[RSSS1967]

Well crap - I did a quick mockup on the new engine to check valvetrain geometry. Installed one head and intake/exhaust lifters in #1. Spun engine over a few times with magic marker on the valve tips. Looks to me like I need a shorter pushrod. I am running stock length pushrods in it right now. Block had maybe .006 taken off to square things up - pistons ended up .008 in the hole. Heads were milled around .025 to help bring up compression. Head gasket compressed thickness should be .039 - this is actually an old gasket that I put on temporarily for the mockup. I was hoping things would even out because cam was reground for more lift and had about .050 taken off the base circle. I actually thought I might end up needing slightly LONGER pushrods, not shorter.

Someone who has been down this road a few times take a look at these pictures and let me know if I am OK, or if I need to dump another $300 on custom pushrods.

 

[1968 hot rod]

install a lash cap on it or .050 shorter pushrods.
make sure the lash cap clears the valve locks.

 

[superstocker72]

get a pushrod length checker! its way cheaper than blowing a ton of money on pushrods that wont work, after you get it right then order the P/R

 

[RSSS1967]

OK, so just for grins I went back out there and tried it again, this time I mocked the intake side up with an EXHAUST pushrod I had from a flat tappet motor. This pushrod is actually about .25 shorter than the stock pushrod.

The marks it left on the valve look pretty good to me!

I am doing these tests with the stock hydraulic lifters. They were pretty much pumped up all the way for the first few rotations. Now they have bled down, so tomorrow it's off to the hardware store to find a bunch of washers I can stack up inside a couple of lifters. Even if the plunger is going down a little bit, it further emphasizes my first test showing that the pushrod might be too long.

Stay tuned...

 

[Tom Mobley]

that last pic is about perfect. But, what's the parts combination here? Extremely unusual to have a Chevy with significantly too long pushrods unless there's some other weirdness. Are those Chevy heads? Possible that those pushrods are longer than stock?

 

[GRN69CHV]

Search for mid-lift geometry method. In short, you measure PR length so that centerline of rocker fulcrum at stud is exactly 50% of lift lower than centerline of roller wheel axle with cam set at base circle and rocker adjusted to "0" lash plus preload for hyd lifter. This allows rocker fulcrum and roller axle to be at 90* angle to valve stem at 50% lift, to net an A-B-A sweep across valve stem. On heads with longer than stock length valves it is common to either need a slightly shorter pushrod, different rocker or compromise contact point of roller wheel at valve stem from exact center of valve tip.

 

[RSSS1967]

Stock block (Gen VI) and Gen VI square port heads. Fel Pro .039 gasket, ARP rocker studs, stock guide plates. Valves are Ferrea / Rev, supposed to be stock length. Lifters are stock GM Gen VI rollers with stock push rods, and the cam is a stock GM billet roller that was reground by Delta Cams to go from .483 lift up to approximately .575 lift. Rockers are Comp Cams rollers, but I have a set of new Scorpions that I will probably use instead - the Comps have some hours on them. I am going to try the mock up with the Scorpions this evening.

I agree that it seems really strange for the stock push rods to be off that far. The second push rod that I tried was at least .25 shorter than the stock one!

 

[RSSS1967]

So are we all in agreement that I am too far off to run this engine with the stock push rods?

 

[GRN69CHV]

Pistons at .008" down, heads cut .025 = .037" shorter pushrods to keep stock geometry with stock base circle cam. You'll need to mock up with the Scorpion rockers which incidentally have a larger diameter roller wheel and will change geometry also.

 

[engineguy]

Tom,
In order for you to get your pushrod length exactly on, you will need to spend a few bucks and invest some additional time. First, as you have mentioned, get an extra pair of lifters (same as you will be running in the engine), remove the hydraulic plunger and have a sleeve machined to convert to solid lifter. Keep this pair of lifters for future checks and engine rebuilding. Next, purchase a pair of adjustable pushrods for this engine. Use the adjustable pushrods with the modified lifters to determine the exact length you will need. Once you have found what you consider to be the exact pushrod length, plot the area under the "curve" for both intake and exhaust - using degree wheel and dial indicator. Adjust each pushrod length, up and down in .050" increments until you have the maximum area under the curve for each valve. Takes some time and effort, but you will have found the ultimate pushrod length for this engine by using this technique.

 

[Rmchevelle]

Stock block (Gen VI) and Gen VI square port heads. Fel Pro .039 gasket, ARP rocker studs, stock guide plates. Valves are Ferrea / Rev, supposed to be stock length. Lifters are stock GM Gen VI rollers with stock push rods, and the cam is a stock GM billet roller that was reground by Delta Cams to go from .483 lift up to approximately .575 lift. Rockers are Comp Cams rollers, but I have a set of new Scorpions that I will probably use instead - the Comps have some hours on them. I am going to try the mock up with the Scorpions this evening.

I agree that it seems really strange for the stock push rods to be off that far. The second push rod that I tried was at least .25 shorter than the stock one!

You say the cam was reground. That was a big increase in lift. How much was taken off the base circle in order to get you that much of an increase (nearly .100)? That'll throw your pushrod length off.

 

[RSSS1967]

Delta took off about .054 from the base circle to increase the lift. Remember, you have to factor the 1.7 rocker ratio to translate from gross valve lift to lobe lift. If the base circle is made smaller, I expected to need a LONGER pushrod, not shorter. As I stated in my original post, I was hoping that the material taken off the heads and deck surface would come close to making it a wash and allow me to use my stock push rods.

These are the push rods that GM used on the non adjustible rockers. Could this be the problem?

 

[kirkwoodken]

There is an old saying in my neck of the woods. "Assumption is the mother of screwing up." Don't assume that the factory push rod length and geometry is CORRECT. I discovered this with my first Z/28. One of the first things I checked when I got it was valve clearance. On trying to move the feeler gage, it was being dug into by the edge of the valve stem. Well, that won't work. Adding .080" length gave a pretty even pattern on the top of the stem, so I ordered some pushrods .080" longer than what I had. Remember, it came from the factory that way.

While I had the manifold off, I noticed it was sucking oil around the intake ports. Checking the manifold with a straight edge, it was very warped. I ended up making some smaller gaskets to place over the port areas to add pressure to the leaking parts and that worked. Again, that's the way it came from the factory.

While I had the top off, I figured, why not pull off the front, which I did and advanced the cam 8 degrees. Since the 30-30 cam was made for an injected 327, the factory should have advanced it in a smaller motor.

While the rocker covers were off, I put some Isky hardened keepers in, something the factory should have done with ALL solid lifter engines. But they didn't.

And the biggest mistake of all made by the factory was not putting a scattershield in all solid lifter engined vehicles.

The point of all of this is: don't assume anything. Don't assume the guy who tells you he grinds the valve seat angles to the cube root of the Golden Mean found in the Great Pyramid is smarter than you.

We used to have a loud mouthed engine builder in this area who constantly bragged on how fast he went and how good his engines were. Well, he did go fast, but another not so loud builder was doing big mouth's personal engine work.

I won't describe the way I do push rods because it involves tools I've made, adjustable parallels, dial indicators, nylon plugs that go in the cam tunnels, etc., that make it easier for me, but no more accurate than what others are saying. Not a "better way", but "my way". The results are the same.

Is this a great forum or what?

 

[69-CHVL]

You can take a lifter apart and pack it with JB weld, then reassemble. You really only need one lifter to do the geometry check.

Did you do the test with the lifter adjusted to 0 lash? You have to remeber you will have preload, which will shorten the pushrod especially if you run 1 turn of preload. You may be ok with the stock pushrod.

 

[RSSS1967]

69-Chvl, I have a couple of old lifters that I am going to take apart and stack some washers in. Either that, or I will take an old bold and cut it down to size to act as a spacer.

You are right that I am pretty close with the stock pushrod. I am going to recheck the geometry tonight with the "solid" lifter and the Scorpion rocker arms that I am going to run and see where I am. I borrowed a couple of adjustable push rods from my machinist for the weekend. If I am this close, am I going to cause a lot of wear on the guides and other valvetrain parts? I was hoping to avoid the extra expense of custom push rods, not to mention the turn around time in getting them made. BTW, where is a good source for push rods?

 

[GRN69CHV]

I buy direct from Trend (have every possible pushrod length in stock), Summit has Trick Flow Spec.1'pc pushrods at a decent price per set ( think these are Trend).

 

[GuysMonteSS]

If you want top quality pushrods,you may want to consider contacting Mike "Wolfplace" Lewis.He can get you Manton pushrods,he got me a custom set,and they are very,very nice peices.I am pleased with mine,they are a little shorter than stock length,the Series 5,3/8,0.145 thick wall,they look like they would hold a house up:thumbsup:
Guy

 

[RSSS1967]

If you want top quality pushrods,you may want to consider contacting Mike "Wolfplace" Lewis.He can get you Manton pushrods,he got me a custom set,and they are very,very nice peices.I am pleased with mine,they are a little shorter than stock length,the Series 5,3/8,0.145 thick wall,they look like they would hold a house up:thumbsup:
Guy

What series pushrods did you go with? I am only running .575 lift, so I think a set of 3/8 .065 wall rods would do.

 

[GuysMonteSS]

Mike had suggested the Series 3,but I went with the Series 5,these ones have tool steel tips to match the tool steel adjusters in my Jesel's;

Guy

 

[Tom Mobley]

That Manton stuff is killer, no doubt about that. Spendy though. But, if a guy is running an aggressive roller cam they're worth it.