Rebuilding a 968 engine
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With help from those who have done it. That's the only answer I have right now. More when I have those answers. Also, slight tweak to the plan... I may just go ahead and buy the pistons/rods and leave the deck height on the head alone for now.
Last edited by Mikelly; Aug 17, 2025 at 09:46 AM.
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slight update... Molnar rods and Wossner pistons, Fitspatrick cams, 36# injectors procured. Head & crank go to the shop Monday. Block and other parts are either completely cleaned or being clean by Monday.
Progress...
Progress...
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We chose not to deck the head, removing volume from the chambers, So the geometry of the head stays the same. The cam profile changes are aggressive but not so much that we'll need to worry about anything beyond setting the exhaust cam up with proper degree specification from Pete's spec sheet. I'll need a new chip and we'll run upgraded injectors to help take advantage of the increased compression and the change in lift and duration on intake and exhaust cams.
How are you determining piston/valve clearance with the reground cam and head shave, factoring in variocam changes to valve timing?
I am curious because I am interested in a more aggressive cam but not sure what cam specs can be run with variocam (and haven't been able to find alot of information on this). Is there a maximum cam profile that is known to work and not cause interference or some further documentation or information you can share?
I have read folks like Michael Mount say that they disable variocam when going to a more aggressive cam (which basically converts the 968 head to an S2 head with larger intake valves). I think at that point it would probably be better to run a modified S2 head with 968 intake valves over the 968 head due to the simpler chain tensioner design. Ideally I would like to retain variocam but run a more aggressive cam, just not sure what will work.
I am curious because I am interested in a more aggressive cam but not sure what cam specs can be run with variocam (and haven't been able to find alot of information on this). Is there a maximum cam profile that is known to work and not cause interference or some further documentation or information you can share?
I have read folks like Michael Mount say that they disable variocam when going to a more aggressive cam (which basically converts the 968 head to an S2 head with larger intake valves). I think at that point it would probably be better to run a modified S2 head with 968 intake valves over the 968 head due to the simpler chain tensioner design. Ideally I would like to retain variocam but run a more aggressive cam, just not sure what will work.
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Interesting build. So you are able to keep the Variocam functional? Can you check lift and duration (or just lift) on the cams?
I have only found one cam card for a regrind that implies that Variocam remains functional, the exhaust cam is limited to 268 degrees total duration.
On edit, maybe rethink resurfacing the head? The 968 engines are usually well below their advertised compression ratio.
I have only found one cam card for a regrind that implies that Variocam remains functional, the exhaust cam is limited to 268 degrees total duration.
On edit, maybe rethink resurfacing the head? The 968 engines are usually well below their advertised compression ratio.
Last edited by LTDzak; Oct 3, 2025 at 11:57 AM.
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Alex
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Def. NOT taking material off the head since we went the Wossner piston route. I'd rather not post the specs on the cam since I'll be racing this car. Competitors and all that, ya know? I can tell you that total duration is below that 268 number you mention.
Interesting build. So you are able to keep the Variocam functional? Can you check lift and duration (or just lift) on the cams?
I have only found one cam card for a regrind that implies that Variocam remains functional, the exhaust cam is limited to 268 degrees total duration.
On edit, maybe rethink resurfacing the head? The 968 engines are usually well below their advertised compression ratio.
I have only found one cam card for a regrind that implies that Variocam remains functional, the exhaust cam is limited to 268 degrees total duration.
On edit, maybe rethink resurfacing the head? The 968 engines are usually well below their advertised compression ratio.
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The reason to go with the wossner pistons is more to do with the increased compression. The stock pistons put compression closer to 10.2-10.3:1 and we want to get as close to 11:1 as possible. Still staying on 93 octane.
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Alex
