Fastest928

Not all blocks are created equal. Regardless of when it was manufacturered ... SOME pre s$ blocks had very thick walls, but often they were off center. some S4 blocks had good walls and were perfectly centered, and on and on. Each block is different. That is what I tried to explain to you Norm.

THEN, you need to make sure that the person who bores the block remians on the centerlines ...otherwise, you cant lucky or lose additional wall thickness.

The two thickest blocks I have ever seen were an 88 and a 85. Massive walls.

Remember, people made the cores ... and they are not perfect.

Marc
DEVEK

figgen

'85 block cleaned up a bit

slate blue

O.K I may have found a suitable candidate for boring, all walls measured with a caliper. Yes I know it could be measured more accurately but we'll get to that later. No wall is thinner than 7.4 mm and the average is 8mm. The thin parts tend to be siamesed. Also I am making some deckplates from a block I will melt down. So I will have plates made from the parent material.

First I will only bore to about 103 mm. Next should anything else be done, fire ringing the block? How much does the ringing cost? Just parts not labour. The block I have is a squirter so I would like to use it.

From my calcs, the thinnest the block will become is 5.7 mm, that figure is conservative. the vast majority of the walls will be 6 to 7mm and more. Have I found a candidate?

I should add that my rod to stroke ratio is a decent 1.84 whereas many strokers are 1.56 to 1.60 as such, leverage on the walls should be minimal.

All input valued.

Vilhuer

It seems wall thickness increases further down in these blocks. Have now measures half dozen different castings and they all have 3-4mm thicker walls at 10cm depth. Average result measured on three different depths is:

1cm deep wall is 8mm
5cm deep wall is 9,5mm
10cm deep wall is 11mm

Normal variation is about +/- 1mm. Water jacket depth is about 11cm on 100mm bore engines.

Has this thickening already been counted for in Reynolds 6.35mm limit? Or is there some more margin to go smaller when wall thickness changes like above? This could make boring little more safe what we think it is.

Measurements were taken with this home made device and slide gage:









Tool looks crude and it is. Despite that it can measure quite accurately. Testing and calibrating it with those four bolt heads gives results under 0.2mm different to direct measurement. When measuring block it's probably at least 0.5mm accurate.

slate blue

I have decided I now have the block I need for this engine I'm building.

Hey Erkka looks interesting and thanks for sharing your idea with us, it is good to know that the block gets thicker rather than thinner.

Also thanks to UTAH Motorsports, they fixed me up with deckplates and ARP head studs, well done guys. We'll be on the road in no time.

Update, don't use deckplates or at least this method, the advise given was bad.

Normy

Mark- you did a GOOD job of explaining that to me, hence my response to this thread, which is what he was asking about in the first place. Thanx for the info!

Sorry, can't make it to Devek Days- I have to go to the simulator.

N!