Question for you cam guru's - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 12-03-2013, 03:29 PM Thread Starter
 
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Question for you cam guru's

I'm not too educated on cams...

Will I keep my brakes with this cam?

SD Performance- Pontiac Performance Specialists

236/245 dur @ .050" lift .578"/.582" lift 112 lobe sep

I'm also assuming I need a 2500 stall converter.

This is for a 461 stroker I'm building. KRE 85cc heads, performer RPM intake, 10.5:1 and still researching carb.

Thanks for any help.
-Norm
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post #2 of 9 (permalink) Old 12-03-2013, 04:00 PM
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It'll be marginal, especially if it's a flat tappet cam. I'm running a solid roller in mine that has 236/242 @ .050 on a 110 degree LSA, and I get about 13" of idle vacuum. A roller profile has 'quicker' opening and closing ramps so it will have less overlap than a flat-tappet will. However, the cam you're looking at has a slightly wider LSA so that might help some.

If it were me, I'd go ahead and prepare for an alternate brake solution (vacuum pump or hydroboost) because I think you're going to be borderline.

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post #3 of 9 (permalink) Old 12-03-2013, 04:05 PM Thread Starter
 
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Thanks for the quick reply.

It is a hyd. roller cam, not sure if that changes anything.

How about the 2500 stall converter, will I need that? Says power range is 2500-6000.

-Norm
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post #4 of 9 (permalink) Old 12-04-2013, 01:48 PM
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Ok then, being a roller will mean it won't have as much overlap as a flat... and you do have a wider LSA than me which will also reduce overlap (but it has more duration than what I'm running so that may be a wash). I still think it's going to be borderline on brake vacuum.

You can put together your own custom Hyrdoboost system using new parts from NAPA for about $500 or so, and that includes a new master cylinder and having custom hydraulic hoses made. Buying an "off the shelf" Hydroboost kit will cost you about a grand. I built my own for my car and it works great. Vacuum pumps also work, but I've been told that they're noisy. I've got no first-hand experience with them.

I'm glad I went the Hydroboost route. It works really well, and now I've got the freedom to run whatever cam I want without ever having to think about the how it might affect my braking. If I ever decide to go to a rowdier cam, everything is already set.

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post #5 of 9 (permalink) Old 12-05-2013, 12:02 AM Thread Starter
 
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Yeah I was researching building my own.

I may have to anyway because my heads and valve cover might not clear my current setup.

Thanks
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post #6 of 9 (permalink) Old 12-05-2013, 10:31 AM
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What I did:

"New" (rebuilt) booster from NAPA, originally spec'ed for a 73 or so GMC 3/4 ton diesel pickup.
New (actually) master cylinder originally spec'ed for a 69 BBC 'Vette with disc brakes.
New power steering pump originally spec'ed for the same GMC pickup (it used a different pulley/offset than my original 69 Pontiac pump so I had to work with the bracketry some to get the belt to line up correctly).
Booster - M/C pushrod that I got from "some place up north" (I'll have to check my records for the location) -- needed because the Rebuilt booster from NAPA doesn't come with one. They 'assume' you'll re-use your original.

Fabricated my own mounting bracket for the booster, welded up out of steel plate.
Laid out my hose routing, measured, then had hoses custom made with the fitting angles and types that I needed.
I cut off the end of the pedal push rod on the booster, threaded it, and used the pedal clevis from my original brake system to mate it up with the brake pedal.

The hose routing goes like this:
1) Pump high pressure out to hydroboost high pressure in
2) Hydroboost high pressure out to steering unit high pressure in
3) Hydroboost low pressure return and steering unit low pressure return both go to a 'T' fitting, then from there to the pump low pressure return.












(5 more images in next post)

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post #7 of 9 (permalink) Old 12-05-2013, 10:31 AM
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(Next 5 images)








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post #8 of 9 (permalink) Old 12-05-2013, 11:21 AM Thread Starter
 
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Nice Bear,

This will help out a lot when I build mine, thanks looks good.

-Norm
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post #9 of 9 (permalink) Old 12-05-2013, 11:21 AM
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Nice fab skills Bear!!
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