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#2466212 - 03/14/18 01:24 AM Cam timing 440
rtandy Offline
member

Registered: 01/23/03
Posts: 83
Loc: melbourne australia
Hi all, I have a 440 with an old Iski 505T solid cam (.505 lift Int and Ex 290/254° @ .050) 9.5:1 compression. My question is, what can I expect as reasonable idle vacuum? I am only getting 9-10 inches at the moment regardless of initial timing, is this the most vacuum I can expect from this cam? Also, I have a feeling that the cam is advanced slightly as when the engine is timed to TDC with the timing light (vacuum advance disconnected) then stopped and rotated to TDC, the rotor button is slightly past the No.1 position. Would this also have an effect on the vacuum at idle?

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#2466219 - 03/14/18 02:10 AM Re: Cam timing 440 [Re: rtandy]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 31224
Loc: Bend,OR USA
I used one of those Isky grinds on a solid roller cam in the first motor I built for a customer, that cam is a really old school design work
I didn't worry about the manifold vacuum and I didn't degree it, I lined up the dots and let the customer have the motor tsk it was a dead dog below 3000 RPM and then it came on like it had a NOS kit on it, I'm going to say it was probably retarded some twocents
On your deal make sure and degree that rascal in up scope Do you know what lobe separation angle it is ground on? If it is ground on a 108 or 106 LSA try installing it 4 to 6 degrees advance, put the intake lobe in at max lift at 101 to 104 degrees after top dead center, that will help the bottom end a bunch scope
Please let us know what you find out work
I ended up using a bunch of different Isky grinds after that one in both street and strip and drag race only cars, all of them where good as long as I degree them in properly up The best solid flat tappet grind was the old 616/590 dual patter cam, it was for drag racing only, the LSA was 104 devil It work really good on the street also with a decent converter installed form 100 to 104 devil To bad they quit listing it in their catalog whiney It can be bought now as a special grind but other company have better cams now shruggy


Edited by Cab_Burge (03/14/18 02:12 AM)
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#2466230 - 03/14/18 05:14 AM Re: Cam timing 440 [Re: Cab_Burge]
rtandy Offline
member

Registered: 01/23/03
Posts: 83
Loc: melbourne australia
Thanks Cab, I really appreciate your reply.
You are spot on about how it behaves, struggles to break loose below 3000 then fries the tyres till I back off. It is ground on a 108 LSA and I get what you're saying about advancing it 4 - 6 degrees. I'm happy to give it a shot but I'm a bit concerned as to what that will do for intake vacuum as I'm already struggling to get a decent brake pedal. Do you think advancing the cam will help with this or could it make thing worse?

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#2466273 - 03/14/18 09:07 AM Re: Cam timing 440 [Re: rtandy]
Skeptic Offline
master

Registered: 01/20/03
Posts: 4252
Loc: The Pale Blue Dot
That's a lot of cam for not a lot of compression- That intake duration isn't really290 at .050 is it? Still I see a vacuum pump in your future, or just switch to manual brakes. twocents
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#2466366 - 03/14/18 12:08 PM Re: Cam timing 440 [Re: Skeptic]
Biginchmopar Offline
pro stock

Registered: 11/22/10
Posts: 1241
Loc: Carson City, Nevada
Originally Posted By Skeptic
That's a lot of cam for not a lot of compression- That intake duration isn't really290 at .050 is it? Still I see a vacuum pump in your future, or just switch to manual brakes. twocents


290* Advertised - 254* @ 0.050"

beer

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#2466368 - 03/14/18 12:11 PM Re: Cam timing 440 [Re: rtandy]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 31224
Loc: Bend,OR USA
I can't help you on the manifold vacuum as I have never used power assisted brakes on any of my half way fast cars or customer motors that needed decent vacuum shruggy
My old 518 C.I. pump gas six pack motor had less than 6.0 inches of vacuum at or below 1000 RPM with the solid roller cam that was 260@.050 on the intake and 266@.050 on the exhaust lobes ground on a 108 LSA installed at 106 intake lobe centers shruggy The only reason I know that is trying to get the six pack to idle real low (800 to 850 RPM) in gear to show some of the local "experts" that you could make a Holley carb. idle like that with a little effort up haha stirthepot
Have you thought of using a electric vacuum pump to help on your brakes work shruggy
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Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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#2466527 - 03/14/18 04:26 PM Re: Cam timing 440 [Re: Cab_Burge]
dogdays Offline
I Live Here

Registered: 01/20/03
Posts: 16213
That design is at least 40 years old. That means moderate lift with big duration at 50 lift which means low idle vacuum. I think 9 - 10" vacuum at idle is pretty representative as to what this cam can do.
IMHO advancing the camshaft will increase the idle vacuum. If I'm wrong some angel of mercy will certainly tell me so.

http://iskycams.com/cart/index.php?main_page=product_info&cPath=12_14&products_id=148

The cam is not very aggressive compared to more modern high lift cams. It also has 0.028" lash so the lift is really around 0.480". The highest lift Bullet 0.904 lobe for the same 0.050 duration gives 0.578" gross with 0.008" lash for 0.570 lift.

There's the info, do with what you will. I often wonder whether some of these old lazy grinds might be good starting points for regrinds.

R.




Edited by dogdays (03/14/18 04:27 PM)

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#2466717 - 03/14/18 10:59 PM Re: Cam timing 440 [Re: rtandy]
rtandy Offline
member

Registered: 01/23/03
Posts: 83
Loc: melbourne australia
Thanks to everybody for your replies.
Seems everyone I talk to over here just wants to sell me a camshaft and I've grown kinda fond of this old stick.
I'd prefer to try and get some vacuum out of it and bring the power on sooner by advancing it a few degrees.
I'll give it a try and keep you posted.


Edited by rtandy (03/15/18 12:39 AM)

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#2466733 - 03/14/18 11:30 PM Re: Cam timing 440 [Re: rtandy]
GTX MATT Offline
master

Registered: 06/05/06
Posts: 4843
Loc: CT
9-10 honestly sounds pretty good to me for that cam, what are you idling at 1200 RPM? I would expect that cam to pull 6-7 inches at 950 RPM.


Edited by GTX MATT (03/14/18 11:32 PM)
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#2467073 - 03/15/18 07:03 PM Re: Cam timing 440 [Re: GTX MATT]
dogdays Offline
I Live Here

Registered: 01/20/03
Posts: 16213
Hey, if you're satisfied with the performance, go ahead and use it. Here are some advantages:

1. You already have it
2. The slower ramps should allow running less spring than an ultra modern lobe
3. Should be easier to get valvetrain to last at higher rpm
4. Should not wear as quickly
5. You don't have to worry about flow at 0.700 inch lift, mid-lift flow is more important.

R.

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