|
924Board.org Discussion Forum of 924.org
|
View previous topic :: View next topic |
Author |
Message |
Carrera RSR
Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK
|
Posted: Sat Dec 14, 2019 7:01 pm Post subject: |
|
|
safe wrote: | Its NEVER cheep to properly rebuild an engine, regardless the cost of the vehicle.
This is the downfall of the 924, it costs $1000 so the hillbilly who owns it doesn't want to by 4 new good tires, he buys 3 different kind of used tires. A relay fails, that costs money, he has a switch left over from a tractor. Lets put that in, lets drill a hole in the dash for it... etc.
Soon this car is a pile of junk tons of "customisations" that gets left in a field to rust away. |
_________________ 1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252 |
|
Back to top |
|
|
safe
Joined: 18 Mar 2017 Posts: 592 Location: Sweden
|
Posted: Sat Dec 14, 2019 7:53 pm Post subject: |
|
|
Fasteddie313 wrote: | safe wrote: | Lighter pistons would be better over all for the engine. |
My problem is that I would need bolts in order to change the pistons in any 2.0 shortblock.. Be it my current block, or more likely the replacement when I finally blow mine up..
Might be cheapest just to find another 931 engine to blow up, or a 2.0 shortblock if my head survives the inevitable catastrophy, but would need the pistons replaced, thereby requiring new rod bolts $$..
This just seems ridiculous money for some bolts.. Head studs are half the price..
We already know a lot can be ground off our rods to save weight and they are still plenty strong..
Why can't we find some more available and sanely priced bolts to do the job, and possibly even modify the rods to work with them?
The rods could possibly be reemed to take a slightly larger diamiter bolt?
The rods could possibly be modified where the head of the bolt meets the rod?
ideola wrote: | M10x1.0 Porsche Rod Bolt |
They are 10mm dia?
What is so complicated about finding bolts to fit these holes?
BMW M10 rod bolts are 10mm
https://www.summitracing.com/parts/arp-201-6304/overview/
$108
Too short? Take some material off the rods so they fit?
10mm=0.393701"
7/16"=11.1125mm
Ream the holes out to 7/16?
49 results of cheap rod bolts in 7/16..
https://www.summitracing.com/search/part-type/connecting-rod-bolts/thread-size/7-16-in?N=thread-size%3A7-16-in&SortBy=Default&SortOrder=Default
ARP has all sorts of 10mm bolts..
https://arp-bolts.com/kits/bulk.php?PL=89&M=2&W=*&D=8&P=15&WS=13
Can't make anything fit? |
Anything made in small batches will be silly expensive. If ARP had something that would fit straight on, like the head studs do, they would just sell you that. I think its almost crazy that they would just 10 sets.
Modifying the rods foe a "standard" ARP bolt, its interesting but way out my comfort zone both skill and tool vise. Its not some job for a drill press and a grinder.
A rod bolt is not just a bolt, there is a reason the fit of the bolt is really tight, it guides and locate the rod cap very precisely.
A machine shop could probably do it but what would the cost be?
If the rpm is kept to the stock rev limiter I would be much much more comfortable with reusing the so called one time use stock bolts.
The price for 931s will rise. In Europe you find rough ones below $10000, really nice ones are closer to double that.
Money invested properly in a 931 will pay back. |
|
Back to top |
|
|
TJC
Joined: 04 Apr 2010 Posts: 828 Location: Central-ish Arizona, USA
|
Posted: Sun Dec 15, 2019 1:52 am Post subject: |
|
|
Fasteddie313 wrote: | safe wrote: | Lighter pistons would be better over all for the engine. |
My problem is that I would need bolts in order to change the pistons in any 2.0 shortblock.. Be it my current block, or more likely the replacement when I finally blow mine up..
Might be cheapest just to find another 931 engine to blow up, or a 2.0 shortblock if my head survives the inevitable catastrophy, but would need the pistons replaced, thereby requiring new rod bolts $$..
This just seems ridiculous money for some bolts.. Head studs are half the price..
We already know a lot can be ground off our rods to save weight and they are still plenty strong..
Why can't we find some more available and sanely priced bolts to do the job, and possibly even modify the rods to work with them?
The rods could possibly be reemed to take a slightly larger diamiter bolt?
The rods could possibly be modified where the head of the bolt meets the rod?
ideola wrote: | M10x1.0 Porsche Rod Bolt |
They are 10mm dia?
What is so complicated about finding bolts to fit these holes?
BMW M10 rod bolts are 10mm
https://www.summitracing.com/parts/arp-201-6304/overview/
$108
Too short? Take some material off the rods so they fit?
10mm=0.393701"
7/16"=11.1125mm
Ream the holes out to 7/16?
49 results of cheap rod bolts in 7/16..
https://www.summitracing.com/search/part-type/connecting-rod-bolts/thread-size/7-16-in?N=thread-size%3A7-16-in&SortBy=Default&SortOrder=Default
ARP has all sorts of 10mm bolts..
https://arp-bolts.com/kits/bulk.php?PL=89&M=2&W=*&D=8&P=15&WS=13
Can't make anything fit? |
This is the kind of thinking that fostered the "hot rod" age from back in the 40's and 50's here in America and I for one applaud it. I have to agree, there probably are other alternatives out there and something that could be explored. As I mentioned in my previous comment there may even be a different rod that could be adapted. On a side note, I have seen many references about the 944 issues with crappy rod bearing availability that has led to modifying the Porsche rod to take a much better bearing that is a Toyota, (I believe), application originally.
Bottom line folks, where there's a will, there's a way !!! _________________ '95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!
www.ttrs1.com |
|
Back to top |
|
|
MikeJinCO
Joined: 08 Jun 2010 Posts: 1228 Location: Maysville, Colorado
|
Posted: Sun Dec 15, 2019 5:30 am Post subject: |
|
|
I have wondered about other bolt use also. I have put out a call to local race group for a BMW bolt to see close it would be, we have 5 or 6 BMW 1600-.2002's around and have several blown motors this year. _________________ Mike
'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild) |
|
Back to top |
|
|
Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
|
Posted: Sun Dec 15, 2019 6:32 am Post subject: |
|
|
M10 bolts are...
Underhead Length (in):2.330 in.
Underhead Length (mm):59.18mm
How long are 924 bolts?
M10= Rod Bolt Head Style:E
What do 924 bolt heads look like? _________________ 80 Turbo - Slightly Modified |
|
Back to top |
|
|
924RACR
Joined: 29 Jul 2001 Posts: 8815 Location: Royal Oak, MI, USA
|
Posted: Sun Dec 15, 2019 8:19 am Post subject: |
|
|
924 bolt heads are what I'd consider a very basic round head, like K or W.
Fine, you made me do it... photo album with some very recent pics of rod bots, intact and busted...
https://www.facebook.com/photo.php?fbid=10212999631540325&set=a.10212999625340170&type=3&theater
There's one pic in there that shows just the bolt head, after being snapped off the end of the rod (showing the Kamax 12.9 designation)... and another that, in context, shows the loose bolts. _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
Back to top |
|
|
MikeJinCO
Joined: 08 Jun 2010 Posts: 1228 Location: Maysville, Colorado
|
Posted: Sun Dec 15, 2019 9:28 am Post subject: |
|
|
Measured a used bolt at 65.5mm OA length with a head thickness of 5.0mm.
Read some other sites that said that if switching rod or main bearing bolts the bores must be resized due to the different clamping pressure. I did the calcs and the clamping pressure of the stock bolts at 43 ft lbs torque dry is 431 lb. This based on at measured diameter of 0.3225" on the yield strength of the used grade 12.9 bolt. _________________ Mike
'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild) |
|
Back to top |
|
|
Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
|
Posted: Mon Dec 16, 2019 1:17 am Post subject: |
|
|
MikeJinCO wrote: | Measured a used bolt at 65.5mm OA length with a head thickness of 5.0mm.
|
M10 bolt
Underhead Length (mm):59.18mm
65.5-5=60.5-59.2= difference of M10 bolt = 1.3MM shorter
And your used bolt might even be stretched?
Take 1.3mm off the bottom cap and BAM..
If even necessary..
MikeJinCO wrote: |
Read some other sites that said that if switching rod or main bearing bolts the bores must be resized due to the different clamping pressure |
If this was true then it would be required for ARP too, no? _________________ 80 Turbo - Slightly Modified |
|
Back to top |
|
|
safe
Joined: 18 Mar 2017 Posts: 592 Location: Sweden
|
Posted: Mon Dec 16, 2019 1:32 am Post subject: |
|
|
Fasteddie313 wrote: |
If this was true then it would be required for ARP too, no? |
You should always check the size and roundness of the big end at full torque on every rebuild. Resize if out of spec. |
|
Back to top |
|
|
safe
Joined: 18 Mar 2017 Posts: 592 Location: Sweden
|
Posted: Mon Dec 16, 2019 7:06 pm Post subject: |
|
|
As reference, the ARP and original are identical, except the stamping on the head. ARP on top.
Edit: Holy sh**, that was huge!.
See pic further down.
Last edited by safe on Tue Dec 17, 2019 2:25 am; edited 1 time in total |
|
Back to top |
|
|
924RACR
Joined: 29 Jul 2001 Posts: 8815 Location: Royal Oak, MI, USA
|
Posted: Mon Dec 16, 2019 11:44 pm Post subject: |
|
|
safe wrote: | Fasteddie313 wrote: |
If this was true then it would be required for ARP too, no? |
You should always check the size and roundness of the big end at full torque on every rebuild. Resize if out of spec. |
Funny, I was just having dinner last night (up here in the frozen north) with a table full of racers, including a past SCCA National Champion, and this exact topic came up; he popped a motor in his (formerly front-running) Prod car at VIR due to exactly this, didn't re-line-bore the mains on his block when he rebuilt it with new ARP main bolts, and spun a rod bearing as a result.
Now I gotta find a local shop that'll do that; the one I've been using doesn't have that tech... _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
|
Back to top |
|
|
TJC
Joined: 04 Apr 2010 Posts: 828 Location: Central-ish Arizona, USA
|
Posted: Tue Dec 17, 2019 1:53 am Post subject: |
|
|
Dear safe, please delete and compress your photo and re-submit as every message after it is expanded , LOL!!! _________________ '95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!
www.ttrs1.com |
|
Back to top |
|
|
Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
|
Posted: Tue Dec 17, 2019 1:57 am Post subject: |
|
|
Well, it probably isn't worth all that just to install upgraded pistons unless your looking for more than 400 hp or so, which I'm not..
Or, might as well buy custom rods, maybe even to fit more available pistons..
Nah.. The OEM stuff will probably hold fine for long enough up to 20-25psi and be plenty fast enough..
safe's pic resized..
_________________ 80 Turbo - Slightly Modified |
|
Back to top |
|
|
safe
Joined: 18 Mar 2017 Posts: 592 Location: Sweden
|
|
Back to top |
|
|
Juho
Joined: 03 Oct 2018 Posts: 381 Location: Finland
|
Posted: Tue Dec 17, 2019 7:50 am Post subject: |
|
|
SOMEONE MUST TRY THESE, imagine if they were actually good. |
|
Back to top |
|
|
|
|
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|