My 427 SOHC Build..... Finally the time has come!

[cobracammer]

Be careful.  I had mine at 14.7, and although it idled perfectly in the driveway, but as soon as I went out on the road, it died.  Still working through my understanding of it all.  Lol

[My427stang]

So, your info is really good, but, you may be fighting the simple programming capability of that system.

In my experience, as long as the IAC value doesn't sit on an extreme, 0-10 or 90-100 (assuming your scale indicates % open) I let it sit wherever it wants.  The idea is that as long as it has room to open or close as required, I don't care if it's at any exact point

That being said, I didn't comprehend that 13.5 is their default, they must expect that the system will be used with cams with some overlap and then just account for the raw fuel. 

Now, one concerning thing, at idle, white smoke, usually isn't fuel.  Fuel will be black or hazy dark gray, and to be honest I have never seen an engine smoke at idle due to unburned fuel.  Once you goose it, it usually will barf our a black puff, but to have white smoke to me sounds like oil (very light blue, not white) or antifreeze (white steam), additionally check your brake fluid level to make sure it isn't sucking brake fluid due to a bad booster or master cylinder.

As far as your question on a/f ratios for cammers, I'll jump in but I am NOT a cammer guy.  First, true the cammer is likely prone to more scavenging which will pull more through at overlap, hemis do that.  However, usually not so much an issue at idle, there just isn't that much of a negative pulse in the exhaust with no load and low flow.  Additionally, comparing one a/f number to another is very difficult, location of the sensor, type of sensor, how the programming interprets it, is all different.  All you can do is loosely compare information, especially at idle when exhaust flow is low.

For giggles, how far away is your O2 sensor from the head, just a WAG, don't need you to measure it unless it's easy.  Also, is it pointing at some upward angle?  I actually have mine slightly too far back (right behind the collector on the H pipe) and I had to program a delay into the tuning to account for the location.  Of course yours can't do that, but that could explain some goofy behavior.

If there is any way to take a movie of your smoke though, I think it would help, for the tuning setup you have, it shouldn't be smoking and the description, to me anyway, doesn't sound like fuel.

One last comment, can you shut off learning, and if yes, do you when programming and test driving afterwards?  I have had very good luck with programming until I am happy, then enabling learning afterwards

[jayb]

Your cams aren't real radical but they are not real mild, either.  I don't think there's anything wrong with a 13.5:1 A/F at idle, especially in light of the SOHC chamber, which is not particularly efficient.  I also think you are always going to get some fuel smell out of the exhaust; I always do.  If it runs well at 13.5 I'd leave it there.

[My427stang]

Your cams aren't real radical but they are not real mild, either.  I don't think there's anything wrong with a 13.5:1 A/F at idle, especially in light of the SOHC chamber, which is not particularly efficient.  I also think you are always going to get some fuel smell out of the exhaust; I always do.  If it runs well at 13.5 I'd leave it there.

Jay, as I said, I have zero experience with cammers, did do some EFI 426 Mopar Hemi stuff a long time ago, but that was in 1998 I think with the original Holley TBI, good for it's day but not good LOL

Question though, if the chamber isn't too efficient, why only 30 degrees of total to make peak power?  Seems counter intuitive, usually it takes a very good chamber to get total that low

[Barry_R]

Stop worrying about A/F readings at idle.  Many aftermarket O2 sensors and systems do not have the capability of getting good data at low airflow, where exhaust system reverse pulses and temperatures can be highly variable and influence the readings.  Set idle where it runs the best.  Smelly exhaust can also come from being too lean - unburned hydrocarbons from a sparse mixture.

[cobracammer]

Actually just remembered the last video I took of the car running in the driveway, it had no smoke and was at 13.5.  Vacuum brake tube sucking break fluid possible.  Ill try and take another video, but ill leave it at 13.5 because it runs well there.  Thanks guys. 

[jayb]

Jay, as I said, I have zero experience with cammers, did do some EFI 426 Mopar Hemi stuff a long time ago, but that was in 1998 I think with the original Holley TBI, good for it's day but not good LOL

Question though, if the chamber isn't too efficient, why only 30 degrees of total to make peak power?  Seems counter intuitive, usually it takes a very good chamber to get total that low

That's a really good question Ross, and I have wondered about that myself.  A full hemi chamber like the SOHC has is generally considered to be a poor chamber, what with the big piston dome required that inhibits flame travel, lots of surface area, and no quench area.  And, I have had people who ran these engines back in the day, Jim Barillaro for example, tell me that he used to run up to 38 total on his engines.  But on the dyno, anything past 31-32 degrees results in a power reduction.  I pushed the timing once with one of my SOHCs and had to back out of the pull when it started audibly knocking.  So, I don't know why they only like 30 degrees or so of timing, but it certainly isn't because they've got an efficient chamber.

[machoneman]

Jay, didn't Barillo run alky or a light alky/nitro load in his cars back then? I'll venture he was talking only gasoline....or was he?

Oh, and on what octane fuel did you SOHC start knocking when you have to pull the timing back? 114+ race fuel?

[jayb]

It was a 12:1 SOHC and it was knocking on 111 octane Rocket Brand racing fuel, if I recall correctly.  And I'm pretty sure that Jim B was talking gasoline, because we were talking about my engine at the time.  But of course Jim has run the Methanol/Nitro mix in some of his cars...

[cobracammer]

Hey all.  I also noticed that since I have had to snug down the valve covers to stop oil seeping through or around the cork gaskets, the sparkplug tube O-rings no longer seal the lip of the tube to the lip of the valve cover.  This is also letting oil "mist" out of this space.  I am thinking that I can either wait until the new valve cover gaskets Jay has been speaking about become available, or I can contact Doug over at PrecisionOilPumps and order a second set of spark plug O-Rings and double up each tube? 

[Heo]

I had worked a litle with British bikes and they got full hemi
chambers.I think they lose power with more ignition because
the ineficient chamber cant take any more ignition.  And the
combustion starts acting up before they start knocking just a
theori i have no sientific tests to back it up. They are said to
like dual plugs though
And take a Flathead for
example, They dont have anything near a efficient chamber and
dont like  much ignition att all and have realy low compression.
But they could run higher compression and more power out of
a flathead than a overhead valve engine before they "invented"
the squisch area in the combustion chamber. The old overhead
valve chambers was just a round hole with straight sides and a
flat bottom with 2 valves.They have wery rough idle and feels
tired compared to a Flathead. Many makers went back to flatheads
from Overhead valves

[jayb]

Jason, you should be able to get those O-rings anywhere, they are a standard size.  Also, you could just use a blunt screwdriver and push them down into the recess in the valve cover; that will seal up the leak.

[cobracammer]

Hey Jay.  Ok cool.  I will try pushing them down first  :-) 

[cobracammer]

Ok, I have crawled all over this engine top and botton.  I don't see any obvious leaks.  I can say with 100% assurance that valve covers are not leaking.  Took a light and saw it was dry all the way around.  Then on to the distributor.  Marked a few points so I can relocate it back perfectly.  Then I pulled it.  The o ring was on the distributor!  Good and bad news.  Then I thought about the stud for the distributor hold down.  Pulled it out and it did not seem to have any thread sealer on it ( or if its even supposed to)  for good measure, i added the sealer and tightened it back down.  The stud actually pertrudes into the crankcase so possible oil can seap out.  Then i noticed the o ring that came with the distributor actually was not a tight seal in the intake!  I think this might be the issue!  Need a beefier o ring for the distributor.   This might be an issue with the intake as it was Robert Ponds prototype intake.  Possible the hole for the distributor was machined a tiny bit to large.  This might be the only leak.  I think it was traveling which made it hard to track

[cobracammer]

OK Update.  I decided to see if after adding thread sealant to the distributor hold down stud, and a good cleaning of the distributor and O ring...  if we still had a leak.  Start getting things narrowed down one at a time.  Put all back together. Started the car, checked the timing (Still at 12 degrees initial) and let it warm up.  While it was Learned on this go around that I could still go down "1" on the accel fuel and it doesn't stumble or hesitate.

Got back into the driveway and popped the hood......  OIL!  The distributor area was all wet again and dripping down the side of the block.  Its almost surely the O ring.  Think I need a stlightly thicker one to seal it up.

Secondly, after trying to push the o rings around each spark plug tube down a little with a flat tip screwdriver....  All this did was allow more oil to splash out!  LOL  This time oil had forced out around each spark plug (mainly 6-8) .  So much so, it was on the valve cover, spray in the intake manifold, some was on the throttle cable bracket, and more importantly, Some sprayed to the back of the manifold and started to leak down the bell housing......

So my only problem at this point is O rings!!!  LOL 

For a small test, I had a wide rubber band.  I wrapped this around the grove of the distributor flat and then put the o ring back on.  I wanted to space the o ring out a millimeter or so (the thickness of a rubber band.  When I tried to reinsert back into the block, it would not sit flush with the intake.  So the o ring in there is too small, but adding a rubber band of thickness is too much?  Maybe I need the old fashion tubular o ring and not the wedge shaped one that came with the MSD distributor?  As for the Spark plug tubes, I am going to try and get another 8 O rings and just double them up.  They were not a problem until I needed to wrench down on the valve covers (due to shrinking cork gaskets).  As soon as I did, that opened up the space between the lip of the o ring and the copper spark plug tube.  These 2 things seem to be my oil leaks.