High(er) compression pistons for 308 QV

I'm considering new pistons with higher than original compression ratio (in example 10.5:1) for my 308QV, 1983, US model. Are there anyone here that can recommend a fabricate or dealer preferably in Europe. I'm not very experienced in piston swap on engines with hard chrome liners (Nikasil, I think the name is) so what do I do if the liners are worn out of spec or damaged in any way? Is it possible to get the liners bored up to first oversize and re-chromed or do I need to invest i cast iron liners etc. I have search a bit on Fchat without finding much specific information on this subject related to QV engines so any input, hints or good advice is much appreciated. For your information I'm considering to combine the new pistons with a slightly tuned set of cams and efi.

Best, Peter

 

Wossner pistons in Germany can make pistons and probably have a 308 QV piston on file already. They can easily modify that design for higher compression.

As for the liners, if the Nikasil is in good shape you can deglaze them with an aluminum oxide Flex hone, 240 grit. This method is factory recommendation for installing new piston rings on otherwise good condition Nikasil liner engines from Audi/BMW/Porsche/Mercedes. If the liners are not good then replace them. I have not personally had 308QV liners refurbished by a company like Millennium cylinder, but I have with several 911 engine liners refurbished and it has worked out very well.

 

No one I am aware of is making nickasil replacement liners. Even Ferrari.
Bore and replate what you have.
Putting a new piston in a used liner is no better in nickasil as it is in an iron motor.

 

This is a 308 QV Nikasil liner re-plated by Millennium:

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As far as pistons go you could contact Scott from Nicks Forza. Few if any I know of are offering pistons for QV. Scott has been helping me with a problem child QV I have here and has been a big help.

 

Another option for QV pistons is Wiseco - forged pistons, rings, circlips in stock or high compression ratio for about $1,100.

They are in Ohio (made in USA) and made me stock compression pistons for 85 euro (9.2:1 I think). Can provide a contact there if needed

 

Thanks a lot to all. It's seems like there is several realistically options to pursue when it comes to pistons. Re-conditioning the Nikasil liners locally might turn out to be more problematic and sending 8 liners to Millennium will be a costly affair. I will keep you posted when I know more about the actual condition of my liners and what route I choose to follow. What about "sports" camshafts for the QV. It again seems like tuned camshafts are readily available for the 2V 308 but not so much for the QV. Have anyone here good experience with any particular fabricate / design for the 308QV. I'm only looking for moderate increase in power, driveability and stable idle is important for me.

Best, Peter

 

If you keep the stock injection system you really cannot do much to the cams. Many years ago when I did more custom engine work I worked with one of the Iskandarian family members trying cams to work with Bosch CIS and found only very mild cams can work with it. Very little more than stock typically.
Its why when I built my 328 engine I went after displacement and compression. The only other way is some kind of supercharger.

 

Yup. I'll add that the other issue is the springs. A cam profile that is more aggressive and it actually doesn't take much, the increased ramp rate exceedes the springs capability and inertial float starts to occur from 6k rpm and up depending on ramp rate. That can be mitigated a bit by dropping weight and going with shim under and light bucket followers. But should be handled by new springs.
So in order to utilize hotter cams you need to replace not just the cams, but buckets, shims and springs. Then update the CIS to EFI.

Ferrari actually engineered the valve train right at the limit. No more no less then what was needed. That makes simple upgrades a bit more involved and of course more expensive.

 

Thanks - much appreciated info. EFI is serious considered as mentioned in my first post. This project is still on the drawing board level but is already crowing arms and legs. I now realize that it is a more complex and expensive exercise to modify a Ferrari engine than I initially thought and that I need to revisit my old school books stored in the attic.... I'm in it for the fun and learning, so pure hobby.


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"The only other way is some kind of supercharger."

There you go!! Easier, less expensive, less trouble, far more power available, no adverse effect on drivability.

 

Yes and no.
The catch 22 is the CIS. You'll need the rare WUR from the Porsche turbo of the era or the odd ones found in the mondial. They sport a reference chamber to enrich for positive air pressure. Otherwise the CIS will go lean very quickly. Given the costs and rarity... EFI is the better fix.

EFI alone bumps hp/tq a solid 30 sometimes a touch more depending on engine condition.

Personally after yrs of testing and building both of all flavors. My preference is NA first and increasing displacement. Once the engine has hit 3.5L or 4L then add boost. Unless you're going with a turbo but that's another ballgame.

These engines need low end tq first.

 

THIRTY?

 

Yup.
CIS is highly restrictive to air flow for performance. Excellent for cruising and efficiency. The mass air door flapper requires air mass aka dynamic force to open to provide fuel. That force restricts air flow and 'deadens' response. Essentially it's another throttle body.

 

Just out of curiosity, in all the attempts over the years to modify CIS cars, has anyone ever thought of removing the plate in the mass air door completely and replacing it with an electronically controlled motor, ie drive by wire ,to control the valve for fuel delivery? I know it's easy to say, but in theory wouldn't it work?