Has anyone had experience with valve guides moving inside the head? this could be caused from either : 1. Overheating of the engine? 2. Incorrect machining from the factory? I'm in the process of getting my rear head redone, and they called me today to say that the valve guides all need to be replaced. he said that you could push them out with your finger! this is after my episode outlined in "308 Cam belt broke anyone wanna help" basically belt shedd bunch of teeth, then made piston to valve interface - could that have done it? Never had blue smoke on start up, or what I would call excessive oil consumption.... any ideas Verell?
I guess its possible that if the piston hit the valve and put enough side load on the stem that it elongated the guide hole in the head. Either way you have to fix it.
I know I'm fixing the back side, I'm worried about the front side ... if overheating would have caused this... I dont want to take the Friggin engine out to get to the other side.
Having Valve/Piston contact will cause the guide to hammer into the guide bore enough to damage it, making the bore a sloppy fit. There are no oversize guides available, unfortunately. if the damage is slight, you may be able to save the head by having guides knurled on the OD to help snug up the fit. Some Loktite will help it seal. A machine shop can do this easily. I suggest SI valve for the guides, and you will have to get the seats reground after doing any guide work, as the relationship to the valve seat can change. Might be a good time to pull the other head and get a valve job, as you are half way there. If only one head lost the belt, there shouln't be any damage to the valve train on the other head. Lack of oil smoke would indicate a good guide seal/valve stem fit. HTH
thats what I was thinking, the guy from the shop called me and said that that he thinks it was caused by overheating??? which I would be supprising... cause I dont think its ever overheated while I have had the car... althought that was the issue when I had my engine rebuilt by FOA about 7 years ago... the block had warped, and they could not line bore it... I;m about over this giant pile of ****! called a Ferrari!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Owning a ferrari sure is a love/hate relationship, cant remember how many times I wanted to burn my 308 to the ground but when it works right, I love it again.
I find it hard to believe the block was warped that far off. But if it were, regardless, what about the heads? I did not know oversize guides were not available, Kermit are you sure they cant be got from another source? Spirot, is it possible you could detail just what exactly FOA did, and what was replaced during your overhaul? Sounds like you have a different block, was it new, did it come with different heads? Where did your old block go?
Well what FOA told me back in the day was like this: While at a track meet, one of the mechanics noticed that my oil pressure gauge was reading low.. he said when we get it back to the dealer ship we'll just pop a new sending unit back in.... ( I was storing my car at the dealer ) - the service manager called me and said that its not the gauge or sending unit ... the engine is low on oil pressure... we will only know once we get in there.... so I said rip it apart and fix it... they found #5 main bearing cap laying on a windage tray, put it back on torqued it up and the crank would not turn.... then they started to measure and found that the block had warped... so new block, I have the old one at my parents house... ( very expensive coffee table for the garage) ... they redid the heads... and put it back togehther... Ive always had an oil leak on the front side of the engine, before and after the rebuild... while I've had the car its never overheated ... its gotten hot... past the 195 mark but never pegged it temp wise... I've always made sure I Have had plenty of coolant, & top it up ever time i take it anywhere ( if its needed it ) I did have the radiator repaird - several small pinnhole leaks... but again its always run fine and only ever creeps up while in traffic...which I avoid like the plauge. what I find so wierd is that the shop guy is saying that this would be caused by overheating... I cant believe during the 1st overhaul... this was not caught?... the shop guy said that I should have had hi oil consumption... which i did not... same 1qt every 2 - 3 months... I do have a couple leaks...which are common but I never had hi oil consumption... and never saw any smoke in the exhaust... not even on start up... normal steam when its cold outside... everything was typical.??? what are the chances he is totally right?
Paul, it might be possible, but I haven't come across any oversize guides. I had to turn one out on the lathe the last time I found an oversize hole. Lots less hassle than the alternative, weld and remachine. Spirot, I just dont see it. Main caps just do not "fall off". IMO, overheating the motor badly enough to cause a main cap to fall off would have to have been a total meltdown of the motor. The heads would have gone much sooner. It is not possible to put enough heat to the main bearing cap and mounting to cause it to come apart without first losing the upper end. If one looks at a cross sectional view of the motor, it just does not have the design flaws that would allow this sort of failure. The head gaskets, cam bearings etc. would fail sooner with increased heat. However, it may be possible to warp a block too much to be of service by overheating, but that would be a pretty extreme case. The blocks are not supposed to be line bored as such, but honed into alignment with a lapping bar. They discourage boring, as it removes a bit of material, which can adversly erffect many things including cam drive gear alignment
If you have loose valve guides it's likely because the last set were improperly installed. You should have the guide bores cleaned up with a reamer or a boring bar in a milling machine (more accurate but more expensive)and install oversize guides which you can have custom made or turn down larger guides for another engine. Sometimes Ferrari blocks will warp due to corrosion between the block and the cylinder liners. It's more common on the 12 cylinder blocks because they are longer but we've had binding crankshafts free right up after pushing out the liners. You should definitely re-do the front head. It comes off without removing the engine and the engine will run much better for it. Don't forget that the power comes from the head and if the valves leak, which they start doing after only 10,000 miles, you're losing power. Also Loose guides in the rear head and a loose main bearing are frightening enough that I would take the whole engine appart. Make sure you check the oil pump(s) too ( dry sump cars have two oil pumps). Wil
You should still fix up the front head (The engine doesn't have to come out to remove the front head). Otherwise you're doing half the job which equals a half-a**ed job. Wil
If it were mine I thik I'd leave the front head alone. The only reason the rear head came off was all due to the timing belt failure. I think the valve guides on the rear head got pushed when the valves bent. On a side note: Wil, you wouldn't have family from the Northfield, N.J. area would you?
