my 340 valvetrain

[1970340t/a]

Hey why didnt you guys tell me that i couldnt go over 480 lift on my my non adjustable rockers?

[TK]

Who said that? You can, you just cant go much over 480 without head work. (Beaten this horse already)

Who said that? Because I have lots of SB's out there that do.

In fact, that arcticle with the 415HP 318 had stock valvetrain, and over 500 lift.

[TK]

http://www.popularhotrodding.com/eng...n_systems.html

[aarracer]

Say it is'nt so.. Yes you can.

[cageman]

567 lift on the 340 in my brothers hobby stock, stock rockers, hydro cam.
Thing pulls hard.

[bulldog426]

my dad has a 340 with a 502 lift cam with stock rockers, never a problem who told you that??? if it was summit or jegs, yeah they'll tell you that, when i was picking out a cam for my big block, seemed like every cam i looked at the summit guys said i needed adjustable rockers, come to find out they were full of it... alot of times they'll tell you that just to sell you something...

[1970340t/a]

yeah it was one of the summit guys so what is the hightest lift i can go with my stock rockers the heads are j heads with 2.02 and 1.60 there stock just been completly redone.

[TK]

You need to measure the distance from a closed valve to where the retainer hits, the top of the valve guide, with the seal in place.........

If it was me, I would have the springs balanced, guides cut, and be good for high lift, reliably.

[Tarrbabe]

Most of us know that the stock LA rockers can work with up to .509 and in some cases more lift. The real deal is that as you get larger lift, the Hyd. rockers are more flexible than the Solid Rocker systems. You can try using
.600 cams with a stock setup but you will have PROBLEMS.
YOU shouldn't come here and blame the majority for some single persons input. Remember, there are a lot of us here and we will share but Nobody has all the answers. I would never tell someone that was looking for HONEST info a lie.
I will tell you that I believe in over building an engine. My 340 has a Racer Brown Cam and I'm using the old 273 solid rockers to ensure proper cam action without the flex that is there in the HYD rockers. I only have .485 lift from my cam at 1.5 rocker ratio. But I know because of the stiff construction, I am covered with true valve action. Then if something happens, I know it's not from being cheap and ending in costing me much more. Build it right and build it ONCE.

[rampage_82]

Well there is that... I've been guilty of going the cheap route, and it ended up costing me more that if I'd done it right the first time, but other times it works fine.... The thing that I would suggest is to get the right springs, and the valves set at the same height, if that is correct, then your stock rockers will be fine to well over .500",

[passing you]

Maybe just go ahead and have the guides cut down and for positive 'viton' seals.

[Cudafever]

Originally Posted by TK

You need to measure the distance from a closed valve to where the retainer hits, the top of the valve guide, with the seal in place.........

If it was me, I would have the springs balanced, guides cut, and be good for high lift, reliably.

Installed my checking valve springs into my spare X head (these heads have never been rebuilt) today. I removed what was left of the petrified umbrella valve seal and check retainer to guide clearance.

Guide to retainer was .615"

petrified valve seal at stem opening, .120"

.120 from .615=.495" lift

Sure glad i didn't go with 1.6 rocker arm when i upgrade from stamp steel......

.474 lift w/1.5 rocker arm and .506 lift w/1.6

Actually, i would have been fine as the X head, on my cuda, are a dual spring with a .050" retainer on them.
So on my cuda the max lift would have been around.545 lift(retainer to guide.....Not spring capability)(Didn't check these heads, just guessing)

[TK]

Yyyyep.

I been preaching this for years..... Seems to be the one thing the magazine readers, internet mechanics, and people with more knowledge than me forget.

With big springs, you have to cut down the spring base too, to get the proper closed height.

Also too, heads are different from year/casting/day. the 302 heads on my stroker were not even good for 450 lift.......

Been there, done that, wayyy too many times. (And every set of heads I have built, needed it, because, I rarely have an engine with under .500 lift. The 318 for the ramcharger I am starting will be smooth idling 525 lift......

[passing you]

Instead of cutting spring pads you can also use pop up retainers to resolve installed height issues, that is when there's not enough installed height.

Of corse if using double springs, you'll have to cut the inner spring pad to fit the inner spring.

[DonCarr]

Stock rockers never hit a 1.5 ratio, supposed to be lucky to get 1.4.

And rubber seals squish if they have to.

[passing you]

yeah I've heard the same like 1.45 instead of 1.5
I run the 1.5 bushed from mopar which are spec 1.5 or thats at least thats what they say.....

[DonCarr]

Stock hydraulic rockers are supposed to be highly underrated, especially with a high intensity cam. The low ratio allows higher revs and/or lower spring pressures. Hughes used to post recommended spring pressure. The circle track guys would know.

If cam lobe at 1.5 ratio is 0.510, then it's 0.476 at 1.4, even a bit lower adjusting for odd lifter bore angles. Just suggesting the suggested cams should work.

Should be checked with a dial indicator anyhow . Could spotface the valve guide down a bit if worried.