engine assembly problem

[badsix]

[Jack Staggs]

I apologize if I have offended you in any way. It was not my intention. I can only respond to what you have written.

[356JAGER]

JD,
The following would likely be of great help:
http://www.precisionmatters.biz/pdf/compression-ratio.pdf

http://porsche356enginebuild.blogspot.com/search?updated-min=2009-01-01T00:00:00Z&updated-max=2010-01-01T00:00:00Z&max-results=5

A copy of Duane Spencer's Complete Porsche 912 Guide. The section on
engine assembly is also helpful.

There are many great sources of information for these engines, Jack being one of them. They aren't that complex, but like most things, the devil is in the details. Hope this helps.

Cheers,
Joel

[Meissen540]

Mr. Six,
May I shed some light on the exchange as a casual by stander.
I believe Jack was assuming you did NOT assemble the top end to be able to check the actual valve clearance. Measuring parts and adding the dimensions up will not work in this case. I believe your jumping from a binding issue with the crank in your discussion, to valve/piston clearances was a bit confusing. Jack was apparently responding to your writings, which the sequence of is a bit confusing, and providing sound advice to save you some $$$.

Like Mr. Szabo I find your blown I-6 interesting. I once toyed with a Chevy 292. A strange beast in the Chevy world as all parts were unique to that engine only. Zero interchange with a SBC. It was clearly designed as a very Heavy Duty engine. I was told it was the engine of choice for the dirt trackers in the 6 cyl. division. A very stout powerful I-6.

My 2 cents
Tom

[badsix]

I apologize if I have offended you in any way. It was not my intention. I can only respond to what you have written.

aw don't let it bother you Jack we'll get over it i'm sure.
I really do appreciate your assistance.
thanks Jay D.

[Jack Staggs]

OK, fair enough . Were you able to assemble the case with crank and cam installed, with no binding, turning it through several revolutions, all the while checking end float of the crank? You should have at least 1.5 mm or so without the flywheel attached. Much less can cause problems during later shimming of the flywheel. I am pleased to hear that you had the piston crown angle corrected to 22*. You seemed a bit reluctant here:
http://www.abcgt.com/forum/4-356-Forum/15705-356-compression-ratio.html#15705
Did Walt also cut the exhaust valve pockets deeper? I often see contact witness marks on the piston here when later style pistons are fitted. On A/B heads, the valves protrude into the combustion chambers further than C/912 heads, which NPR pistons (and other 1720cc pistons) were designed for. The problem is found on the TDC exhaust stroke, when the exhaust valve is still slightly open at piston TDC. That's why you must put the lower end all together first, then fit the P/C, heads, and valve train to check valve to piston clearance. 60cc volume on the head is a good #. C/912 heads have a much smaller#. If the pockets have been cut, you may be able to install the cyls with NO shim underneath, achieving a static compression ratio of 8.7 or so to 1, a pretty low number for these engines. 8.2 is a bit anemic. After all, it's a Sports Car. I have a notation about negative dome value somewhere (x value according to Harry) for NPR modified to MY spec. It may be close enough for your calculations. I will try to find it, if you like. You will likely have to shim the rocker arms out a bit to get proper adjustment. VW / 356 link pin shims are a good fit here. 1 or 2 will under each rocker will probably be ok. Rocker angularity is a concern to some, but for street cars, it seems to be OK, IMHO.

JD, I have no question about your mechanical ability. If I were to attempt to install a blower on ANY engine, I would be completely in the dark! When I said " you don't know what you are doing" I should have said "on these quirky engines". It was not meant to be insulting. I apologize once again.
On the other hand, you came asking questions about how to do. We are doing the best we can to help.
Thanks.

[badsix]

OK, no I did not have Walt cut the valve pockets. I think we kind of came to think they would be ok. anyway case is together with cam and crank and they turn nice and free with about 1.5 or a little more endplay. I used just the 6 main case nuts torqued to 30#. then cylinders and pistons with out rings, taped solder to the valve pocket area. installed heads and torqued to 30#. valve adjustment at 0 lash and no cylinder base gasket. made one revolution and checked the solder it was about .063 or 1.53 mm. with the .23 to .25 base gasket installed I should have 1.75 mm total is that going to be ok. when I did this I forgot to check the area that was cut to 22*for head clearance. when I get some of these thing cleared up i'm going to go back through do it all over again just to double check everything.
thanks Jack your the best Jay D.

[Jack Staggs]

Well, I checked the spec I have for 86 pistons for MY 22* mod, and show an x value of -5.21. Yours may be close to that. The dome value you posted in Compression does not exist in my Secrets book. The closest # to that is for a stock S90, not even close to what you are using. My best GUESS from calculations here is to use two copper shims under the barrel to give a static compression of less than 8.8/1 + or -?? Your # s don't aways jive.

[badsix]

Jack here's what I did. i machined a 1" piece of plexi-glass with a hole in it apr. 19mm deep the dia. of the id of my cylinders. then I put a step on the out side this is so it fits over the cylinder about 3-4mm just like the head would. I then machined a plug that fits in this step were the cylinder in going to go. with the plug in place I filled the cavity and recorded the amount 65cc. then i rotated the piston to tdc checked with a dial gauge. now I put the pexi-glass cavity down ( the one I measured before AT 65CC )on top of the cylinder ( cylinder has 1 base gasket ).I then took another measurement 58cc, the difference between the two was 7cc. that 7cc should be the volume of the top of the piston. is correct or did I miss something.? actually this should calculate deck height and piston volume or i'm I dreaming
thanks Jay D.

[356JAGER]

JD,
I posted this earlier. I think if you read it you'll find the answers you're looking for including piston dome volumes.

www.precisionmatters.biz/pdf/compression-ratio.pdf

Simple kit to CC your heads is found here.

http://vwparts.aircooled.net/Cylinder-Head-CC-Measuring-Kit-Type-1-p/head-cc-measuring-kit.htm