Core Plug Hole Diameter
Turbo Mini Forums

Hey Guy, just had a quick search but couldn't find anything, can anyone tell me the diameter of the core plug holes, im just drawing up some adapters for dry decking.

1972 998 TURBO SLEEPER

from memory its about 33.30mm i bought some 33.7mm cds with a 3mm wall to turn down for mine...

also coincidently seems to be perfect for a good manifold

Edited by Brett on 3rd Nov, 2009.

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Cheers Brett, im going to have some made out of aluminium, how did you mount yours to the block? im planning on having a flange and four bolt holes

1972 998 TURBO SLEEPER

For the cost of the materials and the machining i was quoted £60 to have some made at a local machine shop.

Fast Carl on the other hand sorted me some out for a very very good price, so i would send him a pm.

cheers, but my technical director is going to run some off in his lathe for me

1972 998 TURBO SLEEPER

Ah can't beat knowing somebody with the tools for the job.

i have not built mine yet but i intend on running a small flange around the outside (welded) and 4 m4/m5 cap heads, similar to the med kit but in steel and diy with my limited tools :)

i intend on testing it with a very slight taper to try get an interference fit

i need to buy a lathe :'(

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Yes i moved to the darkside

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that look great Brett, exactly my intension. what are you using to plug the water holes up with?, i was planning to use some tapered brass plugs.

1972 998 TURBO SLEEPER

ahh sorry lol didnt mean to miss lead you thats the med ones i have some m8 grub screws for the small water ways (there about 5-6 mm std)
and for the big ones about 12mm i have an m14 tap and some bolts i am going to cut down, the measurements of the waterways are a little vague because of the differences between all the holes lol

i was advised by a few guys on here bolts grub screws and lock tight are more than enough

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a couple of things to consider also the water port interferers with the engine steady and fitting the same size port into the head leaves very little meat in the side, i bought some 25mm ish tube also to make the head port so i will either have to step the size down for the silicone transfer pipe or slightly change the design

iirc the diameter of the rest of the coolant system is less than that anyway so should cause no more restriction

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lol thats cool it did look really nicely machined lol. i was wondering about tapping and using studs, i was just unsure about the CTE mismatch between steel and the iron block. i was considering brass and it expands faster than iron and ill only ever force itself tighter into the holes.

1972 998 TURBO SLEEPER

they way im doing it the plugged holes would easily be able to be removed again for no reason really but i wont need to have my head and block skimmed after as i can screw them into the block a little further than flush,( dont know how to describe :()
i think for the application its being used to hold back water at sub 1 bar pressure the expansion rate wont be too bad with the locktight on top of that im hoping, well other people havnt reported problems.

it would be like the expansion differences with the block and the cylinder head studs
if the brass inserts work out not too much more expensive and the head and block skim is on the cards anyway then i dont see any other drawbacks of using brass over steel
for me cost played the biggest part i got every thing to plug the waterways for less than a tenner

Yes i moved to the darkside

Instagram @jdm_brett

Less than a tenner nice one. your method sounds like a perfectly sensible method. im really going to consider it. your right about the CTE mismatch between the block and the head studs. cost is also playing a huge part for me typically. i cant wait to see it when your done. thanks for your help

1972 998 TURBO SLEEPER

I blocked up the block instead of the head, seemed to work well! :)

If you dont block up the holes in the head as well, what is the point?

This is how i did mine, the adapter is one of Fast Carls, and its 32mm OD And the only thing sealing it to the block is an O ring

Edited by Sprocket on 8th Nov, 2009.