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Old 03-21-2014, 08:27 PM
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Velve Springs: How do I know which size will replace existing ?

Hi all.
Another question. (More and more coming. lol )
I have no idea what cam is in my 67, 396.
I have the heads off and am thinking of replacing the double
springs with a beehive spring to save the weight upgrade the heads.
Is there some way to figure out:
A - what is in there now, and
B - is there a rule of thumb on what to use to replace them ?
And lastly (for now) would a good machine shop be able to tell me ?
Thanks !
Dom

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Old 03-21-2014, 09:42 PM
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IF you can find a shop that will work with you..

Here is basics what you need to know about your springs..

Installed height.. from spring seat to the underside of retainer.
Spring pressure at installed height. Spring pressure at max lift of cam.
Diameter. Inside diameter to clear the seal and guide/outside diameter to set properly in spring seat.
Coil bind/max compression of spring
Diameter of retainer and location of the inner "steps" that contact the spring
Angle of the valve locks, stockers are usually 7 degree.

Machine shop will have equipment to measure all this. Simple stuff, Cost is minimal..

Hydraulic flat tappet hot rod cams usually like 110-120 psi. at installed height. Be real careful with flat tappet cams in BBC's. They were known to eat cams back when the oils were actually good..

Cam manufacturer will spec what they want for springs etc. Installed heights cam be changed with shims, different height retainers and - or + valve locks.

Last edited by BOBCRMAN@aol.com; 03-21-2014 at 09:54 PM.
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Old 03-21-2014, 10:31 PM
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X2 on this. Your in it this far check that camshaft out real good as well. BBC really are hard on cams and springs. You might fing some numbers on the end of the cam that could identify it then you could go with what the manufacter specs.
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Old 03-22-2014, 07:16 AM
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Quote:
Originally Posted by tresi View Post
X2 on this. Your in it this far check that camshaft out real good as well. BBC really are hard on cams and springs. You might fing some numbers on the end of the cam that could identify it then you could go with what the manufacter specs.
Was hoping not to pull the cam but, if I want to work this engine, that's where it leads.
Thank you.
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Old 03-22-2014, 07:21 AM
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Quote:
Originally Posted by BOBCRMAN@aol.com View Post
IF you can find a shop that will work with you..

Here is basics what you need to know about your springs..

Installed height.. from spring seat to the underside of retainer.
Spring pressure at installed height. Spring pressure at max lift of cam.
Diameter. Inside diameter to clear the seal and guide/outside diameter to set properly in spring seat.
Coil bind/max compression of spring
Diameter of retainer and location of the inner "steps" that contact the spring
Angle of the valve locks, stockers are usually 7 degree.

Machine shop will have equipment to measure all this. Simple stuff, Cost is minimal..

Hydraulic flat tappet hot rod cams usually like 110-120 psi. at installed height. Be real careful with flat tappet cams in BBC's. They were known to eat cams back when the oils were actually good..

Cam manufacturer will spec what they want for springs etc. Installed heights cam be changed with shims, different height retainers and - or + valve locks.
I was hoping to do a little to the top end and put it back together but this is getting more and more intensive. I read Vizard's book and by the time I do all this, it would be almost the same amount of time and $ to go with a 454.
Except for the guides, exhaust seats and valve job, I'm going to leave the rest alone and put it back together. For the money, a 454 will be in the future.
Thank you so much for all your insight and help !
I'm sure there will be more questions coming up. lol
Dom
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Old 03-22-2014, 04:33 PM
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Another one for valve springs - sort of

I took the springs off today. Had some rough tops (of the valve) I had to file a little to get them out. The questions is: at the top of each valve guide there is a nick and a rough piece of metal sticking up. (like when you drill something and the bit gets stuck at the end)
It's on each guide. Since nothing hits the top edge of the guide, what could have caused it ?
Any ideas ?
Thanks,
Dom
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Old 03-22-2014, 07:04 PM
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Look closely.. Probably has had inserts done on the guides, an old way of doing guides was to tap/thread the guide. Then a spiral insert, much like a long heli-coil, was installed. A reamer cut the ID to correct size. leaving a small indent at the end of the guide.

Only real problem with this setup is it was too labor intensive and isn't used much any more. It also ruins the guide for simple fixes later.. Now the guides must be replaced.. Which is a bad deal on GM BBC heads. As the stock guides, in production are inserted, then gang bored for the valve stem. Leaving the guide center at an off set from the OD. Replacement guides are machined around a center. When installed in an old casting. The new valve centerline can be off bad enuff to require all new seats.. and gets $$$$$ the more you get into it....
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Old 03-22-2014, 07:16 PM
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Just a question Bob...could a liner like a K-Line be used in a spiraled wound guide?? Or does the spiral tap cut deep enough into the guide the the ream for the K-Line liner doesn't remove all the spiral cut??
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Old 03-22-2014, 07:29 PM
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Quote:
Originally Posted by ericnova72 View Post
Just a question Bob...could a liner like a K-Line be used in a spiraled wound guide?? Or does the spiral tap cut deep enough into the guide the the ream for the K-Line liner doesn't remove all the spiral cut??
Correct. There is a way to use K-line liners in some instances.. IF the original repair can be removed ( there are several different styles) and the guide can be reamed to the next oversize.. There are special thick wall K-line type inserts that could be used.. Nobody around here has the tooling tho. I am sure a local shop would do it for the customer if the customer bought the tooling $$$$$$$
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Old 03-23-2014, 07:40 PM
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Valve guides / Seats

Quote:
Originally Posted by BOBCRMAN@aol.com View Post
Look closely.. Probably has had inserts done on the guides, an old way of doing guides was to tap/thread the guide. Then a spiral insert, much like a long heli-coil, was installed. A reamer cut the ID to correct size. leaving a small indent at the end of the guide.

Only real problem with this setup is it was too labor intensive and isn't used much any more. It also ruins the guide for simple fixes later.. Now the guides must be replaced.. Which is a bad deal on GM BBC heads. As the stock guides, in production are inserted, then gang bored for the valve stem. Leaving the guide center at an off set from the OD. Replacement guides are machined around a center. When installed in an old casting. The new valve centerline can be off bad enuff to require all new seats.. and gets $$$$$ the more you get into it....
Bobcrman:
Thanks for your suggestion.
I looked down the guide holes and I see an insert with a spiral in most of them. Looks like there are 2 without, but, maybe I just can't see them.
Should I just leave them alone and put the valves back in, or, can a good head shop drill these out and put in new ones in ? (I know you said it's $$$$) Since these heads haven't been touched since the mid 70's, I have no idea if the existing guides will hold up to today's gas. But, I'm sure I would still need new seats. Or,should I start looking for another set of heads ?
Thanks again,
Dom
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Old 03-23-2014, 08:05 PM
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Guides have little to do with modern fuels. They need to be tight tho. So the new seats are concentric and true.

A laymans check for guide wear goes like this..Remove valve from the guide and clean. Looking for wear on the stem. You can see the wear in the plating of the stem. Take your finger tips and lightly go over the area where the pattern ends and fresh plating is visable. You should feel no ridge.

Now, clean the guide with brushes if possible and dry it. Insert the valve, raise the head of the valve about 1/2 in. from seat and try to wiggle it sideways in all directions. A good guide will have little if any side movement..
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Old 03-24-2014, 07:30 AM
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Quote:
Originally Posted by BOBCRMAN@aol.com View Post
Guides have little to do with modern fuels. They need to be tight tho. So the new seats are concentric and true.

A laymans check for guide wear goes like this..Remove valve from the guide and clean. Looking for wear on the stem. You can see the wear in the plating of the stem. Take your finger tips and lightly go over the area where the pattern ends and fresh plating is visable. You should feel no ridge.

Now, clean the guide with brushes if possible and dry it. Insert the valve, raise the head of the valve about 1/2 in. from seat and try to wiggle it sideways in all directions. A good guide will have little if any side movement..
THANK YOU !
I will do that tonight. They were tight getting out so I'm optimistic about them still being good.
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Old 03-24-2014, 12:51 PM
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Valve Springs: How do I know which size will replace existing ?

Quote:
Originally Posted by Dom L View Post
Was hoping not to pull the cam but, if I want to work this engine, that's where it leads.
Thank you.
If you plan on re-useing your camshaft mark the lifters for the cylinder they are in. In my opinion I would replace it with a mechanical flat tappet or a roller cam.
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