What the heck am I supposed to do with big CIS runners?

[dd74]

Okay, here's the deal: so I'm cleaning out the garage and I find two boxes: one contains big CIS runners (78-79) and the other contains the appropriate airbox. So you know me - not one to waste xtras - especially now that my 3.2 idea is gone to ashes - I'm thinking, let's play Frankenstein...

With that said, I have asked around about port matching these big runners to the heads which will be Dremeled out to port match. But while I'm in there, trying out 20/21 or 964 cams. Who knows when I'll do this - I'm just asking around for now.

So that's the set up. Anyone care to analyze it and what sort of horsepower I could get. I'm figuring 210 max.

Again, the engine would be a 3.0 with 9.3:1 compression, '78-'79 CIS and 20/21 or 964 cams. '74 heat exchangers and a Triad are already in place.

So...what are your collective thoughts?

Thx.

[Porschekid962]

DO IT! While your doing that, lop up the airbox and get it ready for the Tbitz efi. Then extrude hone your runners, port match them, port match the exhaust, toss in 964 cams, then go and have fun fun fun. This way when you slip on the 98mm p and c's in a year you just need to remap and go, fun for the whole family!

cheers, ryder

[dd74]

Yeah, I've been thinking a lot about Tbitz's EFI. Hmmm...that claim of 23 more horsepower on a stock SC is very intriguing.

Conceivably, Tbitz's EFI, 20/21s, 98mm pistons = 240-250 hp?

Or am I kidding myself?

[Superman]

There have been many claims about other fuel systems that make more hp than CIS. But most experienced folks dismiss those claims. I do. With other fuel systems, ANY other fuel systems, you'll have better throttle response. I agree that's important. Carbs feel like 50 more horses. But dynos don't lie, and none of those systems actually make more horses than CIS.

Yeah, I'd put a polish on those heads if you're going to dremel them anyway. Not sure how much it would help to polish the runners. Actually, the narrower runners have certain advantages. The air velocity is greater, helping to pack more volume into the chamber. Makes for better low end response. But the earlier SC air/fuel system is more robust and will make more horsepower.

My SC, with '74 HE, later CIS system, later pistons, 20/21 cams, made something like 174 or 184 lb/ft at the wheels (whatever.....with the 15% driveline loss it comes out to 205 at the flywheel). I suspect you can indeed make 210, just not at the wheels. Very possibly 215 or 220 in fact. I'm told it makes for a spunky engine. And 9.3:1 P&C sets should be available for a song. Then I wouldn't be surprized if the 98 mm P&C sets, which are shaped better than the 9.3:1 "turbulence" pistons and larger of course, could very concievably put you close to 250 or 240. But.....they're not available for a song. No matter how nice your voice sounds.

[dd74]

Originally posted by Superman
No matter how nice your voice sounds.

Dog gone it, Jim: I knew you were going to say that!

[Superman]

I've got a daughter who's old enough to start making me grandchildren, so I'm developing the appropriate type of humor sense. I've been a bit corny since I became a dad, and planning to take that to a new level.

And I'd love 98 mm Mahle jugs with about 10:1 dome-shaped pistons, and carbs, but I've got other stuff to do with three grand (plus two for the carbs). Heck, building monster motors for these things makes sense only for some folks in certain applications. For the rest of us, there are the 993 Varioram engines. That would be my pick. But then, we've gone over that.

But yeah, you could make your engine noticeably more fun, for a song. I'd suggest something like "Have I Told You Lately That I Love You." Or maybe just "Highway Star."

[dd74]

Jim, you're all ham...now pass the cheese...

[rdane]

I was thinking you should ask the wife?

Same story different day..215, 220 at the crank, on a good day.
BTDT.

[tsuter]

An SC is good for an easy 310 crank with stock CIS...of course I do have a seventh injector and few extra psi.

[dd74]

Originally posted by rdane
I was thinking you should ask the wife?

Same story different day..215, 220 at the crank, on a good day.
BTDT.

Yeah. No getting around the BTDT of the same question.
That leaves me no other option but...

a turbine engine from a helicopter. Who needs a 915 gearbox anyway...

[rdane]

Originally posted by dd74
That leaves me no other option but...
a turbine engine from a helicopter.

Cool...I'm in for a group buy Lets get Tyson started on the conversion kit.

[dd74]

If Jay Leno can do it, we can too. C'mon! Let's lock arms in unity!