PocketAces
Well-Known Member
Sunday morning I loaded up the engine and hauled it to the body shop. Mike let me use the booth. That's the same pallet and stand my dad and I built to ship the engine from Pennsylvania to California.
65 Dart 273 Engine Rebuild
- Thread starter PocketAces
- Start date
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PocketAces
Well-Known Member
I painted the engine with SPI Epoxy Primer (red oxide with some white added) and Restoration Shop single stage acrylic urethane in International Harvester Red 2150.
I also painted another batch of black parts. SPI Epoxy Primer (black) and Hot Rod Flatz urethane chassis black.
I've got all my 2 bbl parts painted and ready to bolt on if I ever want to go back to the stock configuration.
I also painted another batch of black parts. SPI Epoxy Primer (black) and Hot Rod Flatz urethane chassis black.
I've got all my 2 bbl parts painted and ready to bolt on if I ever want to go back to the stock configuration.
trapster
Well-Known Member
Nice
Your work is amazing. Can't wait to see it finished. When do you think you will have it ready? Next year?
PocketAces
Well-Known Member
My valve adjusting screws were backed all the way out, and the tops of the cups were coming very close to the bottom of the rockers.
View attachment 1.jpg
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So I decided to try a shorter set of pushrods. I ordered a set of Comp Cams 782116 Hi-Energy Pushrods. They measure approximately 1/8" shorter than the stock push rods.
View attachment 3.jpg
I put them in on the drivers side first. Went OK with maybe 1-2 turns remaining on top of the rocker.
View attachment 5.jpg
But when I installed them on the passenger side, the second one I adjusted bottomed out before getting the lash down to spec.
My next thought was to switch over to longer adjusting screws with lock nuts. http://www.summitracing.com/parts/CRN-99802-16/
Before the rebuild, I had a problem with loose adjusting screws so I bought these adjusting screws and installed them with the stock push rods.
http://www.forabodiesonly.com/mopar/showthread.php?t=165437
But they were too long and hit the baffles inside the valve covers when the valves opened. To solve that problem I had to drill holes in the valve cover baffles to make space for the adjusting screws. I really don't want to drill holes in my new commando valve covers, so my hope is that the shorter push rods will compensate for the longer adjusting screws.
I installed the old rockers with the longer adjusting screws and adjusted the valves.
View attachment 6.jpg
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Then I checked for clearance between the adjusting screws and the baffles. It's really tight. They actually touch without the valve cover gasket. But with the valve cover gasket installed and snugged down, they don't touch.
My hope is that the valve cover gasket doesn't relax to the point where they touch. I also hope that after the cam is broke in and all the valve train parts are seated, that I will need to turn the screws in a bit farther to get the lash back in spec. Worst case, I guess I could grind a bit off the tops of the adjusting screws.
View attachment 1.jpg
View attachment 2.jpg
So I decided to try a shorter set of pushrods. I ordered a set of Comp Cams 782116 Hi-Energy Pushrods. They measure approximately 1/8" shorter than the stock push rods.
View attachment 3.jpg
I put them in on the drivers side first. Went OK with maybe 1-2 turns remaining on top of the rocker.
View attachment 5.jpg
But when I installed them on the passenger side, the second one I adjusted bottomed out before getting the lash down to spec.
My next thought was to switch over to longer adjusting screws with lock nuts. http://www.summitracing.com/parts/CRN-99802-16/
Before the rebuild, I had a problem with loose adjusting screws so I bought these adjusting screws and installed them with the stock push rods.
http://www.forabodiesonly.com/mopar/showthread.php?t=165437
But they were too long and hit the baffles inside the valve covers when the valves opened. To solve that problem I had to drill holes in the valve cover baffles to make space for the adjusting screws. I really don't want to drill holes in my new commando valve covers, so my hope is that the shorter push rods will compensate for the longer adjusting screws.
I installed the old rockers with the longer adjusting screws and adjusted the valves.
View attachment 6.jpg
View attachment 7.jpg
Then I checked for clearance between the adjusting screws and the baffles. It's really tight. They actually touch without the valve cover gasket. But with the valve cover gasket installed and snugged down, they don't touch.
My hope is that the valve cover gasket doesn't relax to the point where they touch. I also hope that after the cam is broke in and all the valve train parts are seated, that I will need to turn the screws in a bit farther to get the lash back in spec. Worst case, I guess I could grind a bit off the tops of the adjusting screws.
Something is wrong. Get a checking pushrod and get custom pushrods. Maybe the block is off side to side or one head is milled more than the others. Are the valves sunk too far in?
PocketAces
Well-Known Member
I had hardened seats installed in the heads. I don't think they're too deep. I cc'ed all the chambers earlier in this thread. They're not too far out of line from what others are seeing. Sunken seats might explain having to back the stock adjusters out so far with the stock push rods, but it wouldn't cause the aftermarket adjusting screws to hit the baffles. That's just cam lobe height + push rod length + adjuster length > deck height + head height + valve cover height. We only did clean up cuts on the decks and heads.
There is a small difference between the banks, but I don't think it's anything to worry about. I cc'ed the cylinders and the chambers and then matched the head with smaller chambers to the bank with higher deck height. Earlier in the thread you can see the results and the CR is pretty consistent between all the cylinders.
I probably would have been OK with the stock push rods and adjusters. As everything broke in, tightening the lash would have improved the situation. I may also be OK with these shorter pushrods and longer adjusters. Worst case, I'll grind a bit off the adjuster screws if I have to or maybe switch back to the stock hardware.
I call it tolerance stacking. A few thousands here a few thousands there and pretty soon things don't fit. I couldn't use the stock pushrods so I got some shorter ones and some rocker shaft shims to make it work right. You'll get it. You've done some great things so far. tmm
PocketAces
Well-Known Member
Thanks Toolman. What length push rods did you end up using?
For proper geometry you want to have one thread showing below the rocker arm. work from there. We have confidence in you.
Dang, I don't remember. I have looked for my notebook but can't find it. I'll look in my receipt file. Give me a few min. tmm
I think I found the receipt. I got them from Summit. They are part number # SUM-G6420. They are 7.234 long. Hope this helps. tmm
PocketAces
Well-Known Member
If that's the overall length then it would be surprising that you got them to work. If that's the effective length, then they're pretty close to the shorter comp cams rods I'm using. I know you milled more off your heads than I did which would make those push rods a better fit for you with the stock adjusters.
My plan is to start up the engine with the shorter Comp Cams push rods and the longer adjusters and see if I hear any interference.
With the stock pushrods, I couldn't back the adjusters off far enough to get the adjustment without the cup hitting against the rocker. I wish I had taken pics of that. The shorter pushrods allowed a few more threads to be exposed. This is a after shot with what I felt was the proper geometry. tmm
moper
Well-Known Member
Two comments -
1. pushrods have no effect on geometry with a shaft rocker system. They are simply parts that fill the gap between teh lifter and rocker.
2. Your geometry does not look that good. Can you take a picture looking down the line of valve stem tips with that rocker in place? Are all the valve tips at the same height?
The valve job and the centerline of the rocker shaft does. In this case - I think the valve job is not quite right. The valve tip should begin almost centered on the valve tip at rest. It should bee slightly towards the rocker stand. As the rocker moves and the valve opens it should go past dead center, and then at mid lift be centered but offset slightly to the valve cover rail. At full lift it should be back towards the rocker stand. Your's looks like it's on the inside edge of the valve tip at rest. The valve is "too long" effectively. My guess would be the seat was sunk into the head, the seat angle was cut too deep into the new seat, or the valve is too long.
PS - shims under the shaft should be able to provide a fix - but it will effect the pushrods further.
1. pushrods have no effect on geometry with a shaft rocker system. They are simply parts that fill the gap between teh lifter and rocker.
2. Your geometry does not look that good. Can you take a picture looking down the line of valve stem tips with that rocker in place? Are all the valve tips at the same height?
The valve job and the centerline of the rocker shaft does. In this case - I think the valve job is not quite right. The valve tip should begin almost centered on the valve tip at rest. It should bee slightly towards the rocker stand. As the rocker moves and the valve opens it should go past dead center, and then at mid lift be centered but offset slightly to the valve cover rail. At full lift it should be back towards the rocker stand. Your's looks like it's on the inside edge of the valve tip at rest. The valve is "too long" effectively. My guess would be the seat was sunk into the head, the seat angle was cut too deep into the new seat, or the valve is too long.
PS - shims under the shaft should be able to provide a fix - but it will effect the pushrods further.
PocketAces
Well-Known Member
Are you commenting on my valves or ToolManMike's?
C130 Chief
Mechanical Genius
Your valve tips look tall relative to the rocker shaft. The rocker tip should contact the center of the stem, otherwise accelerated guide wear will occur. This is commonly a result of having the valves and seats ground causing the valves to sit lower in their seats. You have a range of options to remedy this situation. Install oversize valves and/or insert seats (most expensive) have you existing valve tips ground (a little expensive) or shims to raise the rocker shaft (cheap) You may need to use a combination of the last two. Once the rocker to valve geometry is correct you can measure for custom pushrod length if need be.
From the Chrysler Racing manual "the ideal adjustment for the rocker adjusting screw is to have only one thread showing below the rocker arm with the valve lash set properly ( two may be OK, three shakey, etc, but high rpm makes one more desirable)." Generally you are right, but on a small block to get the right geometry this is one of the theoretical points that gets your rocker arm radius near the center of the valve tip. It is also where to have the rocker arm adjusting screw when measuring for the optimal push rod length.
C130 Chief
Mechanical Genius
Actually the 1 thread exposed ideal condition is the best compromise between adjuster screw rigidity and clearance between the pushrod cup and rocker body. Rocker geometry and contact patch are strictly a function of rotational center of the rocker relative to the valve tip.
Inquiring minds want to know. I replaced all the valves and wondered if the stems were longer than the stockers. Those were done at the machine shop and I didn't measure over all length before and after. I used shorter pushrods to get the adjusters right and then shimmed the rocker shafts up to get the rocker tip to valve tip closer to good. tmm
That makes sense. However the farther the adjuster ball is from the rocker shaft center the more it moves in a non linear motion. In other words the pushrod cup end will be moving farther away from the rocker shaft instead of opening your valve. Also Since the shaft location is fixed, can be changed with shims in only one direction, and the valve tips are also fixed, dependant on valve job and guide center, one should see how important a good machinist becomes on a Chrysler.
Do you remember what the valve spring installed height was on your valves? Were they stock valves?
moper
Well-Known Member
I think you're misinterpreting the context. Usually those comments refer to selecting the correct pushrod length. The issue with too many threads is valvetrain stability and loss of lift due to adding to the already existing angle - and yes, 1 to 2 threads is correct and that's set once you have the rockers and lifters in place. However that's after the geometry is set which as I noted has nothing to do with pushrod length.
Rocker geometry is the path of the rocker as it goes through it's motion and the relationship of it to the valve tip. It's affected by three things: the valve job (basically the placement of the tip or "valve stem height"; the location of the centerline of the rocker shaft (the axis around which the rocker travels); and the manufacture of the rockers themselves which vary considerably especially in the performance aftermarket.
I consider shims as somewhat of a "rig" for two reasons: they are not as stable in terms of supporting the shaft (like the too many threads bit), and because the valves are tipped in towards the shaft centerline when you raise the centerline of the shaft you're also moving it over towards the valve at the same time. So while you may be able to center the tip, you may not be able to correct the angles between the rocker tip and valve tip which can mean less rpm (effectively weakening the valve spring due to less leverage), more stress, lost lift at the valve, and premature wear on the tip and valve guide becase the valve is pushed more sideways rather than down.
To OP: I was referring to the engine you pictured - not Toolman's. The issue is not whether or not it will run. I'm sure this 273 will run. It's a question of overall how well will it run, and for how long. This is a fixable issue and i'd fix it.
What you are saying is true. I know it is a nit. But if you are buying longer adjusters and shorter pushrods, you are basically using a 2 piece pushrod hinged at the ball, not at the optimum pivot point but farther down. Which is rotating in a larger arc about the rocker shaft. Which is what the OP has done. Will it run, probably, but why? I would advocate using the stock adjusters get optimum length pushrods, it seems he has two different lengths anyway, and be done. And all his interference problems go away, and his engine runs better. You and I know what Geometry is, I'm just including more of it. I do know it is a nit.
moper
Well-Known Member
Ah, gotcha! You're working on the adjuster/ pushrod issue.
I'm working on the geometry/valve stem height issue with the thought that if the valve heights were right the adjusters and pushrods would not be a problem.
I'm working on the geometry/valve stem height issue with the thought that if the valve heights were right the adjusters and pushrods would not be a problem.
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