690 valve length and spring height

[Skip FIx]

OK i have seen spring installed specs for stock length valves in 690s as around 1.6", closest thing to listing for valve length is 5.11??

So adding 5.330(BBC+.100) would give around 1.88 like a BBC spring??

Is there a exhaust valve to block issue with high lift cams?

[Gerry]

Skip,

As you probably know, the exhaust valve moves in a direction toward the cylinder wall. The stock 1.720 exh. valve can open about .650 before hitting the cylinder wall on a passenger block and a little more, about .720, on a truck block. If you increase the exh. valve diameter you will have to notch the cylinder wall accordingly.

[jim_ss409]

I was just checking out an article from Feb. 99 Car Craft with Curt Harvey as the source of information and it agrees with what Gerry says.
When I got the parts for my heads I didn't write the part numbers down like I should have but I'm pretty sure I've got standard length big block valves. I'm not so sure about the springs though. That same article suggests small block Mopar springs but I'm not sure that's what I have. I got my parts from Curt. http://www.mr409.com/
The one thing that I wanted to point out was that the valve and the rocker stud are not parallel, they get closer together at the top. So if you use a valve that's too long you can run into problems with rocker arm fit. As it was I had to go quite short on the pushrod length in order to keep the rocker tip centred on the valve. This was with Scorpion 1.7 big block rockers.

[CDNpontiac409guy]

EXCELLENT point, Jim :cheers :cheers :cheers

[Skip FIx]

There are alot more 1.800 and 1.88 springs to choose from.

For those of you interested a new rocker arm that might help is available from Crower. A BBC that has a 0.090 offset trunnion(pivot) they made for longer valves.Can get them in 1.8 ratio also.

Do you guys make the swap to 7/16 studs over the 3/8 pinned factory ones? Or keep the 3/8 and use a stud girdle?