What RPM range for FK89 cam?

[Greg Ward]

Hi guys,

Can anyone give me some real world specs on what sort of rpm an FK89 is supposed to make its max power at?

I know it will all depend on combo of size of engine, compression, heads and lift etc, but is there a suggested max power rpm?

I can't find the info in any engle literature.

Thanks,

Greg

[Udo]

This depends on cc and heads . It can work up to 8500 with smaller cc engines

Udo

[Greg Ward]

Thanks Udo,

It's not my engine, I'm using a JPM cam and heads, but it is a friends engine 1916cc and 044 Ultra Wedge port heads 42 x 38 valves 1.25 rockers and approx. 11:1cr.

The problem is knowing where it "should" make max power, it may rev to 8500, but should the max power be at  7500, 8000?

We will find out for sure in a couple of weeks once it is on the dyno, however, I just wanted to know what roughly he should be expecting to see max power at, in other words if it all falls flat at 7000 then surely it's not correct for a cam that is billed as a drag race only cam.

[Fiatdude]

It is all the ingredients that make up the soup -- -- Your intakes, heads, valves, springs, and exhaust all play a part in where your engine will sing at -- that is why when an engine builder hits upon that magic combination that really works well together is a special thing.....

I really like the ultra wedge ports -- had them on a 2165 that broke 300 HP











with a turbo

[leec]

Thanks Udo,

It's not my engine, I'm using a JPM cam and heads, but it is a friends engine 1916cc and 044 Ultra Wedge port heads 42 x 38 valves 1.25 rockers and approx. 11:1cr.

The problem is knowing where it "should" make max power, it may rev to 8500, but should the max power be at  7500, 8000?

We will find out for sure in a couple of weeks once it is on the dyno, however, I just wanted to know what roughly he should be expecting to see max power at, in other words if it all falls flat at 7000 then surely it's not correct for a cam that is billed as a drag race only cam.

Ultra wedge ports have a 46mm inlet?
An FK87 would be better.

[dangerous]

On larger engines I have built with this cam,
it came on at 4000 and peaked in the 6800 to 7200 range. (shift 8 to 10% past the power peak (limiter at 8000).

This was with valves 'sized' to match the rpm peak,
in relation to the engine size.

Ultra heads have a 46 valve and are probably too big for a smaller engine, unless you rev it to the moon.
...and this assumes everything else is sized to THAT rpm range.
Normally due to the slow air speed, and disappointing cylinder fill, they will rarely peak where it should.

There are some simple base-line formula,
that will tell you what rpm the power should peak at, for a given capacity and seat throat.

But this assumes the flow, intake length and volume, and lastly the cam, are matched to the desired rpm of power peak.

FK89 was very smooth on the valve train unless the hot lash was too great.

[Greg Ward]

Ultra wedge ports have a 46mm inlet?
An FK87 would be better.

Yeah, sorry, they look exactly the same cnc porting as the ultra's but are the 42 x 38 variety not 46 and not Ti valves.

[dangerous]

Here you can work out what the smallest point of the port needs to be(valve throat).

http://www.wallaceracing.com/ca-calc.php

and others here:

http://www.wallaceracing.com/Calculators.htm

[Greg Ward]

Here you can work out what the smallest point of the port needs to be(valve throat).

http://www.wallaceracing.com/ca-calc.php

and others here:

http://www.wallaceracing.com/Calculators.htm

Cool, thanks, I'll take a look at that - what valve clearances did you end up running? I'm sure it would end up worse hot with steel pushrods, my friends are still Al...

[Udo]

I think the most powerfull engines with that cam are the CB progas and the super stock engines :-) So if you have ultra wedges you are on the right way

Udo

[dangerous]

Zero cold with chromoly and .004" with alum.

[Chris bugster]

Did I read correctly that he wants to use an fk 89 with 1.25 rockers?
Tried that once and it was much lazier and made over 20 hp less than with 1.4s.

[Jon]

My 2176 with fk 89 peaked at 7670

[Greg Ward]

That's interesting Jon, what heads were you running?

[Jon]

48x40 CNC competion eliminators, with super short induction runners, valve to top velocity stack 280mm. 800 mm from valve to collector start.

[Chris bugster]

That short runner sure makes a big difference.

[folkevogn]

48x40 CNC competion eliminators, with super short induction runners, valve to top velocity stack 280mm. 800 mm from valve to collector start.

Are you sure the total induction lenght is 280mm! If I remember correct the carb is 180mm(ish) That leaves 100mm from valve to carb! I got different heads than you but my CB44 heads is around 80-90mm from valve to the intake runner. I for sure would struggle to fit 10-20mm intake runners 

[BeetleBug]

48x40 CNC competion eliminators, with super short induction runners, valve to top velocity stack 280mm. 800 mm from valve to collector start.

Are you sure the total induction lenght is 280mm! If I remember correct the carb is 180mm(ish) That leaves 100mm from valve to carb! I got different heads than you but my CB44 heads is around 80-90mm from valve to the intake runner. I for sure would struggle to fit 10-20mm intake runners 

Please post the picture of your engine JHU so that everyone can see your intakes