Probably Beating a Dead Horse, but... Cams?

I know it's hard to believe we don't have a valve spring height mic, but in the school's defense, their focus is on restoration to original condition - not really performance. They just order factory everything when it comes to stuff like this. lol
 
Are they having you guys grind the VJ with interference angles?
 
You MUST change the springs. There is no point in putting a performance cam in the motor and use old weak springs that go into valve float just as the engine starts to get exciting!
 
So, 1.880" ish with sbc retainer, and 1.928" with valve faced and tipped. What do the seats look like? You'll gain more there. Fwiw, I do not use interference angles, 45 on both seat and valve.




Grind seats just enough to clean them up. If top of 45* is too large, use a lesser angle stone/cutter to bring top of 45 in. A 35 would do there, 30 would be less desirable, but better than having top of 45 bigger than valve. I would shoot for .015" smaller than valve for what you are doing. If after top of 45 is established, check width of 45, and if it's too wide, use a 55 -60 cut under the 45 to narrow the seat. I'd go .060" wide on int and .070-.080" on exh for your needs. If you don't care about a few horse, and will not bowl port, you could go a little wider. Although, fwiw, later GM heads have pretty narrow seats compared to old stuff.......

Anyone has opinion on springs, let's hear it.

I've not seen retainers that reduce valve height, only Make it larger. So, assuming a -.060" is the best available, my hunch/swag from above was on;

It looks to me that the 1943 elgin spring is the best bet. Anyone see a better option , please say.

125# @1.750", 325# @1.200" [363 lbs/inch]

Let's say that you end up with 1.900" of room with the stock chev retainer after a valve job. Reduce that by .060" with a minus lock = 1.840".

So, .090" taller than the spring's closed spec. 363 x .090" = 32.67# change.

125 - 33 = 92 lbs seat. Add .490" lift = 178# for 270 open.
Click to expand...
 
dave brode said:
So, 1.880" ish with sbc retainer, and 1.928" with valve faced and tipped. What do the seats look like? You'll gain more there. Fwiw, I do not use interference angles, 45 on both seat and valve.




Grind seats just enough to clean them up. If top of 45* is too large, use a lesser angle stone/cutter to bring top of 45 in. A 35 would do there, 30 would be less desirable, but better than having top of 45 bigger than valve. I would shoot for .015" smaller than valve for what you are doing. If after top of 45 is established, check width of 45, and if it's too wide, use a 55 -60 cut under the 45 to narrow the seat. I'd go .060" wide on int and .070-.080" on exh for your needs. If you don't care about a few horse, and will not bowl port, you could go a little wider. Although, fwiw, later GM heads have pretty narrow seats compared to old stuff.......

Anyone has opinion on springs, let's hear it.

I've not seen retainers that reduce valve height, only Make it larger. So, assuming a -.060" is the best available, my hunch/swag from above was on;
Click to expand...

Seats look really good, just gonna clean them up a bit. I've attached a photo of them for your viewing pleasure...

Those springs sound good to me. Now, are those going to be too much to break in the cam with? What's your suggestions there?
 

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You could lap them in with compound and see what they look like. If they don't lap right in, they need ground imo.

Measure the o'd of the 45* seat in the head. If it is not smaller than the valve, you should use a 30-35? stone or cutter to reduce the o.d. of the seat. Then you can measure the seat width to determine if you need a bottom. This is not race only stuff. It should be done on EVERY valve job.

Stock spring = 1.400" solid and .490" theoretical lift = 1.890". You said 1.928" spring installed height with caddy retainer. [round up to 1.930"]. Leaves .040", correct? Not enough.

You could run the new springs with the stock locks, and you would lessen spring force by 21.78 #. [363 lbs/in] 363 x .060" 21.78. Apx 70 cl and 248 open. Quite safe, but I would keep rpm to 3000 max until locks are swapped. Most guys would just put the - locks in and go, but if you don't mind the extra work, I would do it.

Dave
 
Okay, sounds great.

So, I guess that's our final verdict, since nobody else has any other suggestions - the Elgin 1943 springs with -.060" locks and stock Cad retainers?
 
I'm just waiting for the "FINAL" OKAY from those who know a hell of a lot more than me.

I arrived in Portland, Oregon this evening but as far as I know my cell phone and credit card will work from here as well as from home.

Best,

d
 
My recommendation is to see how things measure up after all machining.
Locks are cheap, get a couple different heights.
They don't always stack up the way they are listed (-.030, -.060)
 
Darius said:
I'm just waiting for the "FINAL" OKAY from those who know a hell of a lot more than me.

I arrived in Portland, Oregon this evening but as far as I know my cell phone and credit card will work from here as well as from home.

Best,

d
Click to expand...

Portland will never be the same...
ciao,
mario
 
At the risk of sounding frugal, the shipping and subsequent upcharge for spending less than $100 per order exceeds the cost of a few sets of locks or misc parts, including the not fondly looked upon but appropriate to use thick valve shims, if need be.
 
8ad-f85 said:
At the risk of sounding frugal, the shipping and subsequent upcharge for spending less than $100 per order exceeds the cost of a few sets of locks or misc parts, including the not fondly looked upon but appropriate to use thick valve shims, if need be.
Click to expand...

Seems reasonable to me. :D

d
 
Okay, so, after machining, and with a *little* harder tapping on the valve tip to get the locks to seat, I got a reading of 1.960" with stock retainer and locks.
 
Weighed a few valves tonight;
2.020" sbc 4.91 OAL dished face, no undercut, 118 grams.
2.190" scj/bbc 5.2?" OAL 11/32 undercut, dished face, 134g.
OEM 69 472 intake valve, 130g.
2.300" bbc 5.335" OAL flat face, undercut, 160g

This might illustrate why more spring than stock is needed to rev them up a bit.
The 2.020" can go 7000 rpm @ .500" lift with a $40 1.250" spring for seasons of racing.
The 2.190" doesn't need a nasty spring when compared to the OEM Caddy valve.
 
What do you think, Dave?

I need to get this stuff coming pretty soon, the block is almost ready to be painted and start with reassembly. I've got everything but rod bearings, a new valley pan, head bolts and exhaust bolts, and springs/locks.

Btw, are there any cheaper alternatives to MTS's head bolt kit? My girlfriend works at Fastenal, and they sell grade 9 bolts... Could I substitute any other bolts in for the official ones?
 
What's wrong with your stock bolts?
I wouldn't ever consider asking about the re-use of stock springs and budget valve train if the dollars were spent on aftermarket bolts.
If by chance you had a broken one from them being seized at removal, it would be acceptable to sub another stock bolt.
If your grade 9 bolts were intended for a comparable torque spec as stock bolts, then as a set yes.
Just one or a few might be asking for trouble.
I'd believe user error to be far more common than those head bolts failing.
 
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