I was having a great day, on my way home from American GM day display, car was running great. I stopped for fuel and heard a rattle as I was leaving the servo. Thought it was a broken valve spring or rocker and limped home. Here are the results. I removed the covers and number 3 intake had no oil on the roller rocker, unlike all the others. Pulled the plugs as well and #3 was wet with fuel/oil. Pulled the rocker to check the valve spring and the valve stem moved around about 1/8th inch. figured it was the valve guide and started removing the intake. The heads are coming off tomorrow as it is 11:30pm here. The heads are 074 castings and I am not in a position to dump them for some newer alloy heads. I am hoping they are easily repairable. I will also drop the sump as the metal from the damaged rocker arm is no where to be seen in the head. I will pull the oil pump to check the screen as well. Any suggestions on other things to do?

That's the valve guide in the port. There was some metal shavings lying in the port. I will see if there is any damage to the piston/bore tomorrow.

Shattered pushrod seat, I will be looking for the pieces in the sump

 

James,

I feel your pain. My motor destroyed all the conrod bearings last week and HOPEFULLY should be back in time to ship over to OZ on 8 Dec 2005.

You can do almost everything EXCEPT pull the crank with the engine in the car. Heres the problem though. If you ahve material, an by the looks of it lots of it, then you really need to remove your oil pump and clean that, you also need to check all your bearings for scores/scratchs from the metal thats floating around. Probably easiest in the long run to pull the engine, strip it, clean it and assess what broke.

Hopefully a bad lifter or a wiped cam caused the problem and you can get out of it with some minor parts and and move one.

Hope it works out. Look forward to seeing the car when I get home.

Cheers,

Pete

 

Pete,
The small amount of shavings were in the intake port. Hopefully any shavings that made it into the combustion chamber will have also blown out the exhaust. I will find out when the head comes off.
The only other metal should be from the shattered pushrod seat on the roller rocker. could not spot any metal around the valve which is why the sump is being dropped.

 

good luck after head come off

 

OK, Head is off and at the engine guys. The knock in guide had come out and they can't find the reason (yet). They tried refitting the guide in the head and it is tight. No scoring on the valve stem, it still slides freely in the guide. The engine guy is going to examine the other guides to see if the problem is this cylinder only or all the guides. If they find more faulty guides the other head comes off as well. They can repair the guide by reaming and using an oversize guide.
Lucky for me the shattered pieces of the rocker were caught in the oil around a head bolt. I will still drop the sump and flush but at least I have found all the big bits and most of the small pieces.
There are some Aluminium shavings on the piston but the bore is looking OK. I will clean them all up and go right over the bore and check the piston.

Now for the "while I am at it...."
The motor always seemed to valve bounce at 5500. The springs have 120lbs at installed height and this should be able to control the valves to 7000. I am using Rhodes lifters, .520 lift cam designed to work from 2000-6000rpm, Yella Terra 1.7 roller rockers, 3/8 pushrods and have plenty of oil pressure.
I would like to get to 6500 revs with no problems. Any suggestions?

 

Beehive springs and retainers might be an option or a double spring set-up

 

I already have double springs and I believe they are the original factory set. the heads are 074's, Basically L88 from a 69. I have considered new springs but the ones on there still have 120lbs.
Could springs fatigue and still give the 120lbs seat pressure at 1.94 installed height?

 

Installed height on a BBC should be 1.88, but .06" won't make that much difference.

Your hydraulic cam and lifers won't rev to 7000. If you change to a solid lifter cam, no problem.

 

Sorry, quoting from memory is not always the smartest thing to do. I am pretty sure I measured the seat pressure at the correct installed height, 1.88.
The hydraulic cam should be good for 6000 though, heck the new LS7 is good for 7200 and I am pretty sure that is hydraulic, albeit a roller.

 

I too would give the beehive springs a try, remember the BBC does not have the best vlv train geometry.

Also with a hydraulic non-roller you'll be limited in terms of RPM. Hell my stock LS-5 gives up at anything over 4,200 rpm, yuck!

carbster...

 

Hi

I am with GDaina, solid lifter setup will solve the problem.
Hydraulic cams don't like it at this high revs.
I can rev my old L71 heads easy without any problems.

Günther

 

Do yourself a couple of favors here. First, have the machine shop "pin" the guides, that was a very common problem with the 074's (dropping guides), second, get rid of the "cast" rocker arms, and third, let 'em step the guides down to .343" stems with bronze liners, and replace the valves with the smaller stems. Everything works much better. One final note, use spring cups/locators under the springs, not shims. Thanks, Gary in N.Y.
P.S. Those were the heads that also needed the longer (bottoms) on the exhaust rocker studs.

 

Well I am glad the cylinders didn't get mashed up. I get freaked out when I see any metal in an engine.

Sounds like the heads are the only problem. I am having some success also. My motor is back in the car. Now to get if they can only get it to run

 

If there are metal particles laying in the engine, chances are those particles circulated throughout the engine like they did on mine...chewed up the oil pump gears, wiped out all the rod and main bearings, put scratches in the piston skirts and cyl walls, but not deep enough to buy new pistons or bore the block.

I was going to do this on the cheap and just replace the bearings, but thought about it and decided to pull the block and have it boiled....actually had no choice as the crank had to be turned .010, .010.

 

Gary, could you please eloborate on why I should replace the existing roller rockers and what you mean by the heads needing the longer bottoms on the exhaust rocker studs.

I currently only have one head off and by the sound of it I need to pin the guides on both heads. Things are tight so I probably will not go the smaller valve stems
Thanks,
James

 

Captain James,any good news yet?......hope it goes well.....john

 

Sort of good news.
My engine man has done some investigating and Nissan aparently had a similar problem with the V6 alloy heads, Guides dropping out that is.
They fixed the problem by grooving the guide and using circlips to locate the guides. My man says it is easier (read cheaper) than pinning the guides. Meanwhile I still have to remove the other head and drop it off to them. I am planning on using spring locators in the heads and possibly new springs with a higher seat pressure. Also thinking of dumping the Rhodes lifters and going for a set of quality anti pump up lifters. Still waiting on Gary's response why I should dump the existing Roller Rockers before I purchase a new rocker or set of rockers. At least I will only be off the road for a week or so.

 

James,i too can't see what is wrong with the yella terra rockers...i've got the platinum ones and will be interested to hear gary's reasoning.....i used bronze guides in my brodix heads and the engine revs cleanly to 7300 rpm(its supposed to go to 7500+ but ive never bn game to do it)...i know your bbc is different but plenty of ski race bbc engines run cleanly to 7500......john

 

Most of the opinion here is that the limiting factor is the hydraulic cam and lifters. I believe I should be able to get to 6000 cleanly with a sorted Hydraulic set up and hopefully 6500. I don't wish to rev the engine any harder than that.

 

Just a quick point,
Whenever I rebuild an enginge, I always drop a rather powerful magnet in the sump - just in case any bits start floating past.