| Author |
Message |
Matthew J. Morgan (Kermit)
New member
Username: Kermit
Post Number: 42
Registered: 8-2001
| | Posted on Monday, August 26, 2002 - 9:33 am: | |
Yes Peter, I have looked at different liners. The problem that I see is the distance between the bores (cylinder centerline). With the stock 308 bore, there is already considerable flat between. There is certainly a bit to be gained there, especially if the Sleeves are custom machined, with this fit tightened up. What concerns me is twofold: The wall thickness between the bores becomes so thin I would worry about flex. Then one must consider coolant flow. If the bores are opened up too far, it will restrict the flow. Perhaps "steam holes" ala Chev 400cid small block, where they actually siamese the casting there. |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1974
Registered: 12-2000
| | Posted on Monday, August 26, 2002 - 1:56 am: | |
Kermit, the article isn't too indepth, but I can get a copy if you like.
As for your question about the over-bore threshold: In the two years that this site has been up, I have never seen one member try this during their rebuilds...
Have you considered making your own liners, that have thicker walls to support a bore greater than 83mm? (If you say that at 88mm, the stock walls get too thin, then move the walls out. Although now that I think of it, probably at the sides, you'll still won't have the room...). |
Matthew J. Morgan (Kermit)
New member
Username: Kermit
Post Number: 38
Registered: 8-2001
| | Posted on Saturday, August 24, 2002 - 4:01 pm: | |
Dave, I don't think that is possible. The bore would have to be as Peter says 93mm There is not enough room for a bore that big. The cylinder centerlines are too close.Earlier I posted that we were doing a pair of 85mm bore 71mm stroke 308's I must correct myself as they are 83mm, not 85. Too tired to think straight I guess. Peter, do you have a copy of that 4 liter material? I would like to see it. Here is a question for all: What is the practical overbore on 308's. Not some "time trial grenade" , but a safe, reasonable bore? Anyone? |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1961
Registered: 12-2000
| | Posted on Monday, August 19, 2002 - 12:35 pm: | |
The 408 4WD Prototype used a 4 litre motor, the claim written in "Ferrari Story" #16 was that the dimensions could not be accommodated in the existing V-8 block, so they cast a new one (Type F117. 93mm bore, 73.6mm stroke). |
David Jones (Dave)
Junior Member
Username: Dave
Post Number: 241
Registered: 4-2001
| | Posted on Monday, August 19, 2002 - 11:04 am: | |
Kermit, on those (mythical?) 4 liter motors, I wonder if they are using a 328 crank, and then playing with different rods and moving the piston pin holes? |
Matthew J. Morgan (Kermit)
New member
Username: Kermit
Post Number: 34
Registered: 8-2001
| | Posted on Monday, August 19, 2002 - 9:17 am: | |
Hi Dave, Yes I have heard about those (mythical?) 4 liter motors too. I would like to know how they arrived at that displacement. Right now we are putting together two 85mm bore 308's, one 2V and the other 4V, both injected. This is about the largest practical bore I am comfortable with. Some time back I studied the block / liner thickness issue. My conclusions at the time were that 88mm would be about max, and that being on the edge. The cylinder walls get real thin at the sides, and there is the coolant issue to deal with. I doubt very seriously that 4 liters is possible without a serious increase in stroke. If it could be done, the intake and exhaust will not flow well enough to feed that much bigger motor. If it could be done, how long will the transmission last? Anyone have real info /pics?
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David Jones (Dave)
Junior Member
Username: Dave
Post Number: 239
Registered: 4-2001
| | Posted on Saturday, August 17, 2002 - 7:51 pm: | |
Hi Kermit, from chatting with a few Ferrari engine builders I have learned that the 3.0 liter engine can be bored and stroked to about 4.0 liters, but I am not sure in which combination to get there...
It would be good to know the max sleeve bore that one could use on a 308...
I have had a quote of about 90 bucks a hole for new sleeves made, but I'm not sure the max I can reliably go...
I'm thinking at around 4liters you would start to pick up some much needed tourqe. |
Matthew J. Morgan (Kermit)
New member
Username: Kermit
Post Number: 33
Registered: 8-2001
| | Posted on Saturday, August 17, 2002 - 7:13 pm: | |
Thanks all. I'm still studying the crank alloy a bit though. I'm beginning to wonder if Siluminum isn't an advertising name and not a proper metallurgical term. I felt it was really a lot like 356 alloy, popular in aftermarket hi perf parts, and I was thinking 4043 would be the best choice.4047 is higher yet in silicone, but is expensive when you can find it. I too like to use 5356 on castings, and have always had good luck. No kidding about the castings. The 4V seem to be a hell of a lot better, with the 348 the best I have seen so far. The first 2V I ported was an eye opener. As I cut into the side of the port, it started to look way to much like a silver Aero Bar. |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1950
Registered: 12-2000
| | Posted on Friday, August 16, 2002 - 11:20 pm: | |
...Also in that 308 V-12 conversion manual, he suggests to use 6061 for the needed additions to the block (engine adapters, bellhousing spacers, etc...). 6061 contains magnesium, silicon and copper... |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1949
Registered: 12-2000
| | Posted on Friday, August 16, 2002 - 10:55 pm: | |
5356 is fine for castings, but 4043 is the best filler material for this.
I had to repair one of my cam caps (tightened too tightly, long story...) and used 4043. Ferrari's casting quality was poor, but it welded without problems...
As for the crankshaft... Your guess is as good as mine. I'd imagine you probably need to stick-weld it (SMAW), using some-sort-of nickle rod. In the David Goldsmith 308 V-12 conversion manual, they needed to extend the tranny imput-shaft gear and had the part analysed. That gear was determined to be 9310-9320. Maybe its the same as the crank??? |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 289
Registered: 11-2001
| | Posted on Friday, August 16, 2002 - 7:44 pm: | |
Yes
I just had my head "cam bearing journal" welded, honed, and generally cleaned up by the machine shop I used. The machinist is a very excellent welder and a top notch professional. He just took one of the old main caps and practiced on it to get the weld to form a perfect bead and away he went. The head did have some porosity but it did not hurt the cam journal. After welding, he made a jig (I helped) to hold a honing rod, mounted a cutting bit in it, and bored the journal and the cap back to size. It was great, and it works great. One head saved. With heads going on ebay for $4900, I was quite pleased.
I did not weld my crankshaft, but I imagine it can also be done. The trick is to find a very good crank grinder afterwards. There is one here in redwood city but "good" costs mucho dinero. I just straightened the crank, grounded it for undesize bearings and got going with it. |
Paul Newman (Newman)
Member
Username: Newman
Post Number: 336
Registered: 12-2001
| | Posted on Friday, August 16, 2002 - 6:09 pm: | |
The block and heads can be tig welded. They are aluminum. Ive seen repairs done to them in the past and mitchell just had his head and block repaired due to spun bearings and damaged cam journals. The crank is forged and can be welded and remachined or stroked if you will. |
Matthew J. Morgan (Kermit)
New member
Username: Kermit
Post Number: 31
Registered: 8-2001
| | Posted on Friday, August 16, 2002 - 5:43 pm: | |
The only thing that mentions what the engine parts are cast from is Allen Bishop's wonderful book. It says that they are cast out of Siluminum, a high silicon, high copper content alloy used for it's strength and resistance to thermal stress. None of my welding vendors have any idea what is the metallurgical content. As I have in the past spent a few years as a welding instructor, specializing in TIG ( also known as Heliarc), I need the info in order to properly weld blocks, etc. Typically, I have a 308 head with the usual end cam bearing journal toasted. It will have to be built up and reamed to make it a serviceable casting once again. There is also a block from another 2V with a hole from a rod bolt. If I can find out what filler rod to use, these, as well as others can be saved. In the past, saving aluminum racing blocks has been successful.
As long as we are on the topic of alloys. What about the crankshaft?
All things considered, there has to be a way to save the odd "hurt" one with buildup and nitrating. And I must confess, I would like to see a longer stroke, if the journals can be built up. Anyone out there know? |
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