318 thumper cam

[Max lobato]

Working with a 318 with stock valvetrain. Had a thumper cam installed when the engine was rebuilt and did not thimk about pushrods and valve springs until it was too late. How do i know which srpings and pushrods i will need for my application?

 

[1967coronet440]

Working with a 318 with stock valvetrain. Had a thumper cam installed when the engine was rebuilt and did not thimk about pushrods and valve springs until it was too late. How do i know which srpings and pushrods i will need for my application?

Call comp

 

[PurpleBeeper]

Definitely call the cam company. Also, I highly recommend that you research your exact cam very, very carefully for piston-to-valve clearance issues. Normally you'd put clay on top the pistons & I'd suggest pulling the heads off, BUT if you're not wanting to pull the heads off, then be sure that cam in that motor won't make the valves hit the pistons. The good news is that you can install valve springs (using compressed air in a spark plug hole & the piston all the way up) without taking the heads off. I think you can probably use your stock pushrods (in most cases), but you will need the springs. I also advise that you get single springs (not dual) if they make singles strong enough for a "thumper". At least on big blocks, dual springs would require pulling the heads off & likely small blocks too.

 

[Bill Monk]

Working with a 318 with stock valvetrain. Had a thumper cam installed when the engine was rebuilt and did not thimk about pushrods and valve springs until it was too late. How do i know which srpings and pushrods i will need for my application?

Definitely need to talk to Comp but you will likely have to change the springs and buy one adjustable pushrod so you can get a correct length then order a set at that length. You get the most out of your cam and maybe save yourself some serious trouble.

 

[Max lobato]

Definitely need to talk to Comp but you will likely have to change the springs and buy one adjustable pushrod so you can get a correct length then order a set at that length. You get the most out of your cam and maybe save yourself some serious trouble.

You were right. Comp did suggest a diffrent spring how do i go about checking for pushrod lenght? Everything i see onnline deals with roller rockers and not the style on my heads

 

[1967coronet440]

You were right. Comp did suggest a diffrent spring how do i go about checking for pushrod lenght? Everything i see onnline deals with roller rockers and not the style on my heads

View attachment 409433

Comp didn't mention about pushrods or rockers? I would call them back and ask

 

[Max lobato]

Comp didn't mention about pushrods or rockers? I would call them back and ask

No i talked to them twice. Never mentioned it. They told me what springs locks and valve guides i would need but never mentioned me needing new rockers. Pretty much told me to get an adjustable pushrod abd figure out what size i will need

 

[1967coronet440]

No i talked to them twice. Never mentioned it. They told me what springs locks and valve guides i would need but never mentioned me needing new rockers. Pretty much told me to get an adjustable pushrod abd figure out what size i will need

Might not need to change rockers, not 100% sure though. Go back to your builder he should've recommended all these changes up front and know exactly what you needed.

 

[Max lobato]

Might not need to change rockers, not 100% sure though. Go back to your builder he should've recommended all these changes up front and know exactly what you needed.

the bottom end was built a few years ago. Heads were done last year. Might just need to take what i have to the local shop. See if he can work out this mess

 

[1967coronet440]

the bottom end was built a few years ago. Heads were done last year. Might just need to take what i have to the local shop. See if he can work out this mess

I've never measured for pushrod length not really sure even how to do it, someone with more know how will chime in

 

[Max lobato]

I've never measured for pushrod length not really sure even how to do it, someone with more know how will chime in

The local shop mentioned to check how far down the push rod goes down into the plunger of the lefter when the rockers were bolted down.said it shouldnt be more thn .030.but i didnt kno where the lifters should be when the measurment is taken. Also how accurate eyeballing .030 seems sketchy to someone who has not done it before

 

[Ugk]

It's not I good cam, I pulled one out and it's on my shelf, had a couple lifters that lost there keeper clip, pin that holds lifter together. That cam has no vacuum for brakes and hard to tune, likes lots of timing, better have a good starter. There's lots of cams out there for the sound, lunati voodoo is another and probly makes for a funner driving car. Best advice is from everyone telling you to talk to a builder. Changing a cam later isn't any fun.

 

[rumblefish360]

Hughesengines (.com) has a tool you can rent and it will come with instructions on how to measure the pushrod length. IF you purchase thenoushrods from them, the tool rental cost will be taken off the price of the pushrods.

Hughes also has roller rockers that are very nice.

 

[Bill Monk]

I've never measured for pushrod length not really sure even how to do it, someone with more know how will chime in

make sure you are on the base circle of the cam, tighten down the rockers and adjust the pushrod to get the right preload on the lifter and you got it.