I've got one for y'all... see if you can figure this out...

[toddtheodd]

So...
I have a pretty freaking radical cam in my 72 c-10...
355, XE274 cam, Trickflow 23° 62cc heads, Performer RPM intake, 750 cfm carb, and Hooker comp headers... stock torque converter...
So... here it is.
Of course my truck runs like crap from idle to about 1200 rpm... but if I pull the choke (not enough to mess with the rpms, but just a smidgen) it runs fine (no bogging down) up to 1200, at which point I open the choke back up again, and away I go...
So... It's like it needs to be richer at off idle to 1200 rpm... is that the metering rods that would change that?

[coopdeville]

get a stall converter to start! 2500 would be perfect for the street.

[toddtheodd]

Yeah... B&M recommended their 2400 stall converter...
I'll be able to afford the converter in not too long... but the price tranny shops want to charge to put it in is insane...
I would really rather just have a standard tranny anyway.

[CHEMPOWR]

That radical cam may have little to know vacuum at idle so it may be causing trouble with the carb. Do you have edelbrock or holley?

[vectorit]

Originally Posted by coopdeville

get a stall converter to start! 2500 would be perfect for the street.

I agree.
That stock TC is killin your combo.
How does it ridle when it's in neutral?

[toddtheodd]

Originally Posted by CHEMPOWR

That radical cam may have little to know vacuum at idle so it may be causing trouble with the carb. Do you have edelbrock or holley?

Edelbrock 750cfm Performer.
I think it might be too... I know I'm not making enough vacuum for the power brakes at idle. Fun in parking lots... you know.
But then again... it fricken idles at 450 - 500 rpms in gear... Which is the torque converter I'm sure.

I know that at idle, the vacuum should be higher, and so the metering rods should be pulled down leaning out the motor, and as vacuum decreases, the metering rods should be lifted up richening it...
So... with the vacuum too low, the meter rods would already be up, running to rich at part throttle, but then again... why would closing the choke help that since it would make it run richer? Unless closing the choke increasing the vacuum which would then be getting a better signal to the metering rods... Oh hell... All these motors need to run is fuel, air, and fire... but once running, it sure is tricky to get them running "right".

[toddtheodd]

Originally Posted by vectorit

I agree.
That stock TC is killin your combo.
How does it ridle when it's in neutral?

Idles fine in neutral... but I'm having to give it a lot of initial timing to get it running right. Makes it hard to start when it's warm, not to mention that I'm sure I'm not where I want to be with the vacuum advance on the dizzy. It's not pinging, but I'm not feeling the love this motor should be giving me...
Then again, I am still breaking it in, and don't even have 100 miles on it yet.

One of the things that I'm sure is the torque converter is that no matter where I have it in neutral, 1200 rpm or 700 rpm, when I put it in gear, it drops to 450-500 rpm. Lopes like a mother at 500 rpm too... I don't mind that low of idle because of the way it sounds, but it's killing me with the stuttering and bogging down until 1200 rpm when taking off.
Which is really weird that the choke helps with that... even when it's already all warmed up.

Would closing the choke that little bit be increasing my vacuum maybe?

[CHEMPOWR]

Thats what i'm thinking. partially closing the choke increases vacuum at the carb. I will have to think about this as it has been years since I tuned an edelbrock. I have been playing with fuel injected cars for the last 5 years. I think you can get a tuning get and measure vacuum at idle and either replace the springs in the metering rods....

[cparman]

like chempowr said. high lift cams have no vacuum at idle. IF you have a Holley carb, you could change the power valve/valves in it to a lower number than is on it now. Might help. The simple/free stuff: get a vacuum gauge and see what you have before making any changes. You make no mention of what kind of ignition system you have. If HEI good! If points/bad. After checking vacuum, take a spray bottle of water and spray the edges of the intake manifold looking for a vacuum leak, and do the same around the base of the carb. If you have a leak, while doing this you will hear the engine rpm pick up. If no leak is found try adjusting the timing with the vacuum gauge hooked up and adjust the timing for hightest vacuum reading. If you get this far, you might have a dragging starter when cranking, or a pinging when accelerating. If so, back the timing down a tiny bit

[toddtheodd]

Originally Posted by cparman

like chempowr said. high lift cams have no vacuum at idle. IF you have a Holley carb, you could change the power valve/valves in it to a lower number than is on it now. Might help. The simple/free stuff: get a vacuum gauge and see what you have before making any changes. You make no mention of what kind of ignition system you have. If HEI good! If points/bad. After checking vacuum, take a spray bottle of water and spray the edges of the intake manifold looking for a vacuum leak, and do the same around the base of the carb. If you have a leak, while doing this you will hear the engine rpm pick up. If no leak is found try adjusting the timing with the vacuum gauge hooked up and adjust the timing for hightest vacuum reading. If you get this far, you might have a dragging starter when cranking, or a pinging when accelerating. If so, back the timing down a tiny bit

Ok... so... where do I hook the vacuum gauge up? Unplug the brake booster maybe, and use that port? Or can I use one of the ports on the front of the carb.
How much is a vacuum gauge...
Oh, and I've already sprayed starter fluid all around the intake and carb, and lines, with no change in rpm. I've also capped all the ports and checked the motor to see if a line was leaking. No change between all capped, and all hooker up like normal.
I've already got the dragging starter problem, but with the aluminum heads and 93 octane fuel, no pinging yet. Though it's really hard to hear over the "apocalyptic exhaust".

Edit:
I sure do wish I had the vacuum gauge in my dash... I have all the other gauges, so I've been thinking of hitting up the junk yards to find the vacuum gauge too and put it in with the others.

[Ben IV]

i have the exact same cam in my truck but i also have a 2500rpm stall converter. Id say that getting a stall converter would be the first step in figuring out your problem then you could properly tune the carb.

[toddtheodd]

Originally Posted by Ben IV

i have the exact same cam in my truck but i also have a 2500rpm stall converter. Id say that getting a stall converter would be the first step in figuring out your problem then you could properly tune the carb.

Did you have someplace put in the torque converter for you?
If so... how much did they charge. My local shops want WAY too much to do it... to the tune that it would only be like, $200 more to have the whole frickin thing rebuilt.
I can't believe they want to charge so much just to switch out the torque converter...

[LockDoc]

-
As far as the vacuum you might try putting a small vacuum reserve tank on it to see what it does. It may improve the brake situation.

LockDoc

[PHAT TONY]

If tipping the choke helps-it's lean. Edlebrock carbs leave alot to be desired tuning wise; get a Holley 650-700. Try un-hooking your vac advance, set the timing for about 34-36 degrees total (may need to have the distributor curved to bring in 20-24 degrees by 2200+ rpm).

[2tons of fun]

dude, you seriously cant install a torqueconverter?

its 11 bolts, a jack and stand and 1hr tops.

[VetteVet]

This may help or maybe not but it's a good read.
http://www.edelbrock.com/automotive_...ers_manual.pdf

[CHEMPOWR]

I had to reread your initial problem...

Sounds like you have problems with idle with a reasonable timing value but if you advance timing you can get a decent idle but the truck is hard to start when warm.

I would start from scratch so you don't have patch work tuning here.

Set base timing to reasonable setting 10-15 degrees BTDC. Measure vacuum now to see if it is below what edelbrock recommends. If the carb is getting the correct vacuum signal and jetted correctly it should idle OK but the truck should be a little sluggish with off-idle acceleration since it is probably not in your power band due to the large cam. The carb may be a bit lean since it sounds like you have a pretty well built motor with nice heads and all. You may need to rejet the carb wether or not your vacuum is low.

A stall converter will help with off-idle acceleration but not off idle "running".

[Ben IV]

Originally Posted by toddtheodd

Did you have someplace put in the torque converter for you?
If so... how much did they charge. My local shops want WAY too much to do it... to the tune that it would only be like, $200 more to have the whole frickin thing rebuilt.
I can't believe they want to charge so much just to switch out the torque converter...

i put it in when i installed the engine, like said above it isint hard to do. I also agree with phat tony about swapping to a holly, I had an edelbrock carb and it never seemed to want to keep a tune. I love my holley stays tuned.

[67chevemall]

Toss the automatic junk at your enemy and get a standard.

[LONGHAIR]

Originally Posted by PHAT TONY

. Try un-hooking your vac advance, set the timing for about 34-36 degrees total (may need to have the distributor curved to bring in 20-24 degrees by 2200+ rpm).

It would be far easier to just swap to the correct converter.....
Timing "gimmicks" are just that and will just make things worse.
You really need to have the vacuum advance and have it work correctly. If your vacuum is really that low, it is not pulling the advance in.
An adjustable vacuum advance canister is probably going to be required.
There are just too many things going on here that are "adding up" to your problems. Until you correct the idle in gear issue, everything is just a fight to cover it up....rather than actually fixing it.

[mclairmo]

Get a Holley with annular boosters or the new Summit brand carb that is like the old discontinued Holley 4010. They work better with cams like yours.

[cparman]

You should be able to buy a cheap vacuum gauge at a parts store/or if you have a harbor freight. The one response you have that states he has the same cam, and that you really need a looser converter kind of sums it up. The shop that wants $200.00 to install YOUR converter is cheap in my opinion. The tranny Pull in our trucks is a gravy job, but it is still worth 3-4 hours labor at my place. That equates to $80.00 X $ = $320 plus some fluid.

Originally Posted by cparman

like chempowr said. high lift cams have no vacuum at idle. IF you have a Holley carb, you could change the power valve/valves in it to a lower number than is on it now. Might help. The simple/free stuff: get a vacuum gauge and see what you have before making any changes. You make no mention of what kind of ignition system you have. If HEI good! If points/bad. After checking vacuum, take a spray bottle of water and spray the edges of the intake manifold looking for a vacuum leak, and do the same around the base of the carb. If you have a leak, while doing this you will hear the engine rpm pick up. If no leak is found try adjusting the timing with the vacuum gauge hooked up and adjust the timing for hightest vacuum reading. If you get this far, you might have a dragging starter when cranking, or a pinging when accelerating. If so, back the timing down a tiny bit

[toddtheodd]

Originally Posted by 67chevemall

Toss the automatic junk at your enemy and get a standard.

I would actually LOVE to do this. I can't stand autos anyway... but I REALLY can't afford the swap.

[toddtheodd]

Originally Posted by cparman

You should be able to buy a cheap vacuum gauge at a parts store/or if you have a harbor freight. The one response you have that states he has the same cam, and that you really need a looser converter kind of sums it up. The shop that wants $200.00 to install YOUR converter is cheap in my opinion. The tranny Pull in our trucks is a gravy job, but it is still worth 3-4 hours labor at my place. That equates to $80.00 X $ = $320 plus some fluid.

I didn't say the shop wanted $200... I said that for $200 more I could have the transmission rebuilt.
They want somewhere around $400... Screw... That...

[70clone]

Throw that edelbrock away holleys are great but obsolete barry grant is the way to go.