new roller rockers and smoke

[lord_cobra]

Hello,

I am new to the forums but after doing some searching it looks like there are some pretty experienced people here. Anyways my problem is that in my 69 Mustang with a 302 I put different heads on that I ported and polished a little bit. On these heads I put on Harland Sharp 1.6 roller rockers and installed guide plates and hardened pushrods that are stock length. After getting everything installed I have tried adjusting the rockers a couple of times because of clacking but still have work to do with them. Any tips on adjusting would be helpful. The problem that I would really like some advice on is that while I have it running and I rev the engine I get a small backfire out the carb. The carb is a Holley 600 with vacuum secondaries. Also the engine seems to smoke a lot by the headers. Now the smoke could be from oil still on them from when I was messing with the rockers but I read somewhere that it could be from not having the oil baffles in the valve covers. I had to remove them from mine to clear the rockers, don't know which new valve covers I want to get yet. Anyways any help would be greatly appreciated as I would like to start driving it again.

Thanks

 

[danny clemens]

Did you have the correct length pushrods in? It is important that you keep the valvetrain geometry correct.

 

[oz]

What heads did you put on? Were they refurbished (guides, seals, valve job, etc)? Did you check the geometry of the new rockers to the tip of the valve?
Did you add the proper lifter preload? ...contrary to popular belief, if you have hydraulic lifters you DO NOT have to adjust them with the engine running. Go 1/2 to 3/4 turn past zero lash and lock them down. If you take your time and do it right, it works every time.
If you have too much preload and an intake valve is being held open as a result, you will have a consistent backfire through the carb and a rough running engine.
Put a vacuum gage on this engine and see if the needle is steady. If it's very jerky or there is a regular drop, your valves need adjusting.

As for the smoke, make sure that your pcv/breather system is not sucking oil into the carb. If necessary, convert your 'screw-in' breather to a 'push-in' type (where there is a 3" tube attached to the valve cover where the oil filler would go) and put your pcv hose on a breather that sits on top of the tube. Ask me how I know this...

 

[69Rcode_Mach1]

First things first verify your timing, this is a valve adjustment issue, but you need to make sure the timing is set properly first. Then you need to go through and adjust all your valves properly. Valves being out of adjustment will cause your car to backfire out of the carb.

 

[lord_cobra]

Thanks for the quick replies. The pushrods are stock length and I checked where the rockers ride on them with assembly lube. The timing should be pretty good it is advanced 8 degrees right now and I might advance it a little more. What is the best way to get the rockers to zero lash. The first time I put them on I tighted the rockers down with no load on them until the pushrods were hard to twist with my fingers and then tightened them another 1/2 turn. The next time I did it since they were clacking pretty good after getting on it for awhile I loosened them all then spun the engine over without the distrubutor hooked up ( it is a DUI eltectronic) and tightened all the loose nut by hand and did this a few times so they were all close. Then tightened them another 1/4 turn and locked them. The heads are refurbed with new valves, springs, and studs. The engine also has an Edelbrock performer intake and cam.
I thought about the carb sucking oil through the pvc valve also since I removed the oil baffles but the smoke is coming from down by the header mostly on the drivers side. It almost seemed to be getting worse the longer I ran the engine so I was getting worried that it was coming out the head gasket or something. It could be just oil burning off still though, at least that is what I am hoping. Its hard to tell cause there isn't much room.
As for the backfiring if it is a valve staying a little open because of lifter preload would it only happen when revving the engine. The backfire is just a little pop too. I read somewhere that it might be caused by the power valve but I'm not a carb expert.
Kinda sucks cause last night when I working with the engine my starter died. Won't cost much but man is that a pain to switch with the headers on.

Anyways thanks for any help again.

 

[D.Hearne]

To adjust lifter preload before firing the engine, you have to do this when the lifter is on the base circle of the cam lobe. Best time is at TDC of the firing stroke. Get #1 at TDC of the firing stoke ( dist. rotor pointing at #1 on the cap) tighten the rocker nut till the pushrod just tightens up, then 1/2 turn, but no more than 3/4 turn. Rotate crank 1/4 turn and do the next cylinder in the firing order. Repeat till all 8 are done. If they're too tight they'll hold the valve open and you'll get a pop out the carb, not just reving it, but constantly even at idle. Too loose and you'll hear the rockers rattle. To check the Geometry, you need to observe the point of contact where the rocker rides the valve stem, not the pushrod side. The contact patch needs to be as close to centered on the valve tip as possible.