429 Fresh Rebuild

Hi all. I just rebuilt a 1969 429 Thunderjet with SCJ 11:1 Pistons (everything except the heads). It runs awesome....clean, smooth and powerful. After a lot of tuning and testing, it started running like crap with excessive exhaust. I put new spark plugs in and presto. Everything was great again.

Now after about an hour of elapsed run time, it's back to rough idle, hard to start and excessive exhaust. I checked the plugs and they are all carbonned up really bad.

I'm certain that I installed the rings correctly so I'm leaning towards the heads (valve guides). Is my logic sound or could there be something else?

Could be an ignition problem when it gets hot like a box or coil going bad. The other thing I would look at was carb and fuel pressure and things like vapor lock or high float levels, idle screws set lean ect.

If the rings or guides were that bad you would likely see blue tailpipe smoke and the plugs would be oily looking not as you describe.. You need to give more detail, to get better input.

supervel45 wrote:If the rings or guides were that bad you would likely see blue tailpipe smoke and the plugs would be oily looking not as you describe.. You need to give more detail, to get better input.

I believe it is blue smoke and lots of it. Plugs are completely black and powdery (not wet though). Oil doesn't seem contaminated.

1. What kind of rings did you use? What cross hatch finish? 2. What was the ring gap? How where they broke in? 3. What oil are you using? 4. Where all the rings offset properly? 5. Any water coming out the exhaust?

supervel45 wrote:1. What kind of rings did you use? What cross hatch finish? 2. What was the ring gap? How where they  broke in? 3. What oil are you using? 4. Where all the rings offset properly? 5. Any water coming out the exhaust?

I forget what rings. I ordered them through the machine shop where I had it bored out 30 over. I broke it in by running it at around 1200 for 25 min. 10w 30 is the oil. Yes I offset the rings. I'm leaning away from the rings as it is all cylinders with the worst being the front 4.

There is no water coming out.

You need to go drive it on the high way awhile at varying speeds and seat those rings in, if you have not. Check your oil consumption, to make sure that is the problem. Also keep and eye on radiator level to rule out water in exhaust from leaking gasket or craked head ect.

supervel45 wrote:You need to go drive it on the high way awhile at varying speeds and seat those rings in, if you have not. Check your oil consumption, to make sure that is the problem. Also keep and eye on radiator level to rule out water in exhaust from leaking gasket or craked head ect.

so 25 min isn't enough? The car isn't on the road yet so I can't drive it. I'm happy if that's all it is but remember, they are the original heads. Do you not think valve guides could be the culprit?

You need to run an engine under load to seat the rings properly, in my opinion. Guilds or valve seals will usually smoke on start up after sitting, and clear up as the engine warms up, unless they are totally shot. I would want to run it on the road and not idle a lot if it is possible until the rings are seated properly also. What is your timing set at? Not saying that is your problem, but may be part of the issue.

supervel45 wrote:You need to run an engine under load to seat the rings properly, in my opinion. Guilds or valve seals will usually smoke on start up after sitting, and clear up as the engine warms up, unless they are totally shot. I would want to run it on the road and not idle a lot if it is possible until the rings are seated properly also. What is your timing set at? Not saying that is your problem, but may be part of the issue.

6 deg. but not sure at what rpm. 800 is my guess. I wish I had a leak down tester.

pull vac off dist, plug/cap vac hose, set at 10deg at idle.

I don't know your combo but you might try 12-14 and check your total and see how it does.

ROAD RAGE wrote:pull vac off dist,  plug/cap vac hose, set at 10deg at idle.

really? Specs say 6 deg. (without vacuum advance)

Your engine discription leaves a lot to be desired. Are you running a points SCJ distributor? Are you running a Blueprint SCJ mechanical cam? SCJ intake and original carb.? What octane fuel?

supervel45 wrote:Your engine discription leaves a lot to be desired. Are you running a points SCJ distributor? Are you running a Blueprint SCJ mechanical cam? SCJ intake and original carb.? What octane fuel?

New points in original dist. Original cam and intake and new holley 750 carb. I plan on running 94 but right now it's 91 octane. Oh by the way I switched to an electric fuel pump red for approx. 400 hp. 42 gallons per hour I think. I forget what psi.

pineguy@hotmail.com wrote:

supervel45 wrote:Your engine discription leaves a lot to be desired. Are you running a points SCJ distributor? Are you running a Blueprint SCJ mechanical cam? SCJ intake and original carb.? What octane fuel?

New points in original dist.  Original cam and intake and new holley 750 carb.  I plan on running 94 but right now it's 91 octane.  Oh by the way I switched to an electric fuel pump red for approx. 400 hp.  42 gallons per hour I think.  I forget what psi.

I would check your points gap and distributor rotor and bushings for wear. A new condensor might be a good idea also. You will have to stay low on timing or run higher octane for that combo. Those Holley red pumps are weak, I would have gone with a Blue pump myself. None of this will make it smoke though. I would get an infaered thermometer and check temps. close to the heads and compare cylinder temps with a fresh set of plugs installed.

When I said distributor rotor, I meant the cam lobe that the points ride on. They can wear and affect dwell quite a bit between cylinders.