Mi Head On An 8valve Block. How Much Work Is Involved?

[Anton green 12 1 Cars]

I have heard of people putting MI heads on 8v blocks before when they werent allowed to change the whole engine due to some motorsport regulation.

 

How much work would have to be done to get vital fluids flowing thru the head, or even to bolt the head to the block?

 

Would this result in a good strong engine?

[petert 587]

It bolts on easily. The biggest drama is the top engine mount. It's not unsolvable, just a bit of work. Try to put a 16V mount on an 8V block and you'll see what I mean.

[M3Evo 0]

Don't you need to drill the side of the block for the second tensionser that the 16v has too?

[jonD6B 0]

Which regs.? As the blocks are almost identical except for what has been pointed out.

[petert 587]

Don't you need to drill the side of the block for the second tensionser that the 16v has too?

 

No, it's already drilled and tapped, used as a mounting point for the cam belt cover.

 

The other issue is the dip stick location.

[jonD6B 0]

Is there any consideration that needs to be payed to the fact that the MI pistons have extra cut outs for the extra valves? i.e. Maximum skimming depth (compression ratio gains ).

[jochem 0]

Is there any consideration that needs to be payed to the fact that the MI pistons have extra cut outs for the extra valves? i.e. Maximum skimming depth (compression ratio gains ).

 

I had this on my test setup with a 2L 8v na block and mi16 head. Pistons and valves collide.

[petert 587]

Naturally you'd have to change the rods and the pistons. You could leave the crank and the oil pump.

 

So it becomes a pointless exercise, unless you absolutely have to have an 8V block.

Edited April 21, 2006 by petert

[jonD6B 0]

So really it's just not worth doing time wise and financially. The MI liners are also different iirc, not that this should matter.

[geoffmslater 0]

I am interested in this also, as i have mi16 pistons and liners and 8v block and a mi16 head, and if i could make this into a 16v beast for my second 309 gti it would be terrific. The cost of buying (if i can find one in Nz) a mi16 block or s16 is prohibitively high.

 

Therefore the only real issue is a new top mount is required to be fabricated?

[petert 587]

Therefore the only real issue is a new top mount is required to be fabricated?

 

The 16V mount has 5 bolts, but only 3 can be used as is. You can drill and tap the 4th into the block, but the 5th is an issue. So if you're happy hanging the engine off 4 bolts rather than 5, you have no problems. I suggest you acquire a 16V mount and have a look. Certainly a custom mount is a good alternative.

 

You also won't have oil squirters. Whilst this normally isn't an issue, it's been my experience that Mi16 pistons will pickup on the liners if the standard piston/bore clearances are used without squirters and the engine is worked hard. I'd highly recommend you increase to at least 0.002" clearance.

 

You'll also need to make a custom dipstick holder.

[geoffmslater 0]

Thanks Peter,

 

Custom mount is easy enough for me, Dipstick is likely to be solvable.

 

The oil squirters are a bit of a shame to not have, you mention the concern is pickup for pistons on cylinders, is this their only reason for existing in mi16.

I am not sure but know mi16 rods are floating?(unsure if 8v is same) and wondered if the oil squirters are to help lubricate grudgeon pins?

 

This may be a real option for me to look at in future.

[petert 587]

Mi16 and S16 pistons seem to be in far better condition than 8V pistons, given an engine of similar age. You rarely see an Mi16 piston that's picked up but 205 pistons do it all the time.

[Anton green 12 1 Cars]

I had this on my test setup with a 2L 8v na block and mi16 head. Pistons and valves collide.

Hi all. Thanks for all the replies, I have sketchy internet access at the moment so couldnt get back on topic earlier. I am weighing up the idea of building an engine using a 16valve head on a low compression 1905cc 205 engine (cti). I'd be doing this over quite a long time period as I dont have too much experience with engines so Id half be learning as I went. The idea is to put together an engine with a quite high output whilst retaining reliability. The low compression engine would be used to allow a turbo to be used (low blow).

This would be a project for myself and a couple of friends, eventually being put into a pug.

 

Does someone know or have access to info which would tell me if the 16 valves would hit pistons on a low compression lump?

Edited April 24, 2006 by Anton green

[petert 587]

Hi all. Thanks for all the replies, I have sketchy internet access at the moment so couldnt get back on topic earlier. I am weighing up the idea of building an engine using a 16valve head on a low compression 1905cc 205 engine (cti). I'd be doing this over quite a long time period as I dont have too much experience with engines so Id half be learning as I went. The idea is to put together an engine with a quite high output whilst retaining reliability. The low compression engine would be used to allow a turbo to be used (low blow).

This would be a project for myself and a couple of friends, eventually being put into a pug.

 

Does someone know or have access to info which would tell me if the 16 valves would hit pistons on a low compression lump?

 

Yes, the valves will still hit the pistons. The DFZ pistons actually sit very high, with zero deck height and have a small 9cc dish. The low CR comes from the head, with a 49cc chamber.

 

The 8V pistons are too big and ugly anyway. They weigh approx. 120g more than an Mi16 piston. They do make good paper weights however.

[Anton green 12 1 Cars]

Yes, the valves will still hit the pistons. The DFZ pistons actually sit very high, with zero deck height and have a small 9cc dish. The low CR comes from the head, with a 49cc chamber.

 

The 8V pistons are too big and ugly anyway. They weigh approx. 120g more than an Mi16 piston. They do make good paper weights however.

Righty. I'll have a look around my Mi engine at the weekend and take things from there..

[veloce200 3]

Mi16 and S16 pistons seem to be in far better condition than 8V pistons, given an engine of similar age. You rarely see an Mi16 piston that's picked up but 205 pistons do it all the time.

do you think the MI16 piston is the right choice for a highcompression 8v motor Peter? Any thoughts on the flat top pistons - same story? (sorry for the hijack Anton!)

[Pug_101 0]

Can the 2.0L Mi16 head be put on the 8V block?

I know that the xu10 head fits and seals, so I am guess it's the same with the Mi16 2.0L head.

If it can are all other concerns the same as already mentioned?

Thanks

[petert 587]

do you think the MI16 piston is the right choice for a highcompression 8v motor Peter? Any thoughts on the flat top pistons - same story? (sorry for the hijack Anton!)

 

I think they're great. They're flat top, light and full floating. You loose a few cc's with the valve reliefs but that's really minute.

 

The 2.0L Mi16 head is almost identical to th 1.9L, and thus won't fit on an 8V block for the same reasons.

[veloce200 3]

I think they're great. They're flat top, light and full floating. You loose a few cc's with the valve reliefs but that's really minute.

 

i guess the key question is do they fit an 8v rod?

[petert 587]

i guess the key question is do they fit an 8v rod?

 

No. You either have to get the 8V rod bushed to 22mm, or use a 16V rod. Rod bushing isn't very expensive, and considering the 8V and 16V rods are otherwise identical, a good solution.

[veloce200 3]

No. You either have to get the 8V rod bushed to 22mm, or use a 16V rod. Rod bushing isn't very expensive, and considering the 8V and 16V rods are otherwise identical, a good solution.

 

thanks. TBH the way business is going the Pug won't do a single sprint this year let alone get the engine rebuilt.I'm thinking of applying for registered charity status for Project Pug!

 

My next sprint was supposed to test tyres but I need clutch, wheel bearings, mot, insurance, and of course tyres - about £900 to do 9 laps! Maybe next season !