[78w72]

Originally Posted by srmmmm

I used the Comp 1.5 roller rockers with their polylocks on 6X-4 heads with the factory rocker studs and a Comp XE276HR cam. My cast aluminum M/T valve covers were about 1/8" taller than the factory stamped metal covers and would not clear the polylocks, even with the 1/4" thick Butler gasket. I had to add Butler's spacer and another gasket for enough clearance.

Then the A/C compressor didn't clear the valve cover and I had to convert to a CVF serpentine belt drive. I wish I had known about the short polylocks. Those rockers wound up costing over $2000.

Wow, thats a lot of spacers! If youre running that big of a cam with poly locks you should consider changing to 7/16 studs... I had 1 factory bottleneck stud break with the xe268 FT cam, luckily the rocker arm & nut with the piece of stud in it just fell off to the side, I was close to home and limped it back with 1 valve being stuck closed.

I got these ARP studs for almost free so I will try to use them but for this engine stock SBC/BBC studs would be fine.

[srmmmm]

Originally Posted by 78w72

Wow, thats a lot of spacers! If youre running that big of a cam with poly locks you should consider changing to 7/16 studs... I had 1 factory bottleneck stud break with the xe268 FT cam, luckily the rocker arm & nut with the piece of stud in it just fell off to the side, I was close to home and limped it back with 1 valve being stuck closed.

That is a bit concerning. The cam lift on the XE276HR is .502/.510 and the recommended Comp springs were installed with the rebuild. All the valve spring seats were milled to the same height for correct pressures. The polylocks really do stick up high on these rockers.

I may be doing a tear down soon if my rings don't seat (2300 miles on the engine and still going through a quart of oil in 600 miles), and will consider changing the studs then. Thanks for the tip.

[78w72]

Originally Posted by srmmmm

That is a bit concerning. The cam lift on the XE276HR is .502/.510 and the recommended Comp springs were installed with the rebuild. All the valve spring seats were milled to the same height for correct pressures. The polylocks really do stick up high on these rockers.

I may be doing a tear down soon if my rings don't seat (2300 miles on the engine and still going through a quart of oil in 600 miles), and will consider changing the studs then. Thanks for the tip.

Over .500 is pretty good lift that would justify 7/16 studs for sure IMO. Especially with a roller cam.

I kept the stock studs on these heads because on a previous 455 6x-4 motor with the same size .480 lift cam I had, I never had a problem after almost 100k hard miles. On this 400 engine I figured they would be ok too and they have been for 15+ years, but after having 1 break I will be changing them out ASAP.

Yeah 2300 miles & still burning a qt of oil there is something wrong...

[peters23]

Make sure you check for clearance between the valve retainer and the oil seal at full open lift. The oil seal bosses often need to be cut down lower to add clearance.

[78w72]

Originally Posted by peters23

Make sure you check for clearance between the valve retainer and the oil seal at full open lift. The oil seal bosses often need to be cut down lower to add clearance.

Why would changing the stock studs to 7/16 studs require checking or cutting down bosses to add clearance?

[srmmmm]

Originally Posted by peters23

Make sure you check for clearance between the valve retainer and the oil seal at full open lift. The oil seal bosses often need to be cut down lower to add clearance.

Thanks for the suggestion. I'll pop a valve cover off and take a look. I imagine I would be able to see any damage to the top of the seals.