New 252 cam and valve geometry questions

[robwymer]

Sorry about the length, I just get started some times and can't stop. I think it's pretty descriptive though.

Well, I got my new 300 six in my 67 stepside. I had it starting and running pretty good, except that whenever I tried to accelerate hard, the top of the engine would squeak loudly and the Holley 390 would cease to deliver fuel. Maybe I need to adjust the fuel bowls or something. But one cold morning I had a hard time starting it. Once I got it started, it ran like an old piece of junk lawnmower, but got better as it warmed up, even though it had a noticeable rocker tap or exhaust leak sound. I had a heck of a time starting it the next time later that day, and when I got it started, it sounded like a lawnmower again.

Thinking I might be missing on a cylinder or two, I checked the plugs and plug wires. The plugs were fouled (at least I'm not running lean), but the wires were fine. I checked the compression, and found no compression in #3 and low compression in #4. As its a new engine, I figured maybe the head bolts worked loose, so I pulled the valve cover. I quickly noticed the source of the tapping, as one of my rockers was sideways. I re-torqued the head-bolts, but didn't find much in the way of loose bolts.

While adjusting the valves again, I noticed that the rocker arm stud on the #3 intake valve had been pushed up about a quarter inch. The #4 intake valve rocker stud was up about a sixteenth. That explained the compression. Upon checking the pushrods, I found the #3 intake pushrod slightly bent and the #4 intake pushrod severely bent and difficult to remove. I thought back on how a couple of the lifters in the reman engine were soft enough that I could compress them some by pushing on the pushrod with my fingers, but assumed that a valve adjustment would keep the right amount of tension on them.

I should also mention here that I swapped in a 252 degree RV cam with a .427 advertised lift. Its re-ground, and I'm guessing its a CompCams model because as far as I can tell, they're the only ones with that duration and the lift is close to the CompCams spec. But looking at my cam's spec sheet, the valve timing doesn't seem close. I would be glad to share these numbers if anyone knows cams.

Looking at my 1967 Ford truck shop manual, a 1967 300 six had a lobe lift of .2490 and a theoretical valve lift of .400. Which value should I compare my advertised lift of .427 against? Not to mention, do I need different lifters, pushrods, rockers and/or valve spring with my cam or should the stock components work? Do I have to use a different valve adjustment procedure than what my shop manual calls for? Finally, I wanted to check the cam again for end play. Is it possible to do so by removing the pushrods, lifters and distributor and trying to move the cam back and forth via a large screwdriver through the distributor hole? If I have to take off the front cover, I have to redo the pan gasket. I really don't to do that unless I have to replace the cam anyway. I would really appreciate some seasoned advice on this one.

Thanks,

Rob

[robwymer]

[LANCE65]

I haven't messed with any Ford 6s,but I dont think you would have a problem with the valve springs at that lift. If you have a couple of lifters that are"soft" enough to compress by hand, then they are not pumping up and that could be the reason for the bent pushrods. If the rocker studs are pulling out of the head, then I would remove the head and have a machine shop either "PIN" the studs or install screw in studs. If you bought the engine at an auto parts stores,return it. You will void all warranties by messing with it. Hope this helps some. Good Luck and keep us posted. You can also post this over at "fordsix.com"
-Lance

[sgs]

Rob,

I'll try to send you in the right direction. It's obvious now what your squeak is. Something in your sideways valve train was rubbing on something. Your engine was asking you to stop at this point. Most of my experience is with large diesel engines with solid lifters or "cam followers" in our industry. Your hydraulic lifters shouldn't be compressible by hand. Something is wrong there. I would start with a complete new set.If you hadn't mentioned the compressing lifter, I would have gone right to a valve adjustment error as the source of your problem. I am assuming that you assembled the engine. If so, how did you adjust the valves? I think that we should verify your method before you repeat the same mistake. Your cam doesn't sound like it's too stout for your stock valve train, but something caused those studs to pull out. Once again, I am suspecting a valve adjustment error. The worst possible scenario is that the valves were out of time enough so that a piston contacted them and tried to push them up while they were traveling down. This would cause your bent push rod and the pulled out stud.

You now have two options. the best option is to get a good mechanic, even a good (emphasis on good) back yard mechanic to help you. pull the head and check that you didn't bend a valve during this event. If there is evidence of piston valve contact, have your machine shop pull the valves and double check that they still seat properly and are straight. It is remotely possible that you could have ruined a piston but I think that chance is slim. While your head is back at the machine shop you can have them pin, your studs or install screw in's. this is something that you shouldn't need, assuming that you are running stock valve springs, but since you have stressed them and loosened at least two, they all should be done. I am assuming that your timing gears are lined up properly. If there is any question, pull the front apart and double check. Reassemble your engine, make sure your valve adjustment procedure is correct and life should be good.

I haven't worked on a 300 six for a long time but memory tells me that you can replace lifters without removing the head. If so the second scenario which isn't what I would do is; Replace all lifters, Pull your studs, all. Tap and install new screw in's while being extremely careful to avoid getting filings in your engine, replace the bent push rods, re adjust your valves, hold a short prayer meeting and start your engine.

Good luck,

sgs