Engine Help Needed

[Dave Cote NCRS#38525]

I am stumped and am hoping someone on this board can shed some possible causes for my engine troubles. 1965 327/350 engine. I took my engine to the dyno for break-in on tuesday. Started right up, set the engine RPM to around 2,000, and let it run for 20 minutes....so far, so good. We shut the engine down, changed oil and filter, and started her right back up for a couple of dyno pulls. The first pull, engine climbing just around 3,000, the engine backfires, shuts off. I pulled the valve covers, and #6 intake had hung open, apparently seized in guide, hit the piston and bent the valve, and pushrod. I took the heads off, took them to a very reputable machine shop and they said the guides were too tight, and installed "K" Line Bronze liners, replaced a couple of valves that were galling. The stem to guide clearance was set up at .0015 (1.5 thousanths). Put the heads back on the motor, started right up, warmed up nicely and tryed another pull.....Well, this time the #4 exhaust hung up and kissed the piston, thus crapping out the motor. The dyno shows EGT's are unusually high, but the carb (2818) was running fine when I pulled it off my previously running motor last monday. We checked the cam timing.....dead on as per the cam card. My question is.....Does anyone have any idea what could be causing the valve stems to seize in the guides, other than inadequate clearance, ect. Both myself, and the dyno operator have fairly extensive engine building experience, but I have never seen anything like this before. The engine is getting water to the heads, cam timing is right on, and overall timing is 38 degrees. Someone Help???? Thanks

[Michael H.]

Re: Engine Help Needed

Hey Dave -

What kind of cam are you using? Did you vary the rpm during the break-in period? What kind of cam lube did you use prior to initial start up?

[Dave Cote NCRS#38525]

Re: Engine Help Needed

I am using the Comp Cams XE268. We moved the RPM's around a bit, and varied load on the engine using the dyno. The cam lobes checked out fine this morning with a dial indicator inserted into the lifter bore. I just got off the phone with my machinist and he told me he thinks the seals were a little tight, and may have been wiping off too much lubrication. I think we will try a little more clearence on the guide, and change valve stem seals to allow a little more oil into the guides. The valve train is getting plenty of oil, but it appears the guides are not getting enough to lubricate, and cool the valve stem.

[Clem Z.]

Re: Engine Help Needed

are you using the all teflon seals because they are too tight for the oil to get thru. i always run a 11/32" reamer thru the exhaust seals before using them. umbrella seals work the best on the exhaust. never use the "O" ring with positve seals because you need the oil to run down the stem. make sure you used molykote in the valve stems and guides before installing them in the heads. i aways put a "cross hatch" pattern on the valve stems using 220 grit emery paper between my thumb and finger while turning the valve and moving it up and down. any valve that show signs of sticking should be thrown away because the stem surface has been ruined. if the guides were honed did you clean then very very clean because the grit from the hone will cause this problem.

[Dave Cote NCRS#38525]

Re: Engine Help Needed

Clem,

Thanks for the response. I talked to my machinest earlier and he informed me that he was going to try to give the guides another half a thousandths clearance, and switch to the umbrella style seals to improve the oil transfer to the valve stems. I assume the machine shop is thouroughly cleaning the guides after honing them, and then putting a good lube on the valves. I will get them back tomorrow morning, and give it another shot. If the same thing happens again, I will have to look deeper at the top end of the motor. Thanks

[Larry S.]

Re: Engine Help Needed

Excellent advise Clem

Dave are you going to take his advice on the replacment of the valves? I would recomend it to your machine shop.Good luck

[Dave Cote NCRS#38525]

Re: Engine Help Needed

Any of the valves that have showed the least sign of galling or heat have been replaced.....

[Werner R.]

Re: Engine Help Needed

dave
here is a beginner question. what is galling??
werner

[Greg Vaka]

Re: Engine Help Needed

You didn't say anything about oiling. When you pulled of the valve covers, was there a sign of adequate oil?

[Clem Z.]

Re: Engine Help Needed

that is when one metal object deposits metal on/in the other metal object from friction

[Dave Cote NCRS#38525]

Re: Engine Help Needed

Engine is getting plenty of oil to the top of the motor. Got the heads back today, and should have it up on the dyno again Monday or Tuesday. Hope the problem is solved. Will let you guys know. Thanks again for the advice.