Head bolts for 32V car
#17
Just for the sake of OCD- Doc's set should be good for an R1 head, used up through early 1988 (engine # 81K 00120, (5-speed), or 81K 05238 (auto)
So R1 head bolts are 180 (928 101 231 01) and 130 mm (928 101 233 01), and R2-R5 head bolts are 149 (928 101 233 02) and 199 mm (928 101 231 03)
Interestingly the R1 head bolt numbers are listed on the bottom of the M28.43/44/45/46 page in the '85 PET- were they spec'd as replacements or something?
So R1 head bolts are 180 (928 101 231 01) and 130 mm (928 101 233 01), and R2-R5 head bolts are 149 (928 101 233 02) and 199 mm (928 101 231 03)
Interestingly the R1 head bolt numbers are listed on the bottom of the M28.43/44/45/46 page in the '85 PET- were they spec'd as replacements or something?
#18
Basic Sponsor
Rennlist
Site Sponsor
Rennlist
Site Sponsor
Interestingly the R1 head bolt numbers are listed on the bottom of the M28.43/44/45/46 page in the '85 PET- were they spec'd as replacements or something?
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
#19
Former Sponsor
Quality of the (stainless?) steel is important for torque to yield fasteners and i think OEM is just the best way to go for peace of mind. After all, how often do you do head jobs. I think ARP makes stud kits for 928 motors, that way you can just use nuts. Although you'd sacrifice serviceability since you can't remove heads with motor in situ. Need to remove motor.
My belief is that the head studs were of "too good" a quality and did not stretch as much (if at all) as the factory head bolts or studs. That stretch is really important for clamping the head gaskets down and keeping them clamped as the engine heats and cools.
The other problem was that ARP wanted you to heat the engine up, let it cool down, and re-torque the hardware. While this sucks, on a 951 engine (you have to remove the cam carrier), this sucks in an unimaginable way on a 928.
The result was that it was virtually impossible to keep head gaskets in these engines, when using the ARP hardware, when the stock stuff worked quite nicely.
ARP always recommended using the stock specification for torque and perhaps a higher torque might have stretched their studs and made the difference. I just didn't feel like I wanted to do that research, for them, and simply went back to the stock pieces.
#20
Archive Gatekeeper
Rennlist Member
Rennlist Member
Ugh, goddadammeet- Verbus 11.9, not 10.9:
#21
Addict
Rennlist Member
Rennlist Member
[QUOTE=Rob Edwards;10907036]Ugh, goddadammeet- Verbus 11.9, not 10.9:/QUOTE]
I dug out some '87 head bolts this morning (for entirely irrelevant reasons) also Verbus 11.9. They aren't plated like your photo though. If they weren't plated from the factory I wouldn't use them as head bolts.
Observations and thoughts
The '87 head bolts have I would judge a rolled thread and the bolt shank is only around 10mm dia.
Rolled M12 thread to give stronger hold in the block
Narrower shank to reduce the torque required to stretch the bolt (Bear in mind you could lift two or three 928 with just one of these bolts in tension)
I reckon these are not bolts torqued to yield. I think they sit in the elastic region throughout there cold- hot cycle. I'ld have to try and put numbers to it to be surer.
I dug out some '87 head bolts this morning (for entirely irrelevant reasons) also Verbus 11.9. They aren't plated like your photo though. If they weren't plated from the factory I wouldn't use them as head bolts.
Observations and thoughts
The '87 head bolts have I would judge a rolled thread and the bolt shank is only around 10mm dia.
Rolled M12 thread to give stronger hold in the block
Narrower shank to reduce the torque required to stretch the bolt (Bear in mind you could lift two or three 928 with just one of these bolts in tension)
I reckon these are not bolts torqued to yield. I think they sit in the elastic region throughout there cold- hot cycle. I'ld have to try and put numbers to it to be surer.
#22
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,470
Received 1,624 Likes
on
1,061 Posts
Well, that should make them easier to find. Not.
Jon, are you saying that the '87 head bolts you have are M10 bolts with a narrower-than-10mm shank? I'm not following.
I am not convinced also. Turn-to-torque does not automatically mean torque-to-yield. However, the math has to be done.
I am not convinced also. Turn-to-torque does not automatically mean torque-to-yield. However, the math has to be done.
#23
Nordschleife Master
Join Date: Dec 2004
Location: Guelph, Ontario, Canada
Posts: 6,164
Likes: 0
Received 5 Likes
on
5 Posts
Ugh, goddadammeet- Verbus 11.9, not 10.9:/QUOTE]
I dug out some '87 head bolts this morning (for entirely irrelevant reasons) also Verbus 11.9. They aren't plated like your photo though. If they weren't plated from the factory I wouldn't use them as head bolts.
Observations and thoughts
The '87 head bolts have I would judge a rolled thread and the bolt shank is only around 10mm dia.
Rolled M12 thread to give stronger hold in the block
Narrower shank to reduce the torque required to stretch the bolt (Bear in mind you could lift two or three 928 with just one of these bolts in tension)
I reckon these are not bolts torqued to yield. I think they sit in the elastic region throughout there cold- hot cycle. I'ld have to try and put numbers to it to be surer.
I dug out some '87 head bolts this morning (for entirely irrelevant reasons) also Verbus 11.9. They aren't plated like your photo though. If they weren't plated from the factory I wouldn't use them as head bolts.
Observations and thoughts
The '87 head bolts have I would judge a rolled thread and the bolt shank is only around 10mm dia.
Rolled M12 thread to give stronger hold in the block
Narrower shank to reduce the torque required to stretch the bolt (Bear in mind you could lift two or three 928 with just one of these bolts in tension)
I reckon these are not bolts torqued to yield. I think they sit in the elastic region throughout there cold- hot cycle. I'ld have to try and put numbers to it to be surer.
I have been in the auto industry for 20 years and measuring engines and transmissions is the bread an butter of my living. While I don't engineer engines, I have worked with those engineers daily for the last 20 years.
Once you understand what happens during yield, you would understand that you NEVER want it to yield. You need to be to the point where as the engine heats up the stretch will still NOT be at yield so that when it cools it will return to the original length and not lose the holding force.
#24
Addict
Rennlist Member
Rennlist Member
No - M12 thread but rolled not cut. (Thread proud of the shank) Bolt shank is less than 12mm dia apart from approx 5mm length immediately under the head.
#25
Addict
Rennlist Member
Rennlist Member
Certainly not my idea of fun.