Jebbysan

Look at these....
http://www.jegs.com/i/Comp-Cams/249/954-16/10002/-1

Jebby

bronzebb

That 954 Spring is the 929 spring in the Compcams catalog. Which brings up more uncertainty to this situation.😁 The important thing is the 200# seat pressure.

bronzebb

This is killing me.
The spring rate for the 953 is 473#/in. The free length I just measured is 2.282". So seat load at 1.900 should be 0.382 x 473= 181lbs. So a 030 shim should get me right around 200# seat pressure.

GOSFAST

Hi bronze, you have a first name maybe??

Take a few minutes and put up more of the components in the program, block, pistons, crank, piston/deck, etc. More specifically the head casting number, 842's or 074's?? With these early heads you want spring locators and like George also mentioned above, some lightweight retainers. A set of Comp's tool-steel's would be fine here!

If it is these early castings you might want to speak with your machinist/builder about having the longer bottom exh studs installed. This was almost a mandatory procedure for ANY roller builds back then. If not, you do run the risk of breaking-off a rocker stud boss on the exhaust's! The later 077's were the same, just did a set recently for a customer in Indiana!

The spring mentioned above, Comp's 954's we use on the SBC roller platform, would not use this part number either on the BBC. The 1.7 rocker ratio being the main issue!

(Add) One more item I'm having trouble with is the P/V numbers you gave, that's a relatively small cam to be that "tight" on the clearances. Could just be the piston in play?

Thanks, Gary in N.Y.

P.S. ARP has the required studs for this mod, I would also hope you're going with some sort of girdle, regardless of the cam size.

Jebbysan

Gary.....why is the 1.7 an issue?
.640 lift is .640 lift....no matter what engine it is in.
The rated lift is with a 1.7 rocker. The 954 yes is a common SBC roller spec spring.....but it has enough room for what he wants to do.

I agree on the longer exhaust stud......and a girdle is a very good idea...but will not fit under the stock valve covers.

I still would like to see a 953 at 1.850.

Jebby

gkull

If you go to the CC spring page the 953 is listed at 148# at 1.900 installed height and it indicates that it is a max lift of .650 inches. So you can't shim it shorter for more pounds because you have .640 lift.

You could shim up a 919 or 927 because they start at 194# & 201# respectively and they are .700 max lift springs or the 999 is also a good option.

higher ratios like 1.7 or higher ramp rates can cause loss of valve control. You can't start off with new springs with on the minimum # rates. Because you loose 10 or more % of their spring rate in a matter of months of use

http://www.compcams.com/Products/CC-...gn'-0.aspx

bronzebb

The heads are 3904392. I've had them surfaced probably 4 times in 40 years. They were surfaced, maybe milled, when I got them as an 18 year old. They already had the 1.84 exhaust valve and all the rocket studs are helicoid. The stud pockets are about 1" deep. 2 of the intake studs daylight into the intake ports. There is less meat on the bosses with the heli coils. How do you get a longer stud...weld up the hole, drill & blind tap to new depth?

Crank is Eagle forged, Scat forged connecting rods, LM2300 speed pro pistons. Two bolt block w/ ARP main studs. Compcams ultra pro magnum roller rockers.

bronzebb

I'm Terry in Belmont CA.

gkull

Terry, what is your max valve spring diameter? I run the Crane Ultra Pro lifters in both my engines. Very light and durable

I'm not up on BBC stock heads. But high psi 7/16 th arp studs, guide plates, and crane gold stud girdles really keep roller valve train together.

keep your idle speed up to keep the lifters oiled. VR1 oil

bronzebb

The roller rockers will take a big dia Spring. I had to cut the valve seat to 1.580 because the 953 springs were actually 1.550 OD. I called comp cams and they said that was in spec. Should have been 1.539OD. So more mystery to this build. Maybe i need a spring checker.

I can't believe how many little things I've had given check with this roller cam. Seems like 50 times $100 and 3 days or more delay each.

gkull

Don't even think about installing 953 springs on a solid roller motor....................... 148# closed!