[fozwanger]

Would 14:1 CR be too high for a street car and pump gas, n/a?

 

[30psi]

Unless you had very long duration cams then I'd suspect so yes

 

[stueeee]

Unless you had very long duration cams then I'd suspect so yes

And a very light car too.

 

[55chev]

14.1 on pump...... not a chance.:tdown:

 

[Tig]

Theory says you might get away with it if you had a cam with an intake closing event of 90 degrees ABDC, or more. (Effectively 1/2ing the static CR)
Alternatively is there anywhere near you that sells E85?

 

[55chev]

Match the compression ratio to the fuel.if you bleed of cylinder pressure youll have a motor with poor driveability and throttle responce down low,which doesnt make for a good street engine.and thats if it still doesnt pink or detonate.
Why 14.1?

 

[roscobb]

You seem to see a fair number of high spec 'race' engines on Eurodragster with high c/r ratio's like this! - imagine a life on super bollock race fuel.
Its a bit like you filling up the fuel cell of your '55 Marc with that BP 'kin expensive high octane gas - just to go to Ace cafe msl:

 

[fozwanger]

I've aquired a box of BBF parts and in it are some dome top pistons. Done a bit of research and they are Speedway pistons and with a 73cc combustion chamber head will give a cr of 14:1. I'm actually after about 10~:1

That's the reason I ask. Looks like I'm still gonna have to get a set of hypereutectic flat tops

 

[55chev]

10.1 CR is spot on for a street motor on pump,as if you didnt already no.:tup:
Weisco do a good forged of the shelf piston for a BBF @ GOOD MONEY.

 

[fozwanger]

Weisco do a good forged of the shelf piston for a BBF @ GOOD MONEY.[/QUOTE]

I'll have a look. Been quoted £275 for a set that give 10.3:1

 

[chevy2]

10.3-1, thats exactly what i'm running on my s/block chevy,
normally run 38 degrees total timing on super unleaded,
occasionally put in regular 95 octane, havn't suffered any detonation.....yet.

 

[roscobb]

10.3-1, thats exactly what i'm running on my s/block chevy,
normally run 38 degrees total timing on super unleaded,
occasionally put in regular 95 octane, havn't suffered any detonation.....yet.

10.5 c/r on my 489 - 22 degrees initial on crank and 38 degree total, and vacumn advance - never 'pinks' on Shell VPower :tup: dosen't like ANY other gas :tdown: (including the higher octane BP stuff!) and WILL complain :woohoo:

 

[55chev]

Weisco do a good forged of the shelf piston for a BBF @ GOOD MONEY.

I'll have a look. Been quoted £275 for a set that give 10.3:1[/QUOTE]

10.3.1 fine,i ran 11.1 on pump n/a, no problems,i no people running 12.1 but your tunning window narrows a bit.£275 IS A GREAT DEAL.Id go for that.
Best of luck..:tup:

P.S as Ross has just stated SHELL V POWER 97/98 The best fuel .

 

[LUCKY777]

As everyone has already said , 14.1 is a no no , on the street. Never fool yourself in having big compression on the road , enjoy it loads more with less:tup:

 

[Tig]

You can go a bit more with aluminium heads.

 

[v8ian]

Well I must be the odd one out here, Im running about 13.95:1 CR, Street driven in fact driven EVERYWHERE, ! do run it on 99ron, and have run it on 97, but I have never had any problems with, I however run a lot of cam overlap, the 14:1 as stated is static comp, but im guessing the dynamic comp is around 11:1 cylinder pressures are about 260lbs so from memory thats around 11s, The cam I use is a European touring car cam, [Tom Wilkenshaw] ETCC which is limited on its lift to 0.330" at cam which I think is the same as the Rover Twin Plenums, but the cam timimg is pretty wild, but it does work,