hz350

Hi All,

First post for me.

I have a HZ tonner with a 350 SB chev.

I have been searchin through the threads, reading up on gas setups for the SB.

My 350 was built about 10000klms ago, ground up - was built as a stock engine, intended to run straight gas - standard cam, slightly higher than standard comp, HEI ignition with regraphed advance, mildly ported stock heads, single plane mainfold.

It has an Impco 425 mixer (sitting on a holley 650 4brl base plate) and a Type E carb with a 7.98mm x 0.9mm pipe coming from the tank to the lock-off. The gas system was entirely new with the install - about Nov 2005.

Let me say that the engine is reliable, starts first go, every go. I can leave it in the shed for 2 months, turn the key and off she goes. It sounds great, is smooth (as smooth as a SB can be) and gets about 300klms from 60ltrs of LPG.

The issue is, it just doesn't seem to GO! I have a new 2ltr turbo diesel golf that goes harder than this thing.

I know that there are other factors involved. I am having the T400 serviced this week (in case it's some sort of converter issue robbing power) or it could be the final drive 3.36:1 although it goes like its a 2.78:1....

The ute sounds like it goes, it just doesn't seem to pull - it's wierd.

From what I have read so far, the Impco 425 setup should be the goods for this sort of engine.

Perhaps the user 'Gasman' could shed some light on the gas setup for me?

The questions that came to my mind were:

1 - Is the converter / carb for my setup (Impco Model E) too small?

2 - Is the size of the line from the tank too small?

3 - Are the lock offs and fittings too small?

4 - Are there multiple potential issues with my setup?

5 - Am I correct in expecting that this tonner should really boogie with this sort of setup? I know that T400's can take a bit of power from the engine, but I wouldn't have thougt this much...

I have a second tank I plan to put in, how should this be done? Hydrostatic valve for filling and single line to a single setup?

This is a bit of a fun past time for me, so it is interesting to learn about all of this.

If this SB doesn't get up and go, I'm gonna rip it out and put in a Lexus 1UZ-FE Quad Cam V8 that I have in a front cut.

I want to give this SB one last crack!

I know that there are a lot of questions here - and I thank in advance for any help given.

cheers,

hz350

allports

you need to be in touch with 400hponlpg look him up. And the Lexus will not last long on LPG. Just like all the 4valve cruisers that are converted the chew through the exhaust seats.

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400HPONLPG

Ah the joys of LPG !!!
So she dont GO !
First of all we should better define "GO"
Exactly what HP/Torque did it have before converting to LPG ?
Dont Know , what a shame, we have nothing to compare it with !
Well a old HT GTS350 had 250HP in 69 , then again a 308 had 240HP in 69 as well , both of which should are greatly exaggerated. Try 210 and 180 , would be closer !
So its off to Dyno my son , and lets see what it does
Now have the dyno man plot AFR over RPM with HP and Torque in shootout mode
Get a reading of Ignition advance at idle and 3500 RPM (bit higher with a CHEV)
So be careful to ring around and find a Dyno that will plot in RPM , you would be surprised how many dont and give you back useless figures in MPH .
That you should get done for no more than $100

Now once we have the AFR we can begin to see any issues if they are there .
Also ask for a steady cruise AFR reading at 2500 and 3500 RPM.
Now remember the 425 if well set up with a decent convertor should be capable of delivery 250 HP if not close to 300 HP
Once you get the dyno results ,where to go from there ? Get the Dyno results first !!!

hz350

The joys alright!!

Thanks for what is a common sense approach to this little 'problem'

I have the dyno guy booked in for Tuesday next week and he assures me he will get all of these values / readings for me to analyse (ie, post up here for advice)

I don't have any baseline to go from, as this engine was in a Bedford that my father in law had for ages and had been sitting in the shed under a tarp for quite some time. Hence the full rebuild.

I guess from here, it's a waiting game!

Thanks for your help so far.

Cheers,

hz350

400HPONLPG

Inthe mean time mate , just do a wet and dry compression test and record the results , dont want to be barking up the wrong tree do we !!!! LOL
I just hope the Compression isnt one those 8.5 to 1 jobs !! then you will struggling to make 180 hP on petrol !!!!

hz350

Yeah Cool...

come to think of it, I don't remember what comp it is exactly.

What should it be ideally?

Cheers,

hz350

400HPONLPG

For straight LPG , at least 10:1 so when you do the static compression check let hope it goes better than 185 psi .