# Rocker arm ratio



## Rustaholic (Apr 14, 2021)

Ive got a question about 1.5 vs1.65 rockers. I’ve got a 1969 428 10cc dished forged pistons 30 over, forged rods, original nodular turned crank, johnson roller hydraulic lifters, Butler grind BP8022SP cam, edelbrock 72cc aluminum heads round port with Dougs headers. I’m finally ready to set it in the frame with turbo 400 and get it started for the first time. I’ve read a lot of threads on this topic mostly with iron heads. It will be in a 1968 lemans convertible with a 355 12 bolt posi. I started this with the purchase of the car in 2016 so plenty of time to offset the crazy money I’ve put in this thing. The guy that built it gave me some crane gold 1.75 intake and 1.65 exhaust, he had them left over from a build that he had to buy two sets to get that combo. I don’t think its a good idea to break in with that combo and probably not good for drivability so 1.5 or 1.65?


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## Baaad65 (Aug 29, 2019)

I'm no expert that's for sure but I have two cents, I have a Butler motor and have the head build sheet so they showed lift and spring pressure plus coil bind numbers for both rockers 1.5, 1.65 with my cam so I was able to change to 1.65 rockers also it showed the pushrod holes were elongated which your aluminum heads should have. 1.7 is alot so I would check with Butler on all that and I'm just guessing but the dished pistons probably have enough clearance but again no expert so check with one or maybe one will chime in here. If you're considering 1.7 rockers maybe you should re evaluate your cam for a bigger lift, I know it's all together and don't want to go through that hassle neither did I but those big of rockers are going to put more stress on the valve train especially if you're shifting at 6K. Again no gospel here just 2 cents from an amateur.


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## BearGFR (Aug 25, 2008)

I can share my personal experience, it that's helpful at all.

I built my 461 (400 stroker) "the first time" in 2010 with a Comp solid roller cam, their lifters, 72cc Edelbrock heads, and Scorpion 1.65 rockers plus stud girdles. 

It was great and was an honest 11-second car at the track.

It's got a Moser 9" with 3.50 gears, and although at 70 mph it's turning around 3300 RPM, my wife and I took it on the full Power Tour in 2013 and had a blast.

In 2016, also on a segment of the Power Tour with my older son, a rocker arm let go on the way into Wichita KS, put shrapnel through the motor, and after working on it for a couple days in 100+ degree heat in the Motel 6 parking lot, we wound up U-Hauling the car home, missing the end of the Tour.

After quite a bit of (more) research, I wound up with a different cam, another solid roller from Bullet that has more lift at the valves and more duration than the previous cam provided, and does that with 1.5 rockers. It has the tallest lobes that can be installed into a stock Pontiac block without boring it for oversize cam bearings and also has a "gentler" exhaust closing ramp than what's usually found on Comp designs. That all sounded really good to me, considering what had happened. I also went with all Crower parts: their HIPPO cut-away roller lifters and >stainless< full roller rockers. My rationale was that I wanted the top end of the engine to be as strong as I could make it, and I really liked the idea of the 1.5 rockers not putting as much stress on themselves or on the studs. All the engine really "cares about" is what's happening at the valves. It doesn't matter what rocker ratio makes that happen.

In addition to them being stainless instead of aluminum, I really like how the Crower rockers fit. They had much better clearance "everywhere": to the retainer, pushrod, and in the rocker nut slot. I didn't mention this before but on the previous incarnation I'd already had to replace one of the Scorpions under warranty when I found it cracking around the nose where the axle for the valve roller went though. The replacement they sent was a lot more "beefy" in that area (which made the clearances even tighter) and told me that they'd recognized that there'd been a flaw in their initial design.

So, my opinion: On a race engine where you're regularly opening it up to check things, aluminum rockers are probably fine. However with an engine that sees mostly street use that can include the occasional road trip and may not be checked over as often, I'm not sure they're such a good idea. Regardless of use, my experience has led me to the opinion that it's better to get the valve action you want from the cam profile and only go with higher ratio rockers if you absolutely have to. My bullet cam has 251/257 degrees of duration at 0.050 lift and makes .620 lift at the valves - with 1.5 rockers - so it's possible to go pretty rowdy on the cam profile even with 1.5 rockers.

Your mileage may vary. Void where prohibited by law. Past performance is not a guarantee of future return. Slippery when wet. 

Bear


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