Broken TB Damage Assessment

[jlevie]

Since you end up doing a manual valve adjustment on these heads at the end anyway, how important is it really that these are dead on even?

The don't have to be dead on even, but the stems have to wind up within range of the eccentrics.

[wojtek79]

I liked that he mentioned checking valve stem height since that will change when you face the valve and cut the seat. He said that would run about $100-120.

Since you end up doing a manual valve adjustment on these heads at the end anyway, how important is it really that these are dead on even?

[jeffnhiscars]

hey you two... can I resurrect this thread and ask if Intervalves is "okay" whose good or doesnt it really matter when it's not a racecar.

I asked the same question at some point and was advised that they are fine.

[sfinsf]

hey you two... can I resurrect this thread and ask if Intervalves is "okay" whose good or doesnt it really matter when it's not a racecar.

[jeffnhiscars]

Port matching and porting can help, if and only if you know exactly what you are doing and why. Otherwise the odds are that you'll actually decrease flow through the head.

Notice I did not say porting. I think port matching is a simpler principal not hard to makes gains with and some light surface easing that does not change the shape of the air path should be fine.

[jlevie]

Port matching and porting can help, if and only if you know exactly what you are doing and why. Otherwise the odds are that you'll actually decrease flow through the head.

[jeffnhiscars]

That is what I'd expect from a good machine shop. I'd also expect a good shop to take a critical look at the exhaust valves. If there is significant wear, the heads of valves will be too thin and run too hot after grinding.

Agreed. The guy Im getting the head from is hand picking the valves from his collection so I expect them to be good.

I also picked up a die grinder and am considering some minor tidying up..port matching, taking down casting marks..nothing too fancy. Doing my ho0mework now and will practice on the old head to see how I feel about it.

[jlevie]

That is what I'd expect from a good machine shop. I'd also expect a good shop to take a critical look at the exhaust valves. If there is significant wear, the heads of valves will be too thin and run too hot after grinding.

[jeffnhiscars]

The best approach here when using a good machine shop is to tell the shop that want the guides replaced and let them source the parts. That is what I do for valve guides.

Ive been burned so many times letting trade people buy supplies that I try to avoid it but in this case a) they are not all that expensive and b) the shop becomes responsible for the job and cant blame customer supplied parts.

I did just speak with the machine shop that has been doing all the local BMW dealer's work for decades and he said parts & labor on guides is about $13@ (so $150ish for all). The first quote was $5 labor plus I can get guides for $5 so to save $3@ its really not worth the fuss.

I also asked him how often he replaces guides and he said quite often they do them all but that he would check them 1st and recommend whats needed (thats the right answer of course). He did say that the stems rarely are the issue so new guides would be virtually a new head.

Interestingly, the dealer does not supply guides so when they send a head out they take what the shop installs without question.

I liked that he mentioned checking valve stem height since that will change when you face the valve and cut the seat. He said that would run about $100-120.

Seem about right given that the head has already been tested and surfaced ?

[jlevie]

The best approach here when using a good machine shop is to tell the shop that want the guides replaced and let them source the parts. That is what I do for valve guides.

[jeffnhiscars]

After rummaging through a number of options I have landed a replacement head along with the replacements for the damaged parts form my old head. Since it has had some work done to it I am inclined to address the one area of these heads that does not seem to be talked about much...the valve guides.

I see there are 3 sizes available and my machinist says BMW could have used anyone one of them and that the only way to know which replacement guides to order is to knock one out and mic it. Due to distance I prefer to get the guides and drop them with the head....and yes, I know I can probably get away with the existing guides but given the comments that they can start to be a problem at 150-200k and having read (in a porting article) that 7% of performance loss can be from worn guides Im thinking its $120 well spent.

How do I safely remove a guide and is there any other way to know what size guides I need without removing one to measure it ?

[jeffnhiscars]

The Febi rocker arms are fine. I've never had a problem with the VR head gasket, but other have had issues. The best gasket is the OE part, with the Goetze being a good second choice. The Intervalve parts are okay.

Thanks once again. After speaking with Korman I'm inclined to grab a used head Ive been offered as the cost of repairing the cracked tower still doesnt eliminate the risk of hidden issues, may not save me anything in the end and the core may provide some usable parts as well.

Its so tempting in these situations to go overboard "while you are in there" and while I certainly will not go underboard (if thats not a term, it is now), its all about getting it running to see what I have.

...and an OE HG & torx bolt set are $100 total. Thats a no brainer.

[jlevie]

The Febi rocker arms are fine. I've never had a problem with the VR head gasket, but other have had issues. The best gasket is the OE part, with the Goetze being a good second choice. The Intervalve parts are okay.

[jeffnhiscars]

I'll be researching machine shops today and hopefully will find the "right" place and get their input. Meanwhile any component suggestions will be appreciated

I see Febi rocker arms for about $18. I assume they are OEM and surely good enough.

I've read not to use the VR head gasket. Is Goetze OEM or at least adequate ?

For valves I see Intervalve, whoever they are, TRW and of course BMW. I'm always reluctant to use a brand I dont know or to pay for something I don't need to.

TIA for the info.

[TobyB]

Yup- that's what Jon did. But since the towers are pretty thermally isolated, he didn't
have to clamp it, nor did it warp. Preheat, tig, postcool. I did the machining afterwards.

SO don't toss it if you don't use it- it might just save someone's car...

t