L84 valve springs

[Michael G.]

Anybody got a source and part number for correct valve springs for a 63 L84? (standard profile 360 HP aftermarket cam).

Thanks,

Mike

[Joe L.]

Re: L84 valve springs

Anybody got a source and part number for correct valve springs for a 63 L84? (standard profile 360 HP aftermarket cam).

Thanks,

Mike

Michael-----


The original springs used for your application are still available from GM. They're GM #3735381. They GM list for about 10 bucks each.

[Duke W.]

Re: L84 valve springs

Sealed Power VS677. All SBs of that era had the same spring whether a 2-bbl. 283 or 327 FI. The...381 was replaced by the 3911068 in 1967. It has a slightly higher rate. The VS677 in a Sealed Power box is the exact same part as the ...068 in a GM box. You can buy them at any NAPA store, or on the Web for about a buck apiece. In fact you can buy just about any exact OE replacement engine part in the Sealed Power line of Federal Mogul manufactured parts. GMs parts are the exact same thing. The only difference is the box they come in.

Apparently GM still has ...381s in stock and they've been raising the price every year for the last 42 years to cover inventory carrying costs. They should just scrap the remaining stock of 381s. Only a fool would buy them at ten bucks apiece.

With careful attention to installed height and lifter preload/lash adjustment, the ...068 will yield a valve train limiting speed of about 7000 with an OE hydraulic lifter cam and about 7200 with an OE mechanical lifter cam.

Duke

[Joe L.]

Re: L84 valve springs

Sealed Power VS677. All SBs of that era had the same spring whether a 2-bbl. 283 or 327 FI. The...381 was replaced by the 3911068 in 1967. It has a slightly higher rate. The VS677 in a Sealed Power box is the exact same part as the ...068 in a GM box. You can buy them at any NAPA store, or on the Web for about a buck apiece. In fact you can buy just about any exact OE replacement engine part in the Sealed Power line of Federal Mogul manufactured parts. GMs parts are the exact same thing. The only difference is the box they come in.

Apparently GM still has ...381s in stock and they've been raising the price every year for the last 42 years to cover inventory carrying costs. They should just scrap the remaining stock of 381s. Only a fool would buy them at ten bucks apiece.

With careful attention to installed height and lifter preload/lash adjustment, the ...068 will yield a valve train limiting speed of about 7000 with an OE hydraulic lifter cam and about 7200 with an OE mechanical lifter cam.

Duke

Duke-----


Just to be clear here. The 3911068 did replace the 3735381 for the 1967 model year for PRODUCTION. However, the 3911068 never replaced the 3735381 for SERVICE to this very day. As you say, the 3911068 can definitely be used for 55-66 small block SERVICE and, most likely, to advantage. Nevertheless, the 3911068 is not the "correct" spring for 55-66 applications and is not currently the GM SERVICE piece for 55-66 applications.

I actually doubt that current GM stock of the 3735381 is decades old. I could see where GMSPO would only be too happy to rid themselves of this part number and replace it with the 3911068 if GM felt that was an appropriate SERVICE replacement. They do this sort of thing all the time. The fact that they've kept it around makes me wonder.

[Duke W.]

Re: L84 valve springs

I wonder why the keep the 381 in stock, too. The 068 was released concurrent with the new for 1967 3896929 camshaft, but was also used with the "old" 3863151 camshaft, and this spring continued to be used on nearly all SBs through at least 1979 (including the L-46/82 and LT-1 cams) , so it is well proven. It has slightly higher seat force and rate.

Testing with my collaborators has also shown that this spring (with careful installed height setup) yields very high valvetrain limiting speed - about 7200 with the LT-1 cam and at least 6800 with the "Special 300 HP" cam that uses the ...929 exhaust lobe on the exhaust side and the ...151 lobe on the inlet side. But you can only get useable power on a 327 to these rev levels with massaged heads, and, of course, a connecting rod upgrade is very prudent for revving to these levels.

Considering the approximate dollar a piece price, the ...VS677 ...068 clone is a hell of a bargain, and it assures OE valvetrain durability with OE cam lobes.

I recommend them for all SB rebuilds with any OE cam lobe.

Duke

[Stuart F.]

Re: L84 valve springs

Just for the heck of it, I'd like to ask a related question;

My L-76 63 340hp still has it's original valve springs. The engine has close to 45 years and 45k miles on it. Is there a certain limit on age/mileage that one should set to change the springs or would you base it on performance only?

Mine will still pull 7000, but it seems to strain a bit now more than years past. It spent several lengthy periods in storage (once with the valves collapsed for about 18 months), and I've always been concerned about their relaxing. It doesn't show any degree of oil consumption or tell-tale exhaust smoke, so I assume the guides and seals are still ok. Also, the valve settings I have done on a regular basis showed the rockers to still be good (they set and hold well). I've also done some spot checks on the wear surfaces of a few exhaust rockers over the years and they look fine for the mileage.

Stu Fox

[Duke W.]

Re: L84 valve springs

Even the early OE SB valve trains are very reliable. I see no compelling reason to change the installed ...381 springs though if you were to refresh the heads I would install new ...068 or equivalent springs.

And, of course, if you were to go through the entire engine I would recommend the LT-1 camshaft

One actually has to wonder why Chevrolet redesigned what appeared to be a very successful spring, however, Chevrolet learned a lot about valve train dynamics in the 1960s - primarily with their use of the Optron beginning in the early sixties - and it shows when you compare the early base and Duntov cam lobe design details to later lobe design details, and I expect that what they learned is behind the design of the ...068 spring.

BTW, assuming your car has the OE rods, I would not rev it beyond 6500 and replace them if you get to 90K miles.

Duke

[Michael G.]

Re: L84 valve springs

Stu, we all strain a bit more than in years past ....

Duke & Joe, Thanks, for the input, I'll try the NAPA clone, seems like an easy choice, $1 vs 10. Hopefully that'll stop any more rocker studs from pulling out.

Mike

[Stuart F.]

Re: L84 valve springs

Duke;

Thanks for the advice. I've decided some time back that I had nothing to prove to myself anymore going to 7000, and I rarely ever compete anymore where I would want to go long for fear of loosing time or distance with the next shift. I'll take your advice and I too will start to gather up new valve train parts for the day they become necessary. Maybe I'll get my son to pay for them cause I'm not sure it will be in my lifetime.

Mike;

Thanks for letting me insert my questions in your thread. Believe we both learned some things. And yes, we are all showing a little stain with age. I'm even afraid to throw another power shift lest it be mine or my Vette's last, Ha!

Stu Fox

[Duke W.]

Re: L84 valve springs

Stu, we all strain a bit more than in years past ....

Duke & Joe, Thanks, for the input, I'll try the NAPA clone, seems like an easy choice, $1 vs 10. Hopefully that'll stop any more rocker studs from pulling out.

Mike

If rocker studs are pulling some kind of "gorilla" valve springs are probably installed, and from your description of the camshaft I don't think I'd place an even odds bet that it's actually a Duntov cam - either OE or an exact aftermarket replacement.

Duke

[Michael G.]

Re: L84 valve springs

Duke, since I've got the rockers off, I think I'm going to try to measure the cam lift, just to verify it is a Duntov clone cam. Can you tell me what the intake and exhaust lobe lifts of a Duntov are?

Thanks, Mike

[Duke W.]

Re: L84 valve springs

Lobe lift is 0.2625" on the inlet side and 0.2665" on the exhaust side, which is listed in the 1963 Corvette shop manual.

Duke

[Michael G.]

Re: L84 valve springs

Thanks Duke,

I had looked in the manual first, but all I saw listed in the Engine Mechanical specs section was the lift measured at the valve stem side of the rocker. I should have looked two inches up, at the Camshaft specs

Mike