340 mopar rocker arm/shaft strength

[statsystems]

If I were to have a hyd. roller 340 (410 ci stroker), built on a budget, would stock rocker arms be fine at 140/closed 365/open spring pressure? Camshaft 234/246 on a 110, .550/.550. Wont be turned more than 6000 rpm max. Likely will peak about 5200rpm, and shift no higher than 5500-5800 tops. If stock rockers wont work, what is adequate?

I wouldn't do it. A set of 273 rockers is cheap. I wouldn't run stamped steel rockers on my lawn mower.

What kind lawn mower do you got!?!

I have 3.5 acres to mow. I've souped up the old riding mower.

[ProPower engines]

If I were to have a hyd. roller 340 (410 ci stroker), built on a budget, would stock rocker arms be fine at 140/closed 365/open spring pressure? Camshaft 234/246 on a 110, .550/.550. Wont be turned more than 6000 rpm max. Likely will peak about 5200rpm, and shift no higher than 5500-5800 tops. If stock rockers wont work, what is adequate?

I realize you are trying to do this on a tight budget but unless you are using the 308 casting 360 head you will be in trouble with push rod interference.
To keep it simple go with the EQ magnum heads with the LA intake pattern. They sell them dirt cheap on ebay and they use a conventional stud mount rocker.. I do quite a few 408 mopars and the EQ head has the clearance for the push rods to clear with only a bit of grinding.

As mentioned the push rod angle with the older heads are very bad and the EQ heads allow for several conventional roller rockers to be used.
I am doing some heads now and they are almost as good out of the box as the Hughes heads and much less cost.

[Geoff2]

SupStk,
If your Mopar rockers 'locked up' after torquing the shaft bolts, it means you over-torqued the bolts!

Using your logic, every SBM will have locked up rockers if they use factory rocker shafts......

[ProPower engines]

SupStk,
If your Mopar rockers 'locked up' after torquing the shaft bolts, it means you over-torqued the bolts!

Using your logic, every SBM will have locked up rockers if they use factory rocker shafts......

Either that or the shaft towers are not parallel end to end. I use a ball mill to correct the heights in the milling machine.
It makes the job much nicer when the mounts are all in the same plane end to end.

[Krooser]

Crane makes ductile iron rockers or you can find them on Fleabay...

[SupStk]

SupStk,
If your Mopar rockers 'locked up' after torquing the shaft bolts, it means you over-torqued the bolts!

Using your logic, every SBM will have locked up rockers if they use factory rocker shafts......

Either that or the shaft towers are not parallel end to end. I use a ball mill to correct the heights in the milling machine.
It makes the job much nicer when the mounts are all in the same plane end to end.

Guess using alot if extra clearance covers a multitude of sin at the factory level.

[DaveMcLain]

Crane makes ductile iron rockers or you can find them on Fleabay...

Are ductile iron rockers really stronger than steel ones? That seems doubtful to me.

[statsystems]

Crane makes ductile iron rockers or you can find them on Fleabay...

Are ductile iron rockers really stronger than steel ones? That seems doubtful to me.

Strong enough for most applications. I've used bushed ductile iron rockers on W-2 heads at 8200 and 280 on the seat with a bit over .700 net lift and never hurt one.

[Geoff2]

This shaft rocker design that Chry used on the 318/340s entered the world in 1958, with Chry first BB engine, the 350 cu in low block. These early engines until the early 60s differed from the later BB & SB engines in how the r/shafts bolted to the head. All SBs & later BBs had the shaft towers in the head machined with a semi circular recess, so that the shaft sat in the recess & was held in place by a bolt & special washer. Early BB heads had the shaft towers machined flat. Five alum blocks were slid onto the shaft & these blocks were bolted to each of the five shaft towers. I presume Chry went to the later design because it was cheaper to produce, & it was trouble free if correctly installed.

Chry BB stamped rockers are very strong; only reported problems I am aware of was occasional punching through the p'rod socket. For the 6 pack engines, Chry made rockers that were thicker in the PR cup area because of the heavier springs used in those engines. I did a deflection test under load on a production rocker some years back & was unable to measure any deflection. Chry made the same beefed up rocker arm for the SBs.

[Krooser]

Crane makes ductile iron rockers or you can find them on Fleabay...

Are ductile iron rockers really stronger than steel ones? That seems doubtful to me.

Are we sure the OEM rockers aren't ductile iron? How many thousands of rockers did Gotha mfg. back in the day? Likely ductile iron, too. Isky too?

Often the terms iron and steel are used improperly.

Not a criticism.... just wondering?


https://en.m.wikipedia.org/wiki/Ductile_iron


https://www.scribd.com/document/2126120 ... le-Rockers

[DaveMcLain]

Crane makes ductile iron rockers or you can find them on Fleabay...

Are ductile iron rockers really stronger than steel ones? That seems doubtful to me.

Are we sure the OEM rockers aren't ductile iron? How many thousands of rockers did Gotha mfg. back in the day? Likely ductile iron, too. Isky too?

Often the terms iron and steel are used improperly.

Not a criticism.... just wondering?


https://en.m.wikipedia.org/wiki/Ductile_iron


https://www.scribd.com/document/2126120 ... le-Rockers

I was just thinking about the factory stamped steel rockers that came on most Chrysler wedge engines. If you think about the overall design it is genius in how it works. It allows the pushrods and valve stems to be on different planes yet still can be produced using an inexpensive stamping that doesn't require any precision fit onto a fancy ground shaft. It gives a lot of surface area too which allows it to handle pretty high loads without trouble if the shafts are installed facing the right direction and not upside down.

[Geoff2]

Yep, ingenious.
But having worked on Chryslers for more years than I care to remember, it doesn't surprise me.....

[pdq67]

Off topic, but not really...

My Buddy Doc had a '70 Duster H/T with the slant-6 in it.

We were changing oil one afternoon and It was just sewing machining right along.

I asked when was the last time he had the valves adjusted and he said never AND it had 175,000 miles on it.

MOPAR did something right as I see it back then.

He still has the car, less engine and trans, but the whole uni-body sub-frame holding the rear end in place is rusted out.

pdq67

[Geoff2]

Mopar has been doing something right for a looooong time....