A modern mechanical cam and springs requires what work on the heads?

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trebor75

trebor75

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Have a 1965, 273 commando. Previous owner swapped the mechanical cam, lifters and rockers to hydralic and put a 340 cam in it. He did not change the springs, though. I'm plying with the thought of swapping it back to mechanical since my friend have mechanical rockers, rockershafts and pushrods on the shelf. Then go for a modern mechanical cam and springs. Before going into what cam to get. "Moper" wrote earlier in another thread:

"Factory type seals are too wide for the dual springs modern cams need. The seal wont fit in the spring. So you have to cut the guide smaller in diameter. The stock retainer will hit somewhere around .520 or so depending on the engine so at the same time you make the guide shorter. Also, the spring won't fit in the spring seat on the head. You have to cut the spring seats for the inner spring too."

So this means that with any modern cam, I have to pull the heads and get them to a machine shop? This is whats put me of the idea a bit. Since this is to be done on the cheap side or else I'll just be happy with what I have now. It would be fun though to run it with a more radical mechanical cam

This is the setup today:
273 Commando - 1965
Cam: 268/276 duration and 429/444 lift
Edelbrock D4B intake / Edelbrock 600 Performer Carb
Pertronix Ignitor
Hooker Headers
2.5" Dual Exhaust / Flowmaster Super 44
727 auto / Shift Kit
10" 4000 stall TCI converter
8 3/4 - 3.55 - SureGrip
 
If you have to run dual springs for the cam you are using that is true. I'm running a .510 lift solid cam with a Comp 926 single spring. I still had to machine down ( shorten ) the valve guides for retainer to seal clearance though.
 
skrews said:
If you have to run dual springs for the cam you are using that is true. I'm running a .510 lift solid cam with a Comp 926 single spring. I still had to machine down ( shorten ) the valve guides for retainer to seal clearance though.
Click to expand...

Thanks. The cam I was looking at is the Comp cams XS274S: Duration 274/280, Lift .502/.511. So I guess the valve guides will need to be shortened and the heads come of to do so.
 
You need to look carefully. Some companies spec dual springs rather than single-with-dampener because of the faster ramps on modern cams. The duals need the seats cut and the guides cut. Depending on the lift you may need to shorten the guides as Skrews says. It's not a "must do" in some cases - but you have to make sure you understand when you're looking at the cams.

edit: - you may also save some $$ by running a beehive spring. Then it's just the guides and not the spring seats too.
 
moper said:
You need to look carefully. Some companies spec dual springs rather than single-with-dampener because of the faster ramps on modern cams. The duals need the seats cut and the guides cut. Depending on the lift you may need to shorten the guides as Skrews says. It's not a "must do" in some cases - but you have to make sure you understand when you're looking at the cams.

edit: - you may also save some $$ by running a beehive spring. Then it's just the guides and not the spring seats too.
Click to expand...

Thanks. Taking this into consideration and me not wanting to pull the heads for machining. To be on the safe side so to speak. What lift would be max?
 
In most cases, with mild cams under .550 lift, you can find a single spring that will work fine, as long as you aren't planning on a full race or competition engine. That's one area where I actually like Comp. They have several different single springs that will work on many different applications. As long as you find one that has a similar seat pressure, open pressure and spring rate, you can use it.
 
RustyRatRod said:
In most cases, with mild cams under .550 lift, you can find a single spring that will work fine, as long as you aren't planning on a full race or competition engine. That's one area where I actually like Comp. They have several different single springs that will work on many different applications. As long as you find one that has a similar seat pressure, open pressure and spring rate, you can use it.
Click to expand...


x2
 
Thanks for the input guys. And what would you say max lift would be before the retainer hits the valve guide?
 
Because of machining tolerances, it varies. I always cut the guides down starting at .480 just for the hell of it. I'd rather do it than have the result from not.
 
And will these these COMP Cams Valve Springs 901-16 or 926-16 work with the cam above mentioned and stock retainers?
 
There's a Comp behive 26986 that will work and shouldnt need any cutting - but you will need retainers and locks. Otherwise the only springs they reccommend for that cam are dual assemblies.
 
moper said:
There's a Comp behive 26986 that will work and shouldnt need any cutting - but you will need retainers and locks. Otherwise the only springs they reccommend for that cam are dual assemblies.
Click to expand...

Thanks Moper. They sure know how to charge for them also :)
 
As some have stated there are single springs that are plenty strong for that mild solid cam. I never touch Comp for springs and Tim @ Bullet has what you need. Remove a spring and measure what you have for seal/retainer clearance and your installed height. He has a few good springs that will likely work and 125-140seat/325lbs open should work fine for your combo.
 
moper said:
There's a Comp behive 26986 that will work and shouldnt need any cutting - but you will need retainers and locks. Otherwise the only springs they reccommend for that cam are dual assemblies.
Click to expand...
I have no experience with this spring but it could work fine as well as others.
 
Which valves do you have? Factory or aftermarket? If stock/factory designed valves - No - the kit won't work as described because the lock set is for aftermarket valves. You will need the locks for use with factory valves. There's a two groove lock and a 4 groove lock because the intake and exhaust valves have different grooves on them. The lock package you need with factory type valves is 606-16.
 
moper said:
Which valves do you have? Factory or aftermarket? If stock/factory designed valves - No - the kit won't work as described because the lock set is for aftermarket valves. You will need the locks for use with factory valves. There's a two groove lock and a 4 groove lock because the intake and exhaust valves have different grooves on them. The lock package you need with factory type valves is 606-16.
Click to expand...

I have factory valves. I very much appreciate your help and knowledge. My stock locks and retainers wont work with the Beehive springs I suppose?
 
I've heard you guys talking about the Comp 901 springs. What lift are they good for? tmm
 
toolmanmike said:
I've heard you guys talking about the Comp 901 springs. What lift are they good for? tmm
Click to expand...

Yes, I've seen them being recommended a lot while searching for springs. They way cheaper then the beehives atleast.
 
The 901-16s are a general purpose performanc spring. They'll do alright for a bunch of camshafts, especially under .500 lift. but it's not lift that makes a spring usable. It's pressures and the shape of the lobe plus the rpm potential. The XS274S needs a dual spring, or more pressure than a standard sinlge w/dampener spring. The beehives can have a heavier spring rate and cover more rpm range due to the design. So a single beehive can do more than a single w/dampener and some lighter dual assemblies.
And yes - the beehive needs special retainers and locks - and you'll need the 606-16 set of locks.
 
moper said:
The 901-16s are a general purpose performanc spring. They'll do alright for a bunch of camshafts, especially under .500 lift. but it's not lift that makes a spring usable. It's pressures and the shape of the lobe plus the rpm potential. The XS274S needs a dual spring, or more pressure than a standard sinlge w/dampener spring. The beehives can have a heavier spring rate and cover more rpm range due to the design. So a single beehive can do more than a single w/dampener and some lighter dual assemblies.
And yes - the beehive needs special retainers and locks - and you'll need the 606-16 set of locks.
Click to expand...

I went with the beehive's in the end. I actually had to get 627-16 locks because of the 10 degree retainers. Thanks for all the input. Looking forward to this project.
 
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