They are not flat, wrong description.


Edited - they appear to be perfectly flat - at least to the naked eye after checking some that I have.

The TSB says the cam is low taper, it says the tappets are flat faced?

6-paks had street hemi springs. they had a yellow stripe vs the hipo wedge being all red. they were a high rate spring which was common back in the day. actually a fairly crummy spring but we used them not knowing better.

i can't imagine any flat tappet cam lasting more than a few minutes without some taper. the low taper was to carry the extra spring pressure. this is one reason for the better rocker arms too. i remember back in the day busting so many of the 1968 rockers that i'd carry a small bag of them in the trunk. 6-paks had chrome stem valves too. factory wedge valves weren't very good for abuse so the chrome stem helped but didn't solve the erosion at the top of the stem were the rocker made contact. eventually the chrome stem and hardened tip ended most of those problems.

The factory parts manual will show the part numbers used, that would be the reference needed. Looking at my manuals I see the following.

1969
Hemi - 2899549
6bbl - 3418491

1970-71
Hemi - 3418491
6bbl - 3418491

So the answer is both yes and no. In 69 the 6bbl did not use the Hemi springs, in 70-71 they did.

i suspect there may have been a manufacturer or supplier change for the part number change. original single street hemi springs had the yellow stripe and at some point later they were a green stripe. so there was a change and the 34xxxxx number tells me sometime after 1970. the 28xxxxx number would be correct for '68 and '69. anyhow i have some yellow and green stripe springs and the wire size, height, and spring rate are the same. i remember buying this stuff back in day but that's been so many decades ago.

All I can say is that the 4bbl 440 used a different part number spring, same as the 383's did in 69. In 70-71 they used one of two different springs, depending on application I suspect Magnum vs non-Magnum type differences here. No mentions in any of the springs listings of stripe colors so no help there.

Nowadays, there are better choices.

i just did a rough calculation on hipo wedge and street hemi spring rates. the wedge came out 270lb rate and the hemi about 350lb rate. actual numbers would need to be calculated using actual real world springs but hopefully you folks get the idea.

i just dug up some spring info i done some time back. hipo wedge spring i checked was 100lbs@1.900", 238lbs@1.400". street hemi 95lbs@1.900", 300@1.400". noticeable difference in rate. both springs coil bind rather quickly with the dampner being the primary offender.

the non-hipo 256 cam did use a different spring. most i've seen were painted a greenish color and i think may have had an extra 1/2 or maybe 1 coil. the hypo wedge has,IIRC, an extra coil than the street hemi. factory cams back then had very mild ramp speeds and long closing ramps which didn't need a lot of spring. they were only 4500rpm engines.

It's no paper weight, just use the crowned lifters with it (new). Break it in normally and use a zinc oil, good to go.

Does anyone have a pic of the six pack rocker arms vs the non-six pack rockers? Is there a part number stamped in them for identification purposes?

Excellent research. Since I have an A12 I frequently find myself restricting a Six-Pack discussion to 1969 which can be, as it is in this case, a mistake. Thanks for the clarification.

think the "6pak rocker" was standard on 4bbl engines. my '69 r/t (4bbl) has the original rockers on it and they are the improved version vs the '68 and earlier. i don't have any original '68's but do have mopars re-pops and there is a noticeable difference. i'll try get some pics of the two later. the later rocker was used on '70's smog engines too so you're not boxed in by "6pak specific".

Thank you. You know, looking at it again, the statement that the 6bbl never used the Hemi springs is correct. The Hemi, however, started using the 6bbl springs in 70-71. Semantics? maybe, but interesting.

As for rockers, when I converted my 64 413 to 906 heads I also used the later style rockers and there was a noticeable difference in metal thickness. At least to the eyeball, if I ever measured it I have forgotten those numbers, that happened in 1988 so time erased those memories, lol. My 413 was a bit of an oddball. It was originally stamped with a T then over stamped with a V. Indicating, to me, it was a 63 413 put into a 64 model car. The casting number ended in 3200, 63, it had rocker stands, last used in 63, and 4 bolt valve covers, again last used in 63. I do not recall the SPD of that car, it may have been an earlier 64 MY one. Who knows.

The hemi changed from a flat tappet cam and lifters to a hydraulic setup in 1970. That's why the springs changed.

What I read too

I corrected my post, the lifters I have appear to be flat as described.
The cam they ran on (low taper lobes) have wear across the whole width of the lobe but has a higher wear pattern to one side.

I corrected my earlier post where I said the lifters were not flat.

the heavy duty so called 6pak rocker

the older '68 style rocker

street hemi springs on the left, yellow and green stripe. wire size, height, width, spring rate the same. spring on right is a magnum replacement (without red paint); same specs as stock 4bbl.