compression ratio thoughts suggestions

[Chico]

Hi all


Im just about to order some barrel shims, and wanted to see what people thoughts were on compression ,
I was going for 7. something but can easily have anything from 7.3 ( 1.5mm shims) to 8.3 (no shims)

so 7.3 , 7.6 , 7.8, 8.1 , 8.3 ?

Its a w100 cam low revving ( under 5k rpm) 1776

Most of my journeys are short 20 miles a day or less but a few hills , normally have a mower and a few tools/ fence posts in the back , not looking for speed just a little more up hill oomph
not changing gearing at this time either .

Is lower better ? or do i hedge my bets and go in the middle ?

Greatfull for any advice

Chico

 

[megaaircooledvw]

What dizzy ,carbs.

 

[Chico]

Hi Sorry

svda electronic ( accuspark at mo , might change to petronix or 123 when funds allow

twin 40 idf webers

Thanks
Chico

 

[megaaircooledvw]

For me I would go for 8.5 to 1.

 

[Chico]

Ok

Thats higher than i thought !

First Build , so was thinking lower better ( between 7 and 8)

could you explain your reasoning , remembering I'm new to this !

Thanks

Chico

 

[Chico]

between 7 and 8 ( to sure where the smilie cam from )

 

[megaaircooledvw]

Stock is 7.5.

 

[atafonso]

You want a dynamic compression to be around 7.3-7.5:1. So your STATIC compression will be higher than that. To calculate dynamic compression, use a calculator from Wallace, check on Google , and put the details including the degrees your cam closes the intake valves ABDC. I normally use static of around 8:1 on a W100 to achieve 7.3:1 dynamic.
Abel

 

[K@rlos]

Ok

Thats higher than i thought !

First Build , so was thinking lower better ( between 7 and 8)

could you explain your reasoning , remembering I'm new to this !

Thanks

Chico

More compression means more power and torque BUT start going really high, and you start getting into heat and clearance issues. 8.5 is a senseable compression for a mild engine.

 

[Trikky2]

Agreed. 8.5 works well.