Valve lash settings

[Joe C.]

Re: Valve lash settings

It has nothing to do with racing. The LT-1 cam has greater low end torque and better low speed operating characteristics than the 30-30 cam, which makes it a better choice for a NON-race car. The 30-30 IS essentially a racing cam.

And again, I defy anyone to CONSISTENTLY tell the difference by idle sound alone.

If you want to argue about "correct" restoration, how many guys today are painting vintage Corvettes with lacquer as opposed to a modern system that they then try to "massage" into looking like lacquer.

There's certainly more to discuss on this issue than arguing about two camshafts that are nearly identical and indistinguishable other than to a vacuum gage. Recall that the LT-1 cam uses the 30-30 lobe on the exhaust side advanced 4 degrees. The primary difference is its use of the L-72 lobe on the inlet side which is effectively about 8 degrees shorter.

How about pre-'67 non-SHP engines. Most are restored with the "incorrect" '67-up 929 base camshaft (which are indistigishable from each other to all but a detailed crank angle-lift check with a dial indicator) or the 929s replacement - the 839.

Shame on them!

Shame! Shame! Shame!

Duke

Duke,

The 3849346 is not a racing cam.
The 3927140 is a racing cam.
The 3965754 is a racing cam

[Dan H.]

Re: Valve lash settings

Thanks Joe, I'll watch my symantics from now on! Previous owner put engine together and still runs great so I haven't been in there yet! I do like the LT1 cam, the car is driven alot and that's my purpose to have it be 'user friendly' until the next rebuild. This set up works well with the FI,
don't want to lower vacuum anymore though.
Dan

[Joe C.]

Re: Valve lash settings

Thanks Joe, I'll watch my symantics from now on! Previous owner put engine together and still runs great so I haven't been in there yet! I do like the LT1 cam, the car is driven alot and that's my purpose to have it be 'user friendly' until the next rebuild. This set up works well with the FI,
don't want to lower vacuum anymore though.
Dan

Symantics? OK, I used to use Symantec's Norton antivirus, but now I use AVG Antivirus, which works much better, and is FREE!

Semantics. That's more like calling a "reservoir tank" a "surge tank".

Installing the LT1 cam in a "fuellie" is a very good move! It's a nice, mild, streetable cam which is closer in design to its "Duntov" grandfather, than was the "30-30"; its a much better match for the L84's induction system. The "30-30" is happiest with headers, a low restriction dual plane intake with no carburetor heat, or a single plane intake, like the Victor Junior, and a 750 cfm carburetor (with annular boosters).

Joe

BTW: I think that your "fat cat" avatar is one of my favorites of all time!

[Stuart F.]

Re: Valve lash settings

Hey Guys;

This is one of the best threads I've seen in a long time. I think it was Dan that said his 64 still had the original 236 VAC. Hang onto it Dan as long as it works. I've been thrashing the bushes for one for a long time. I've bought three already from reliable sources and none of them meets specs (all in @ 8") except that they are stamped "236". My application is on my 63 340 hp (w/ Duntov). My vacuum normally is a steady 14" @ 800 rpm, and with the B20 VAC currently installed I'm seeing all in @ 11.5 to 12.5", which is fine until the engine sees more heat in traffic. Then the idle vacuum hunts down into the VAC top range which causes stumbling and rough running, i.e., the problem is compounded by a drop in vacuum advance, etc., etc., etc. In other words; I bump into Duke's 2" rule. This problem is further exasperated when I adjust the valves down to .008" and .016" where I like them. The steady vacuum is then 12.5 to 13.5".

I have two more orders in; one with "gmpartsdirect" and another with "volvette" (Volunteer Corvette) in Tennessee. The latter I have talked with and they promised to test the unit they are getting for me b4 shipping. Course, Ill be paying a premium for it (about $40.).

Stu Fox

[Stuart F.]

Re: Valve lash settings

I'm inclined to call a "Reservoir Tank" a "Surge Tank" on occasion because I used to design Radiators for Young Radiator long ago, specially those for Peterbilt and Kenworth trucks (my pre-GM days). My GM days were at the former Locomotive division though where I last wrote the Service Manual on their new "H" series Diesel Engine (4 cycle over 1000 C.I./cylinder). I was writing about "P" tube piston cooling long before it's use on the new LS-9 Corvette engine, and the Germans were using that method in their engines in WW1. As the saying goes; there are very few really new ideas - but, many refinements of old ones.

That "H" engine uses a diamond valve arrangement w/ intakes at the 12 and 3 o'clock positions, and exhausts at the 6 and 9 o'clock positions to create a swirl effect. This a new design engine that goes back to push rods for valve and unit injector operations. Push rods are not dead yet!!

Stu Fox