Hey guys I have only one valve that gives me problems It needs a shorter pushrod.But I would like to have adjustible rockers.Could I just buy one rocker for now and slide it one with the rest of my non adjustible rockers to fix just that one valve.Will buy the rest as the money come in.

 

That'll work, the ratio will be 1.76 vs 1.73 but that won't really matter. Use care when removing the rocker stands as they are a tight fit and you might scratch the shaft or damage the stand. Don't forget the pushrods are different.

 

hey jspegg i was wondering if you dont have an underlying problem why is this one giving problems ? bad lobe on camshaft-lifter? rocker ? stud pulling out of head? might want to check these hope that helps!

 

I dont know why this one gives me trouble.It started when I noticed that the 2 cyl. exuast side pushrod was bent when I replaced it my 2 cyl. would not fire, the exuast tube on my hedder would not get hot but it was getting gas.So I did a copression test and it had no compression but if I backed off the rocker bolts some it started getting compression.I tried to find a shorter pushrod but I would have to have on specially made.I did a vavle lash check on it and that cylinder had on lash at all.the intake side is fine its just the exuast side.Right now I drive around with my rockers arm a little loose so that cylinder will hit.

 

here is 2 cents worth...your #2 ex valve seems to be longer than it should be for some reason. and there is also a possiblity here that the valve hit the piston (hence the bent pushrod) This "valve stretching" is not too common, but it does happen. Usually this happens to an exhaust valve...let me know if you ever dive into your underlying problem. You did not mention if the compression is up with the other cyls.

Wayne

 

DON'T DO THAT!! Running with the rocker arm bolts loose is NOT GOOD.

The rocker arm stand carry oil under pressure and carry oil to the valve / rocker arms... With a loose bolt the oil will just go out the first hole it can. You will do damage.

Take a straight edge and remove the rocker arm. Place the straight edge over the valve tips, they should all be the same height. The edges of the valve tips are hardened but can be filed down to match. look at the rocker arms for a mushroomed tip as well, I've seen this many times and had to toss out two sets because of this.

You will cause problems running with a loose bolt - the main bearings can starve and you might end up with a MUCH bigger problem. Don't forget they have three different bolts 2 short, 1 long with reduced shank, 1 longer with reduced shank. The longest goes where the oil hole is and the short ones at the ends, this is important for proper oil flow.

 

[font color=red size=2]Checking the valves with a straight edge is a good idea. If one or more valves are taller than the others, that usually means you need a valve job. The seats get worn away and the valve has to go farther and farther up to seat, thus pushing against the rocker. If there are any uneven valves, pull the heads and have hardened valve seats put in. That's what I had to do to my 390 last fall, it runs WAY better now...

Just a thought.

Marty

"Cleverly Disguised as a Responsible Adult"[/font]

 

Let me update yall.I took a straight edge and laid it over the valve tips with the rockers off and 5 vavles were taller than the other 3 alot taller. So I did a valve lash test to find out which one was right the shorter one's or the taller one's, the shorter one's were right which means the other 5 valves are to tall probably worn seats like yall said.4 out of the 5 are exaust valve's.Most of them are just barley seating enough to get compression 4 of the 5 run about 100 lbs except for the 2 cylinder which is the one that gives me the most trouble it is way to long.So yesterday I went and bought a grinder and grinded off on the 2 valve so I could tighten the rockers down all the way and still get that cylinder to hit.Thanks for telling not to leave the rockers loose I never would have thought of starving the mains and belive me I dont want to do that.Saturday me and my dad are going to grind off on the other one's to get it where it needs to be.When to valve seat all the way I get 150 lbs of compression.So it should run alot better.I not grinding is not the right way to fix but its better than nothing when your broke.

 

Now that you've ground away the tips of the valves, you may have a problem with the valve tips mushrooming. The tips were hardened.
Jason Kendrick
1970 F100 Custom 390/C6
1978 F150 Ranger Lariat Supercab 460/C6

 

Well considering my problem is worn out heads instead of pulling the heads off and having them redone.I can grind the tips off and then if they mushroom out and give me trouble I will do a head job.I dont have the money to do the heads right now.And besides I have been told I cant put reworked heads on and old motor because It will hold higher compression than the rings and will blow the rings out.But my rings are still good I have around 150 lbs of compression would they hold up to new heads.

 

I've heard the same rumor about new/rebuilt heads causing old rings to fail. Has anyone else experienced this first hand? But I agree with you. With out the money to repair the heads or buy a custom made pushrod or two, shortening the valve is about your only option. I would pull the valve cover in a week or so and check that valve tip to see how it's doing.
Jason Kendrick
1970 F100 Custom 390/C6
1978 F150 Ranger Lariat Supercab 460/C6

 

150 is close to stock, A new 390 should be in the 170~180 range and that's not too far from where you are. I'd have the heads done when you get a chance and then if the rings go later, I'd re-ring it or consider a rebuild. You can check the rings by looking at the amount of blowby, usually this can be done by looking at the amount of presure in the valve covers. Also a good PCV system will help the rings to seal.

 

I dont have any blowbye But I found out yesterday that the compression gauge I was using was bad.I bought a new one and my compression is 130lbs on the drivers side and 120 on the passanger.Considering the engine has over 100k thats pretty good.I take very good care of it.So putting new heads on would probably be to risky.My rings are in very good shape I dont have any blowby I dont smoke any I dont use oil my plugs are good and clean.My rings would probably hold high compression, my heads is probably why its only 130 to 120.But to me it would be to risky to try a set of new heads,No money and no place to pull and take engine apart.Do you think maybe putting a used set of heads on there would be ok.I thought about finding a used set of heads maybe from a salvage yard and just checking them out to make sure they look good and put them on there.

 

I don't like that idea. I put a rebuilt head, new valve job, milled... on an engine that had over 200,000 and that was 5 years ago, it still runs great. It's not an FE, but I still wouldn't second guess putting new heads on an old engine. I just can't see the rings being so bad that they would get much worst with new heads.

Not to mention, I would never put a used head on an engine. Not that it wouldn't work, but I just don't like the thought that it could have cracks, worn guides... Either way it sounds like you would want to keep the low compression based on the old heads not sealing as good as new ones, it's just not a good idea no matter how you look at it.

I'd just have your's redone with hardened seats and examine the condition of the bore when the heads are off, look for scratches and scuff marks, try to wiggle each piston at various points in the bore.

I really don't see a problem with new heads on an old engine, and old unknown heads are most likely a waste of time.

 

[font color=red size=2]I have a 73 390 that has about 85K on it. Last summer I did a valve job - new valves, guides and hardened seats. I put them back on my 85K bottom end and haven't had any problems. It runs very good - lots better than before. I would go for the valve job, if I were you. Your bottom end sounds very strong, it can handle it. IMHO - of course.;-)

Marty

"Cleverly Disguised as a Responsible Adult"[/font]