92 968
#31
I will be changing all belts, rollers, water pump, cam chain and pads. Im still undecided on head gasket and front seals. Will most likely do front seals. Am now also pricing fuel lines, water lines, some power steering lines and battery to alt/starter cable.
#34
Instructor
Regarding head resurfacing -
Overhead cam heads must be fixtured and indicated flat before resurfacing, otherwise the cam journals are pulled out of alignment, so any warp preceding resurfacing just reappears upon removal of milling clamps. It is good advice to resurface (fixtured flat) in the case of excessive pitting or welded repair etc., but not advisable if the gasket surface is in good condition. Warp will be pulled back to flat under cam bolt tension.
If the head is not flat already, cutting it so that it is - while fixtured in a relaxed state - will leave the cam journals out of alignment thus ruining the head unless one is willing to re-bore the journals and find cams ground for the oversize condition.
I just did the head gasket, lapped the valves, and put in new valve seals on a Mercedes 190E and in the course of that project found someone who has broken two camshafts because this concept was not observed.
I've had to fix a lot of parts over 30 years as a machinist because someone before me did not consider "relaxed" vs "load" fixturing.
Overhead cam heads must be fixtured and indicated flat before resurfacing, otherwise the cam journals are pulled out of alignment, so any warp preceding resurfacing just reappears upon removal of milling clamps. It is good advice to resurface (fixtured flat) in the case of excessive pitting or welded repair etc., but not advisable if the gasket surface is in good condition. Warp will be pulled back to flat under cam bolt tension.
If the head is not flat already, cutting it so that it is - while fixtured in a relaxed state - will leave the cam journals out of alignment thus ruining the head unless one is willing to re-bore the journals and find cams ground for the oversize condition.
I just did the head gasket, lapped the valves, and put in new valve seals on a Mercedes 190E and in the course of that project found someone who has broken two camshafts because this concept was not observed.
I've had to fix a lot of parts over 30 years as a machinist because someone before me did not consider "relaxed" vs "load" fixturing.
Last edited by Z3M&968; 07-26-2021 at 08:47 AM.
#35
Rennlist Member
When you say fixtured do you mean having the cams installed and torqued down before milling the head ? Or is there some other way in the shop you simulate this condition? Does having the actual cams bolted in and torqued impede the machinery to hold/mill head ?
#36
Instructor
OHC heads are a different animal entirely than traditional heads. Here's a good cut and paste from another site:"If the face of an aluminum head is warped, don’t assume the only way to straighten it is to grind metal off the face until it is flat again. The whole head is warped. If the head has one or two overhead camshafts, the cam bores will also be misaligned in most cases. The best fix here is to straighten the head BEFORE it is resurfaced. This can greatly reduce or possibly even eliminate the need to remove more than a couple thousandths of metal.
Aluminum heads can be straightened by counter-shimming the head on a heavy steel plate (place shims under either end of the head to offset the amount of distortion), clamping it down, then heating it in an oven to about 425° F for several hours, then letting it slow cool. The goal is to get the cam bores straight. Once they are in alignment, chances are the face of the head will be reasonably flat, too, and require minimal machining to refinish the surface.
Another method for straightening aluminum heads is to use a torch to heat the top of the head, starting in the center and working towards the ends. The trick here is to keep the head temperature under 500° F to prevent softening the head too much."
Last edited by Z3M&968; 07-30-2021 at 09:57 AM.
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gsx9522r (07-30-2021)
#37
Z3 thanks for the head info and wires are in the mailbox just need to go get them. I decided to purchase the timing belt kit with rollers, front seal kit with races and a valve cover gasket kit. All from paragon. Ill still be purchasing a few other items probably form sunset.
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Z3M&968 (07-30-2021)
#38
Instructor
Z3 thanks for the head info and wires are in the mailbox just need to go get them. I decided to purchase the timing belt kit with rollers, front seal kit with races and a valve cover gasket kit. All from paragon. Ill still be purchasing a few other items probably form sunset.
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gsx9522r (07-30-2021)
#39
Thanks I did forget about that. I'll order one when I place the order with sunset.. im sure ill be on here quite a bit once i satrt the work. Im hoping to start next weekend.
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Z3M&968 (07-30-2021)
#40
Drifting
doing the oil housing, you will need the pressure release valve alignment tool and associated crush washers.
there is a little L bracket on the back of the lower balance shaft housing that needs to be snugged to the front housing, torqued to the cover and then torqued front housing.
here is the cam pad walk through from 12ish years ago for searches at a later date...https://rennlist.com/forums/968-foru...oner-pads.html
there is a little L bracket on the back of the lower balance shaft housing that needs to be snugged to the front housing, torqued to the cover and then torqued front housing.
here is the cam pad walk through from 12ish years ago for searches at a later date...https://rennlist.com/forums/968-foru...oner-pads.html
Last edited by thomasmryan; 08-01-2021 at 10:51 AM.
#41
Addict
Rennlist
Lifetime Member
Rennlist
Lifetime Member
Z3 thanks for the head info and wires are in the mailbox just need to go get them. I decided to purchase the timing belt kit with rollers, front seal kit with races and a valve cover gasket kit. All from paragon. Ill still be purchasing a few other items probably form sunset.
Would really like to see pictures and details when you pull the cams as I most likely will need to do that at some point.
#42
Do you know if the Paragon kit uses genuine Porsche or some OEM parts supplier parts? I'd check pricing at Delaware Porsche also as that's who I've been using since Sunset started charging sales tax.
Would really like to see pictures and details when you pull the cams as I most likely will need to do that at some point.
Would really like to see pictures and details when you pull the cams as I most likely will need to do that at some point.
#43
Instructor
#44
Cab top
Well ive ordered almost everything i hope to need. Im sure things well come up as i progress through the repairs mentioned earlier. Now any advice on a reputable vender for a new top? Ill probably go with A5 german canvas/cloth. But not sure who to buy from. I will let a local upholstery shop do the install.
#45
Well im very disappointed with sunset porsche. I placed 2 orders with them one arrived quickly the other i was told a few parts had to come from Germany. They said they can express ship them and be in in less than 2 weeks. I paid extra to express ship them. I then receive an email 3 weeks ago saying all items ready to ship and. As of Friday it has not shipped. Order was originally placed 8/8 today 9/19. I called and all they say is i dont know why it hasnt shipped. But it would go out right away. That was last monday still hasnt shipped. I will call one more time tomorrow then file a complaint with my credit card company.
As an update i have begun disassembly but am patiently awaiting parts.
As an update i have begun disassembly but am patiently awaiting parts.