mystery cams

gumba · 07-12-2005, 10:43 PM

The cam numbers are 901 105 103 & 104 02. The Carquip site lists the 901 105 103 00 as 1966 906 cams. What do the last two digits signify?
I'm disassembling a 2.8 twin plug motor that came in a race car I bought a few years back. Looks like the head studs stretched, 60% leak down on #1. The case has been time certed and they look fine. I torqued the heads (26 lbs) late last year, now they are all loose, about 20 lbs. Leak down earlier this year was at 5-6%.
'74 rsr w2.8

camgrinder · 07-13-2005, 09:20 AM

Measure the lobe heights. If they are close you have 3.0 RSR cams, if not you have 906 cams. I am guessing they are rsr cams, but factory racing camshaft casting numbers are not 100% reliable.

gumba · 07-13-2005, 05:20 PM

Approx. 37intake/36exhaust. I'm assuming the lobe closest to the cam gear is the exhaust.

camgrinder · 07-13-2005, 09:09 PM

You have 906 cams. Depends on which side cam you measured, as to which lobe is intake and exhaust. Looks like you measured a left side cam.

gumba · 07-13-2005, 09:29 PM

Yes, I measured the left side cam. I'm going to have the motor rebuilt and use it in my street car, and as a back up motor for the track car. Any advantage/disadvantage to this cam? The motor was putting out about 255 flywheel hp, pulled strong from 4500-7000+. Thanks for the information.

camgrinder · 07-13-2005, 10:58 PM

The 906 cams are ok in a 2.8 litre engine. There are some better cam options. Are you using the center oiling on the cams or do you have later cam housings?

gumba · 07-13-2005, 11:33 PM

I'm using the center oiling cam housings.

camgrinder · 07-14-2005, 09:00 AM

Stick with the 906 cams unless you want to swap out the camshaft housings. Center oiling billets are not available, and the cost to rifle drill and put holes in the lobes and bearing journals in the currently available billets is expensive.

gumba · 07-14-2005, 09:26 AM

I would consider swapping out the housings if there was a cam that worked better for what I want to do. Also, I have no idea what the value, if any the 906 cams with housings would have.

camgrinder · 07-14-2005, 09:34 AM

Original 906 cams can bring serious money.
If you give me the details of your engine build I can give you some cam options.

gumba · 07-14-2005, 09:56 AM

2.8 twin plug. 92mm p&c (not rsr). The comp. ratio was about 9.25/1. Ran fine on pump gas, a little snappier on race gas. 7R case, stock crank. 46mm webers, tall pmo stacks. Put out 255 flywhell hp. I would stay around that h.p. What's "serious money" as I may consider selling the cams to fund the 2.8 rebuild.

camgrinder · 07-14-2005, 10:09 AM

My DC60 profile is the best replacement for the 906 cam. You will see a HP improvement. It has more valve lift than the 906 cams and the power band is slightly lower. I expect the curve would be 4000 to 7000 in a 2.8L. You can pick up a little more torque by bumping the compression to 9.8-1 since you have twin plugs.
Depending on your current valve springs, you may have to upgrade.

gumba · 07-14-2005, 02:09 PM

Thanks for the info. Your DC60 sounds like a better choice. I figured I would have to switch to a better spring.

ChicagoPete · 07-21-2005, 02:00 AM

I am interested in the 906 cams and housings....if you are looking to get rid of them...would like to see pictures!

gumba · 07-22-2005, 05:09 PM

ChicagoPete,
Sent you a pm.

ChicagoPete · 07-22-2005, 06:22 PM

Gumba....Didn 't Get one...

gumba · 07-23-2005, 10:26 AM

Cams are listed here:
http://there.dino.com/harold/index.cgi?page=9062