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Discussion Starter #1
Hi All :lol:

So, you have to do one of the following:

Produce a V8 from 2 x V6 units or from 2 x straight four units. Are there any reasons that absolutely rule out one or both options above ??

I know a straight 8 has been made from 2 x straight 4's end to end, so I guess a V8 could be made from 2 x V6's in much the same way (I don't have room for a V12!!)

Although, with 2 x straight 4 units, you could keep the twin spark element, if you wanted to!

I guess a custom crankshaft would be needed in any case.

Best regards,

Paul.
 

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There are quite a few examples of a compact V8 made from two motorbike engines. That crazy thing that was on Top gear a while back had one. Can't remember the name! it demolished everything round the track but couldn't get over a speed bump so didn't go on the board.

What was it called...
 

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thats what i was thinking surely you would end up with a w12 vw phaeton / bentley engine.
Could you put then in line for a V12? But to get 8, you'd have to chop the end off one of them. I'm no mechanic, but I can't see that working. All the oil would spill out the hole. ;)
 

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Could you put then in line for a V12? But to get 8, you'd have to chop the end off one of them. I'm no mechanic, but I can't see that working. All the oil would spill out the hole. ;)
That would make it a proper Alfa engine then. Top up the oil every 10 miles.:lol:
 

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Discussion Starter #10
Hmmmm.. thanks for your valued input, some of you. :rolleyes:

V6 hughes and Bazza: Genuinely, thanks for your reply. It all depends on the configuration. If you graft one bank of V6 cylinders (3 cylinders) onto another V6 unit, then you get a kind of W9, rather than a W12. But that would be a pretty immense job due to the split lines and oilway configuration in the lbocks and heads.

The link above shows how it's been done to make a straight 8. The guy grafted all four cylinders from a straight 4 onto another straight 4. So I'm guessing the theory goes that you could graft less than all the cylinders onto an existing unit, hence take 2 from a V6 and add to another V6 to make a V8. Regarding the oil problem, you could just keep topping it up I guess, or fabricate it so there are no holes. Whichever works out the cheapest option!:)

As things stand today, I think it should be at least possible to take the flywheel end of a V6 with the first 2 pairs of cylinders, and graft it (no holes!) onto the fan belt end of another unit with 2 more pairs of cylinders. Leaving 2 lumps with 2 cylinders in each to sell on Ebay as a V4 project! I guess it wouldn't be too expensive an investigation to get two old V6 units and a big band saw!

Of course, this is all under the assumption that it IS worthwhile doing this, for whatever reason (genuine V8 availability and wanting to leave original V8 units for Montreal owners).

Thanks again.:)

Paul.
 

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Even if you could overcome all the problems of joining two lots of two-thirds of V6 engine together (oilways, coolant flow, crank, sump etc), if you're thinking about using Alfa V6s there's the problem of them being 60 degree V6s - V8s are usually if not invariably 90 degree. I imagine you'd need some fair old counterweighting on the crank for balance.

If not a Montreal V8, how about one from a Thema 8.32?
 
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There are quite a few examples of a compact V8 made from two motorbike engines. That crazy thing that was on Top gear a while back had one. Can't remember the name! it demolished everything round the track but couldn't get over a speed bump so didn't go on the board.

What was it called...
the caparo t1 :thumbs:

but it had a custom built v8

hammond quote "it has its own bespoke built supercharged v8 rather than cobbling two old motorcycle engines together"
 

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Discussion Starter #13
Thanks for the comments.

I've considered a few other V8 engines in another post. A few possibilities were suggested, the Lancia unit being one of the best!!

If the 'heart over head' decision is that, for whatever reason, it has to be an Alfa unit, and it has to be a V8, then I have 2 options: find and buy an alfa V8 unit or, by some as yet unknown means, 'make' one.

I think it's the RST V8 that you may be thinking of. It's fundamentally made from 2 bike engines, I'm told, and it turns out 380 bhp in the normally aspirated version!! Also, it's only 550mm sq envelope, so nice and compact.

Custom built would be great but a little beyond my means. Unless an unkown relative pops off and leaves me a suitcase full of fifties, that is!

Paul.
 

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Discussion Starter #14
GTV116, thanks for that. You make a really good point. I'm guessing I would need a custom crankshaft anyway so maybe the could be incorporated into the design - or is it already designed into the V6 crank ?

Cheers,

Paul.
 

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I doubt you could use many aspects of V6 counterweighting in a V8, the firing intervals in a V6 are 120 degrees apart. Getting the counterweighting right on a one-off V8 would (I imagine) be complicated, expensive and time-consuming. The 60 degree vee angle you'd inherit from using Alfa V6s would only make things more difficult.

If you're determined to build your own V8 (I wish I had the resources and/or balls) out of other non-V8 bits, you'll almost certainly need to design and build your own crank and sump, as a minimum. Given this, it might be easier to start off by deciding to marry two Twin Spark engines (from a 75) on a flat-plane crank, like Ferrari used, which should make the crank design easier. That way you'd retain the four-distributor set-up that the 33 Stradale used.

As this is post #116 for me, and we're talking about Alfa V8s, have this German market Alfetta with Montreal V8:
 

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Discussion Starter #17
Thanks GTV116. You make some sound points. So far, it's sounding do-able. The timing does seem to be quite limiting regarding the 60 degree V8 issue. I wonder whether you could do something canny with the crank i.e. not flat but with throws at 120 degrees to each other.....

Two straight fours seems feasible. A new crank and sump and mating two blocks together is within the realms of possibility at least, if a little pricey. Twin spark would be a nice feature to retain.

The stradale had 2 x 8 point distributor with 4 coils (at least the pics of the one I have seen did!)

Thanks for the pic - maybe a new source of V8 engines to pursue???
 

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The stradale had 2 x 8 point distributor with 4 coils (at least the pics of the one I have seen did!)

Thanks for the pic - maybe a new source of V8 engines to pursue???
I got confused between the distributors and the coils :eek:, you're right.

I think, althought I'm not 100% sure, that the Alfetta GTV V8 was made in Germany by a German tuner. Essentially a Montreal V8 in an Alfetta shell, with one or two changes like badging and a 'sud Sprint dash, there were plans for a production run of 200, but the tuner became bankrupt after only two had been built. Take from that what you will: it's either proof it's fine to use a Montreal engine for your own ends, or a cautionary tale about what the attempt will do to your finances.
 
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