Freddie's Transplant

[falcon cobra]

So why are the plugs black if it's very lean at idle?...jh

[pbrown]

Maybe that plug was from after a drive. The wideband O2 tool does not lie. It's definitely very lean at idle.

[MacDee]

So why are the plugs black if it's very lean at idle?...jh

My guess is it may have had too much choke. With the way I had my choke adjusted, my start-up routine typically had it running choked and on fast idle for a good five minutes before it would idle on its own.

Could that cause sooty plugs?

[pbrown]

Just out of curiosity, I called Quick Fuel Technologies. They make an replacement billet metering block that is fully tunable. Sadly, they do not have one for the 390. They did tell me that they could take the stock style cast block and modify one for changeable air bleeds, power valve circuit and IRFs for about $50. One of these would mean that we could do some idle jet adjustment without altering the original metering block.

Another option is to just alter the original metering block to get more fuel at idle.

Let me know if you want to pursue any of this.

[MacDee]

Hmm...
You mentioned the air bleeds could be modified by replacing the bleed inserts with drilled-out set screws? Theoretically, wouldn't that allow going back to "stock" settings at a later date?
I'm curious about this, because at some later date I may want to change to a "milder" cam, and then perhaps need to go back to something closer to "standard" air bleeds.

[falcon cobra]

Hey Kenny, does your MSD box cause nighmares when you use a timing light like gary says his does? I have never heard of that, I don't remember timing a motor with a MSD, if I did I never found a problem....jh

[pbrown]

Hey Kenny, does your MSD box cause nighmares when you use a timing light like gary says his does? I have never heard of that, I don't remember timing a motor with a MSD, if I did I never found a problem....jh

My timing light works fine with the CD multi spark boxes. I also have an older Sears Craftsman that also works with MSD.

[pbrown]

Hmm...
You mentioned the air bleeds could be modified by replacing the bleed inserts with drilled-out set screws? Theoretically, wouldn't that allow going back to "stock" settings at a later date?
I'm curious about this, because at some later date I may want to change to a "milder" cam, and then perhaps need to go back to something closer to "standard" air bleeds.

Yes. All of the bleeds could be changed to screw in types so that the carb can be returned to stock. I can do this for you if you want to make the changes.

Can you also post your cam specs? Is it the 274/274 112*?

[redfalken]

Hey Kenny, does your MSD box cause nighmares when you use a timing light like gary says his does? I have never heard of that, I don't remember timing a motor with a MSD, if I did I never found a problem....jh

My older Craftsman works but I did borrow a dial back light that was giving me some numbers that were WAY out of range. Of course MSD makes one that works fine. I did some internet research and brands that work or not are all over the place.

[MacDee]

Can you also post your cam specs? Is it the 274/274 112*?

Yes, that is exactly right: 274/274 int/exh duration, 112 deg lobe centers.

[falcon cobra]

Do you happen to know what the duration is at .050?

[pbrown]

Do you happen to know what the duration is at .050?

Adv Duration = 274/274
@.050 = 224/224
lift = .450/.450
lobe center = 112
RPM range = 2800-6700


I've been reading a lot and posted a couple of threads in the ether. I've had two people say that this cam needs more initial advance which I'm thinking is a good idea. I'd like to set it to about 20 BTDC. This will mean that the mechanical advance will need to be limited to 16-18 for a total advance of 36-38.

Another more advanced tuning site theorized that the lean condition was because of the cam overlap mixing exhaust in the cylinder at idle much like an EGR valve would. He speculated that the plugs would also look sooty as they do even though we are way lean.

[falcon cobra]

Wow thats a lot of cam for a C-4 , and 2800 to 6700 , my 5.0 runs only 2600 @ 60mph, and it has a E-303 which is 220@ .050 and it's 12in vac at idle 900rpm, are you sure it don't have a bad vacume leak? my trucks 2.3 motor has a cam thats 224in 234ex @.050 and it shows 15in. vac @1000rpm....jh

[pbrown]

are you sure it don't have a bad vacuum leak?

I was thinking the same think earlier in this thread. We resealed the intake with Permatex so that is leak free for sure. The carbs small vacuum ports are both capped. There is only the C4 vacuum modulator and PCV valve in place right now. It would be easy to eliminate both of these just to be sure.

[64racer]

I'm running a Crane cam Dur. 244/252 @.050 lift is 553/572 108 lobe sep.
I am at 12deg. and 36 total. That's with a C4 and 5000 stall. I just put my car on the dyno at Maxwells performance in Marysville two weeks ago.
It is a 306. After some carb tuning (750 dbl pumper) we got 304hp and 445ft lbs torque. At first it was 300 and 408 on first pull. The better torque should help some off the line. I had it running a little to rich. It has been running 12.25 to 12.30s et. Might be time for a 363ci next year!