Compression ratios

[bitwrx]

Evening all,

Along the lines of my compression volumes post the other day:

What CR should I be aiming for? When do I have to start running on 98 octane? How much do I have to change the ign timing?

Standard MG Metro is 10.5. I think.

Current spec is:
Rebuilt MG Metro.
Regrind, new bearings etc.
Centre main strap
ARP con rod and head bolts
11 stud head.
Ported and polished head on standard MG valves.
Standard pistons and rods.

All running through:
Minispares SC gear kit
X pin diff

Don't know how much relevance any of that had, but some of it may have a bearing.


Again, I shall be expecting an answer from each of you.

Ta,
Charlie

[Mr2Mike]

If you are running the stock MG Metro cam then I wouldn't take it any higher to be honest.

[woooorrb!]

I'd get a 286 cam and 1.5x2 Su on there as quickly as possible and leave it at that. Any less and you are doing your gearbox no favours for what it can do.

[Snake the Sniper]

As said, if you've gone to the expense of a SC gear kit, you may as well use it by sticking a hairy(er) cam in. Which will require different carb(s) and a different advance curve.

[bitwrx]

Indeed. A little under cammed/carbed, but student budgets don't agree with doing everything in one hit. So the plan was to start at the bottom and work my way up.

Plan is to get the Megajolt working on this build, then cam later when I have a bit more money for that and some other shiny bits. Should be ok as long as nothing falls apart and goes munching through the box.

Looks like I'll stick with standard unless anyone's got a convincing argument any other way?

Thanks so far though,
Charlie