1967 Fairlane 390 do-over

[Cobrajet2]

So, today I braved the cold and messed around in the garage checking some stuff on the Fairlane. Compression and leak down.  Testing showed I had 2 weak cylinders on leak down. #5 at 17% and #7 at 18% after a little oil in #7. That cylinder was 22% at first.

Compression-wise 7 of the 8 cylinders ranged from 151 to 162. The one weak cylinder was #8 at 140.  This motor had no issues during break-in and probably has less than 1000 miles on it.

cyl.    comp.    leak-down
1        155       8%
2        160      11%
3        157      11%
4        156      10%
5        162      17%
6        160      8%
7        151      18%
8        140      13%


Motor is a .030 over 390 with C8OE N Cobra Jet heads.
Cobra jet exhaust manifolds
Comp XE 274 cam kit. Lifters, springs and hardware all matching. Ford adjustable rockers.
Pistons are Silvolites (I think)! maybe part# 1130, but not sure. Cannot find the old box. 
PI intake with a Holley, Ford distributor with a Pertronix.

[RJP]

Your minor compression variation numbers are not your problem. Your worse leak-down [17-18%] can be considered normal for a fresh, unbroke-in engine. If it were mine I'd put the timing light down for now and just crank some advance into the distributor while the engine is running and see how the engine responds. I'd bet the engine would smooth out, vacuum would come up, water temp would drop and you'd gain some, or maybe a bunch of low end response. Do NOT leave the timing as is if this helps. Now hook up the timing light and see where the timing is. If the timing light indicates an over advanced initial timing @ idle [and at say 3000 rpms] look for the timing pointer and dampener marks to be off and correct as needed. Don't use "book" timing specs as you'll need to experiment with a timing curve that works for your engine. Stick with some safe guide-lines here...Try 12-16 deg advanced @ idle, 34-36 [centrifugal] at 2800-3200 rpm then if you are using a vacuum advance adjust as needed for good drive-ability with no pinging or detonation. 

[Heo]

I se you have around 7 in vaccum! I have a 282 S cam single plane intake
ported heads and i have 11 in vaccum so something wrong there i think

[Cobrajet2]

I was back out in the garage today messing with the Fairlane. First, I had to go thru and clean torpedo heater as it suffered flame out shortly after start up. Got it going and got some heat.

As recommended, I put a timing light on it after warming it up. Light was only reading 5 degrees initial. Put some advance in the timing to where it smoothed out a little and sound good by ear.  Put the light back on and it read 23 degrees idling. Goosed It up to +or- 3k rpm and light read 50 degrees. Vacuum improved a little.

I made up a piston stop out of a spark plug non fouled and will check TDC next. I think I can fit the 18 inch Moroso degree with the motor in the car.

I also releaked cylinders 5 and 7, and got better numbers than before. I guess because the motor was still warm this time. The plot thickens.

[Cobrajet2]

Have the heads off now. Lots of crud and
contamination for less than 1000 miles.

I was able to verify that there was no slippage in my balancer. Bought a degree wheel and it checked good.  I wanted to see what piston was used because I could not remember the part number I supplied, so off came the heads.

[Cobrajet2]

The cylinder walls don't seem to have that nice dull-gray crosshatch look to them either. Hard to tell from the pic, but the walls are shiny with fine scratches all seeming to go one way instead of a crosshatch pattern. Guessing it will have to come all the way apart now, unless we find something really wrong in the heads, which were re-done, although a long time ago.

[My427stang]

So first, I would say with a piston .020 or so down the hole, and the heads you run, assuming an 8554 head gasket, you just have low static compression for the cam.  Depending on how much your heads and block were cut, and using the blue gasket, you could be at 9:1 for a cam that would prefer 9.75-10:1 in a 390, add the 60 degrees of overlap and you lose bottom end

Low compression and overlap will also show itself as low vacuum as well, even worse if timing is late.

Those cylinders don't look bad to me, it will be interesting to see what the heads do, but I don't expect much wrong. 

So you could just advance the heck out of the cam, but if you advance that cam, assuming you advanced it to 102, you'd gain some torque, however that piston likely doesn't have a lot of room for the intake valve. You would have to measure clearances, both lift and radial (especially radial)

I see three courses of action after you determine if the valve job is good, and they  apply even if you find something in the heads.

1 - Put it back together, crank up the initial to about 16, recurve the distributor like RJP said. "Tune it option"

2 - Put it back together, checking valve clearance and advance the cam 2-4 degrees and recurve the distributor like RJP said.  "Drive up low end power and tune it option"

3 - Rebuild it to modern specs, (leave the cam at 106, .045 or so quench, lots of room for valves, forged pistons, modern ring set, cc the heads, deck it to make sure it's straight, and get at least a 1/2 point of compression more up to about 9.9:1, and then recurve to something like 12-14 initial, 36 total all in by 2800.  "The best option if budget allows"

The thing I'd like to point out though, is the heat is likely only related to performance if your ignition timing is retarded.  If it is not late, then it is a likely separate issue, and likely more related to the fan you run. 

Again though, I'd really look close at ignition timing, we know you are low compression for the cam, so it won't ever be low end torquer without changes, but the combination of heat and low vacuum indicate ignition timing issue.

If that is not the case, then I would add compression or advance the cam, and then go find why it runs hot

[Cobrajet2]

Thanks for the response, Ross. You are correct on the 8554 head gasket. A friend is going to help me check out the heads, and I hope there is something there to explain the oil contamination, rather than the rings. Still more investigating to come and I'll post.

Thanks,
Mike

[57 lima bean]

When doing a leakage test I've always removed (don't just loosen) the rocker shafts.This will eliminate any potential of a valve being open.