Measuring Compression Ratio - pushrod length impact with 0.080 gasket??

aintgotitmusthaveit Officially Full-On Dubber

295 posts · joined Jun 2006 · 11 May 2009, 11:41 pm

#711793

HI Y'all
Nearly finished my supercharger set up and about to try it out .
http://forums.aussieveedubbers.com/viewtopic.php?tid=75111
I am concerned however that the current engine may have too high a compression ratio for boosting.
Has anyone measured compression ratios. If so how does one do it?
Came across this
http://www.discovery-carhire.com.au/widget/compcalc_help.html
But how does one measure things like combustion chambe volume??

Anyway I am assuming my compression is likely to be high. My current 0-100 times are mid to high 7s and the dynoliscious program estimates I have roughly 100hp on the assumption the replics weighs about 850kgs with me in it.
Specs for the engine are meant to be this :
http://forums.aussieveedubbers.com/viewtopic.php?tid=61971&page=1#pid586478
Except it did not come with electronic ignition or 44 idfs (std points and 40's... don't ask 😠)
All I have verified is the heads are 044s.

vw54 Administrator Always Waiting 4 Friday

16,723 posts · joined Aug 2002 · 12 May 2009, 6:30 am

#711810

to measure your compression ratio you will have to pull the engine apart

I read it on FACEBOOK so it must be true

http://forums.aussieveedubbers.com/viewtopic.php?tid=91278&page=1#pid848630

http://forums.aussieveedubbers.com/viewtopic.php?tid=63561&page=1#pid624099

http://forums.aussieveedubbers.com/viewtopic.php?tid=4832&page=1#pid452603

http://forums.aussieveedubbers.com/viewtopic.php?tid=60650&page=1#pid574409

Bizarre Moderator The artist formerly known as blue74l

12,789 posts · joined Aug 2002 · 12 May 2009, 8:35 am

#711822

Engine must be apart to do this - measure the deck height and measure the CC's of the heads and then put the info in here

http://www.aircooled.net/gnrlsite/resource/specgeninfo/calcs.htm

Futue te ipsum!!!

vw54 Administrator Always Waiting 4 Friday

16,723 posts · joined Aug 2002 · 12 May 2009, 11:38 am

#711849

Barry

thats a great size and very useful tool

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I read it on FACEBOOK so it must be true

http://forums.aussieveedubbers.com/viewtopic.php?tid=91278&page=1#pid848630

http://forums.aussieveedubbers.com/viewtopic.php?tid=63561&page=1#pid624099

http://forums.aussieveedubbers.com/viewtopic.php?tid=4832&page=1#pid452603

http://forums.aussieveedubbers.com/viewtopic.php?tid=60650&page=1#pid574409

trickysimon 100km/h is only 9 seconds away

1,473 posts · joined Dec 2007 · 12 May 2009, 6:35 pm

#711917

vw54 wrote:Barry

thats a great size and very useful tool

X2

aintgotitmusthaveit Officially Full-On Dubber

295 posts · joined Jun 2006 · 12 May 2009, 7:22 pm

#711945

But that is my point. How do you measure the combustion chamber????

hellbugged 48's and straight cuts

5,080 posts · joined Apr 2003 · 12 May 2009, 7:29 pm

#711947

with the valves in, you will need a CC kit.......

it involves a perspex sheet circular "plug" that sits neatly in the head....lightly greasing the edges to seal off the chamber

....you then fill the combustion chamber with auto matic trans fluid through a small hole (like 2c piece size) in the perspex with the aid of a syringe........

.....by keeping check of how much fluid goes in and then out of the syringe to fill the chamber, you know the CC's!!

the idea of the trans fluid is that it wont hold bubbles, and the perspex is that you can see when it is full.........any trapped air is manouvered around till it goes out the "access" hole in the plug

Craig Torrens 6 times Australian, 7 times State Hillclimb Class Champion

8,040 posts · joined Jan 2003 · 12 May 2009, 7:32 pm

#711948

with a burette...........the head needs to be off the motor, and then setup level on a bench with the combustion chamber facing up..............using the burette measure how many cc's it takes to fill the combustion chamber.

hellbugged 48's and straight cuts

5,080 posts · joined Apr 2003 · 12 May 2009, 7:33 pm

#711949

😁...........yeah, mums measuring jug won't cut it

aintgotitmusthaveit Officially Full-On Dubber

295 posts · joined Jun 2006 · 12 May 2009, 7:34 pm

#711950

CRaig does one use acohol ( worried about surface tension and miniscus?)
How do you block the valves?

hellbugged 48's and straight cuts

5,080 posts · joined Apr 2003 · 12 May 2009, 7:35 pm

#711951

put the valves in, and use auto trans fluid

use those calcs above and change the cc's by 1......it doesn't effect compression very much at all........there will be varience between each chamber anyways.

there are good calculators on the CB performance site home page too, gearing and tyre diameter etc

Craig Torrens 6 times Australian, 7 times State Hillclimb Class Champion

8,040 posts · joined Jan 2003 · 12 May 2009, 7:38 pm

#711953

alcohol evaporates........so no dont use it.

cb john Wolfsburg Wizard

470 posts · joined Jun 2007 · 12 May 2009, 7:40 pm

#711959

We are using kerosene - less messy than ATF...

Craig Torrens 6 times Australian, 7 times State Hillclimb Class Champion

8,040 posts · joined Jan 2003 · 12 May 2009, 7:46 pm

#711964

check that you're not getting any leakage via the valves first, by filling the ports with kero and seeing if it leaks past the valve head and seat...............if you do you will need to lap the valves and seats first.

aintgotitmusthaveit Officially Full-On Dubber

295 posts · joined Jun 2006 · 12 May 2009, 11:45 pm

#712028

thanks boys. Now just have to find the time to pull the heads off.
If I have to decompres I am guessing spacing under the base of he barrels is preferable.
How hard is this to do?

aintgotitmusthaveit Officially Full-On Dubber

295 posts · joined Jun 2006 · 13 May 2009, 12:14 am

#712035

THanks Reub.
On the assumption that I am currently at about 9.5:1 (guessing a combustion chamber 51cc) and when I boost I would probably want to drop to about 8:1
IT means I will need to increase my deck height from about 0.03 to 0.1! Do 0.07" head gaskets make sense??
Are the susceptible to blowng? Thats why I tjhought I would be best off spacing the cylander up particularly when ithecrank case would not seethe pressures the head would see. Bt I have never done this before! Any advice fropm experience will be much appreciated

greedy53 Bishop of Volkswagenism

3,062 posts · joined Mar 2006 · 13 May 2009, 3:50 am

#712046

just get a compreson test kit screw it in the plug hole and turn the engine over with foot flat on the go pedal and the coil wire out good luck

👍👍😂🙅🥷😬🤓

vw54 Administrator Always Waiting 4 Friday

16,723 posts · joined Aug 2002 · 13 May 2009, 7:05 am

#712051

yes your better fitting spacers under the barrels to reduce the compression on a blown engine

If you fit inside the head you have more surface area for leaks or blow outs to occur

we have proven this with the vintage drag car by torching cyclinder heads due to the copper casket spacer being eaten away by volatile combustion

I read it on FACEBOOK so it must be true

http://forums.aussieveedubbers.com/viewtopic.php?tid=91278&page=1#pid848630

http://forums.aussieveedubbers.com/viewtopic.php?tid=63561&page=1#pid624099

http://forums.aussieveedubbers.com/viewtopic.php?tid=4832&page=1#pid452603

http://forums.aussieveedubbers.com/viewtopic.php?tid=60650&page=1#pid574409

hellbugged 48's and straight cuts

5,080 posts · joined Apr 2003 · 13 May 2009, 6:30 pm

#712125

vw54 wrote:yes your better fitting spacers under the barrels to reduce the compression on a blown engine

If you fit inside the head you have more surface area for leaks or blow outs to occur

we have proven this with the vintage drag car by torching cyclinder heads due to the copper casket spacer being eaten away by volatile combustion

true that!

waltermitty Legend when my beer goggles are on

1,993 posts · joined Aug 2002 · 13 May 2009, 7:09 pm

#712131

if you want to lower the compression and get each chamber balanced / cc ed figure out how many ccs volume you need without using a spacer to achieve your desired compression ratio. then use a die grinder to remove chamber material and achieve the cc you need check by ccing as you go, get all chambers the same and required cc for the required compression and do away with the bother and complication of spacers and have y76our heads balanced.M

23 windows ...8 too many!

hellbugged 48's and straight cuts

5,080 posts · joined Apr 2003 · 13 May 2009, 8:03 pm

#712146

good point Watermitty........not easily done and will depend on what's been done to the chambers already but will keep the deck height nice and low, which yes, will have many benefits for a blown motor (or any motor)

Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 · 13 May 2009, 9:25 pm

#712174

aintgotitmusthaveit wrote:thanks boys. Now just have to find the time to pull the heads off.
If I have to decompres I am guessing spacing under the base of he barrels is preferable.
How hard is this to do?

Nick i ran CB copper head shims
most of the turbo guys on Shoptalk swear by them sayign they give a better seal on boosted engines

no idea if its true but i was happy just with the easy compression drop

aintgotitmusthaveit Officially Full-On Dubber

295 posts · joined Jun 2006 · 18 May 2009, 10:31 pm

#713306

Have decided to use spacers under the head.
Q. What is the most one can adjust tapets before longer pushrods are required.
Will I get 0.080" out of it?
I know I can adjust it out, I am concerned with any effect on valve position resulting from having a different throw on the rocker arms.

aintgotitmusthaveit Officially Full-On Dubber

295 posts · joined Jun 2006 · 19 May 2009, 8:12 pm

#713453

Anyone??

hellbugged 48's and straight cuts

5,080 posts · joined Apr 2003 · 19 May 2009, 8:16 pm

#713455

wait and see..........it one of those things you have to look at when it's all changed

very VERY basically here........at half lift, the tappet adjuster should be "square" to the valve........i'll try to find some good links that i have seen before..........some pics in my engine build thread

DRY BUILDS ARE YOUR FRIEND!