Hi all! I am interested in building a hot 302 with a flat (180) crank. The main reason is that I raced a friends Boss 302 engined 1970 Mustang in a couple of ASCAR races over here in the '80's and the motor was a full on Boss with a flat crank. Not only did it sound the asbsolute business, but it totally outperformed the lightweight IROC Camaros with less cubes. My questions to this knowledgeable forum is these:1. what, if any are the performance advantages gained by running a flat crank. 2. What is the best complementary exhaust system for this arrangement and 3. What are the penalities vis a vis balancing the reciprocating assembly? (I have heard there can be serious dynamic balancing problems using 180 cranks) Your kind assistance would be appreciated.
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Flat Cranks
- Thread starter Keith1
- Start date
Lynn Larsen
Lynn Larsen
Keith,
I know this subject was discussed a while back. I did a search on "flat crankshaft" older than 1 week in this forum and got 165 hits. I would try this also if I were you.
Regards,
Lynn
I know this subject was discussed a while back. I did a search on "flat crankshaft" older than 1 week in this forum and got 165 hits. I would try this also if I were you.
Regards,
Lynn
I also think a flat-crank V8 would scream in a GT40, but to do it right would cost a LOT of money.
1) My understanding is that the exhaust scavenging can really help a flat-crank engine perform.
2) The best exhaust consists of a tri-Y setup.
3) The best way to address the vibration issues inherent in a flat-crank engine is to use the lightest possible reciprocating assembly...custom steel crank (the guys at Crower would love to build you one), very light (titanium?) rods, and race pistons.
1) My understanding is that the exhaust scavenging can really help a flat-crank engine perform.
2) The best exhaust consists of a tri-Y setup.
3) The best way to address the vibration issues inherent in a flat-crank engine is to use the lightest possible reciprocating assembly...custom steel crank (the guys at Crower would love to build you one), very light (titanium?) rods, and race pistons.
Lynn Larsen
Lynn Larsen
Keith,
As Mark pointed out, it's not that it isn't a good idea, but it is so far out of the mainstream, most people don't want to go there, even if they could afford it.
As I recall from the previous discussions there are some destinct advantages, not the least of which was the absolutely unique exahaust note that they have.
Good luck with your search! I am kind of a fan of the unusual and things out of left field.
Regards,
Lynn
As Mark pointed out, it's not that it isn't a good idea, but it is so far out of the mainstream, most people don't want to go there, even if they could afford it.
As I recall from the previous discussions there are some destinct advantages, not the least of which was the absolutely unique exahaust note that they have.
Good luck with your search! I am kind of a fan of the unusual and things out of left field.
Regards,
Lynn
I'm kind of curious about this. I've never heard of this before, and I don't recall hearing anything on here about it. I've searched the archives and can't find anything relevant.
If you search for flat crank, you get any post with 'flat' or 'crank' in it (LOTS). To search for posts with both 'flat' and 'crank', you need to search for +flat +crank.
This gives very few responses, and I can't find any relevant, apart for one post which referred to it while discussing a Boss engine.
Perhaps it was discussed on another forum?
If you search for flat crank, you get any post with 'flat' or 'crank' in it (LOTS). To search for posts with both 'flat' and 'crank', you need to search for +flat +crank.
This gives very few responses, and I can't find any relevant, apart for one post which referred to it while discussing a Boss engine.
Perhaps it was discussed on another forum?
Yes I kinda OD'd on FLAT Tyres, FLATchat, FLATulence and FLAT Tappets too. But no worries, I've got stuff on this technology somewhere around, I guess I'll just have to go dig for it. 180 cranks have always been around, but kind of rare. It is an alternative route for a V8 albeit, as previous posters have said, expensive, but what the heck! You should hear the glorious noise they make!! And if there's a horsepower advantage too....... /ubbthreads/images/graemlins/cool.gif
Lynn Larsen
Lynn Larsen
That discussion (Big four) was regarding firing cylinders in pairs and the change of crank and cams in a particular engine.
A flat plane crank V8 does not have to fire two cylinders together to make a big bang engine. The DFV being a case in point.
A flat plane engine is like running two four cylinder engines together but 90 degrees "out of phase" (assuming 90 degree V of course /ubbthreads/images/graemlins/smile.gif).
After looking at the "Big four" thread again I realise it should be possible to have a different crank with cylinders 1-2 lined up together and cylinders 3-4 lined up etc. It'd be nasty though.
Maybe you were onto something Ron. /ubbthreads/images/graemlins/blush.gif
A conventional V8 (eg 302 windsor) with crossover pipes should sound flat planeish, mine certainly does, although it doesn't seem to want to rev as high as a DFV for some reason. /ubbthreads/images/graemlins/smile.gif
Tim.
A flat plane crank V8 does not have to fire two cylinders together to make a big bang engine. The DFV being a case in point.
A flat plane engine is like running two four cylinder engines together but 90 degrees "out of phase" (assuming 90 degree V of course /ubbthreads/images/graemlins/smile.gif).
After looking at the "Big four" thread again I realise it should be possible to have a different crank with cylinders 1-2 lined up together and cylinders 3-4 lined up etc. It'd be nasty though.
Maybe you were onto something Ron. /ubbthreads/images/graemlins/blush.gif
A conventional V8 (eg 302 windsor) with crossover pipes should sound flat planeish, mine certainly does, although it doesn't seem to want to rev as high as a DFV for some reason. /ubbthreads/images/graemlins/smile.gif
Tim.
Once you have a flat crank, you no longer need a 180 degree exhaust, because the firing order is lined up on both sides.
You will need a different cam for that firing order, and the distributor wiring will need to change.
It's essentially the same as two 4 cylinders joined at the crank.
I believe ballencing is actually easier, but in terms of engine vibration it will be rough, like a big four cylinder engine without a ballence shaft, not as smooth as a conventional V8.
Everything that I have heard is that it's a lot of work with very little improvement. But, you do get better exhaust scavenging and reduced rotating mass.
One other reason not to do it is spares and repair. An oddball flat crank cam has to be ordered, it can't be bought off the shelf. A mecanic working on it might say the firing order is all screwed up, I'll fix that.
If you are prepared to deal with that and the exhaust note, go for it.
You will need a different cam for that firing order, and the distributor wiring will need to change.
It's essentially the same as two 4 cylinders joined at the crank.
I believe ballencing is actually easier, but in terms of engine vibration it will be rough, like a big four cylinder engine without a ballence shaft, not as smooth as a conventional V8.
Everything that I have heard is that it's a lot of work with very little improvement. But, you do get better exhaust scavenging and reduced rotating mass.
One other reason not to do it is spares and repair. An oddball flat crank cam has to be ordered, it can't be bought off the shelf. A mecanic working on it might say the firing order is all screwed up, I'll fix that.
If you are prepared to deal with that and the exhaust note, go for it.
Lynn Larsen
Lynn Larsen
Didn't have time to read it close, I thought it was the discussion I was thinking of. I must have been in the ones that went to the bit bucket when we switched the software.
whatever,
Lynn
whatever,
Lynn
Near enough I think Lynn. It does discuss them and it's the only flat plane discussion I remember but then I haven't been here as long as you. /ubbthreads/images/graemlins/wink.gif
Built2rev, I like the exhaust note but they have to be revving before they start sounding good. At low rev's they sound a little ordinary when compared to the basy rumble of a conventional V8. Personally I think the same can be said for conventional V8's with crossover exhaust.
Tim.
Built2rev, I like the exhaust note but they have to be revving before they start sounding good. At low rev's they sound a little ordinary when compared to the basy rumble of a conventional V8. Personally I think the same can be said for conventional V8's with crossover exhaust.
Tim.
Thanks for the link to that thread guys. It would seem that the limited benefits are outweighed by the cost/complexity. As I said previously, if it was that good an idea, everyone would be doing it. Maybe my friends quick Boss Mustang was just simply....quick! flat plane crank motor or not! Just trying to be different in a increasingly corporate and structured world....
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