oldscutlass74

Have a '68 rocket 350, 5.7 with '74 7-A heads. I race my car, over 3 years it has sat a lot and the engine has run for probably only 3-4 hours in that time because I don't get to race often. It has always been strong but just this week I checked my valve train and all rockers were loose. We made adjustments and retightened but it seems the lifters are collapsing because you are able to push the pushrod down into the cam with almost no effort. Is this due to how much the engine has sat? The lifters would pump back up with oil after we ran it and gave it some oil pressure, but then would go soft again. They are not staying, and some of the rockers are bottoming out on the threaded bolt when we tighten them. The cam and lifter set I have is a performance comp cams model # CL510991-08. Any ideas/comments are helpful.

Thank you,

Steven

oldcutlass

I would not run that engine after adjusting the lifters the way you did. You need to google the EOIC method for adjusting valves and readjust yours. If your out of adjustment at the rockers you will cause harm to your engine if you mange to even get it started.

oldscutlass74

Hello,

Have a 68-70 oldsmobile rocket 350 with '74 7A heads. Hydraulic flat tappet lifters are collapsing. I've had these lifters for about 3 years, raced with them a few times. Probably only 3-4 hours of engine running time in those 3 years, it say mostly. Engine was rebuilt when they were put in and always taken good care of. The lifters have gone soft and caused a tapping. If I press the pushrod in and out i can manually pump them back up with oil and they become solid, but after a few cranks of the engine they go soft again. My engine has good oil pressure. I disassembled and the lifters, cam lobes and pushrods are in excellent condition. Only thing damaged is bottom of rocker arms as they are bottoming out on the studs when tightening. What is the reason for this?

Specs:

Crane cams aluminum roller rockers - 80-1.60, -11

Trick flow pushrods 8.500 .080

Howards cam performance hydraulic lifters 91411

Howards cam hydraulic flat tappet camshaft CL510991-08

Thank you,

Steven

OLDSter Ralph

Do you have guide plates for the push rods ? Do you have the correct rocker arm studs ?

oldcutlass

There is no need to start multiple threads for the same issue, it just confuses things.

66SportCoupe

You haven't told us what rocker setup you're running. If it's adjustable or not.

66SportCoupe

Ok my bad. It seems you have roller rockers and full adjustment. When lifters bleed down there may be some slop however with a roller rocker and hydraulic cam it should not move much