8V Mi16 Bottom End

[dartman 4 1 Cars]

spent over an hour searching the forum and now the time has come...

 

8v head on mi bottom end?

Will the 16v Pistons have too much compression or can they be used with the 8v head?

Is it better to run them with 8v Pistons?

And what modifications does the block need for mounts and belt tensioner?

 

Basically I keep smashing my 8v bottom ends up and thought about using the stronger mi bottom end with my longman 8v head.

Cheers

[davemar 16]

The 16v pistons have the cut-outs for the 4 valves, so probably won't match with the 2 valves of the 8v engine. I'm not entirely sure where the extra strength is in the 16v block.

 

What's dying in your 8v bottom end? Could you have an oil supply problem?

[petert 588]

I've used Mi16 internals and it works fine. CR will be approx 11:1. The only snag with the 16V block is the position of the dipstick. If you're perdantic you can drill the 16V block in the 8V position.

[wicked 103 3 Cars]

. I'm not entirely sure where the extra strength is in the 16v block.

 

 

Oil spray bars for the pistons is only improvement afaik...

[Anthony 1,003]

There's more ribbing on the XU9J4 block compared to the XU5/9 8v block, particularly noticeable on the rear.

 

8v:

 

 

Mi16:

 

 

The holes are all present AFAIK to use the 8v tensioner, engine mount etc on the Mi16 block, but as Petert says the dipstick is in the wrong location and there isn't the hole present in the usual 8v location.

 

The rebuilt 1.9 8v engine I bought last year was rebuilt into an Mi16 block after the original 8v cracked.

[welshpug 1,661]

you could use the XU7 block too, that has a bit more ribs than the MI.

[dartman 4 1 Cars]

Basically it can't handle the power at high revs and the crank flexes too much causing bearings to go and I just thought it would be easier to use an mi bottom end as there built to withstand more power and rev fairly high, just to clarify I can use the mi Pistons? Is the clearance the same as the 8v ones? And everything else is good to go mounting wise etc, just confused about the dipstick, in what way is it in the wrong place?

Cheers for your help

[welshpug 1,661]

Don't rev it so hard then...

[dartman 4 1 Cars]

It's a compition race car hence remaining 8v for class regs otherwise she would be 16v

Think it's just a safer option for an mi bottom end then trying to strengthen the 8v one.

[welshpug 1,661]

Doesn't matter what it is, race rally sprint etc, if you're revving it too hard you're revving it to hard.

 

What exactly is the engine spec parts used etc? what rpm limit and where is peak power?

 

if its a properly specced bottom end there wont be any significant differences between 8c and 16v bar piston crown design, you could use the very same rods, granted the 16v crank is fully counterweighted but I doubt that will help, the TD crank in Colin satchells engine only has 4 though it is made from stronger stuff and gets revved over 8k, that is however in an iron block.

[petert 588]

If you want a tough engine, put a turbo diesel crank in the Mi16 block.

[welshpug 1,661]

think laterally, bore a td to 85mm add some forged 8v pistons and rods and a suitable 8v head.

[allanallen 528 2 Cars]

Anthony, yours was slightly different again as it's a 4x4 block!

[Anthony 1,003]

What's the difference beyond the lower engine mount being missing one of the bolts on the Mi16x4 block?

[Tom Fenton 1,542]

No bolts missing, just required a spacer making, have a look you'll see.

[dcc 855]

Are standard blocks not a direct bolt up to the 4x4 gear then?

[dartman 4 1 Cars]

This is the thing, it's a standard 8v bottom end with an uprated head on it, came off the dyno at 180bhp but instead of making a stronger 8v bottom end which costs a lot of money, I have an mi bottom end and just wondered if I could bolt the head on and go play in time for next race, saves all the ball ache of running in bearings and piston rings etc, as were half way through the season just want to get it out.

[dartman 4 1 Cars]

But that's besides the point as I will be building a fully forged bottom end over winter, I just want to know what's involved in putting an 8v head on a 16v bottom end to get me back racing ASAP,

I know it runs a different mount, but concerned about belt tensioner and piston clearances and now also this dipstick situation.

Many thanks for your help.

[welshpug 1,661]

I don't see a stock compression 1.9 bottom end making 180 bhp, does it have 1.6 pistons on it?

 

how many failures have you had and what exactly is giving way?

 

 

DCC above has a 175 bhp 1.9 8v, its had well over 10k miles of death since I built it, the onloy special bits in the whoile engine isdouble valve springs and a PH4 newman 300 Degree cam.

[dcc 855]

I think it runs arp bolts too.

 

I know of a few making quite peaky power, but as with everything bhp is not a comparable figure really... my '175' made only '113.4' at a local rolling road, where megane 225's were aparently making perfect 223-226.

 

We worked out my cr to be about 11.98-1 in the end, tbh its a bit too snappy for a road car, but good fun.

 

88mm xudt crank, mi16 pistons on 8v or 16v rods, 8v block, you do get more cr using the mi pistons.

 

You could always bolt the head to a gti6 bottom end!

[dartman 4 1 Cars]

The compression comes from a huge head skim it actually peaked on the rollers at 200 so I just knocked off a bit, and it runs a longman head 309 degree cam and twin webers, it lasted 3 laps of brands hatch Indy before bearings let go, admittedly this was more then likely a oil problem but I wouldn't have thought the 8v bottom end would like that power through it for 20 minutes so whilst the engine is out just thinking of quick options to get it running again as said don't have time or money to run in bearings and rings this time in the season.