| View previous topic :: View next topic |
| Author |
Message |
BillA
Joined: 27 Dec 2002
Posts: 170
Location: Syracuse, NY
|
 Posted: Tue Sep 06, 2005 11:33 am Post subject: Engine questions |
 |
|
| I purchased a set of VENOLIA pistons from a company here in the states, PAECO and they were supposedly rated for 10:5:1 compression and bored 1.016 mm over. Well, after all the work was done on the lower end my machinist reported that I'd be lucky to get 5 or 6:1 compression, due to the fact the pistons now sit further down in the cylinder. He gave me a few ideas on how we could bring it back up to what I was looking for. His first idea was to deck the block about 1.30 mm. However, he is worried about how much this would affect the belt tensioner, any idea? He then suggested looking for either longer connecting rods or crankshaft? So this is where I am at right now. Anyone have any suggestions? Also I am using a 931 head on an N/A block, which I currently installed on my 78 just to see how it performs, thanks Peter for all of your help! |
|
| Back to top |
|
 |
Lizard
Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada
|
| Posted: Tue Sep 06, 2005 11:36 am Post subject: |
|
|
I would recommend that you contact Peaco and ask what there suggestions are.
if the pistons are meant for an NA head then you would be seeing about 8:1 or 7.5:1 CR with the 931 head.
_________________
3 928s, |
|
| Back to top |
|
|
leadfoot
Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia
|
| Posted: Tue Sep 06, 2005 7:16 pm Post subject: |
|
|
Try and exchange pistons....or stroke the crank.
Considering that your block has been bored for these pistons then exchanging them might create an issue if you can't find same piston.
Stroking would allow around 10mm extra height, apart from that your looking at minor changes for head shaving (absolute minimal) and using a copper head gasket (might give you half a point extra comp).
Stroking will obviously change displacement and consider this for racing rules limitations.
Leadfoot
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress... |
|
| Back to top |
|
|
John Brown
Joined: 07 Nov 2002
Posts: 903
Location: Leesburg VA
|
| Posted: Tue Sep 06, 2005 11:26 pm Post subject: Re: Engine questions |
|
|
| BillA wrote: | | I purchased a set of VENOLIA pistons from a company here in the states, PAECO and they were supposedly rated for 10:5:1 compression and bored 1.016 mm over. Well, after all the work was done on the lower end my machinist reported that I'd be lucky to get 5 or 6:1 compression, due to the fact the pistons now sit further down in the cylinder. He gave me a few ideas on how we could bring it back up to what I was looking for. His first idea was to deck the block about 1.30 mm. However, he is worried about how much this would affect the belt tensioner, any idea? He then suggested looking for either longer connecting rods or crankshaft? So this is where I am at right now. Anyone have any suggestions? Also I am using a 931 head on an N/A block, which I currently installed on my 78 just to see how it performs, thanks Peter for all of your help! |
Sounds very much as if there was a communication disconnect between you and PAECO as to the fact that you are using a 931 head??
It's going to be much cheaper and/or satisfactory to just get the proper pistons versus machining the block, stroker crank, or long rods. Even if you have to shell out another $600 for another set of pistons.
The easiest way to get quality pistons for a 924 is call JE. They have on file the specs for pistons with any combination of head (924/931) and cr you wish.
_________________
John
80 931 - #931 44Cup
99 Escalade - tows track cars
gone but not forgotten: original 924.org car - 82 |
|
| Back to top |
|
|
leadfoot
Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia
|
| Posted: Wed Sep 07, 2005 7:51 pm Post subject: |
|
|
Are the Venolia's cast or forged, because the JE's are forged are they not??
Leadfoot
_________________
1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress... |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
924 FAQ (Technical)
