Scat Cam and lifters, something is wrong Options

[Bruce Edge]

Hey All,
I was trying to get a motor built this week before going on a trip. All was going well until I bolted the rocker arm assembly on. If someone could at least give me some idea of what could be going on, so I can feel better about straightening it out when i get back.
1.7 stock, went with Scat c35 cam with lifters to match, so I could run dual carbs. New P&C stock, rebuilt heads stock, no fly cuts, stock original springs, original alum push rods.
When I rotate crank, it binds or lock up with valve springs depressed. Valves are adjusted. I can pull rockers off and crank spins freely.
has anyone heard of a problem using stock rocker and push rods with this Scat cam.
I measured lifters, push rod sets about .07 deeper in scat lifter. Also noticed where push rod seats in Scat lifter, there is not a taper like the stock lifter, and push rod can hang on edge of dished hole. Sorry for all the rambling and if I not making sense, just dis regard.
Just trying to get some peace of mind before leaving town.

Thank for any suggestions,
Bruce

[Mark Henry]

What's the lift? sounds like you're binding the spring coils or or the retainer is hitting the valve guide tops

[Mark Henry]

For sure that's what's happening, your rocker geometry is all wrong, you need at least HD single springs, custom length PR's, 911 adjusters, the guide tops trimmed, spring check....etc.
You can't just slap that cam in.

495" Valve Lift with stock 1.3:1 Rockers, 285 degrees of advertised duration, and 246 degrees of duration at .050", on a 108 Lobe Center.

[Bruce Edge]

Hey Mark,
Thanks for looking at my post. I think lift on that cam is 381".

Thanks.
Bruce.

[Mark Henry]

Hey Mark,
Thanks for looking at my post. I think lift on that cam is 381".

Thanks.
Bruce.

At the cam, .381 X 1.3 rockers = .495 total lift at the valve.
That's a fair bit of lift, the hot cam I have in my 2.6L (102x78mm) only has .012" more lift at the valve. Where I got the specs from, aircooled.net says "HD springs required".

You can use a set-up on a drill press with a rod and a dial indicator so you can see when you reach spring coil bind.

[wndsrfr]

Be careful that you're not binding valve on piston also...
I'm assuming that you started with proper clearance with valves closed....(006" IIRC?) and tappet adjusters in mid range for best geometry...
If you've still got coil bind do what Mark said about springs... but then check valve to piston clearance with clay or solder

Cheap easy remedies for geometry issues include adjusting rocker shafts up a bit with shims under the mounts and cylinder base shims which will reduce compression ratio a bit as a consequence.
Be very careful...
There's a good write up by Jake about geometry issues that you should read three times...

[Bruce Edge]

Thanks guys,
I was trying to build a plane Jane motor for a econo cruiser.
As my other car has 180 hp type 4. I’ll be in Germany for a
Couple of weeks, so I’ll have something to think about.
Hope I can follow the Forum over there.
Thanks,
Bruce

[ChrisFoley]

Shoulda used the C25 in that case.

[Mark Henry]

Shoulda used the C25 in that case.

(IMG:style_emoticons/default/agree.gif) C25 will work with stock valvetrain.

As a note to the C25, when I got my 914 (2002) and SDS EFI I built a junkyard stock 2.0, all used parts, 1.8 heads, Ljet runners and a Djet TB/plenum with a C25 cam. It ran real good, as good as a stock Ljet. Since it was a step up from the 1.8 it had more power too me, but I had a 914 friend drive it and he said the power was about the same as a 2.0 D-jet.
So the C25 is likely better than a stock cam for carbs, but don't expect any big power increase.