choosing a cam?

[Jared]

so i have been reading up on a few cams, but i am still not sure one what would be the best choice. engine specs are 2109 (94 x 76). 10.8 CR. valves are 40mm and 35.5 iirc. rods are 5.4. i'm looking to get about 150hp. where do i start?

Also, i'm running 40idf's and have looked at FK 45 and FK8. i already have a set of 1.4 rockers so i would like to use them.

[Zach Gomulka]

Carbs are too small for 150hp.

[Jared]

Ok so i am now going to be running IDA's. No one else has any input on this?

[John Maher]

Jared, you can definitely make 150bhp+ with Weber 40IDFs
Sorry to disagree with you, Zach  

I've built several 2110c bus engines (82 x 90.5) with the same valve sizes you listed (40mm x 35.5mm), using Engle FK7 w/1.4 rockers. The engines make just over 150bhp between 5900 and 6100rpm. Torque is just under 160ftlb (fw).

The heads and manifolds need work to achieve the amount of flow required but it's certainly possible to hit your target.
In other words your current spec is more likely port limited than carb limited.

I can't say for sure what the max bhp potential of a pair of 40IDFs is... the 40IDF equipped engines I've been building are designed specifically for Type 2s, where a decent spread of torque is the priority as opposed to maximum top end power. I'd take a guess maybe something around the 160bhp mark might be close to their max? You could probably get pretty close to that with an FK8 if you don't mind running a bit more rpm to get there.

If you can achieve your peak power target with smaller valves, ports, carbs etc... you have a more efficient engine, with good throttle response and excellent driveability. You'll have more torque throughout the rpm range than an otherwise identical engine fitted with IDAs.

PS... this ain't an anti-IDA rant. Horses for courses and all that  

PPS... just re-read your spec.
10.8 CR. Is this a street motor on pump fuel?
If so, too high for an FK7 or FK8 IMO. You'd need to run more duration to get dynamic CR down to a reasonable level.
Need more info.

[Jared]

The heads have been ported to the point of welding them up. This engine will be a fun play car and will also be driven on the street. I'm not worried about fuel. I figured i would be running 100 in it. so should i be looking for a lower CR?

[Zach Gomulka]

You know more than I, John
I enjoy reading what you have to say.

[Torben Alstrup]

Hello
I´m not disputing that 160 hp through 40 IDF´s isnt possible. But anything above approx 135 hp requires a little more than "garage" knowledge. 40 Dells on the other hand follows up to about 155 hp without too many struggles.
At least that´s what I see.

As for cam recommendation, I would recommend the Web 86B. Unless you have hogged the ports to the large side for the combo. Then the FK8 would be a better bchoice. The 86B dont like large slow flowing ports.
T