Head gasket choice question for modified 944 turbo

[blade7]

looking good Dan...I have zero experience with sleeves ..the engineering side of my Brain would question possible hot spots due to water passage being blocked between the cylinders..I would expect hotspots due to this
Pete

The 2.7 and S2 blocks have siamesed cylinders Pete, ie they are joined together. They are usually reckoned to be superior to 2.5 blocks with the free standing cylinders. Alusil cylinders are also supposed to transfer heat to the water jacket more readily.

 

[Eldavo]

Got them from eBay but seen them on aliexpress- paid about £50-60 IIRC.

Got them all fitted with a new header tank but car is running poorly and in need of some investigation so not had the opportunity to really test them.

Need to get the head off and dive into cylinder 4 as I can see some scoring with my scope. Might end up having to farm it out to EMC for a similar job to yours - will just have to see what happens when I can be bothered to start dismantling it.

 

[Dan944t]

Hi Pete ,
a bit later than intended but I have measured the tab two different ways with a digital depth gauge and also vernier and I’m getting 23.4 would these be accurate enough or would I need to get the manual micrometer out? I’m thinking no but correct me if I’m wrong .

so do I assume It needs .6 of a mm + what ever serdi machined off my block + crush measurement of a gasket to make sure that I make the correct compression and not too close as to induce detonation?

Unfortunately I couldn’t get hold of John today maybe he was out for the day or maybe his on holiday? As I couldn’t get hold of him yesterday iether?

this and a few questions on the pistons rings gaps on my Iasa’s is probably the only area I’m not 100% on and am in need of help to get the measurements right.

Atb
daniel

 

[Dan944t]

Got them from eBay but seen them on aliexpress- paid about £50-60 IIRC.

Got them all fitted with a new header tank but car is running poorly and in need of some investigation so not had the opportunity to really test them.

Need to get the head off and dive into cylinder 4 as I can see some scoring with my scope. Might end up having to farm it out to EMC for a similar job to yours - will just have to see what happens when I can be bothered to start dismantling it.

Thanks eldavo,

i truly hope you dont have to go to go to the extremes that I did as mine was split straight through so to keep the engine numbers the same I had to get them milled out and could have turnt it into a 3ltr and stoked it ect but didn’t want that as I love the way it puts down the power in 2.5 form so went for the same size just .4 larger I think it is.

there is a company in U.K. that can rehone the Allusil properly but I forget who does it. Maybe ask john Mitchell as maybe it was him who I had the discussion with, I don’t think it was John at serdi ?

i love your collection of Porsche’s by the way! Love to see a picture of them all

atb
daniel

 

[PSH]

Hi Pete ,
a bit later than intended but I have measured the tab two different ways with a digital depth gauge and also vernier and I’m getting 23.4 would these be accurate enough or would I need to get the manual micrometer out? I’m thinking no but correct me if I’m wrong .

so do I assume It needs .6 of a mm + what ever serdi machined off my block + crush measurement of a gasket to make sure that I make the correct compression and not too close as to induce detonation?

Unfortunately I couldn’t get hold of John today maybe he was out for the day or maybe his on holiday? As I couldn’t get hold of him yesterday iether?

this and a few questions on the pistons rings gaps on my Iasa’s is probably the only area I’m not 100% on and am in need of help to get the measurements right.

Atb
daniel

Hi Dan

Looks like you may need a HG as thick as mine....23.4 is past Porsche's wear limit of 23.6mm, this isn't a problem (within reason) you just need a thicker gasket...Porsche makes two gaskets...standard is 1.1 and then there's 1.4 for when the head has been machined. 1.4mm is 55 thou, IIRC mine is 60 thou. Don't worry about crush measurement, this is allowed for and the cometic isn't going to crush as much as a standard Porsche gasket.
Re the gap for IASA rings, when I researched this I used a formula I found online that IIRC gives ranges of gap according to car's power and use. I used this to calculate the gap and then phoned IASA's technical department in Argentina to get them to check my figures. I suspect that your car will be close to mine so you may wish to follow suit, I think that the figures are in my build thread, I'm useless at using the search function on this forum...lol
I can't remember the formula but it should be easy enough to find via google, I may have put it in my thread but alas my memory isn't great these days.
I've had no problems with the gaps used but do check for yourself, I wouldn't want to be responsible for any damage to your engine....John may be able to help too?
cheers

Pete

edit...sorry I meant to post this to help......

 

[Dan944t]

Thanks Pete on both things.

regarding my gasket size assuming I need the .6mm / 60 thou to make up the original 24mm spec - one question I’m trying to get my head around... if serdi did in fact take some off my short block to accommodate the new cylinders say .2 am I right in thinking I need to find a mls gasket of 80 thou/.8mm thick then I’m good to go??

Thanks
daniel

 

[PSH]

Hi Dan, I added an image in my last post so you can see Porsche's figures...I would be very surprised if Serdi took anything near 0.2mm off, that nearly 8 thou...assuming the block was in good condition I wouldn't expect them to take off any more than a couple of thou...hopefully less...

Pete

 

[Dan944t]

Cheers Pete, funny enough I found exactly this piece earlier online but becuase it talks about a normal 1.4 gasket It obviously has its set crush and is most probably way safe at that size? But I can’t use that type so I was unsure which to go for.

I was hoping serdi hardly hardly took any off also becuase the block was in great nick when I cleaned it up brought it in to them, I was just using the .2 mm as a way of getting my head round what I’m gonna need to take into concideration.

Right so if i talk to them and they say .10 though at most, can I assume that I only need a .6mm thick/60thou mls cosmetic at 100.5mm bore

just looking at LR site for it and would I be right in saying I need the 101.5m bore .060” mls 5 layer ?

ill add pic below I will cal Lindsey and John tommorow fingers crossed and see what sort of timescale they can get it delivered to me? I’ve not a clue just hope it’s not a month as I’d like to put the head in the engine once I start building it instead of having to wrap it up and wait a month but we’ll see.

https://imgur.com/a/5P5Ol3M

Thanks for you and everyone’s help so far as always ?? I appreciate it allot

atb
daniel

 

[PSH]

hmm..I'm trying to think now...perhaps 100.5 is standard with 101.5 being the first stage bigger?...I told you I have memory issues these days...lol I think mine must be 101.5mm? again it should hopefully be listed in my thread. I do recall my gasket is 60 thou as I wrote it on the cometic sticker on the car. Just found my thread while typing this...gap details here. https://www.porscheclubgb.com/forum/tm.aspx?m=705721&mpage=4
Having found the thread with the spec listed on the first page I can confirm that my pistons are 101mm so the gasket must be 101.5mm

Pete

 

[Dan944t]

Cheers Pete ??
atb
daniel