8Ba with Big Cam idle/hg

Jeep09

Jeep09

Member
I have a Mark Kirby, Motor City Flatheads motor from 1994 that was a garage find, no miles unused.
We disassembled & confirmed all components. I am running an Offenhauser 4 barrel intake with a Holley 8007 390 cfm 4 barrel.
I have an small cap HEI non vacuum distributor.

Cam specs are
intake 28-73 / exhaust 73-29 ; .420 lift, 272 duration

I have about 6 hg inches at idle of vacuum
7* initial timing; mechanical advance only, see timing pict.
idles about 950 rpm , T5 5 speed & 3.73 rear axle ratio

Just working through a tune, my 1st flatty
 

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Looks great. You were fortunate to have found that MCF engine. It's a collectible. Mark was a great flathead guy.
 
Need to be running around 12 deg initial and back off some of the mechanical advance in the distributor.
 
Looks like you should have about 25 degrees total advance - all in early. That part is good, though as FlatJack noted, you could lower the mechanical and add some initial timing. The max you want is about 24 - 25 degrees (all in). Hopefully you have an adjustable timing light as well as a TDC marker so you can actually figure out what the real timing is - as I don't trust any "chart" to be accurate.
 
Your vacuum seems very low. I have a cam with roughly the same duration. My vacuum is 18" and pulsing because of the inlet valve opening early. Cam is "Hotrod" or similar name, around 274 degrees, bought from H&H.
Not very practical for street use.
 
Jeep09 said:
I have a Mark Kirby, Motor City Flatheads motor from 1994 that was a garage find, no miles unused.
We disassembled & confirmed all components. I am running an Offenhauser 4 barrel intake with a Holley 8007 390 cfm 4 barrel.
I have an small cap HEI non vacuum distributor.

Cam specs are
intake 28-73 / exhaust 73-29 ; .420 lift, 272 duration

I have about 6 hg inches at idle of vacuum
7* initial timing; mechanical advance only, see timing pict.
idles about 950 rpm , T5 5 speed & 3.73 rear axle ratio

Just working through a tune, my 1st flatty
Click to expand...
543472


543474
 
As others have written definitely a great looking engine and great find.

One detail has me wondering the 390 CFM carb is rather small. From my experience it would be a lot better with 500 to 600 CFM. Another area of concern is the oil filter I prefer Motorcraft FL-1A filters especially the way the MCFH oil system is designed with the feed oil line coming directly from the oil pump cover. The FL-1A flows oil with less restriction since the passages are ovals {more open area} compared to the round holes found on many oil filters.
Ronnieroadster
 
Ronnieroadster said:
As others have written definitely a great looking engine and great find.

One detail has me wondering the 390 CFM carb is rather small. From my experience it would be a lot better with 500 to 600 CFM. Another area of concern is the oil filter I prefer Motorcraft FL-1A filters especially the way the MCFH oil system is designed with the feed oil line coming directly from the oil pump cover. The FL-1A flows oil with less restriction since the passages are ovals {more open area} compared to the round holes found on many oil filters.
Ronnieroadster
Click to expand...
I'm just getting sorted out with this one. I don't think I'm running lean. 390 seems like a good starting point.
Ill look into that filter idea for next time I change oil. Thanks
 
Jeep09 said:
It runs true & has been in place for about 500 miles
Click to expand...


Looks good from here. In fact the whole thing looks great! The 390 carb won't make it run lean if it's too small (quite the opposite in fact) but might limit power at the top end if the engine can handle more.
 
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