2270 Engine Build - Need Help w/ Valve Geometry!

[Bsherrard]

Greetings all Type 4 experts. I have reached the point in my engine build where I am setting up the valve geometry with an adjustable pushrod to establish the pushrod length. I am building a 2270 Type 4 that is from and going into a 1976 Porsche 912E. The specs on the engine are as follows:

Cylinders - 96mm (original Mahle bored to 96mm)
Crankshaft - 78mm Stroker CTWD T1RJ
Pistons - Custom JE
Camshaft - Webcam 9500 1.065 B/C 104 L/C Camshaft
Heads - Hoffman RS+ Cylinder Heads w/ valve upgrade
Lifters - Solid (Parkerized)
Pushrods - Manton Chromoly - custom length (if I figure this out!)
Rockers - 914 1.7 w/ 911 swivel feet adjusters and solid spacers

I have been following "Jakes ultimate valvetrain geometry article" to try to establish my pushrod lengths but am at a complete loss - no matter what shims I use (I have tried everything from no shims to .20 of shims) or what length I set my adjustable pushrod at I simply cannot get valve lift less than .520.

I have been able to get a good setup with a valve lift of .520 and excellent alignment of the adjusters at half lift BUT...

My cam card indicates 0.50 for both intake and exhaust. The Raby article indicates there is a 5% allowance of this value which would put the target range for lift at 0.475 - 0.525. The information from Hoffman for my heads indicates a recommended maximum lift of .515.
So while my lift at .520 is within the 5% allowance, it is above the maximum lift recommendation for the heads.

My questions are as follows:

1. Any recommendations for what I may be doing incorrectly or can change to reduce my valve lift closer to the .500 target for the cam card and within the .515 limit of the heads?
2. Should I expect that I will have to custom measure / cut each pushrod individually on a build like this?
3. What kind of variation should you get in the lift when you adjust the pushrod? it doesn't really seem to make much of a difference in the lift (only +/- .05") no matter how much longer or shorter I make it.
4. Any other pearls of wisdom anyone would like to impart as I hopefully finalize the build.

Any help would be greatly appreciated!

Here is a link to my original post to this forum when I started this build: viewtopic.php?f=1&t=150041&hilit=lift
Yeah - I know...a long time ago.. what can I say...Work / Family / more work / more family...you know how it goes.
Brook Sherrard

[cgates30]

Brock,
I went through this a couple of years ago when I rebuilt my engine, and never felt like was able to make significant changes by shimming, etc. I ended up "going" with what I had, so I'm sure it wasn't optimal. My engine leaked oil (first engine build for me) and then one of the EGR injector ports that connect to the heads "blew" out. I'm currently disassembling the engine again so I can get the head repaired and then reseal the engine case. I'll follow your thread to see if I can learn how to do the VTG. By the way, do you have a link you can send/share for how to set the geometry?
Thanks,
Craig

[Bsherrard]

Craig
Try this link
https://web.archive.org/web/20120223161 ... d.php?t=25

We’re you running fuel injection or were you running carbs and had the ports plugged?

Also I found your post when you were doing your VTG and the comments about checking the actual rocker arm ratios. I am going to look into that and see if that is part of the problem.

Thanks for the information on your travails.
Brook

[cgates30]

I am running fuel injection and the engine is basically stock aside from the 96mm cylinders. While I do have the entire smog component set, I decided to plug those ports with short bolts, thinking I could ditch the EGR system. I'm not sure if plugging with bolts was a good idea or if that was related to my blow out problem.

[patto]

Hi Brock,

Have you clearanced your rockers to fit the swivel feet? hopefully the link works below or look up bugguy67 he modifies the rockers so you can use stock geometry

https://www.thesamba.com/vw/classifieds ... id=2130116

[wreck]

Something to take into account is the rockers are not 1.3 ratio . research I did came up with an average of 1.32 on the intake and 1.25 on the exhaust . As long as the springs don't bind and you have clearance from the end of the guide to the keepers just concentrate getting the lifts close on all 4 cylinders and the rocker perpendicular to the valve at 1/2 lift .

[Bsherrard]

Patto - yes I did clearance the rocker arm for the swivel feet and have no issues with the ability to have adjustment room when I am at the .520 lift with proper alignment at half lift.

Wrek - I understand about the spring bind but not sure what you mean about clearance from end of guide to keeper? Also are you saying that as long as I do a play dough test and have clearance from valve to piston the extra lift is not a problem?

Thanks

Brook

[Bsherrard]

Patto - yes I did clearance the rocker arm for the swivel feet and have no issues with the ability to have adjustment room when I am at the .520 lift with proper alignment at half lift.

Wrek - I understand about the spring bind but not sure what you mean about clearance from end of guide to keeper?
When you say get all 4 cylinders the same I assume you mean all 4 intake valves the same and all 4 exhaust valves the same not all 8 valves the same?
Also are you saying that as long as I do a play dough test and have clearance from valve to piston the extra lift is not a problem?

Thanks

Brook

[wreck]

Brook I think .500 thou lift is getting close for the valve spring keeper and collets to impact the valve guide on a stock head . Ham heads have most likely been set up for more lift and stock , but it still must be checked . If you use very light springs ( the springs on the stock rocker shafts are good for this) when setting the geometry . at full lift you should still be able to depress the valve more before the keeper and collets hit the end of the guide . at least .040 . If you don't have clearance the tops of the guides can be clearanced a little .
yes the 4 intakes the same and the 4 exhausts the same . on a non race engine that you are not trying to get the last 1 hp out of this doesn't have to be to the last thou . my 2.6 has a 10 thou spread on the intakes , from .530 to .540 and about the same on the exhaust .500 to .510 . It runs very smooth .A lot of people don't check each valve . And yes to get them all even you would most likely need 8 different length push rods .

[Clatter]

OK,

This is a deep subject,
And a lot of time words written about it make things worse

Jake's tutorial does a rather odd thing that most don't, in that he continues to adjust the length of the pushrod shorter, or longer, then towards ideal, and uses the fact that ideal geometry, given it's 'squareness' gives you max lift.
Said another way, too long or too short of a pushrod length will give less than full lift.

This is a good practical way to ensure that your geometry is correct - max lift comes from good geometry.

What I am getting from your question here,
Is that you are trying to limit your lift by altering geometry.
That would be a bad idea IMHO, because you want the right geometry.

If your heads won't deal with the lift, you need to address that in other ways,
Not by doing up some bad geometry.

Make sense?
I might have you wrong..

[Clatter]

Factory rockers are all over the place.
Their overall ratio will vary between the same intakes/exhausts a lot.
You will see variation between intakes and exhaust as 'Wreck' said; the intakes lift a lot more than exhausts.
Here was measurement of all 8 during the 'cheap junk' build in my sig.


So don't let yourself get driven nuts my variation in lift..

I do like to try and make all pushrods the same length,
Do your measurements to set ideal pushrod length in average for all valves,
Then you don't have to keep track of which pushrod goes in which hole.

Sometimes I end up with four for one side and four for another,
But only on a type 1 where the specs are looser..

[Clatter]

As for room at total lift,
You'll have to pop the keepers out and look at the setup disassembled.


Try and measure 'installed height'.
Assemble the retainer and keepers without the spring.
See if you can't measure how big the spring will be when installed; valve fully closed.
This one can be tricky.
They make special indicators for this, but always seem to be for big Chevy size springs.
A caliper can get you close if you hold your mouth right.

Then go smash the spring fully compressed in a vise, and measure it's overall length.

The difference between the numbers is your 'clearance to bind'.

Was always taught you want .060"..
Some will go .040",
And most have much larger numbers because they don't shim the springs tight.

And that brings the question of how thick the shims are under the springs...
Maybe that's your fix right there; thinner shims?

This is a deep subject.

[Clatter]

Clearance from retainer to guide:

You'll need a light checking spring in place,
And your indicator on the retainer to show valve lift/travel.

Compress the spring until you have your largest lift number,
Then measure how much more room you have until the bottom of the retainer touches the top of the valve guide.

Again, 060" is a good target number.
You want a bit of room for valve float on a missed shift,
But as much support for the valve stem by the guide as you can.

[Bsherrard]

Wreck & Clatter - much good information to digest here but I definitely feel like I have a better grip on what I am doing now.
Many thanks!!
Brook

[Bsherrard]

Clatter
When you say thinner shims under the springs - am I correct that this would give more clearance to bind allowing for more lift than the original limitation of the head design?
Brook