem 5" of vacuum etc.
Proform bodys are lean at idle especially with a 3310 metering block, after the car is back together try it.