KADE at 14.2:1

[Uniac]

as the title says, my KA will be running 14.2:1..now my questions, think it'll take the boosted compression, and what fuel mods should i do to insure it won't lean right out and blow...also anyone think it'll run on pump gas...specs...3" from header back..header is 2.5" ported pollished head, sohc pistons, shaved head, 12lbs flywheel, act 6puck clutch, chrome rings, UR pullies, twin exhuast cams, and some electronic shit.

any comments appreciated, thanks guys...help on setting the cams right would eb great.

[TheTicTac]

I don't think sohc pistons will net you 14.2:1 and forget about running on pumped gas even if you get that CR.

[Uniac]

re-read the specs, shaved head .035" and we get 94 here in ontario

[wootwoot]

even with 94 that might be pushing it. detonation is going to be your undoing on this motor even if it does last for some time. reguarding your exhaust, why are you going to be running 3" catback? n/a engines need back pressure so i'd go with 2.5 inch. have you allready checked with your head being decked at said height that you will have proper valve clerance?

[Uniac]

oh forgot to mension the jic suppresion valve. it quiets it down and creates all the back pressure i need in the city, hwy i'm in 8000rpm land so it don't matter...

Yeah we checked the clearence, i was good ot .040" with the nissan headgasket, but the felpro was a lil more clearence, it just won't blow out as easy
I was wanting the head to blow out before to motor blew...yeah detonation is my worry, i know a/f gauges are gay, but i'm gonna run 1 just to get an idea. Fuel wise i dunno what i'll do maybe an safc or a fpr or somthing i dunno yet. I got to break it in so i won't be using a shit load of fuel to begin with so i should be ok for now.

[TK]

i don't think i've ever seen a engine with that high compression run pump gas before... 11.5-12:1 is pushing the limits even with retarded ignition timing.

[LanceS13]

...reguarding your exhaust, why are you going to be running 3" catback? n/a engines need back pressure so i'd go with 2.5 inch...
And I thought that myth was busted years ago...

[wootwoot]

ok let me elaborate, naturally aspirated engines benefit from some back pressure unless all the power is wanted only in the upper rpm range. is that better?

[LanceS13]

Velocity, not backpressure. Backpressure is bad...always.
IIRC, 3" has been dyno proven on the KA for gains throughout the power band...besides, with a 14:1 CR I hope the engine is gonna spend most of its life at high rpm anyway. No sense in putting around town on an engine that will likely need over 100 octane to run right IMHO.
On a side note...here's some interesting reading I just came across: http://members.uia.net/pkelley2/DynamicCR.html

[mav1178]

ok let me elaborate, naturally aspirated engines benefit from some back pressure unless all the power is wanted only in the upper rpm range. is that better?


KA w/ 80mm exhaust:

http://www.worldwidechang.com/Pics/Cars/MyCar/Dyno/NewDyno/IntakeExhaust1.jpg

-alex

[projectRDM]

KAs don't rev to 8k rpm. And a 14.2:1 CR on 94 octane will last exactly 20 minutes. So my guess is either A) you're full of shit and talking out your ass, B) an idiot, or C) all of the above.

[nightwalker]

Whoa! 14.2:1!!! Why didn't you pick 15.0:1? would have sounded more believable...;)

[orion::S14]

Header tuning is more important than exhaust size...if you have a decent header with the proper sized collector, that will add the the scavenging you need by keeping the velocity high...and then it doesn't matter what's behind it...and bigger has proven to be better here.

2.5" exhaust will be a power limiter at some level, but 80mm will support more than a N/A KA can flow, so go with that.

That being said, if I were doing only and intake and exhaust, I'd go with a 60mm exhaust. But with a header, ECU, intake, etc...I'd go bigger.

- Brian

[orion::S14]

Oh yeah...and to run any reasonable amount of timing advance, you'll need race gas, like C16.

The Datsun Z cars guys do 13:1 all the time, and run race gas...and make great power.

- Brian

[Zemus]

I also have been looking into doing a racing motor, with high comp and bascilly what he is looking to do, but running 12:1 or so. I was also looking into running 50mm Side Drafts, Large headers, and side exhaust (out the front driver fender behind the wheel.) I also want higher durration cams than what he is running, Like 270 or 260. But Im trying to find out if it would be worth all the money to do the carbs.

Also With the side exhaust not sure if I should run like STRAIT 3 inch out to the fender or just 2.5 out the fender?

How much power are you looking for with your current setup on 14.2:1 compression Uniac?

[sykikchimp]

To run pump gas, you'd have to run some hellacious ignition retard. Some JWT adjustable cam sprockets would help immensely as well. Either way drivability will be horrible on the street. Your also gonna need some sort of standalone engine management to really take full advantage of it.

The bottom line is that kind of compression is for race only cars that spend the majority of their lives at WOT, and then get rebuilt after a race... maybe 2.

[Uniac]

well if she don't last, i'll put my spare head on, and bring the compression down. simple as that. I think it'll be fine. But we'll see i guess.

And to all the unbeilivers, i'll dyno the bitch when it's broken in,


Ok nother question, what sparkplugs and what range...that's been bugging me all day/

[andrave]

are you sure shaving the head .035" raised compression 3 point???