Are These Factory Rocker Arms on my 1973 340ci ?

[Moparfiend]

These look factory to me and not like my 318 stamped cupped rockers! But not familiar with the 340 set up. They look cast and fairly robust.

 

[Bighead440]

No, 273.

 

[Moparfiend]

No, 273.

So if not stick I assume they used a cup style. I don’t know much about this engine as I boUght it as is. It is running duel springs as well and I am wondering if this is a solid cam set which might explain the addition of adjustable rockers. Also they look like a nice long reach so maybe for spring clearance?

 

[Bighead440]

So if not stick I assume they used a cup style. I don’t know much about this engine as I boUght it as is. It is running duel springs as well and I am wondering if this is a solid cam set which might explain the addition of adjustable rockers. Also they look like a nice long reach so maybe for spring clearance?

My experience is they start rubbing the retainer/spring around 1.50" diameter. You can buy pushrods cup and ball either way (hyd or solid) pretty easy, so if it has lash, I'd suspect mechanical flat tappet. I used 273s on a hot 360 with a 247/254*@.050" hydraulic cam and Rhoads V-Max lifters for a 7000rpm stable setup. So it could be for precise lifter preload.

 

[Moparfiend]

My experience is they start rubbing the retainer/spring around 1.50" diameter. You can buy pushrods cup and ball either way (hyd or solid) pretty easy, so if it has lash, I'd suspect mechanical flat tappet. I used 273s on a hot 360 with a 247/254*@.050" hydraulic cam and Rhoads V-Max lifters for a 7000rpm stable setup. So it could be for precise lifter preload.

Roughly how much spring pressure did that set have? If I had a spring pressure gauge I might be able to determine what type of lifter/cam set up I actually have right?

 

[Moparfiend]

Would a hydraulic flat tappet ever use a duel spring set up?

 

[Bighead440]

Roughly how much spring pressure did that set have? If I had a spring pressure gauge I might be able to determine what type of lifter/cam set up I actually have right?

People mix and match, you'll have to measure the lift to get an idea. See if any of the rockers have slack when the adjacent valve on that same cylinder is halfway open.

 

[Bighead440]

Would a hydraulic flat tappet ever use a duel spring set up?

Possibly, on an A-engine with high rpm capability and/or high lift, it's common. Usually it indicates a solid cam, though.

 

[wyrmrider]

stock good pieces
check and see if you have a solid cam
dual springs give a hint that you do
if loose you'd be hearing it- too tight and solid you can burn valves
you can check and see if you have tappet clerance or preload
if clerence check and see if they are all the same write it down
how old is the timing chain?
does it look like positive stem seals- valve guides machined?
have time post up a compression check- you need it for a baseline anyway
good find

 

[Builderguy]

This is a stock 340 (1973)

 

[Moparfiend]

stock good pieces
check and see if you have a solid cam
dual springs give a hint that you do
if loose you'd be hearing it- too tight and solid you can burn valves
you can check and see if you have tappet clerance or preload
if clerence check and see if they are all the same write it down
how old is the timing chain?
does it look like positive stem seals- valve guides machined?
have time post up a compression check- you need it for a baseline anyway
good find

Thanks WR I did a static compression or cylinder pressure check on each cylinder. They are very high. I am running TRW-2322 forged 12.5,1 pistons.
Pressures:

 

[33 IMP]

I doubt anyone would put together a 12 1/2 motor with double springs, and a hydraulic cam. I also doubt you will be able to feed that thing pump premium! Do you have a source for 100LL?

 

[Moparfiend]

I doubt anyone would put together a 12 1/2 motor with double springs, and a hydraulic cam. I also doubt you will be able to feed that thing pump premium! Do you have a source for 100LL?

I do actually 100 AND 110! But not using it. Running 92 octane. I have it running without detonation by slowing the advance curve AND slightly retarded 17 degrees idle and 31 all in with a 14 degree advance limiter bushing on a variable MSD advance controller hooked up to my 6AL. I still need to find someone local who has a Whistler so I can actually find out what my actual compression ratio is. I also need to put in a higher stall converter and am attempting to get one. The world only noticeable detonation occurred at WOT under load btw. Times are tuff right now so much of my work is delayed. But was curious about the lifters as they were not like my 318’s. Thought the 340 might have come with these since it is a higher revving motor than the 318. So now it might at least indicate if its solid or hydraulic. I will check my valve lash and see if its set for zero lash with preload or if they are gapped for solid.

 

[66Satellite47]

The rockers are 273 mechanical style or aftermarket. Likely solid lifter, but racers used the adjustable rockers with hydraulic lifters. Compression numbers sure look like 12+ CR. Low lead 100 should be available at a local airport , 50/50 mix might work, maybe a bit more 100LL. Race 110 may be more expensive. I ran several years on pump premium/100LL mix. But pump premium was a lot better then.

 

[chescharger]

pull a lifter

 

[RemCharger]

Stock 273 rockers have a barrel nut adjuster iirc. And spacer springs? I would guess they are maybe an isky?

 

[wyrmrider]

The will say isky on the side and have a hard pad
he should be so lucky
how many threads show ball to rocker??

 

[wyrmrider]

no need to pull a lifter
stick in a feeler gage
if it goes in it's a solid cam
if set them all to the looser ones but maybe not the loosest if it is way off

 

[66Satellite47]

All the Isky rockers I've seen have the Isky cast in & have the hardened pad. The Mopar versions do not have the casting marks & plain cast valve ends. If there is valve lash, solid cam, no lash hydraulic.

 

[wyrmrider]

do take a peek at the adjusters
early ones had the ball real close to the threads and we set them with 2-3 threads showings
later ones have a neck between the ball and the threads
they need to be set with 0-1 thread showing
if not post a pic from the end at closed, mid lift, open
looks like a great find but let's check the details
YR has posted adjuster detailing points in a stickie at fabo
we want to make sure oil is getting into the pushrod cup
cheers