FK87 with 1.25:1 rockers?

[RUSS74GHIA]

Hi folks,

I'm already running 1.25:1 rockers and was looking to upgrade the cam from a W-120 to a W-140 as I know this set up is tried & tested.

I've been offered a W-125 and an FK87, and as I'm building on a tight budget wondered if I should take up the offer. I know the W-125 will be fine, but the FK87 i'm sure is designed to run with 1.4:1 rockers.

Any thoughts anyone? CR will be around 10:1 and cc will be 1914 - 2110

[wph]

Rule of thumb is if cam is designed to be used with 1.4 ratio rockers the valve events (timing) will be wrong with 1.25's.
You're not going to get what the cam designer was looking for. Match the heads to your engine cc's and intended rpm
and the right cam choice can be made. Cam choice also affects your CR, it's the correct dynamic CR that you're after.

[dyno don]

1:25's can be used on a fk87.....you wont achieve the total advertised lift but if your heads wont flow the figure dont worry...i know of several people using this combo with turbo applications and works bitchin.   there is no worry other than the lack of lift. the engle 140 is a great cam as well but likes the compression up...(as the fk87)...should idle like a stocker but hold on when you get to 4K RPM...and should be noted that these cams should have good trans gears behind them ...hope this helps..

[TexasTom]

I would imagine the 1.25s will limit the rpm potential of the FK87, true?
Seems it would be a bit tricky considering the powerband, then not being able to take advantage of it ... 

[Jim Ratto]

I would imagine the 1.25s will limit the rpm potential of the FK87, true?
Seems it would be a bit tricky considering the powerband, then not being able to take advantage of it ... 

I would think, depending on heads and valvetrain, the opposite would be true.

[TexasTom]

I would imagine the 1.25s will limit the rpm potential of the FK87, true?
Seems it would be a bit tricky considering the powerband, then not being able to take advantage of it ... 

I would think, depending on heads and valvetrain, the opposite would be true.

I'd tend to agree with that statement, depending, as stated, on the heads and valvetrain ... being somewhat mismatched to the chosen camshaft in a normally aspirated combination (FK87 - 320 degrees advertised duration, 276 @ .050", .401" lift @ cam, .564" w/ 1.4 rockers; .483" w/ 1.25s).

Thinking of swapping to an FK-97, but with 1.1 rockers; lift would be .487"!  ... 

Seriously though & back on topic, Russ, what is the main use and purpose of your engine? What heads will you be using? Carburetion? The last thing to choose will be the camshaft.
I ran an FK-87 (with 1.4s) in a 2110 street motor, which also produced a 12.77 time slip with 48IDAs and 42X37 welded Fumios. Would rev to 7K with the belt once I switched my dual quiet packs to a 2.5" muffler on a 1.625" merged exhaust. It was a good combination, but only made really strong power over 3500. Drivability in town suffered, but I was willing to make the sacrifice for those occasional blasts.
I guess my point is that that cam is not exactly a good torque producer, unless maybe you're running a 4" bore.

[RUSS74GHIA]

Well I cooked my motor, almost losing the case.

Whilst it's open I was going to liven it up a little - for drag use, but still maintain it as a road car.

I've actually decided to simply rebulid it and add the twin 40 Dells i've got as the 2010 upgrade (I was running a single this year). Should give me mid 15's. Might even nick a '14' with the belt off and a tail wind

In the meantime I'll get hold of some decent heads and build a stonker for 2011. This will give me time to organise a new 'box and sort a cage out.

Thanks for your input chaps - it's been really useful.