powdered rocker ball broke

[Michael H.]

Re: powdered rocker ball broke

True Mike but they were not running high valve spring rates like today, we had to run rev kits to kept the roller lifters on the cam. Phil 8063

Usually, the extra weight of the roller lifter, compared to a flat tappet design, ate up the additional spring of the rev kit. Almost all roller cams used a rev kit.

For the Trans-Am series, I think SCCA allowed the use of the 140' valve spring that had an open pressure of something like 305 lbs. That spring, in new condition, would usually provide float free operation to around 8000 RPM. I'm sure those numbers sound weak by todays standards.

I don't know what the current rules are for Jerry's car but my guess is that the cam has to have the same lift and duration specs as the original. That leaves the rest open though and I'm sure those guys are using some fancy cams that have a lot higher acceleration rates that would require higher valve spring pressures.

By the way, some titanium engine components will increase an engines RPM range without increasing valve spring pressure.

[Joe C.]

Re: powdered rocker ball broke

Usually, the extra weight of the roller lifter, compared to a flat tappet design, ate up the additional spring of the rev kit. Almost all roller cams used a rev kit.

For the Trans-Am series, I think SCCA allowed the use of the 140' valve spring that had an open pressure of something like 305 lbs. That spring, in new condition, would usually provide float free operation to around 8000 RPM. I'm sure those numbers sound weak by todays standards.

I don't know what the current rules are for Jerry's car but my guess is that the cam has to have the same lift and duration specs as the original. That leaves the rest open though and I'm sure those guys are using some fancy cams that have a lot higher acceleration rates that would require higher valve spring pressures.

By the way, some titanium engine components will increase an engines RPM range without increasing valve spring pressure.

I'm using LS3 beehive springs which are adequate on the seats but the force at POML (.602/.608) is about 70 lbf south of where the cam manufacturer has specified for the cam. There is about .040" space left between the coils @ POML before bind occurs, which is somewhat closer than recommended. Additionally, the rockers are high ratio. I added a rev kit to keep the lifters on the lobes at high RPM's (to make up for the lower than recommended spring rate) and have not experienced any false valve action up as high as 7300 RPM. Using tool steel locks and retainers.

[Michael H.]

Re: powdered rocker ball broke

Additionally, the rockers are high ratio. I added a rev kit to keep the lifters on the lobes at high RPM's ( make up for the lower than recommended spring rate) and have not experienced any false valve action up as high as 7300 RPM. Tool steel locks and retainers.

GM engineering played around with higher ratio rocker arms (1.6?) in the late 60's but found no meaningful gain in HP.

I think Yunick was fooling around with Pontiac rocker arms on his 305" Trans Am engine tests. Probably also 1.6.

I think I have some of the GM engineering dyno sheets here that show the HP numbers that compare the standard 1.5-1 to the 1.6-1 arms.

[Joe C.]

Re: powdered rocker ball broke

GM engineering played around with higher ratio rocker arms (1.6?) in the late 60's but found no meaningful gain in HP.

I think Yunick was fooling around with Pontiac rocker arms on his 305" Trans Am engine tests. Probably also 1.6.

I think I have some of the GM engineering dyno sheets here that show the HP numbers that compare the standard 1.5-1 to the 1.6-1 arms.

Depends on the heads. Stock cast vintage heads will choke at high lift. One good reason that the radical (for its time) 30-30 lifted the valves .485/.485 with 1.5:1 rocker arms.

My 461's flow more at .6" than at .5"..........especially the exhaust, which keeps increasing flow all the way up to .7". The intakes peak at .6". That's why I decided to use the 1.6's.

Yunick knew how to port vintage heads.

BTW: My .030" over 327 (331) makes 435 SAE corrected gross flywheel horsepower @ 6500 RPM.

[Clem Z.]

Re: powdered rocker ball broke

GM engineering played around with higher ratio rocker arms (1.6?) in the late 60's but found no meaningful gain in HP.

I think Yunick was fooling around with Pontiac rocker arms on his 305" Trans Am engine tests. Probably also 1.6.

I think I have some of the GM engineering dyno sheets here that show the HP numbers that compare the standard 1.5-1 to the 1.6-1 arms.

pontic SD rockers were 1.65 as i tried them back in the day. smokey also used BBC 1.7 but you had to move the studs to use them. also needed to modify the rocker covers. some cams go in to valve float at a earlier RPM with 1.6 vs 1.5 rockers. i think the NASCAR engines are up to 2.0:1 rockers

[Jerry G.]

Re: powdered rocker ball broke

Coil bind is not the issue. Plenty of room at max lift. I'm using a relatively low lift cam. approx .540 I .560E. On dyno no run went over 7000. Have 330# at max lift.

[Domenic T.]

Re: powdered rocker ball broke

I saw a small block that pooped the rocker arms and bent push rods.

He said it happened at high RPM's.

His aftermarket spring coil diameter was to large for the cam lift and the coils touched when compressed.

The lifters were hydraulic and when they pumped up he collapsed the spring.

He trusted the speed shop and didn't measure.

Another one was to many valve spring inserts (VSI) that caused the coils to touch and loose the spring action.

DOM

[Joe L.]

Re: powdered rocker ball broke

GM engineering played around with higher ratio rocker arms (1.6?) in the late 60's but found no meaningful gain in HP.

I think Yunick was fooling around with Pontiac rocker arms on his 305" Trans Am engine tests. Probably also 1.6.

I think I have some of the GM engineering dyno sheets here that show the HP numbers that compare the standard 1.5-1 to the 1.6-1 arms.

Michael------


GM did use 1.6:1 rocker arms on one PRODUCTION small block application. That application was 1996 LT4.

[Michael H.]

Re: powdered rocker ball broke

Michael------


GM did use 1.6:1 rocker arms on one PRODUCTION small block application. That application was 1996 LT4.

Sounds like they gave up on it after only one model year.

[Joe L.]

Re: powdered rocker ball broke

Sounds like they gave up on it after only one model year.

Michael------


As far as Corvettes go, 1996 was the last year of the original small block engine (albeit the Gen II variation for 92-96). However, GM did continue to build Gen I and Gen II small blocks for other PRODUCTION applications after that time right up until the time that Flint V-8 engine closed. They made the small block V-8 derived 4.3 V-6 until last year and they continue to manufacture small blocks for SERVICE right to this day (in Toluca, Mexico). However, NONE of these ever used/use 1.6:1 rockers.

[Clem Z.]

Re: powdered rocker ball broke

Sounds like they gave up on it after only one model year.

GM was working it way up SLOWLY on rocker ratios as in 1997 the LS engine series came out in the C-5 with 1.7 rocker ratio. now the ZO-6 engine uses 1.8 rocker ratio. GM does not move swiftly !!!

[Clem Z.]

Re: powdered rocker ball broke

i would order in (1) ZR1118 as it says it has a roller fulcrum and it is 1.5 ratio and 3/8" stud and see if it would work. those other ZR826 looks like it has a PM fulcrum.

jerry did you do this ????

[Michael H.]

Re: powdered rocker ball broke

jerry did you do this ????

I don't think any rollerized rocker arms are allowed in that org, Clem.

[Jim L.]

Re: powdered rocker ball broke

I don't think any rollerized rocker arms are allowed in that org, Clem.

They aren't, but the ones Clem found have a sliding barrel trunnion, similar to F**d rocker arms. They would be permitted, if the dimensions are usable.

Jim

[Clem Z.]

Re: powdered rocker ball broke

I don't think any rollerized rocker arms are allowed in that org, Clem.

it is a stamped steel rocker so i would read the rule real close i build some rockers like this by using oldsmobile rockers and the pivots out of a set of aluminum roller rockers. before we had a chance to use them the track changed the rules to allow steel roller rockers and limited the cam lift. the racers were having broken stamped rocker arms so they had to do something. this was 15 years ago