| Author |
Message |
Robert Johnson (Carb308)
New member
Username: Carb308
Post Number: 19
Registered: 12-2001
| | Posted on Sunday, October 13, 2002 - 1:27 am: | |
Thanks to all for your input. Sounds like increasing the bore to 83mm is the way to go for more cubes. |
Matt Morgan (Kermit)
Junior Member
Username: Kermit
Post Number: 65
Registered: 8-2001
| | Posted on Friday, October 11, 2002 - 1:55 pm: | |
Actually, the difference between the two are primarily the 308 4V block sleeve bore is 1.5mm than the 328. Although You could easily bore the 308 to fit the wider sleeve base, there is a stroke difference ( 308 @71mm, 328 @73mm). Due to the 2mm longer stroke, the 328 piston will rise 1mm higher , and naturally drop the same amount at BDC. The Wrist pin height is usually where the difference is found in "same block , larger bore" scenarios. In order to accommodate the use of the same rod length (137mm), piston pin to top of piston has to be reduced. This would mean that these pistons would be 1mm below what 308's are. As Bret can tell you, the 308 already is below the block surface. This would result in a reduction of compression that would very probably result in less power in spite of the larger bore.
.No way on the 2V, as Peter posted the piston crown is completely different.
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Nick Scianna (Nick)
New member
Username: Nick
Post Number: 41
Registered: 2-2001
| | Posted on Thursday, October 10, 2002 - 5:07 pm: | |
Hi Brett.Your welcome,for the many hours both Kermit & I spent with respect to your pistons with the Wiseco people,we wanted to make sure that you would get the maximum HP after all the hours that Kermit spent porting your heads,intake runners etc.This is just another example why both Kermit & I go the extra mile for our clients and also to help a company as big as Wiseco with respect to a high compression 4 valve piston design as they did not have a actual high compression design & for other Ferrari owners who may in the future need High compression pistons for their 4 valve engine.I must complement many of the people on this chat site as there has been a great knowledge of information shared between members and that's what keeps the Ferrari passion alive for future generation Ferrari owners. Nick Scianna.
www.nicksforzaferrari.com |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 2073
Registered: 12-2000
| | Posted on Tuesday, October 08, 2002 - 11:05 pm: | |
When dry-building and checking cut-out clearance, a good way of marking the centers on the pistons is to have a very precise punch (an old valve will do. Cut the head off and grind a point on it) that'll fit in the valve guide. Bring to TDC and mark (make sure pistons are dead-center in the cylinder bore). |
BretM (Bretm)
Advanced Member
Username: Bretm
Post Number: 2723
Registered: 2-2001
| | Posted on Tuesday, October 08, 2002 - 10:49 pm: | |
Don't be sorry, lol. You added good info too. I see you mentioned Wiseco, that is who is making mine up. It was pretty complicated as it was the first 4v they were making up. I talked to them today again and they have all the info so are ready to machine them now. It worked out well because Nick Scianna needed to have a set of 4v pistons made up so he helped out with a lot of the info which was very cool of him. There were a few slight differences though so the pistons for him can't be the same as mine even though they are relatively close comps. Even after all this work though I will still have to essentially dry build it and check valve clearance (they want 40 thousandths I think for this size dohc), and if need be we'll bring the pockets down a little bit at work since we have a large machine shop there. |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 2072
Registered: 12-2000
| | Posted on Tuesday, October 08, 2002 - 10:44 pm: | |
Sorry Bret, didn't see you were already responding to this. |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 2071
Registered: 12-2000
| | Posted on Tuesday, October 08, 2002 - 10:42 pm: | |
Nope. The piston crowns are way different - flat top and they have cut-outs for four valves (308 two-valves have a nice dome shape with a hint of a cut-out for each valve). The liners MAY fit, but other than that it wouldn't work.
If you want cc's, punch out the exsisting liners and get some Wiseco pistons... |
BretM (Bretm)
Advanced Member
Username: Bretm
Post Number: 2722
Registered: 2-2001
| | Posted on Tuesday, October 08, 2002 - 10:41 pm: | |
The 308 you could theoretically bore it out to (I think) the 83mm of the 328, 308 is 81mm stock (80.93 actually). The 348 is nikasil already and I doubt you would be able to get smaller bore liners for it. It is already larger than the 328s so you would have to debore it. If you have nikasil liners (starting with the QV) it would be a much more complicated process to debore it. Nick Scianna is actually doing a 2mm overbore 308 right now so he would know a thing or two about it. You would start to change the engine a bit, theorectically it should have a higher rev as it is becoming more of an over square design, that is based on a lot of other things to though too. Also, the valve pockets would have to be taken into account, stock 328 is 9.2:1 I think so I'm not sure if it has pockets in it or not, but if it didn't theoretically you could check the clearances and if needed make them fit your 308 by machining them. It would be an interesting idea, but for what it's worth you'd probably be better off just getting pistons made up because it would be a pretty complicated process. |
Robert Johnson (Carb308)
New member
Username: Carb308
Post Number: 18
Registered: 12-2001
| | Posted on Tuesday, October 08, 2002 - 10:30 pm: | |
Just saw a set of 328 pistons on Ebay. Will a set of 328 pistons and liners fit in a 308 block? 348?
Cheers |