Inliners International Forums General Discussion Engines Self Aligning Rocker Arms

I am finally getting closer to finishing my 292. Taking the head and block in on Monday for final machining. I still need to get a few more items to finish the build, and rocker arms are one of them. I was wanting to use self-aligning rocker arms, like those on the vortec heads. Can small block rocker arms be used on the 250/292 head? The head is actually a Lumped 250 from MrHotRod6. The machinist will not be buying the rockers or push rods for me. Also, is there any advantage or benefit from using a higher ratio rocker? Or is 1.5/1.52 plenty good? Cam is a Tom Langdon grind of 0.439 lift @0.50.

Well, the rocker ratio for the 6 cylinders is much larger at 1.75 or 1.76 depending on who you ask, so the SBC ratio is not a good substitute at only 1.5 or 1.52. Plus, the 6 cylinder rocker uses geometry like the Big Block Chevy, so again the SBC rocker does not have geometry compatible for the 6 cylinder.

Oh boy, glad I asked! Thank you for the info. 1.76 bbc it is.

You're welcome! Actually, the Big Block rocker ratio is only 1.7, and the 6 cylinder is by itself with its ratio. So you will have to get specific 6 cylinder rockers to get the correct ratio.

I shall do that. I don't want to get the incorrect parts for this thing. From my initial search, Melling is the one that comes up for the L6 and not available until April.

The SBC rocker is too short (pallet to pushrod), the BBC is close enough to work.

The 250 valve stem angle is (IIRC) 9 degrees, the BBC is more but appears to work.

You may need hardened guide plates attached to the head to restrain the pushrods, possibly use hardened pushrods?

For some reason Summit Racing's website didn't want to play nice, so I did a different search over at Rock Auto, and ordered some Melling 292 rocker arm kits for $4.76 each kit. The kits are the rocker arm, pivot and nut. Since this will not be a racing engine, it needs to be reliable, and the old stamped steel rockers are tried and true. One less thing to order.

You don't need guide Plates The only time some guys will use a guide plate is when the head push rod hole has been opened up to use a 3/8 dia. push rod. I have ran the BBC rockers for over 18yrs. with out any issues Some guys have also used 1.8 BBc rockers.I have the Comp cams pro magnum roller rockers on my motor. Harland Sharp has roller rockers for our L6s. Other then maybe? the comp cams Pro magnum
Most all others will have a clearance issue under a STOCK valve cover.

I was hoping I didn't need guides plates, but would install them if I needed to. This being a mild cam the new valve train should be just fine with stock-sized 5/16" push rods. No major spring pressures at all.

yes your stock dia. push rods should be just fine. I ran stock dia push rods with my crane cam with a 583-607 lift for more then 17 yrs. with out any issues.

You're an animal!...lol...

DoubleDingo

That is kinda small compared to the one that is now in my 250 with is a 13-1 and the cam is just shy of .700 lift

Just a minor upgrade

Even without symptoms of pushrod flex (begins with tiny scratches or polishing of the tube by the relief hole sides about mid-way), the extreme deck height of the 292 suggest using the largest OD that clears. Adding length greatly reduces stiffness. Top names (Trend, Smith, Manton) can tell you.
OD is far & away more important than wall thickness, even an extra 1/16" is worth having.
A theoretical example, using .100" wall to remove a variable, and changing only OD.
Going up from 5/16" to 3/8" OD more than doubles bending resistance. The weight increase for 10" tube length is about 25 grams each, or 30% more.

^^^ X2

Will bigger diameter rods fit the cup in the the stock rocker?

And are bigger rods needed for a non-race engine? It won't be revved up above 3,000.

Stock pushrods will be fine for your needs.

Cool. Melling has a set.

It won't be revved up above 3,000

1,000 RPM below the stock power peak?
Then, why are you doing this?

Highway cruiser, and I take care of my equipment.

That cam has already moved the power up above 3,000

I guess that's what I get for being completely ignorant and uninformed and taking the information I read and heard for granted. Since the money has been spent and that seems to be the mildest upgrade on 12bolt, I will give it a go. I have to admit buying this 292 has been a learning experience and has surely brought on a lot of negative commentary. I am this far in, I may as well try the parts I've bought.

I did try to find the rpm range on the cam and didn't find one letter or number to describe that, just the lift info on 12bolt. I have a mild torque cam in my 350's with about the same lift, so this one seemed like a good choice.

All that said, my build will be great, or completely suck. Time will tell.

You will have fun with it.
When I was looking for a cam for my292 truck engine I looked at 12 Bolt's cams and the chart had RPM range of each grind. If you get it running and drive it a while and the cam isn't working for your use change it. A cam change is not really big deal. You'll be fine.

At 3,000 the greatest factors in producing power:
1. larger displacement
2. higher static CR
3. reduced pumping loss

3,000 will be the hill climbing, headwind rpm in direct, and sometimes the shift point when getting on the road. 3,000 with the gearing and tire size will be 70 mph in direct. I wish I knew the rpm range of the cam, but I don't.

Did you get the cam from 12 bolt? what is the number? we can look it up. If you haven't used it and it is not what you need maybe you can return it for the one you need. I got mine from Crower but Tom makes on very close to it.

Here is a link to a thread I started a while back when I was pondering a TRUCK 292 build. it started with asking about a cam and pretty quickly got to valves, lumps. heads, and head work. The second post is fro TLOWE and there if a link to his cams and info about them. I Haven't done this build yet but will soon I hope. I have all of the parts.

292 Truck Cam

Yes sir, got the cam from 12bolt, it's the RV/Marine HO Cam Kit, 204 Duration and 0.439 lift. It sounds like a good cam for my needs.

Funny that is the only one of Tom's offerings without an rpm range listed. I'm sure it will put power where you'll want it. Any that bring in torque from Idle on will be good for all-around street use.

I found that odd, but maybe there is some old literature that has the rpm ranges on this Tom Langdon cam grind.

That could be, I bet it is on this site somewhere. Both Toms would know. I just remembered I have an old Langdon Stovebolt catalog in the shop. I'll try to dig it out tomorrow.

If you have the info available I would surely like to see it. And don't call me Shirley! As with anything, the more you learn, the more you realize how little you know. With how far I've got thus far, and all the research, taking weeks or months before buying something, I felt comfortable in what I bought. As the machinist said yesterday, "It will run better than the way it was".

This, after he heard it had two pistons with cracked top rings. He is ready now to finish the lumped head, and prep the block for rebuild.

Edit: Bought this engine without hearing it run. After getting it home, the compression test showed 154-157 across all 6. Tearing it down, no ridge on any cylinder. Valves looked good except for maybe a couple hot exhaust valves. Ironically in 5 and 6 where the split rings were found.

I'm sure it will be a good street cam. The catalog I found is from 1999 and the cams listed were Clifford cams and not much data given. I think there is another catalog out there but who knows where?

So back on the original track - you decided to use the stock rocker set up rather than self aligning, correct?

I'm confused.
Which late L6 engines do not have self-aligning rockers (stud-mount)?

None of the 194/292 engines have self aligning rockers. The OP was confused thinking the SBC self aligning rockers would fit these 6 cylinders. Ford 300's have self aligning pedestal mounts on the later engines though...

Correct, went with stock Melling rocker arm kits.

Thanks CNC-Dude, I was getting ready for work and didn't have a chance to log-in.

Backstory: On my '81 I swapped on vortec heads but didn't know they required self-aligning rockers. It ran great and had for about a year after the swap. Was on the road for a camping trip and about an hour in the truck stops running well, basically barely running. Got towed home, switched cars and went camping. After getting back I opened up the engine to see what happened. #7 exhaust had walked off the valve stem. Luckily it didn't hit the retainer and drop the valve into the piston. I saw that pretty much every other rocker was about to do the same as #7 exhaust. Immediately after that moment I learned about self-aligning rocker arms, and got some stamped roller tip rockers. Wanting to avoid something similar with my 292, I wanted to get self-aligning rockers for it. It was just extra insurance, but not needed. I like to do things right the first time and not have to go in every day or every other day to tinker.

Here is a link to a thread about the Langdon Marine cam. Don't know if it has any info you what.
LINK

There is info on it in the Tech Tips portion of this site, but still no rpm range. I have a feeling it will be fine for my needs, as it doesn't require spring upgrades and is good on the valve train.