valve guide wear ?

[Nucking futs]

Ok, heres the deal, Had my heads redone 25 hours ago, new guides springs and a few new valves. So I was at the river and made a WOT pass and then let off and heard a strange miss in through the exhaust that sounded like a bent pushrod or a broke spring.Did some checking on the water and found nothing as to what i thought it could be. Boat ran good , had all of its power just made a strange little pop pop pop now and then.so i come home do a comp test and all cyl were the same except for #1. was at 110# way off of the rest. I was rolling the engine over and noticed when the # 1 intake valve opened that the lifter was bleeding off and none of the others were doing it. Ok dead lifter no prob got it handled.Put it all back together and it was worse. OK leak down time....HMMM........ no rockers on and had 80% leak down, ok tear the head off and sure enough, wore guide and it took out the seat on the intake valve. no prob found the problem.all others were checked and were like brand new.
So my question is, (25hrs) Why did the guide go so early? spring presures are dead on, push rod length is good or is it just one of those thing that BBC like to do.
This is the second time it has happened but the first time i had like 175 hrs on it and it snapped the ex. valve right at the stem and took out the piston and cracked the cyl and you can imagine the damage.
they are gen 6 heads with 2.19/1.88 valves and have been ported setting on a gen 6 block.
sorry for the long post but does anyone have any ideas as to why this is happening?
Thanks, Tim

[MikeF]

Tim, Did you put them together or did someone else? Maybe the #1 intake was a little sticky or clearance a little too tight (maybe is was not lubed like the rest at assembly)?. The exhaust valves usually get the most abuse.

[Nucking futs]

Mike, I had someone do them. I took it back to them and he said that sometimes they just do that. Just thought i would see if anyone has ever had anything like this happen to them. Im just glad i caught this before CBBB or i would of lost the engine again.

[Floored]

Usually the exhaust will cause grief, but 25 hrs on an intake is just wrong. There is always a reason , sometimes that happens, is not a reason. A mistake on the machinists part is most likely but getting him to admit it and make it right is another. Find a new shop.

[steelcomp]

I don't think too tight a clearance will cause this. It would cause a stuck valve, but if clearance was a problem, then once it wore enough, broblem solved. I'd look at the finish on the stem of that valve. Also, look for poor rocker geometry on that cyl. Are you running roller rockers? Lots to look at when it comes to valve train. You said spring pressures good...wht about installed height?

[Nucking futs]

Installed heights are all the same and good. Running comp high lift roller lifters and roller rockers. Well a new shop may be inorder but the shop i use for my heads is all the do. BPE racing heads in anaheim.
Scott, all the geometry has been checked and double checked. When i had the heads freshened up not all guides were replaced. Im thinking this was one that was not and the guide was of poor quality. Lesson learned, when you change some , change them all for cheap insurance.
Tim

[MikeF]

I don't think too tight a clearance will cause this. It would cause a stuck valve, but if clearance was a problem, then once it wore enough, broblem solved. I'd look at the finish on the stem of that valve.
Tim says the lifter was collapsing. I kinda figured the valve stem is sticking or binding in the guide (guide won't let the valve move). Lack of lube.
Were they bronze guides?
Post a pic of the bad valve stem if it shows the problem.

[wsm9808]

Factory BBC heads have simi finished ID guides installed when they are new. When the original valve job is done they have tooling that finish sizes the guides and cut the seats all in one. But, this can and does cause the Id of the guide to be not concentric with the OD of the guide. Which is not a problem because everything was machined at the same time and everything is true when done. BUT, when you replace a BBC guide with a repacement guide,The new guide is concentric and now may not be true with the valve seat and the spring seat.
Ask your machinist, he will tell you that it usually takes a lot of seat grinding to make the valve seat true with a new guide. What everyones seems to not understand is that the spring seat is now also not true with the new guide. The guide being "canted" in relation to the spring seat causes the spring to force the valve stem to try and run true with the valve spring seat while the guide is tilting the valve stem on a different angle. The spring "sideloading" the valve in the guide causes the new guide to wear extremely fast.
I used to accept that "it just happens sometimes" on BBCs, but my shop has had no problems with BBC guide wear since we started spot facing the valve sping pockets anytime we install guides in a BB head.
Spot face your valve spring seats, your machinist should have a seat cutting tool that has a pilot that goes into the guide and trues the spring seat pocket to the guide. This can be done with a hand drill, but dont, be sure he sets it up on his seat-and-guide machine and sets level on each guide before cutting.

[MikeF]

Sounds legal wsm9808. :D Good post!

[Nucking futs]

Factory BBC heads have simi finished ID guides installed when they are new. When the original valve job is done they have tooling that finish sizes the guides and cut the seats all in one. But, this can and does cause the Id of the guide to be not concentric with the OD of the guide. Which is not a problem because everything was machined at the same time and everything is true when done. BUT, when you replace a BBC guide with a repacement guide,The new guide is concentric and now may not be true with the valve seat and the spring seat.
Ask your machinist, he will tell you that it usually takes a lot of seat grinding to make the valve seat true with a new guide. What everyones seems to not understand is that the spring seat is now also not true with the new guide. The guide being "canted" in relation to the spring seat causes the spring to force the valve stem to try and run true with the valve spring seat while the guide is tilting the valve stem on a different angle. The spring "sideloading" the valve in the guide causes the new guide to wear extremely fast.
I used to accept that "it just happens sometimes" on BBCs, but my shop has had no problems with BBC guide wear since we started spot facing the valve sping pockets anytime we install guides in a BB head.
Spot face your valve spring seats, your machinist should have a seat cutting tool that has a pilot that goes into the guide and trues the spring seat pocket to the guide. This can be done with a hand drill, but dont, be sure he sets it up on his seat-and-guide machine and sets level on each guide before cutting.
That make alot of sence. I will take a trip over to the head shop in the am and ask those questions. The seats have all been replaced with larger ones for the larger valve size.These heads are going to be 86ed at the end of the season anyways but still now i have an idea on way it has happened more then once.The guy that did the heads originally can not be found and thats when i stepped up and found the new place and they have been great.He is going to fix the problem for 35 bucks, so he said it wasnt his fault but he did the heads so he will stand behind his work, just need to pay for the parts which don't cost a ton of money but hey hes eating the labor.

[steelcomp]

Factory BBC heads have simi finished ID guides installed when they are new. When the original valve job is done they have tooling that finish sizes the guides and cut the seats all in one. But, this can and does cause the Id of the guide to be not concentric with the OD of the guide. Which is not a problem because everything was machined at the same time and everything is true when done. BUT, when you replace a BBC guide with a repacement guide,The new guide is concentric and now may not be true with the valve seat and the spring seat.
Ask your machinist, he will tell you that it usually takes a lot of seat grinding to make the valve seat true with a new guide. What everyones seems to not understand is that the spring seat is now also not true with the new guide. The guide being "canted" in relation to the spring seat causes the spring to force the valve stem to try and run true with the valve spring seat while the guide is tilting the valve stem on a different angle. The spring "sideloading" the valve in the guide causes the new guide to wear extremely fast.
I used to accept that "it just happens sometimes" on BBCs, but my shop has had no problems with BBC guide wear since we started spot facing the valve sping pockets anytime we install guides in a BB head.
Spot face your valve spring seats, your machinist should have a seat cutting tool that has a pilot that goes into the guide and trues the spring seat pocket to the guide. This can be done with a hand drill, but dont, be sure he sets it up on his seat-and-guide machine and sets level on each guide before cutting.
Absolutely correct. I guess I ASSumed this was done when guide was replaced and topped. Good post. :D

[wsm9808]

Thanks, i hope the info helps someone. I "learned" about the spring seat problem several years ago sort of by mistake. I was redoing a BBC guide that had failed after only 500 miles, twice. It was a performance head so I was measuring the spring heights with a snap gauge and got interuped by another customer right after I measured that particular spring seat and retainer. When I came back a little later and rechecked the height, It was .010 different than I remembered, After I thought about it I realized I had measured on opposite sides of the spring seat. :hammerhea The guide and sping seat were not true to each other.

[Squirtin Thunder]

Check your PMs