22 replies to this topic

[jime17]

Hi. This is something I know very little about so please be gentle. I'm just after a few pointers. I know the subject can get very complex.

As I've mentioned here previously I've swapped my auto 998 for a manual 998.

The new engine i have has a cam4180 head and I the block is from a metro.

The info available on metro engine configurations seems a bit sketchy. Guesswork site can't find a great deal of info.

The engine number starts 99H907B.

I believe this means it is a low compression variety although I'm not sure.

My old engine is a 99HE21 which looks to be a HC engine. It also has a cam4180 head.

My initial questions are thus..

1. Most importantly i guess.. Have I id' d my new engine as a low compression correctly?

2. Is the compression ratio determined by the head chamber? Or position of gudgeon pins? Or something else entirely

3. With this in mind, would my hs4 with standard AAC needle from my HC engine be ok on a LC? Would it over or under fuel? Or do the different engines draw the same amount of fuel and air but just compress it less/more?

Any help (in non expert terms ) would be gratefully received...

Thanks

Edited by jime17, 18 December 2018 - 09:24 PM.

[absx2]

99HE is an unleaded spec engine as the E denotes unleaded. The 99H engine is high compression as is the HE as the H is for high compression.

 

The CAM4180 on your unleaded spec engine will have hardened valve seats if it is the original head, the other CAM4180 probably wont. Its a misconception that all CAM4180 heads are unleaded.

 

Your HS4 will be fine on the new motor with the AAC needle and original airbox.

The economy engines where higher compression than normal HC motors at 10.3:1, as all A+ motors had flat top pistons I guess it was done by head chamber volume or piston to deck clearance.

If you have any idea what car your engine came out of it would help to make sure the needle is spot on.

[jime17]

Hi thanks for that. Its very interesting.

See ive read that the H in 99H was the orientation of the engine. Ie transverse. It seems a bit of a minefield.

[absx2]

I can`t say i`m an expert on engine numbers so that could be correct but the later 998 head casting points to an A+ motor that should be yellow if it has not been painted and it will have flat top pistons making it a high compression motor. Another way to check its an A+ is to make sure it has a single bolt holding the distributor on.

All a+ 998 motors are of the high compression variety so the needle will be fine. I`m 100% sure the E denotes unleaded.

I have 3 12A 1275 motors which are of course transverse and a couple of 10l moggy motors that are in line so hopefully someone will come along and enlighten us both :)

 

Edit

Just checked Guessworks and its an A+ 998 Metro with a 3.44:1 diff so defiantly a high comp and the AAC needle is fine on an unmodified engine.

[jime17]

Thanks again.

From what v I've read elsewhere I think the orientation letter might have started a bit after the mini was launched.

I'm sure I also read that the metro 1.0 hle was low compression but can't find it anywhere now.

Thanks for your input so far.

Edit - think I was wrong about HLE. Think it was high compression.

Edited by jime17, 19 December 2018 - 07:56 AM.

[nicklouse]

In your engine numbers the H is the orientation yes early ones did differently as do very late numbers.

[jime17]

In your engine numbers the H is the orientation yes early ones did differently as do very late numbers.

Right. So mine could still either be LC or HC.

I need to establish that first before delving into the real world difference it would make. Ie fueling. Carb needle. Timing.

I'd also add that I did a compression test recently and got approx 160 psi across the board albeit with my ancient hawk tester. Not sure if that gives any clues.

Edited by jime17, 19 December 2018 - 07:10 AM.

[ACDodd]

Just look at the piston crowns, dished or flat top.

Ac

Edited by ACDodd, 19 December 2018 - 07:34 AM.

[jime17]

Just look at the piston crowns, dished or flat top.

Ac

They are flat. As far as I can tell by spying through the plug hole.

Is that the way the factory achieved the lower ratio?

[Spider]

The engine number starts 99H907B.
 

 

 

It is from a 1984 Metro City. CR is 9.6:1

 

The original Carb fitted was a HIF38, the Needle is ADP and it used a 0.090" Jet with a Red Spring

[ACDodd]

No, there are 3 ratios, 8.3:1, 9.6:1 and 10.3:1. The deck height is varied to get the 10.3:1.

You don't want 10.3:1, it's to high for today's fuel. 9.6:1 is optimum.

Ac

[jime17]

Thanks MS. Where did you get that info?

So that would have had dished pistons when new to achieve the lower ratio? Or would The head have been machined to a larger chamber...?

That leads me to my second question then... Sorry.

I've a hs4 with aac and red spring.

I believe the carbs to be similar in size ie. 1.5 inch.... should I be changing the needle or am I over thinking?

[jime17]

No, there are 3 ratios, 8.3:1, 9.6:1 and 10.3:1. The deck height is varied to get the 10.3:1.

You don't want 10.3:1, it's to high for today's fuel. 9.6:1 is optimum.

Ac

Thanks ac. Sorry I'm crossing posts here.

So flat piston = 9.6:1 dished piston = 8.3:1 I'm ignoring 10.3 for now. I'm guessing mine's not that.

[Spider]

Thanks MS. Where did you get that info?

So that would have had dished pistons when new to achieve the lower ratio? Or would The head have been machined to a larger chamber...?

That leads me to my second question then... Sorry.

I've a hs4 with aac and red spring.

I believe the carbs to be similar in size ie. 1.5 inch.... should I be changing the needle or am I over thinking?

 

 

The information comes from Factory Records and Data.

 

Flat Top Pistons.

 

The Needle you have would be a good starting point, but I would suggest having it checked on a Rolling Road, while likely close to what you'll be needing, it is unlikely to be right on the money.

[jime17]

The information comes from Factory Records and Data.

Flat Top Pistons.

The Needle you have would be a good starting point, but I would suggest having it checked on a Rolling Road, while likely close to what you'll be needing, it is unlikely to be right on the money.

Right great info thanks. I'll double check it's not had the piston changed when I put my unleaded head on.

To be honest I'm looking for good enough really. I'm not a purist or fastidious about it. I dont have the money to be that way im afraid...I admire the people that are though... I just want to drive it at weekends. When it's not raining

Hope the varied and sometimes vague questions are ok. When you don't know much about something, but know that its important, its difficult to know which questions I should be asking. That's why we rely on you guys to point us the right way...