[rememberfireball#22]

Just watched one of the automotive shows on TV about different ratio rockers. My 68 GTO has the numbers matching 400 H.O. The engine is in good shape and pulls hard. It was just rebuilt before I bought it about 6 years ago. I have no idea what parts were used, but I know it still has the oem rockers. Would I see any change if I installed a set of higher ratio needle bearing rocker arms. The only thing I have done to the engine is sent the Qjet to Cliff and the dist to Suntuned. These two deals made a difference. Thanks, Mike

[tom s]

unless the heads have been clearanced for them you will not be able to run 1.65s.Tom

[rememberfireball#22]

Are you speaking of the push rod holes being elongated.

[tom s]

exactly

[rememberfireball#22]

Tom, I am not a experienced mechanic , but I can do a little. It seems to me that the heads would need to come off for this pushrod work or shavings from grinding could fall into cyl. Am I right? Also would the pushrod length stay the same or would I need to measure and possibly buy new pushrods? My next thought would be is the performance gain that I would get worth this? Also I have no idea what cam was used in the rebuild. The car has a aggressive idle. Also I have a bore scope that will fit thru a sparkplug hole and I looked at the top of piston. There are still the factory valve reliefs in the piston which leads me to believe that it still has a close to factory comp ratio. Also with timing set to specs. it will spark knock if I don't add a little Octane Supreme 130 to gas. I appreciate your reply to me on this. Thanks, Mike

[b-man]

It's a mod that needs to be done with the heads off the engine.

After that you have to check that your valve spring retainers don't hit the seals due to the added lift, and of course that your valves don't hit the pistons.

Pushrod length may need to be adjusted.

Rocker studs should also be upgraded to straight 7/16" BBC type if you're still using the weaker stock bottleneck studs (3/8" threads at the top, 7/16" at the bottom where they screw into the head), the added side loading requires stronger studs (RAIV 400 with factory stamped 1.65:1 rockers all used 7/16" studs).

Even if you did change the performance gain could be nil, or not noticeable.

If it's running hard don't mess with it, enjoy it and possibly upgrade to 1.65:1 rockers the next time you're doing some head work and a cam swap. Not all engines will respond to the added lift, or respond by so little that "the juice ain't worth the squeeze" as Tom would say.

[rexs73gto]

When I put 1:65's on my car a long time ago I didn't have to ream out the push rod area at all. I ran # 48's & they fit with no mods at all. I guess I was lucky as I ran a RA IV cam with a complete RA IV set up . The longer push rods with poly loc's & the 7/16's studs with of course the 1:65 rockers. When I did change them I did notice a pretty good change in the way it ran. I adjusted the rockers to 1/4 turn past & it did make a good bit of difference the way it ran. But again I didn't have to do anything to the heads to be able to put them on.

[dataway]

Would you guys say the increase in pressure on the lobe/lifter is negligible going from 1.5 to 1.65? I'm guessing there would be more static load, and more dynamic load as valve acceleration rates would be higher. I assume the factory specified the larger push rods due to this increase in load?

Reason I ask ... is seems like with the problem some people are having with modern HFT cams that 1.65 could exacerbate the problem. But I don't know ... just asking.

[rexs73gto]

When I put mine on I didn't seem to feel any extra pressure on them as I had them in for about 30K miles & had no problems with them at that time. I didn't use or install any different springs on the 48 heads I had. All I did was install the push rods & the rockers & adjust them & away I went.

[GOAT WHORE]

Originally Posted by rexs73gto

When I put mine on I didn't seem to feel any extra pressure on them

Your not going to feel it, the valve train will however.