Thread: 350 streetable engine continued

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Originally Posted by bad brad

I have purchased a comp cams H270 (PART #12-211-2) and
Comp 981 springs and have borrowed the cutter to take the guide down to 0.660" dia for the spring. My question now is what valve seals do I use?

Use a 0.530" cutter to reduce the guide further and use Viton seals is what I would do. I wouldn't install the seals until I determined that I had sufficient retainer to seal clearance with the 0.470" lift. If I measured a clearance of 0.500" retainer to seal, I'd go with it. 0.030" is all Chevrolet used with the stock arrangement (0.420"/0.450").

Originally Posted by bad brad

I plan on using the original retainers and locks.

Not a good plan in my opinion. Use the retainers that Comp designed to work with their springs. If you use 10 degree retainers and locks, you can use either a standard lock or you can use a -0.050" installed height lock that will let the valve stem tip protrude up past the retainer by another 0.050" over a standard lock. You don't know if the rail rocker is going to clear the retainer with the standard lock, so make yourself an alternate plan (Plan B). 10 degree retainer is part no 750. Standard 10 degree lock is part no 611. -0.050" 10 degree lock is part no 630. Locks are cheap. Buy both part numbers and assemble with the locks that work best on your trial assembly. With the -0.050" lock, the installed height will be shorter and the spring will be stiffer by 18 1/2 lbs. (370 lbs/inch rate spring).

One of the other members may have a better idea. Sometimes I get mired down in the mud of technology and lose sight of the goal.