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Planning a 1270 Street motor

dardoonk

dardoonk

Forum Mentor
How much trouble do you think I am getting myself into building a 1270cc 8V motor for the street? Pulled in a like new 1270 block & JE piston kit, and figured I'd do a little mild work to a small port head & some mild cams. I'm looking for bottom end & mid-range, not revs.

Can I keep the engine cool enough? I'm concerned about the thickness of the liners, but I haven't measured them yet.

Should I go with the 750 oil pump setup and is there any other mod that will help keep the head cool?

Is there a better than stock type clutch setup I should go with?

Recommendations on cams & carbs appreciated too.
 
That's a big 8V'er.:twistedevil:

You might want to figure out some sort of ignition delay to save your starter clutch. Mine made nasty sounds when attempting to start an overbore 8V, and it wasn't as big as yours.:p
 
That is a big 8V...
Ironically, the small head & mild cams you will use for a midrange motor will make it harder on the starter - short cams equal high cranking compression.
I'd go for an 1100G head - the reduction in compression will help lower temps and at that swept volume the ports will still be small - LOL.
The oiling mods are mainly for peace of mind in race motors but it would probably be worthwhile fitting an oil cooler too.

Most of the 8V's that size out here in NZ - or Aussie - are race motors on alcohol so cooling is a moot point...not a problem.
 
need a lot of extras to go with a 1270
oil cooler
750 pump gears
HD clutch basket
Jet kit
pods
clearance the cases
 
What is the compression ratio of the pistons. This would be critical info for a street motor. Is it a factory Suzuki block ???? Anything over a 10.5/1 will have overheating issues. In order to run that big of a motor on the street, reliably, would require sleeves so big they would leave a stock cylinder block without much support (read dish rag).....Billy
 
dardoonk said:
Nobody? Really?? :(
Click to expand...


1 word for you kaboom .

the cases are very thin at 1238 they used to make a support girdle for the engnie cases in like 80 when V&H were really making big engnies out of the 2Vstuff. (avg 12 minutes life)

the left end of the crank will need another bearing support - right where your starter clutch wants to be.

st. gear crank a must

hi ratio oil pump gears

billet output shaft in trans

you are going to have sealing issues. so O ring your cylinders w copper wire.

oil control will be an issue
temperature will be an issue
every part will be a special hard to replace unit.

I quit before I spent a lot of money and just went 16V

a 1105 with 40mm intake valves and shim under 425 web cams can make 140 street HP. 11-1 comp lighten up the bike and do some trans work - a 1100 clutch too Zippy combo on pump gas

a sport bike fan opn the fins will add many years to your pistons and cylinders.
 
Pretty much everything Trip said EXCEPT........... do NOT use copper wire for the block deck orings unless you like leaks or changing that wire. Use stainless wire, or even BETTER, I use PIANO wire & NEVER have to change it & it seals better! You will also need a way to retard the timing for startup & a BIG oil cooler! Ray.
 
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how about sending those babies off to be power ringed while we're at it!!
lets spend his entire 2010 bonus check!:twistedevil:

ok maybe sell the 8 valve stuff and do a 16 valver:)
 
Engine?

Engine?

I agree there, do a 16valver. More power and reliability. I will even sell you all the parts from my old Katana. Think 1290cc's. Maybe an easy and streetable 160 horses. Come by my house again.
Laters
Greg
 
Well, based on everyone's comments, this should be a pretty easy build...Heck, just like a stocker, huh???:) LMAO.

Really, it sounds like I have a lot of sorting out to do. I completely understand the responses that going the 16V route is the easiest way to make power and I'd agree.

Unfortunately, there's something attracting me to trying to pull this off and end up with something way, way different. Well, different enough that I probably won't run into another 8V this big anyway!

I'll make some measurments on the block that I got with the piston kit. It's external appearance is stock, but it's already been re-sleeved. I found no special stampings that it came from anyone notable, but I'll check closer than that. Otherwise, I might have a line on another.

I am not sure what to do about crank bearing support?? I'm kinda gonna need the starter gears. Is there another way to accomplish this?

Clutch basket upgrade?? Is there a 16V basket that was interchangable? Maybe I can find a billet one as I doubt I will find a billet 8V basket.

Billet output shaft?? I think I can get that.

Ignition delay?? I'd thought about that a little.. One thing I was going to look into was to determine if it is possible to do this using a MicroSquirt and either delay, or map it to retard the timing more at tickover speeds?? Just a guess on my part at this point.
 
A lot of problems come with a large 2-valve

A lot of problems come with a large 2-valve

Okay, while I don't think you may need a billet output shaft as you have the old 2.15x18 wheel and aren't drag-racing it, you will be severely restricted by the cylinder head. The old mechanical slide carb head has so small a ports, makes me think it was really a 550. Go to an 1100 G head and some large cams to help it make fair power and much easier to crank and start. When it starts to run hard, watch the alt rotor come off or break of the snout of the crank. Rods may be weak too. If you are going F.I., why not get some big T.B.'s? Maybe the smallest would be 38mm from a GSXR 600. And don't forget to relieve the upper crankcase as the large sleeves need clearence.
What else?
Laters
G
 
dardoonk said:
Really, it sounds like I have a lot of sorting out to do. I completely understand the responses that going the 16V route is the easiest way to make power and I'd agree.

Unfortunately, there's something attracting me to trying to pull this off and end up with something way, way different. Well, different enough that I probably won't run into another 8V this big anyway!
Click to expand...
The 16 valve motor is easier, but dont get discouraged, I smoked many 4 valvers back in the early 80's. Do your homework and ask lots of questions. Someone on here, maybe Racing Jake, once posted a very simple and effective way to retard the ignition timing on start up. It was just a lever that stuck out of the timing cover that allowed the whole plate to be momentarily rotated for starting purposes. When I saw it, I was like "Damn, that could have saved my crank and starter clutch from getting hammered.".....Billy
 
wouldn't a simple ignition power off till the engine's spinning be easier and accomplish the same thing as retarding the timing?
 
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