[64speed]

Originally Posted by Gach

Great ! What did you end up using for rocker arms. Hopefully not the BBC ones. ?

The BBC Chevy ones made the best valve pattern. Setup with Butlers recommended pushrods. I got the crower stainless steel

[Gach]

Not understanding so which ones did you use. Crower or BBC ones. Thanks

[64speed]

Crower stainless but for a BBC

[Gach]

Gotcha

[HWYSTR455]

Butler recommended the BBC rockers?

.

[64speed]

No they provided the pushrod length necessary. I was overloaded with information I didn’t understand yesterday but basically this is my 2nd go round with this. My Pontiac rockers just never made the grade with these heads but the BBC make the grade perfectly

[HWYSTR455]

Originally Posted by 64speed

No they provided the pushrod length necessary. I was overloaded with information I didn’t understand yesterday but basically this is my 2nd go round with this. My Pontiac rockers just never made the grade with these heads but the BBC make the grade perfectly

So you gave Butler the length your builder provided and they shipped you the pushrods requested.

You should ask them about using BBC rockers, see what they say.

Bookmark this thread for future reference.

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[NeighborsComplaint]

Originally Posted by HWYSTR455

So you gave Butler the length your builder provided and they shipped you the pushrods requested.

You should ask them about using BBC rockers, see what they say.

Bookmark this thread for future reference.

.

Already called it after the first motor broke. It's the rockers.

Interesting tidbit ... assume for the moment the OP was running the Lunati 712 cam in the ill-fated motor. With 1.7 ratio rockers his lifts were .606"/.623" (I/E). If the rockers were 1.8 ratio, .642"/.660" (I/E). If the cam was the 713 , then .634"/.640" (I/E) w. 1.7 rockers and .671".678" (I/E) w. 1.8 rockers.

[grivera]

Dave - did the builder have Pontic Crower SS on hand as well or just the BB SS Crowers?

[64speed]

Yes he had a few different brands. Caster1 had the same problem with his engine

[Gach]

The only thing that I can think of there’s a distinct possibility The stud placement on those heads are a little off compared to standard placement. Enough so the BBC rocker work perfectly.

I’ve kind of run into this situation before.

[64speed]

They work and I have good geometry, no problems on the test stand

[Gach]

Originally Posted by 64speed

They work and I have good geometry, no problems on the test stand

I believe it, and don’t think it had anything to do with the original failure. Like I said I’ve run into this situation before.

[64speed]

Originally Posted by Gach

I believe it, and don’t think it had anything to do with the original failure. Like I said I’ve run into this situation before.

Wayne said that it had happened on mine and Tommys engage but obviously he had never experienced it with factory parts.

[1968GTO421]

Originally Posted by NeighborsComplaint

Already called it after the first motor broke. It's the rockers.

Interesting tidbit ... assume for the moment the OP was running the Lunati 712 cam in the ill-fated motor. With 1.7 ratio rockers his lifts were .606"/.623" (I/E). If the rockers were 1.8 ratio, .642"/.660" (I/E). If the cam was the 713 , then .634"/.640" (I/E) w. 1.7 rockers and .671".678" (I/E) w. 1.8 rockers.

Good point, however I believe this time 64speed is using the 041 cam with .470" lift (with 1.5 rockers). With 1.7 rockers lift would be around .533". Many cams have that lift with 1.5 rockers so I think this time he might be OK with those rockers. But I would not go that route. I would investigate the problem Gach mentions in post #1491. I believe Pontiac engineeers knew the limits of their block and didn't exceed the 1.65 ratio rockers. FWIW

[tom s]

FYI,in 1963 pontiac offered 1.75 rockers for it 421 SD heads!I have a half set of NOS ones.Tom

[Gach]

If the geometry is correct, lift not going to matter. As long as the duration doesn’t exceed 200 at .200 lift thats when the issue manifests itself. I doubt his hydraulic roller was.

Here’s what I did fine to be a issue, I’ve found 2 blocks that the lifter bores had hair line crack. Remember certain lifter bore are attached to the block like a cup handle. 2 and #6. I think #2 let go on his block.

[64speed]

Yes it was #2

[64speed]

Back on the road. For some reason the hydroboost seems a little spongier than it was before but maybe it’s just my mind playing tricks on me

[400 Lemans]

Good job.