427 running rich

[55312]

I have a 427 center oiler that is running very rich. A few questions for you guys:

1. Demon says too high fuel pressure can cause this. I have a 650 CFM road Demon on this motor and the pressure gauge indicates ~10 PSI when it's idling. Is this OK? (BTW 650 is not too small according to Barry Grant's formula)
2. This motor came with a NOX setup. I don't drag the car and won't use the NOX for fear of toasting this '64 iron block. Could this be the reason for the rich condition, even though I never use it?
3. This motor is stout and runs well except for the rich condition but here's a real mystery to me: It has a timing notch on the dampner but no pointer or degree marks anywhere. I've had it up on the lift and there is no place to reference the notch. How the heck do I time this thing once I adjust the A/F ratio??? I'm going to take it to a chasis dyno but without finding absolute TDC and using a timing light with the dial, I'm at a loss. Is it common not to have a pointer?

Thanks

Tim

[Dwight]

Your fuel pressure should not be over 7 psi. For street 4 or 5 psi is plenty.
Dwight

[SCOBRAC]

Nothing you mentioned will cause a rich condition. I'm not sure why a Demon would run rich at 10 psi enless it was spilling out the vent holes, but 10 psi will tend to cause the needles and seats to leak, as Dwight said 4-5 psi is pleanty as long as you have a high volume fuel pump.

Your timing won't effect your rich condition directly. You should rather, close the air fuel mixture screws using a vacuum gauge as your guide. As the engine leans out the vacuum will level out and as it gets too lean the vacuum will drop. not the position it begins to drop and back it out 1/4 turn... Do this to both the primary and secondary circuts (and or four corners).

One other thing which really helps is adding a PCV valve... I know it seems counter productive but it is a controlled vacuum leak. It sucks unmetered air into the engine and will lean you right out.

My side oiler was a smelly pig with dual 660 mechanical secondary Holley's on it. It was constantly loading up. The PCV valve smoothed it right out.

[dynoroom]

Originally posted by 55312


I have a 427 center oiler that is running very rich.
Thanks

Tim

One other thing you didn't say was if your air cleaner was in place when it was running rich. If it was check to make sure your lid is at least 3/4" above the float bowl air vents.
You don't need to run your fuel pressure over 7 psi.
Good luck!

[55312]

Thanks everyone. Is there an adjustment for fuel pressure on the electric fuel pump? It's a red Holley. Scobrac - As for the PCV valve, I don't see it in your gallery. Those are the same valve covers I have but the right side has no holes in it for a PVC valve.
The air cleaner is an H&S type soon to be replace with a K&N Extream I ordered a couple of weeks ago. No interference with the float adjusters.

[SCOBRAC]

Actually I just put it on recently. I had been chasing new engine gremlins for a few months, undersized fan, thermostat issues... I got it all dialed in and it ran ok but it was tricky getting the idle to settle down coming off throttle at a stoplight. It would idle fine after about 30 seconds, but from stopping to 30 seconds after stopping it would idle high, 1100-1200 or so. I have it plumbed to the back of the medium rise manifild port with a tee to the power brake booser. There is a one way check valve between the tee and the brake booster to hold as much vacuum to the brakes as possible.

Both my valve covers have screw in breather / cap holes. I put the pcv valve right into the valve cover with an oversized pcv bushing and it corrected the rich condition / off throttle idle problem. I was concerned about brake vacuum to the booster because I only get 5.5" of vacuum. I haven't checked the manifold vacuum since installing the valve but it doesn't really matter, drivability increased and the braking hasn't suffered.

It's hard to say whether your carb is undersized. It depends on how you drive it and what you want it to do. The 8v Medium Rise engine had a pair of 710 cfm 4160 style Holley's. I started this engine on a pair of 450 cfm carbs I ran on my 428. They were ok. But I knew there was more to be had. I really debated on whether to go for a pair of 600's or something bigger. Vacuum secondary carbs will only ever flow what the engine demands of them so while I knew the 427 could never really draw 1200 cfm there was a reason Ford went with dual 710's...

I decided the 660's would be a good compromise. They are excellent. They really woke up the side oiler. I run them slightly progressive and the 660's open about 30 degrees before the secondaries begin to open. That gets me all open in the front primaries, 1/2 open in the rear primaries before the front secondaries begin to open. I am at 3/4 throttle before the rear secondaries begin to open. At WOT everything is open. The effect is pretty impressive. I have no stumble or bog. Just tons of wheel spin.

I recently acquired a 427 equipped thunderbird with a vacuum secondary 750 cfm 4150 holley. It's a mild 10:1 engine, 280 duration solid cam, etc. It didn't seem like enough carb. I found a old NASCAR 750 cfm Holley reworked to flow 932 cfm.

It really woke up the 427. It acts like a completely different engine.

I'm not big on over carbutration but in both cases the changes were dramatic.