Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Technical BBS > 1- Porsche Technical Forums > 911 / 930 Turbo & Super Charging Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Addicted to Racing
 
edbaus's Avatar
 
Join Date: Dec 2001
Location: Ohio
Posts: 4,904
Garage
Piston questions

I have a 930 3.3 from my 79.

I am currently running the stock pistons and an sc cam.

I pulled the motor apart because I spun a rod bearing. What I found is that all of the intake valves have at least touched the pistons.

I had no idea that I needed to recess the pistons for the sc cam.

My next step is to use a pair of 935 camshafts with the motor. Now, with what I have found. I am assuming that I am going to have to have the pistons fly cut. Or use different pistons.

Hate taking even more material out of the combustion chamber to give even less of a compression ratio.

What have others done. Should I stick with the sc cams.

btw, the rest of the setup is electromotive tec3, twin plug, carrera intake, twin turbo using 993 heat exchangers.

Thanks

Ed
Old 06-24-2007, 06:16 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
930gt-40r's Avatar
 
Join Date: Jan 2007
Location: Boca Raton, FL
Posts: 2,063
What about getting a set of J&E s that have a thicker/ taller upper ring land and use larger fly-cuts so you dont compromise compression. If it is the lag that your worried about, why dont you just bump the timing up down low.
In all honosty, the fly cuts would not affect the compression ratio enough to make a diffrence in feel. would need to be re tuned anyway.
__________________
Kris @ Tech9
86' 930/GT-40R Sold
94' Rustang GT daily (long gone)
2008 C6/Z51 Corvette
Old 06-24-2007, 07:53 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
beepbeep's Avatar
 
Join Date: Jun 2001
Location: Sweden
Posts: 5,560
First of all, 935 cams will give you very very peaky engine. It will peak around 7300 RPM, so make sure everything else is to snuff. I recomend aftermarket H-beam rods to begin with.

Second, 935 cams might require cutouts for valves, If stock pistons were just touched by valves, you could just polish them and let some shop cut recesses for valves. Fitting 935 cams also require careful cam timing to get maximum power. That means couple of hours of engine-dyno time as it's somewhat hard to clock the cams with engine installed in car.

Stock pistons are sturdy (boost-wise) albeit pretty heavy. Reusing them and limiting revs to 7000 RPM might work. You would like a pair of Garrett GT30R's to make best use of such setup.
__________________
Thank you for your time,
Old 06-24-2007, 11:01 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 2,774
????

I've got a '78 with SC cams (reground 930 from camgrinder), heads were previously skimmed for 8.0:1 static compression.

It too was apart recently for a spun rod bearing.

The valves don't touch the pistons on my motor, and the carbon deposits had no tell-tales of them getting close.
__________________
'77 S with '78 930 power and a few other things.
Old 06-26-2007, 10:58 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Addicted to Racing
 
edbaus's Avatar
 
Join Date: Dec 2001
Location: Ohio
Posts: 4,904
Garage
Going to send the cams out to camgrinder and get him to verify the profile.

Ed
__________________
Check out the parts for sale:
http://www.demonspeedmotorsports.com
PCA National & NASA Instructor, NASA GTS & PCA GT Class Racer.
See my list of current cars in my garage.
Old 06-26-2007, 11:21 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
930turbo's Avatar
 
Join Date: Jul 2006
Location: Valrico Florida
Posts: 199
SC cams should be a drop-in mod with plenty of clearance. There must be something else that caused the collisions, possible reduced deck-height or retarded cam timing.
__________________
'77 930 turbo Garretson I/C 1 BAR spring, (2) '82 Triumph Bonneville Royal Wedding Edition
Past rides: '74 914 1.9 liter twin plugged track car, '83 928S, '87 924S, '75 911S w '78 ROW 3.0, '72 911T, '70 911T and various other insignificant domestic examples. Happiness is a grey tailpipe! Turbo lag......it's worth the wait!
Old 06-26-2007, 06:57 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
Registered User
 
kellcats521's Avatar
 
Join Date: Feb 2005
Location: Atlanta Metro
Posts: 219
If the timing was set with all of the rockers installed, it would not be out of the realm for valves and pistons to 'touch' during adjustment. If they 'touched' while the engine is/was running, that's another issue.....

Pat K
87 930
Old 06-27-2007, 04:23 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Addicted to Racing
 
edbaus's Avatar
 
Join Date: Dec 2001
Location: Ohio
Posts: 4,904
Garage
Isn't it usually the exhaust valves that have the issue if the car is over rev'ed. (that has been my experience anyway)

Also, these more than touched.

The car ran great. Very strong, if I can talk 1/4 mile times without getting flammed, my g-tech gave me times in the 10's and speed over 120.

The cams were purchased used, so they might not actually be the sc cam grind I was lead to believe. (they are 930's that were reground)

Engine is apart because of a spun rod. Motor ran great for about a year after the top end rebuild, but extra stress on an old bottom end took its toll.

Thanks

Ed
__________________
Check out the parts for sale:
http://www.demonspeedmotorsports.com
PCA National & NASA Instructor, NASA GTS & PCA GT Class Racer.
See my list of current cars in my garage.
Old 06-27-2007, 05:52 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 12:13 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.