Ok i'm doing a manual conversion including LSD shortly and i was thinking why not go the whole hog and drop in a built 6G75 at the same time,so i'm thinking forged 13:1 pistons to take advantage of the LPG,shot peened rods with ARP rod bolts,cams in the very high 200's,springs,head work,72mm throttle body etc

I'd be aiming for 220-250wkw so if anyone can steer me in the right direction on recomended parts to achieve this figure and where to source them.

Cheers

thats a damn high figure for NA, you would need to build that power from increased revs and aggressive timing and pretty wild cams. Why not forced induction?

edit: Jasons VRX is putting out 190wkw NA on a 3.5, so it should be quite achievable with the extra CC.

thats a damn high figure for NA, you would need to build that power from increased revs and aggressive timing and pretty wild cams. Why not forced induction?

edit: Jasons VRX is putting out 190wkw NA on a 3.5, so it should be quite achievable with the extra CC.

The extra 300 CC wont give you stuff all in terms of additional power. The better flowing heads are the key.
Another example is my other 3.5L that made 244wkws NA and that with cams that are close to what T_double_U is talking about using.

*Edit* the current donkey engine has made just over 200wkws from its mild setup. This build up is essentially the same as what Levi had done for his old TJ, except my donkey engine uses a stock TB and smaller 270deg cams than his

thats a damn high figure for NA, you would need to build that power from increased revs and aggressive timing and pretty wild cams. Why not forced induction?

edit: Jasons VRX is putting out 190wkw NA on a 3.5, so it should be quite achievable with the extra CC.

I thought jason was putting out 236wkw's??

I'd like to stay away from forced induction because for 10k i could put on a low boost supercharger or twin turbo's but then i'd just be waiting for it to go bang so i'd have to build a forged engine for another 7-10k so getting close to 20k and lots of time off the road.were as if i stay NA i'd be looking at around 9k all done.

So Jason would i even need to do any head work?

Also does anyone know if my current RPW extractors would bolt up to the 6G75?

So Jason would i even need to do any head work?

Also does anyone know if my current RPW extractors would bolt up to the 6G75?

Answer to both questions is yes i would and yes they should fit.

My pacemaker headers fitted up to a G675, did this just recently when working on the "Donkey 2" engine.

*Edit* I wont go into detail on what to do as im sure i'll be "cut down" by someone else

What sort of LPG system are you considering?

Dave.

Jason-fair enough,would be great if you could send me a PM if you have the time and don't mind.

Dave-i have a prins vapour injection system.

Have you taken into account that it should be optimised for LPG? I'm guessing if you use similar parts and tune to what others have used in the past it won't be tailored to LPG. From memory they like different ignition timing and possibly cams. Might be good for a bit of extra power...

Ollie

Hey Ollie long time no see hope your good mate,yer once i track down a company that can make the cam's i'll see what they have to say in regards to the LPG.I've been thinking about the computer side of things,i'll have steve knight do a live tune on the factory ECU to suit petrol and as i have the equipment to tune the LPG computer i'd have the air/fuel ratio's tweaked as well as the ignition timing using some type of ignition only ECU for the gas.If anyone can see any issues with that idea or have a better idea please let me know.

Another question i have is using 13:1 pistons will there be a clearance issue between the top of the piston and valves when at TDC?

Hey Ollie long time no see hope your good mate,yer once i track down a company that can make the cam's i'll see what they have to say in regards to the LPG.I've been thinking about the computer side of things,i'll have steve knight do a live tune on the factory ECU to suit petrol and as i have the equipment to tune the LPG computer i'd have the air/fuel ratio's tweaked as well as the ignition timing using some type of ignition only ECU for the gas.If anyone can see any issues with that idea or have a better idea please let me know.

Another question i have is using 13:1 pistons will there be a clearance issue between the top of the piston and valves when at TDC?

You'll probably need huge valve reliefs in the pistons and pray to god you never snap a belt. you may possibly need different valve seats too if the heads are not LPG compatible.

Plenty of cam makers out there, Crow, Delta (US) Wade, etc

If you need a heads up on where to send your engine or get info from, I can strongly reccomend to ring ADS engine recon in myaree, they built my TR engine but the guys no longer there, his dad John is and he has about 50 years experience building engines, he knows EVERYONE in WA who can do what and where to go Tyson.... trust me, worth the phone call!

Cool thanks Ben.

I read somewhere on here that the 74 heads have less cc in the combustion chamber than the 75 heads. So in theory if you used 74 heads on a 75 block with the 10:1 75 pistons, you would get your desired comp ratio

13:1 comp ratio seems like a recipe for disaster unless running LPG full-time and car is only for track use.

The 6G75 has a very tight ring pack with top ring only about 4mm from the top of the piston, so the rings are going to get a lot of heat.

The piston would need a big intruder nearly 20cc plus valve cut-outs to get 13:1. To compensate for the extra weight above the pin the piston might need to have a skirt added to compensate to reduce piston rocking at TDC. Excess piston rocking reduces ring seal, that seems already marginal on the 6G75, and adds a lot of piston noise. The rattle and oil consumption of the Chev/Holden LS1 is typical of the problem.

The intruder and skirt is going to add more weight swinging on the thin "74" rods used in the 6G75.

For comparison this is the intruder on the 3.8 MIVEC engine for a 10.5:1 comp ratio.

http://i837.photobucket.com/albums/zz294/AlanJoy/pistontop.jpg

Cheers,
Alan