Gas

[snowbound]

I am told that the gas converter on my 3.5 is not man enough for the job, and I either need 2 of them:eek: or a bigger one. I anted the 3.5L tuned for gas as advised (on here) but had to settle for a petrol tune only for this reason. Thoughts?
Hopefully picture of existing converter is attached

[bee utey]

Yes its probably a bit marginal as they used to be fitted to asthmatic 202 Holdens (3.3. litre) but once again the size of the converter only comes into play once you've reached its delivery limit. If there is insufficient gas flow to run the engine at lower speeds it will be a failure of the mixture adjuster, the gas hoses or the mixer design to allow enough flow. They are easily fixed, sometimes by drilling out some cast inlet a bit.

But if you want a bigger converter go to ebay and look for an OMVL converter, easily good enough for a 5 litre engine. Prices vary from not much to new price, depends on mow much you trust the sellers feedback.

[snowbound]

Thanks Bee I shall go look see! Also, as yous the man who knows, what should the compression be on a healthy standard 3.5? I'm told (I get told a lot & charged for the privilege) that mine is low all round?

[bee utey]

what should the compression be on a healthy standard 3.5?

Check your compression ratio, its stamped next to the engine number where the dip stick goes into the block. If your compression test results are reasonably even but low then you probably have a low compression engine. Way it goes. Also compression testing depends a lot on cranking speed, put in a new starter motor and a truck sized battery and with a warm engine your compression figures will all go up.

Also one cause of low compression can be a slack timing chain, retarding the cam. Rock the front pulley to the points where the chain slack takes up, if the slack is greater than 10 degrees your cam will be out of its best position regardless of how good it is.

Lastly you can do a compression test yourself, buy a suitable tester and likely it will cost you far less than paying someone else to test it. E.g.:

Petrol Engine Compression Tester KIT SET FOR Automotive | eBay (http://www.ebay.com.au/itm/Petrol-Engine-Compression-Tester-Kit-Set-For-Automotive-/310363547866?pt=AU_Car_Parts_Accessories&hash=item48431be8da)

They don't have to be super accurate to give you an idea.

[snowbound]

Well, you live and learn, I never knew about that info being stamped on the block. I was told that my camshaft is sightly retarded as this was standard on them to meet UK emission rules? Having paid $550 for supply and fitting of a new starter motor (compression test was done first before SM it kacked itself)I am keen to get get a handle on what really needs attention and what was possibly an attempt to get more work from me!

Mate, thanks again, you are a legend!