Valve Spring Installation Height? / 2.7 with E Spec Cams

[combatic]

Hello all, I am building up a 1976 2.7 with E spec Webcams and 9:5:1 90mm JE pistons and Nickies for my street car.

What valve spring installation height spec' should I use for this hot rod mish mash?
Waynes book shows the following:

Valve Spring Heights: Intake / Exhaust
911E 1969-71 35.5 / 35 (+/- .3)
911E 1972/73 34 / 34 (+/- .3)
911S 1975/77 35 / 35.5 (+/- .3)

The 'E' Webcam spec (I am installing) vs. the stock 75-77 2.7 intake/exhaust valve lift
E Webcam: .408 / .390
75-77 cam: .405 / .350

Logic tells me to use the 1969-71 spring height settings b/c the 72-72 cam was retarded by 2deg. I want to make sure the valves are performing correctly and I am not causing any undo wear.

[al lkosmal]

Bryan,
I would match to the 69-71 E-cam spec.

regards,
al

[combatic]

Thanks Al! I am going with the 1969-71 911 E settings to match my 05-082 E Spec' Webcams.

Does anyone know what the seat and nose spring pressures are supposed to be for a 1969-71 911 E? I have been searching and I am not finding those numbers.

In my noob research on the subject the fog lifted a little and I realized that the installed valve spring height is all about seat and nose pressures.

Klassic ATS has some great how to vids and they are specifying the #'s below but I want to cross check for my sanity. They don't specify for which cam. The compression distances below include the cup, springs and retainer and I deduced the distance displacement to be 11.5 and 10.5 which looks like a early solex or S spec. E intake/exhaust lift is 10.28 / 9.98 so I think the seat and nose pressures would be different for an E.

Klassic ATS spec's:

Distance (mm) includes cup, springs & retainer

Intake Seat Pressure 44 PSI @ 42 mm +/- 5%

Intake Full Load Pressure 176.5 PSI @ 30.5 mm +/- 5%

Exhaust Seat pressure 44 PSI @ 42 mm +/- 5%

Exhaust Full load pressure 165.3 PSI @ 31.5 mm +/- 5%

[Neil Harvey]

Not to make this too complicated, some added info you should consider here.

Installed height means absolutely nothing if you do not know the condition of the springs. Even new springs.

Installed height is given, figuring the spring are as new or in the same condition as new. If there are any difference in free lengths, this too will change the seat pressure, open pressure and distance to Coil bind. The pressures involved here are the important part, not the heights.

Another distance that needs to be checked is the distance between the upper side of the valve guide seal and the underside of the retainer at full lift. There has to be some clearance here as well. In your case I'm sure you have plenty and plenty of distance to coil bind. The valve lifts are not very big. Cam position (timing) has nothing to do with this. Advance or retarded timing the valve still opens the same.

The seat pressure obtained by any installed height should always be based upon the valve margin widths. The wider the widths the less the seat pressure needs to be. It is all about sealing. The open pressure is based on the cam profile, engine RPM and valve train weights. Sometimes in boosted engines added pressure is used to aid against the exhaust pressure.

Unless the cam profile you are using has above normal levels of harmonics, I would think that a max seat pressure of 70lbs Intake and 80lbs Exhaust will be ok and probably more than required.

Just be careful about the spring conditions before you install. I recommend you have them tested so that any shimming required gives you equal or near equal pressures. If you have them tested, they need to be compressed using the top Retainer and the Spring Base. Measure your Retainer height first for every valve. Record this as you will need this when calculating the pressures at the Installed height.

For the assembler at home, all of this may be very difficult. I am sure there are hundreds of engines out there running just fine when this was never checked. What I am trying to do here is to give some additional info on what is involved here and if you wanted to be sure what is involved when finding out.

I intend to offer later in the year a "school" showing what is involved, how to assemble and what to check for etc. This will include going through and watching the machining process of the case, heads, etc., including the set up of the valve springs as suggested above.

[combatic]

Neil, thank you for your insights.

I am installing new springs and intend to test each spring set and record how much pressure they create at valve close and full open. If there is variance in pressure for that spring set then I will adjust and record the install height variance to achieve the proper pressure for intake/exhaust valves. I believe this is what you describe in when, "shimming required gives you equal or near equal pressures"

How do you verify clearance of the retainer to the valve seal? Are you using math or are you physically compressing the installed valve stem/spring assembly the distance the cam will create at full open and inspecting? I imagine you will not even be able to see the interference if the spring is compressed.

I will look for coil bind at full spring compression but I don't expect to encounter any as this is an E cam with stock springs/heads/valves from a 2.7.

I appreciate the education. I am trying to learn and understand how our engines work and what affect modification or changes have. I could dumb parts swap using the measurment specs and 'probably' be ok but but I would rather know that my changes are optimal for longevity and performance.

[Neil Harvey]

I’ll post some photos tomorrow on what we use and how.

We use a simple 1” tall spacer ring to measure Retainer height. The dial indicator reads the difference.

With the valve installed, the base, the spacer, the retainer and locks installed, the indicator could read 0.435” so the retainer height would be 1.435”.

The easiest way to measure the distance between the underside of the retainer and the top of the seal is to assemble the above parts except the 1” spacer. Holding the valve against the seat measure between the two parts. It has to be more than the lift. Or depress the valve until the retainer sits on the seal. This travel distance needs to be more than the valve lift.

What ever Hot lash you use, this can be removed from the gross valve lift to give you the final net lift number. l

[Neil Harvey]

This is more about going through the process rather than probably needing to. I’m sure you will ha ve a lot of room for coil bind and seal clearance.

[combatic]

Neil,
The dial indicator method of determining the spring install height is clever and less expensive than buying a special P228 tool. I look forward to your pictures/process. I am going to go 3D print a 1" spacer and mic it to see how accurate/square it is.

Can you remove the valve guide seals without damaging them to get to the shims? I had CGARR refurbish my heads before I knew what cams and engine build I was doing so the heads have never been installed and the valve stem seals are new.

[Neil Harvey]

Originally Posted by combatic

Neil,
The dial indicator method of determining the spring install height is clever and less expensive than buying a special P228 tool. I look forward to your pictures/process. I am going to go 3D print a 1" spacer and mic it to see how accurate/square it is.

Can you remove the valve guide seals without damaging them to get to the shims? I had CGARR refurbish my heads before I knew what cams and engine build I was doing so the heads have never been installed and the valve stem seals are new.

Buy a magnetic holder for the dial gage. A small 4" square piece of steel stock. 3/16" thick is always very useful. That can also be used when doing Cam timing.
Here is a piece we use, not such a great photos though. The only one of many I could find today.

The base shims come with two different hole sizes. If the small holes have been used, then maybe the seals have to be removed to remove them. Seals are not so expensive. I think they could be removed without damage, but I would buy some in case. if the larger hole shims are used, these can be removed without removing the seals.

I'll post more photos of what and how we measure retainer heights.

[Neil Harvey]

This is the fixture/tooling we made years ago to measure the retainer heights. It allows the head to be assembled with both valves and will a simple latch it tips the head each way to measure the valve drop.




Make sure when you test the springs you use the retainer and the base as these set the offset between the inner and outer spring correctly.

[Neil Harvey]

These are screen shots of the software we use to give us the info we need. We can test springs get a visual of the spring under compression against a known standard, then use the spring or discard it. We get pressures, coil bind distances and it also calculates the shimming required once we tell it the installed pressures we require.

Certainly makes our job a lot easier.