kens911

Hey I am finally getting around to putting the engine back together I ordered the 964 cam from Steve. The heads were already rebuilt when I got the car and they were already reassembled Does any thing different need to be done about valve spring height? it has the stock 930 cam in before

PorschePhD

34.5 for the intake and 33.5 for the exhaust.

kens911

does that mean changing the springs or the retainers?

PorschePhD

Valve shims will be the adjustment. Just add or remove them as needed.

kens911

ok thanks!! is this any different from the stock setting?

m42racer

Ken,

Do yourself a favor and check the dimensions. Do not assume they are correct. The above information may be correct, for the installed height for these Cams, but check the installation.

If the heads have been rebuilt, you have to check the retainer height and the Seat pressures. Let say the seats were recut, now the Valve will be back into the head further. Maybe the Guides were replaced and the Guide is not exactly in the same position and the top side sticks out further. At the same installed height the bottom of the retainer may contact the top of the guide/ seal.
The springs may be used, and the spring has relaxed a little and the installed height may need to be shortened to obtain the same seat pressure. Now what is the distance to Coil bind? Will the Retainer contact the seal?

What you want is the seat pressures and the open pressures to be what is required to run the RPM's and control the Valve Train parts, and not have Spring Coil bind, or contact between the Retainer and guide. To obtain this, the Installed heights may need to be adjusted. Using the same installed height( as posted) may and often results in different pressures.

Do it right and check the setup. It doesn't take long to check, but the results of not checking will take alot longer.

If you need further info or help, email me and I will tell you what to do.

Surprized somewhat the above information was not included in the earlier posts.

Engine building includes engine assembly, but engine assembly often does not include engine building. There is a difference.

PorschePhD

Yes, I assumed that the information that you are suggesting is already in hand since he just quoted that the heads are newly rebuilt. If he is asking about the height then you can also assume that the question was asked with some degree of knowledge of how to measure it. After all, simply asking for a measurement is not nearly enough information.

Given the heads are new, the seats and guides were done properly and in the right positions and the springs are new that is the measurement you want for a true 964 cam. If done by a good machine shop that information will be with the paper work. Never accept ANYONE’S word for it. Check the specs..

Yes, engine building is far different then assembly. For those of us that build motors we actually know this.

Strokher Racing

How many engines have you built in the last year Stephen?

Eric Hood

PorschePhD

Hmm, I don't know. An average of 4-5 a month. In fact I have 5 I am doing right now. Everything from a 67S to a 996TT. I have another 3 waiting to get on stands. I don't normally have them stacked up, but the average I can do is 4-5 a month. That is a hell of a long month and not average hour days either. There is simply not enough time in the day!!

Strokher Racing

The boards are lucky to have people with tons of experience giving out free info. M42racer by you statements I assume you build tons of engines as well? This is awesome! Nothing like good solid info.

JoeMag

Man, gotta love it when you enter the list and someone just asked the question you were going to ask!

Ken -- fyi... the stock spring height for 930 is 33.5 +/- 0.3mm both intake and exh.

kens911

ok thanks The way i recieved the engine was case together pistons still attached to rods cylinders off heads already rebuilt and put back together. It was appart for a valve job when I purchased the car and the car was disassembled for painting and not reassembled yet. So what I have is boxes and boxes of parts. I have removed the pistons from the rods to pull the rods out and replace the bolts with race ware and also the studs. I got a set of 964 cams from stephan but it's my understanding that the grind is actually slightly different due to a 930 core has to be used to start the grind. I also have a k27 hfs turbo for it . thats where the engine stands at the moment. the Body I have removed the stock front fenders and am prepping the slant nose fenders for paint . I have already welded in the side ducts in the rear and fitted the boxed rockers. so the car will be sent to paint in about a week when the body shop guy can get booth time. so tonights job is to start removing the rods hopefully without dropping any parts into the case. it only has 46 k on the motor so no plans to plit the case

kens911

fortunately when i have trouble identifying any parts I also have an 85 carrera to look at most of the stuff in labled and in bags but not all of it

kens911

oh one more thing the piston tops have a thick coating of carbon on them can i just take it off with an air grinder with a fine wire wheel ? or is there a better way I do NOT want to damage the pistons

m42racer

Actually, the last engine I built was for my shifter Kart.

I am not an engine builder at all. I am a a non professional here, but one who has a keen interest in the building and development of engines and the parts that go into them.

I just look, listen and ask alot of questions. Over time, I have been schooled on how to and how not to do much of this work. When my own engines have been built, I have asked many questions and have learnt alot.