a "260" cam

[chad]

the 250 is being machined for the bronco.

the shop said "from what you say the use will be, compression sought, etc we will get you a 260 cam.' Nothing on lobes, duration etc. What attributes would a "260 cam" have? I seek good tq right from idle to 1500 - 2500 rpm. Will not be in the 3k revs much, probably 70% off rd traveling, hoping for a Carter RBS other stats in the sig. below.

Thank you -

 

[Econoline]

Comp 260H maybe?

 

[wsa111]

The Comp 260 camshaft is an ancient profile.
Go with the Isky 262 super cam or a Schneider in the 260 range.

 

[rbohm]

while the comp cams 260h is an old profile cam, it is still a good one to use. take a look at the variety of cams out there in the 260-270 advertised duration range though, and select the best one that works for you.

 

[chad]

"...best one that works for you..."

I don't think that wuz a prt #. (Comp Camp, Crane, etc but is 'grind' or 'profile', the degree advance duration")

Best one for me - I don't actually know how to pick em.

Looking for something with low rev grunt, not necessarily HP.
He didn't give me the lift, lobe center, etc. Is that something of concern? I can give you other parameters for the build if needed. (This is an extremely low cost build, or one that's done a piece at the time).
JUST CURIOUS
and
this is a machinist that you can't really tell what to order (I had the Handbook w/ recommendations on springs, retainers, etc, etc & since they weren't 'listed' for this motor he wouldn't go 4 them). He will f/u w/the back cut on the valves, 3 angle seat and Zero deck the block (but reports to NOT cc the head).

 

[bmbm40]

Nice to hear about your new 250 getting built.

 

[rbohm]

"...best one that works for you..."

I don't think that wuz a prt #. (Comp Camp, Crane, etc but is 'grind' or 'profile', the degree advance duration")

Best one for me - I don't actually know how to pick em.

picking a cam is actually fairly easy these days. the first thing you want to do is figure what rpm range your engine is going to spend 80% of its time in. in your case you said you are looking for low end grunt more than top end power, which means a street performance cam. thus you want something that works best in the 1000-4500 rpm range. what you do then is start perusing cam catalogs and look at cams that operate in that rpm range, +-500 rpm in general. a few rules of thumb when comparing cams;

more valve lift means more low speed torque
wider lobe separation angles mean more low speed torque
more valve overlap means lower low speed torque

 

[chad]

the lobe, lift and overlap explanation was helpful

",,,your new 250 getting built,"
yeah, budget operation here, so time is the lost factor...
I converted a commercial space in town for the lessee & saved the owner some time/materials. My profit goes inta the bronk. An on-line buddy (invented/manufactures/sells nationally a frnt end system) sent me a '75 'stang 250 frm TN but I got a '69 from some 1 on here that's been @ the shop since March & will be done soon (I hope).

Thank you both!

 

[chad]

now the builder sez he doesn't want the extra 'notches' cut in the crank sprocket to advance the timing. He is lookin 4 a special key (4 the same snout's keyway) to place in there. I remember this idea a lill, but it can't get the right advance (2 - 4*) or B as sturdy/adjustable - can it?

it needs machining too?

thanks again guys

 

[Econoline]

Mr Gasket makes a couple that will work. Offset keys, don't remember the #'s but one is for 2 deg the other is for 4. Make sure he degree's the thing in and doesn't just rely on what it should be. I'd have been way off if I did that with my 250

 

[chad]

I assume the key is not as reliable as the additional notches inside the crank sprocket?

"...rely on what it should be..."
ie automatic, ie set it and forget it, ie don't actually go thu the degreeing process?
How to know which key? How do I know how much advance (2*?, 4*?) will work for me?

 

[drag-200stang]

A key is just as good . The crank bollt has to be torqued to specs. It needs to be degreed ,may be perfect as is or off a mile.

 

[chad]

A key is just as good . The crank bollt has to be torqued to specs. It needs to be degreed ,may be perfect as is or off a mile.

Thanks 4 the reply.
Not as sure how the offset key wrks, I know the cam bolt (& lrger sprocket) but it's not on the crank (where the keyway to advance/retard is I assume). What's this other method, please? I got that it's got to B degreed, just like the "crank sprocket method" as ultimate check and adjustment.

Only familiar w/ extra notches inside the crank sprocket and the degree process. Not what an offset key looks like (I'd assume like any other "woodruff key") & where it's placed. Is the crank snout machined several times w/extra keyways for more options for the sprocket key?
Thanks again

 

[bubba22349]

See below link for what an offset key looks like they are made in both 2 and 4 degrees offset. The other way to do it is at the camshaft with an offset dowl pin or an offset bushing. Lastly you could also have a new key way cut into your timing set crank gear after you degree in your cam to figure out how much you need to change it. Good luck

4 degree offset Woodruff key
http://www.summitracing.com/parts/mrg-9 ... /make/ford

 

[Econoline]

Imagine a woodruff key cut in 2 long ways and put back together w/ the 2 halves shifted slightly or more. One part goes into the crank and the other part goes into the sprocket skewing the 2 one way or the other. Moving the sprocket cw or ccw.

With my build I had to use an offset key and jump a tooth to end up at 3 deg advanced, as close as I could get. I couldn't make it up with an offset key, I jumped a tooth and retarded it with an offset key to get where I ended. It was something like that, it's been a while. I don't remember the degree's per tooth on the crank and cam gears, the cam sprocket is where I jumped iirc. It's easy to figure out. If I hadn't measured it the engine would have been extremely retarded. You don't know where you are until you measure it. Unfortunately, the reliability of the timing set's for these 250's is poor ime.

I did cut the offset key to the face of the crank sprocket and use a piece of the straight key for the balancer. Not sure if that was warranted or not.

 

[chad]

wow, more ways than 1 to skin a cat...
(Four Ways now)
Thanks guys

All these are as reliable/durable as the extra notches inside the crank sprocket?

I;ll B degreein da cam no matter which is used so may B they all R fine...
If so the $17 one is it 4 me. (extra keyways on the snout seem the most expensive).
Here's hopin the cam company sends a degree wheel w/the cam.

(more valve lift (duration ?) - higher number
wider lobe separation angles - higher number
more valve overlap - higher number

On the orig question:
would a 260 duration 112 L/C be more low rev grunt than a 248 108?
Any disadvantages of 1 over the other (besides lower top end & increased gas consumption in the cam I seek)?

 

[pmuller9]

wow, more way than 1 to skin a cat...
Thanks guys

All these are as reliable/durable as the extra notches inside the crank sprocket?

I;ll B degreein da cam no matter which is used so may B they all R fine...
If so the $17 one is it 4 me. (extra keyways on the snout seem the most expensive).
Here's hopin the cam company sends a degree wheel w/the cam.

(more valve lift (duration ?) - higher number
wider lobe separation angles - higher number
more valve overlap - higher number

On the orig question:
would a 260 duration 112 L/C be more low rev grunt than a 248 108?
Any disadvantages of 1 over the other (besides lower top end & increased gas consumption in the cam I seek)?

I also used an offset key on the cam sprocket to get my cam timing closer on a 300 six.

The 248 cam on a 108 degree lobe center will close the intake valve 10 degrees sooner than the 260 cam on a 112 degree lobe center.
Because of that the 248 cam will make more low end torque than the 260 cam but the 260 cam will make more upper rpm power.

It is important to note that the 248 108 cam will require a lower compression ratio than the 260 112.
The 260 cam should have a compression ratio limit of 9.5:1 while the 248 cam should be limited to 8.9:1
That's based on having the piston at zero deck with around a .045 thick head gasket and 91 to 93 octane gas.

If the piston sits down in the bore at TDC and you want to be able to run lower octane gas then the compression ratio needs to be less.

 

[69.5Mav]

Some one on this board had a special cam gear made with different drillings for advance and retarding timing

 

[chad]

"Some one on this board had a special cam gear made with different drillings for advance and retarding timing"

the larger, upper cam sprocket has been redrilled several times for different placements of the locating dowel pin?
How does the driller determine where to drill for 2* 3* and 4* of advance?

 

[69.5Mav]

Don't remember much about it. I was hoping the original poster would chime in or anyone else who knows of this.