View Full Version : Larger OD valve springs SBC


spicewood1
10-16-2009, 12:40:16 AM
Looks like the cam I want to run - Comp XS274S - in a 350 I am building recommends 2 different Comp spring sets and both are larger OD than the stock 1.250" dia seat pockets. The specs on both are 1.430 dia - so how best do you run these springs? My machine shop says its not a good idea to cut the stock pockets that much for fear of hitting water. What have you done? Another guy told me he runs the beehive springs upside down but that sounds crazy.

pdq67
10-16-2009, 01:27:02 AM
Several things are coming to light here!

1st, we can still buy up-side-down beehive springs that were used back then and even from CC. SB springs that fit the stock pocket w/ bigger retainers up top is all.

2nd. I figure a cheap set of Elgin's .600" lift Z-28 type springs MAY just do you fine????

Check out Midwest Motorsports here!

As for cutting through the water jacket, it did happen back then and one way to keep it from happening was to shim the cutter up off the stock seat pocket so that it didn't cut into the water jackets.

Check Chevy Power here, mid '70's to '80's!

pdq67

hhott71
10-16-2009, 11:11:50 AM
Looks like the cam I want to run - Comp XS274S - in a 350 I am building recommends 2 different Comp spring sets and both are larger OD than the stock 1.250" dia seat pockets. The specs on both are 1.430 dia - so how best do you run these springs? My machine shop says its not a good idea to cut the stock pockets that much for fear of hitting water. What have you done? Another guy told me he runs the beehive springs upside down but that sounds crazy.

1.54" DIA. springs can be used on an unmodified 23-500-65 Canfield head. Since you are running a big cam, you need a head that will make the most of the cam.

spicewood1
10-16-2009, 11:11:56 PM
Anybody know how much you can cut the stock GM 186 casting seats? Wish I had aftermarket aluminum heads.

hhott71
10-17-2009, 11:30:55 AM
Anybody know how much you can cut the stock GM 186 casting seats? Wish I had aftermarket aluminum heads.
According to How to Hot Rod a SBC and Chevrolet Power books, 186 and 492's can't handle much larger springs They can be spot faced but you must use a 0.060" shim in the original spring seat and spot it down to that shim. If you spring water (pun intended) the machining are head replacement cost make up a lot of the $1,060 for the complete Canfields.

rustbucket79
10-17-2009, 07:39:44 PM
Anybody know how much you can cut the stock GM 186 casting seats? Wish I had aftermarket aluminum heads.

That cam would work with drop in single springs since it looks like the NET valve lift is in the .490 range. 981-16's if your shop is careful should do the trick, (making sure you have .060" to bind) or 941-16's if it's to spend it's life on the race track running north of 6500.

Isky makes a GREAT single drop in spring that we use in the oval track engines, it's their 235D. http://www.summitracing.com/parts/ISK-235D/