And then I suppose you can leave the head gasket out and just add the compressed thickness of the gasket to the measurement.

 

The radius for the shaft is not machined properly. Check out some recent Speedmaster threads to see discussions about this issue.

 

If you're up for some trig, otherwise, include the head gasket and torque it down properly.

 

Is that gasket reusable then? Probably depends. I have felpro 1008 for my build.
sorry for the hijack Doc.

 

don't overthink it. Measuring without the gasket is fine. If the piston has a valve relief in it, that 268 camshaft usually has no issues with clearance with either rocker. If the ICL is way off, then you can have an issue, but it would have to be WAY off.

 

@DentalDart Here's a post showing the issue.

The whole thread is a good read. Lots of answers.

Here's an image posted of the issue:

 

"Seemed fine". Well did you check it or just bolt um down?

 

LOL...

 

Dental,
Bouncing suspension is caused by failed/failing shock absorbers. Springs could also be sagged, but replacing springs without the shocks will shorten the life of the springs.

 

What did you use? One of the 'cheapest' made parts in the aftermarket are shocks. Most box store shocks are junk when new and wear rapidly. Sadly, good replacements are not cheap.
I went with Viking double adjustables. At around $800 for all 4, they're one of the most affordable options for decent quality adjustable shocks. Hotchkiss also makes some decent ones, but I wanted double adjustable.
I can also say that the adjustments on the Vikings actually make a difference. Turned to full stiff, my car will ride like a dumptruck. Set to full soft, it rides like 'stock'. In the middle, it really helps control the wheels the way I expect and has major impact on traction, wheel hop, etc.
Then I added assassin bars - now there's no tendency for the rear to walk around when I lose traction and the wheel hop is completely gone. It also firmed up the rear suspension a bit and will let me soften the ride on the street. Since I'm on street tires, it actually makes it even easier to bust them loose. Kinda spooky having it haze the tires and loosen up in 3rd gear

 

I know the feeling..
It took me 4 years to get around to buying the Viking shocks. They were $525 when I first found them.. Food for thought ;)

 

Bouncy is caused by shocks, so they are/have failed. There is a reason that Bilstein, Koni etc cost more.....

 

Sounds like good shocks but questionable tires. You might try a 10.5 drag radial

 

I have an 8 3/4 with 3.55 sg sitting in the corner. It's an ebody housing, but I have a b-body housing next to it. One of these days it'll get swapped and installed and then it'll be time for new wheels/tires ;)

 

I put QA1 single adjust on all 4 corners of both my older heaps... what a difference. I keepem set pretty low.. anything over 6 of 13 settings and it you feel every nook and cranny in the road.

 

In the old days, we would put some modeling clay on one piston, assemble one head, one set of pushrods and rockers, slowly turn the engine over by hand, remove the head, and do a look see. If you are going to just change rockers, and want a Mopar site internet friend to approve the change, if something goes wrong, send them a bill.

 

I recommend watching the David Vizard youtube video on LCA selection. Part of his Powertec 10 series. Ep 17 and Ep18 cover rocker arms and discusses when a higher ratio rocker is likely to improve torque and in which situation it will likely reduce torque. Torque is the value we can measure, while power is a value calculated from torque and RPM. LCA is critical to maximise output and needs to be determined using DV's 128 formula;
128 - (cylinder displacement for one cylinder/ intake valve diameter × 0.91).

 

Partly so. Both can cause interference issues, which must be checked every time components of the valvetrain or piton are changed. A high lift rocker may benefit from retarding the cam 2° to 3°. This would increase valve to piston clearance, but the only way to know what the engine wants is to test on a dyno. On a solid lifter combination, tightening or loosening valve lash by 0.002" may be required.
Watch the videos as he has a lot of useful information. Granted most seems to apply to Ford or Chevy engines, the one thing you need to remember is that ports, valves and pistons do not know or respond to what name is on the hood. They respond to airflow and compression ratio. The general rules apply to all, like short turn radius. Once you introduce power adders, some of that changes. Larger, better flowing exhaust becomes important. Turbos respond to low restriction exhaust, from the valve out.

 

Minimum valve to piston clearance occurs at about 10° BTDC or ATDC as the intake valve is opening and before the piston moves away from TDC. Modeling clay is put on the valve reliefs about 3/16 thick. Install light checking springs available at a hardware store. Install the head with the piston down 1/2" to 3/4". Gasket is not required as a gasket will increase your clearance. Carefully turn the engine through 2 revolutions. Then remove the head and cut the modeling clay from center of the engine to the outside, and pry half off. The remainder can be measured with a caliper to determine the clearance. The outside edge of the valve head to the valve pocket can be measured at the same time.
Another tip from DV involes cutting back the deep side of the intake pocket (relieve) toward the cylinder center. This improves low lift flow and promotes swirl. It does not need to be ground right to the bottom of the valve pocket. 1/8" is good and at 30° from the cylinder center line. Check piston crown volume to equalise before balancing.

 

With 0.012 out of the bore you want to watch quench clearance. Probably looking at a compressed head gasket of 0.050" thickness.
For a 0.030 over 340 with 2.02 intake valves, cam LCA for best performance should be 104.6°. A 106° LCA and 1.6 rockers should work well. What is important is the overlap triangle. The high lift rockers snap the valve open quicker, increasing low lift flow during the critical overlap "cycle". This could require retarding the cam 1° or 2°. That aids V-P clearance.

 

Watch the DV video on high lift rockers, Ep 17 and Ep 18. The effective ratio changes as lift progresses. One rocker could have 1.4:1 off the seat and 1.7:1 over the nose. Another could be the other way around. Quick off the seat aids low lift flow with the high ratio coming off the seat. Then if the ratio reduces as max lift is approached, this slows the valve preventing float.
There is a lot more to rockers than meets the eye. Miller made rockers and wrote about mid-lift. Research is required.