Marc's 1990 4.2L V8 Twin Turbo Coupe Quattro

[3bAudios]

*patiently awaits removal of transmission*

:stupid: also, is the coupe tranny the same as the 80/90q?

[SEStone]

Yes, it does have shorter 4th and 5th gear ratios, however.

Sam

[Marc]

Finally got around to tearing down the 4.2

The bores appear to be in nice shape but holey hell is there a lot of carbon on the pistons:





after some razor blade lovin' I brought one of them to what I think they are supposed to actually look like :-P



I need to pick up some cleaning tools to make faster work of it, probably do that tomorrow.

before I could get the heads off I had to deal with the viscus fan assembly. I dont have a wrench thats the right size to remove the assembly, and besides I need to grind off the nub on the serpentine roller anyway for radiator clearance. So I borrowed Haydn's plasma cutter







man thats a fun tool

I also picked up a 4kq prop shaft for my 01E swap, just waiting on lift availability to do the swap (tranny jobs just suck to do on jackstands, especially a custom swap that requires fabrication...)

[PRA4WX]

What are you fabbing for your 01E? Not going the S2 linkage route?

[Marc]

What are you fabbing for your 01E? Not going the S2 linkage route?

mounts.

I'm using stock biturbo s4 linkage and shifter box.

[PRA4WX]

So no on the S2 mounts than either. Gotcha! That will be nice!

[Marc]

So no on the S2 mounts than either. Gotcha! That will be nice!

seems silly to spend big dollars on s2 mounts when a simple set of sheet metal mounts can be welded up very easily.

[PRA4WX]

No argument from me! I meant to say "that will be nice to have the 01E in there." :slap:

[Marc]

No argument from me! I meant to say "that will be nice to have the 01E in there." :slap:

yah, I got what you meant. Maybe I needed a smiley in there? ---> :-)

[Jonathan]

seems silly to spend big dollars on s2 mounts when a simple set of sheet metal mounts can be welded up very easily.

Marc,

Could you clarify this? Does a 01E require custom mount brackets to bolt into a 016 or 01A car?

[Marc]

seems silly to spend big dollars on s2 mounts when a simple set of sheet metal mounts can be welded up very easily.

Marc,

Could you clarify this? Does a 01E require custom mount brackets to bolt into a 016 or 01A car?

yes.

[Jonathan]

Thanks for the quick answer and the bad news. :-) :( I had hoped/assumed that the 016 brackets would bolt up. Now I know what would really be involved.

[Derracuda]

jonathan... with all the floor fab work you've done, tranny mounts are pretty much done in sleep mode

[HT Motorsport]

:stupid:

Mark: I have a set of uber rare UR S8 01E tranny mounts if you wanna look at em

H

[Marc]

:stupid:

Mark: I have a set of uber rare UR S8 01E tranny mounts if you wanna look at em

H

interesting, pretty sure those wouldn't bolt up to my chasis but might be fun to see the design. I've got some plate steel on the way to fab up the mounts so I should be good to go. Maybe I'll come over to cut the steel rather than haul the plasma cutter all the way back over here

[Marc]

Wow, just noticed we're up to 50 pages on this thread :-o

Spent the evening over at Haydn's shop last night to begin the process of stripping the heads down. The heads themselves are pretty clean:



I didn't have time to pull all of the valves (it takes quite a bit of time just to strip out the cams) but I did pull a pair of exhaust valves and there is a ton of carbon on them:





I managed to bust the little locking tab on Haydn's valve spring compressor because I forgot about the step of slapping the head of the compressor when its under tension to release the keepers, otherwise you just wind up clamping down on the compressor till you're blue in the face with nothing happening:



a quick hit with the welder and it was back in action though.

After hearing about Nate's experience of dropping a valve on a bone stock NA 4.2 I was way nervous about the same happening to a boosted version of the same motor so I opted to replace the exhaust valves with 034's oversized Inconel valves (pluss oversized stainless intakes while I was at it :woowoo: ) :thanks:



I'll be back over at the shop on Saturday to finish pulling the valves, then from there I'll be doing some port and polish work, then its off to the machine shop to have them grind the valve seats for the larger valves and perhaps replace the guides if they need it.

Here's a trivia question for the motorgeek masses: WTF is this interesting mark on the area under where the head bolts go for?? Haydn noticed them while I was tearing the head down:

[a_CQ]

6 little squares? No idea..

[RS]

Are those marks proud of the surface or recessed? Those valves should help you out a good bit. The diameter will help you out if you increase the thru-hole of the valve guides, but the fluting will help out too. It won't help with dropping a valve though, as it makes it a wee bit easier to pull the head off of it. Many of the exhaust valves I've seen for boosted engines are not fluted (even if the intakes are) giving up a little flow efficiency for valve and seat durability.

[Marc]

Are those marks proud of the surface or recessed?

proud, which is the weird part. If it were recessed I'd say it was some marking on the bottom of the head bolt washers digging into the head.

Those valves should help you out a good bit. The diameter will help you out if you increase the thru-hole of the valve guides

nope, same diameter shaft as stock

, but the fluting will help out too. It won't help with dropping a valve though, as it makes it a wee bit easier to pull the head off of it.

possibly, but IMO the reason for the valve failures to date are many heat cycles/age fatiguing the stock sodium exhaust valves making failure more likely.

Many of the exhaust valves I've seen for boosted engines are not fluted (even if the intakes are) giving up a little flow efficiency for valve and seat durability.

I think Javad is using the same valves in his mega HP 80tq 5 cylinder so it cant be that big of an issue (I hope ).

[Derracuda]

Are those marks proud of the surface or recessed?

proud, which is the weird part. If it were recessed I'd say it was some marking on the bottom of the head bolt washers digging into the head.
.

did you look at the back side of the washers from the head bolts? no indentations? it could possibly be from manufacturing processes with a robot arm... you know those are strong

[pkw]

probably from clamping and/or fixturing or maybe for identifying it for a specific fastener size..let it go man

[RS]

OK, here's my 1/2 ass theory...

small protrusions symmetric about the axis of the head bolts leads me to believe that they are designed to be flexures during torquing and heat cycles of the cylinder head. Some engine bolts are necked down (threads larger dia than bolt body) to allow them to stretch under loading. Small protrusions from the washer seat would do the same thing.

Hmmm - Having a bigger diameter valve head without a large hole for the air to go through is an interesting fluids problem for me to think about. Flow areas are no bigger which still makes the area for calculating the mass flow of choked flow the inside of the valve seat. As I said though, necking he head of the valve does increase the flow area (and mass flow at choked flow). From the visualization of the flow path, it would seem that making a larger valve head would increase the length of the flow path, possible increasing pressure drop. That said, the seat to valve head area is larger (increasing cooling capability for the valve) but that is countered by the increase in the total surface area of the valve and thus the heat flux.

My gut feel is that any power gains you'd get are from the fluting and porting of the head. Not so much from the increase in valve diameter. I do agree with you that new valves are still less likely to fail than old cruddy 150k mile valves. However I would also like to see a side by side dyno test with knock sensors to figure out if the change in material is creating hot-spots on the exhaust valve heads. Pretty much a destructive test though.....Anyone up for it?

Anyway. Toss 'em in there and feed them some boost, ok? I'll follow you back up to the dyno again.

[Derracuda]

uh, you could take the stock valve seats and bore them out 1mm for more flow... putting in bigger valves seems like a dumb idea without following the rest of the train of thought.

[Marc]

uh, you could take the stock valve seats and bore them out 1mm for more flow... putting in bigger valves seems like a dumb idea without following the rest of the train of thought.

I said I was going to cut larger seats, the guides are staying stock.

[Derracuda]

uh, you could take the stock valve seats and bore them out 1mm for more flow... putting in bigger valves seems like a dumb idea without following the rest of the train of thought.

I said I was going to cut larger seats, the guides are staying stock.

sorry Marc, i wasn't directing that to you. i didn't read where you said that. i just meant the idea behind dropping in larger valves without doing the whole jaeorb. thinner stems = good, thinner stems plus larger seat = bettar