IcemanG17

8.5 CR is just about perfect for a boosted setup like you are planning..... I also didn't know you could vote more than once.....so I only picked #4....bummer

Lizard928

yes 8.5:1 will allow me to run a much higher amount of boost.

We shall see how much it will take to break the 650rwhp mark once I am done!

I have lined up getting the S4 pistons tomorrow. (need to confirm tolerance group is good) Will be taking the block to the machine shop tomorrow too as I have it all split and ready to go. BTW I wouldn't recommend to anyone to manually remove a block with a crank off an engine stand by yourself. They are alittle heavy!

IcemanG17

http://www.rbracing-rsr.com/compression.htm

Lizard
Hmm...8.5CR would allow you to run around 16psi on street gas with ease.....but I think that would be good for just under 600whp..... If you want 650+ then your probably gonna have to run race gas to get the effective CR over 20+... I would say you'll need 21psi on race gas for 650whp....since Todd is at 675whp...at 7.5CR and 28lbs of boost (not sure of exact boost #)

Walt L

Your pretty quick with the Picture Uploads!
It seems like I was just standing there when you took that Pic of the Cylinder Wall, must have a plastic covered computer hiding in that garage full of parts and tools so you don't have to wash the oil off your hands.
I show up to pick up some parts and he puts me to work!! 15 minutes later I'm covered in oil and grime, good thing I was driving the wife's vehicle. ; )
Should have set up a video cam in there, I would have liked to see you remove that engine from the stand all by yourself, for the sheer entertainment value of course!!

Lizard928

Brian,

There are a few differenced between what Todd is doing and what I am.
As well, look at Kuhn's TT setup he is seeing almost 600RWHP on stock S4 internals and 12PSI of boost.
Plus if you remember what Erik had posted you would know that Todd is seeing his spark being blown out at those levels and there is ALOT more power on the table for him.

My plan was actually to run 15PSI on the stock 10:1 CR motor. Using the aftermarket engine management it would be possible. But I would have been nearing the absolute limit of cylinder pressures and would have had to use that PSI not all the time as I may have experianced head lifting.
With 8.5:1 CR I will have no issues breaching the 20PSI range, and I wont be anywhere close to the same cyl pressures.
As well I am going to be running drysump and a custom intake manifold, both of these will give a nice increase in HP. The general rule from all the research I have done is around 15% gain. Though I doubt that it is a linear line (just like drivetrain loss).

Walt, thanks for the bit of assistance it doesnt take much to wash the hands and run upstairs. I am not going to set up a cam, my garage is way to messy for that right now
Let me know when you get that fan and rad in then you can pop round and pay for them so that I can keep up with these projects

Lizard928

Brian, another thing to note,
This engine put down (as it is now) 310RWHP and 320FT lbs with a absolutely crap exhaust, stock intake manifold and it was sucking hot air as the air filter assembly was destroyed so I had no intake tubes running down the side.

Walt L

OOPS, PM sent

Lizard928

slate blue

Colin if block isn't damaged you could get it lapped, that cleans them up. Also if the block isn't good anymore, how thick are the walls? They look around 7 mm thick as a guess. Normally you would be after 8 mm. You have a much better call on this of course.

Greg

SeanR

I picked 3 and ........well..........number 4 of course.

I love the 928 forum.

Lizard928

Greg,
I will measure the wall thickness.
However the damage doesnt appear to be that deep, I may be able to rehone it but I would definetly need a new piston as the one that is in there will be slightly damaged.

Lizard928

Well I took the lower cradle to a local shop and am having them open up the passages in the girdle.

I did notice something interesting on my spare engine though.
Once seperated it was fairly obvious that there was some probably very minor seperation from the girdle to the block. What I mean is that the girdle was almost floating away from the block some! The most apparent location for this seperation was on the second main, which is the one which feeds the #2/6 bearing!

Brian (iceman) if you read this could you get pics of your cradle in this area to see if it had had some floating there too?

I am on my way to get the measurement right now Greg.

Lizard928

Greg,

For your point of interest, all of the cylinders are around 7.94+mm on the engine which came out and are the thinnest I could find on my spare (which is being rebuilt) was 7.99, most are over 8mm

Lizard928

Well I got the heads cleaned up today as well as getting the engine up onto a stand, pulled off the clutch and found a way to prop it open so install should be easy!
I also pulled off the scraper setup and then popped the cyl #6 piston out.
So I figured I would update this.
It appears to me as though the coating on the piston simply wore off. The rings are all fine with no real damage to them. It is just the piston skirt on the one side which is all scratched, along with the corresponding cylinder wall. Then as I was removing it I dropped it and broke a tab off the skirt. good thing the piston was practically garbage to begin with!

I am also curious if anyone has used yamabond/hondabond 4 for sealing the two sections of the block together or to stick with the factory product?

the flyin' scotsman

Your gluing the crank together with Yamabond?

Don't believe there's any diff.

As I recall from my m/cycle racing days the 'goop' was made by one company then branded.