Hi all, I searched the previous threads and couldn't find the specifics on this. I am using Comp cams 31-255-5 for my 90 SD motor, otherwise stock. My pedestal mount non-adjustable rockers were worn out anyway and it didn't make sense to replace them with another non-adjustable set-up. My machinst recommended the Crane retrofit kit (36655-16) which adds guide plates. Therefore non-rail rockers 1.6 ratio (Crane 36800-16) are on the way. He said I can use my stock pushrods.

My questions are: (1) Has anyone had piston to valve clearance issues with the stock flat top pistons with valve reliefs? (2) Do I need hardened pushrods with guideplates? Assuming my 6.93 inch stockers are the correct length - which I'll check when I start assembly

 

You don't need adjustables with that cam. Waste of money buying or converting to them. Replace the stockers with Crane Energizer pedestal rollers. Use the stock length pushrods.

 

From Summit's website:


CCA-31-255-5
Brand: COMP Cams
Product Line: COMP Cams Computer-Controlled Camshafts
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,000-5,200 RPM
Intake Duration at 050 inch Lift: 206
Exhaust Duration at 050 inch Lift: 212
Duration at 050 inch Lift: 206 int./212 exh.
Advertised Intake Duration: 250
Advertised Exhaust Duration: 260
Advertised Duration: 250 int./260 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.462 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.474 in.
Valve Lift with Factory Rocker Arm Ratio: 0.462 int./0.474 exh. lift
Lobe Separation (degrees): 114
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: No
Grind Number: FS XE250H-14

I don't understand exactly why they say it's not computer controlled compatible when it's from Comp's computer controlled product line. Having a lobe separation of 114º it should be SD-compatible. Perhaps a call to Comp's Tech line would clear that up.

I don't think you'd have any clearance issues. I was concerned about the Crane 444211 I installed in mine as it has a valve lift of .530, but I clayed the valves and found I had adequate clearance.

The Crane guideplate conversion kit doesn't require hardened pushrods since the pushrods run inside bushings, so you can use your stock pushrods.

But I have to agree with baddad457. By the time you've laid out 150 bucks for those rockers and another almost a hundred for the guideplate conversion kit, you still only have stock-type rockers for your 250 bucks, which could have been better spent on pedestal mount roller rockers:

http://store.summitracing.com/partde...5&autoview=sku

I'm seeing them from about $165 a set up to $325, in 1.6 or 1.7 ratio. You can always send the others back and all you're out is the shipping.

 

I looked at the Crane Energizers (44746-16), but they're $200 a set anyway, and 1.7 ratio. I know that the retrofit adjustable studs or the pedestal mount are only for mild applications anyway. The 5/16 tapped holes probably can't handle a gigantic lift; and I'm not making any other modifications to the engine. Thanks!

 

The 1.7 ratio won't affect anything, just give it an additional .030 lift at the valve. They work fine with stock length pushrods. The one adjustable conversion kit I've tried was on a 400M. Had a couple studs that I never could keep tight. They were a constant pain in the butt. Pedestal rockers don't have the same problems. Bolt em down, torque em to 25 ft/lbs and forget they're there.

 

Actually, I just checked my order. I ordered the 35-255-5 for 351W...it was recommended by many posts in the fullsizebronc board. I just have to change my plug wires and the SD system is bank fire, it supposedly doesn't care what the firing order is. I thought that the 31-255-5 was the same thing, it's actually got slightly diff specs. Thats interesting that the 31-255-5 isn't listed as EFI compatible but the 35-255-5 is, according to Summit.

 

so are the crane cams pedestal rockers a direct bolt in? Or does it require mods?

 

Bolt them down......

 

alright awesome thank you!

 

The Crane 1.7 Cobra rockers are the cheapest and are a direct bolt on.

 

You have a link to those?

 

try google......works for me......

 

thanks guys

 

The part number for the Crane "Cobra" 1.7 rockers (they're the Energizer line now) is 44746-16