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Twin Turbo 308 and 355 conversion HELP

Hi All

I'm looking into some engine mods mainly a 355 upgrade for my 308. I found on ebay a kit for $1150 that seems to have all that I need to stroke it but wonder if anyone can give me some tips to look out for?

The other mod I'm looking at is a twin t03 turbo set up (again on ebay)again it seems to have just about all I need other than the manifold being for a short block chev ( I'm sure my exhust guy can sort that ) again any input would be much appriciated.



If you thinking about a RPM usa 355 kit don't bother.
The extra money you have to spend balancing the crank you are just better off putting into a better brand such as Harrop, Prostroke or COME.
Those cheap cranks generally require lots of expensive mallory metal to get the balancing correct.
>Trenton's Email

Have you used the RPM product before and if so how long ago?
The specs they are supplying seem quite good and the feed back on the ones they have sold lately seems to be ok.
Stroke: 3.5" / 355ci @ +030
Main Journal: STD Holden
Con Rod Journal: STD Holden
Straight Shot
Nitrided Hardened
Internally Balanced
Chamfered Oil Holes
Ground & Micropolished
Back Drillied Oiling System
Fully Counterweighted 8 In Total
NOTE: Crank is not Cut and Shut

what your looking at paying for a complete kit, is around what you need to spend on pistons alone if your going to add one turbo, let alone two.


But it should be fun until it blows LOL. @ $2400 for the twin Turbo set up I can't resist. I was thinking of running fairly low boost. until the need for speed gets the better of me then I guess thats where the two spare 308's I have will come into play.

When I run out of spare motors what pistons would you recomend to stand up to the Turbo's ?

Go for it.
I think it would be waste of money but thats just my opinion, and after all its your money.
Procomp looks the goods, is sold like its the best, but it is pure crap.
You get what you pay for.
Anything that comes from that factory is very average. Im stupid, cause i have fallen for the sales pitch before, NEVER AGAIN.
>Trenton's Email

I can definatly learn from others mistakes so I will research more and see what I can come up with. Thanks for sharing your experiance with me

Replace Parts Moreoften.


While I agree that you get what you pay for! I also think that just buying the most expensive brand names does not mean you will get the best bang for your buck ! What I'm looking for is not the best part but more the best value part. I'm only looking for around 350hp to the wheels as cheaply as possible.So if you have any sugestions that run no more than $3500 I would be interested to hear it!

The cheapest HP for $$ is throttle in a bottle, nitrous wins hands down everytime.
Buy a nitrous suitable cam, decent pistons & a good fuel pump that is only for the nitrous system, a good cheater kit & you will easily find 350hp at the treads at the flick of a switch & a sedate daily driver when not on the bottle.

visit my shed
>E-mail Me

and add rods.


Great if you live quarter mile at a time but mine is a track car so I need the power to be a bit more constant.Thats why I was looking at the turbo's. My thought was I would only need to run as much boost as I required to beat the cars I was running againts. If I needed more power for a short run I could increase boost. My calculations tell me a 355 with twin T03 at even just a couple of bar boost should put out 300 to 350 hp fairly reliably but higher boost should give me upwards to 450hp when needed more if I want it to be a fire cracker lol. I'm also looking at a super charger but its not stacking up as good.The other option would be a single T70 mounted at the rear of the car.I dont know life would be so much easier if I could bring myself to buy a 3lt twin turbo Lexus v8 but its not holden :-(

Ask around about a 330 stroker.
I think it is the following, don't quote, i could be wrong here.
Offset ground holden crank to suit small journal SBC rods.
Run the 283/327 rods, but they have to be narrowed to suit the holden crank.
350 pistons.
Other then that, a little bit of giggle gas works a treat.

>Trenton's Email

You can run the turbo kits with stock bottom end 308 but cant exceed 5psi through each turbo (equalling 10psi) as that is about all you can reach. This should still result in almost 400hp. If you put forged pistons in the motor and I beam rods that is all you need. You can then wind the boost up to 12psi on each one, resulting in at least 600hp, and then depending on your heads, when you work these later on, the hp gains are unbelieveable. I will just have to trust myself not to wind the boost up until I do the bottom end.

I find it hard to believe a stock 308 with cast pistions will live with 10psi going into it.You will also find head gaskets a problem at that rate.
If going to go the turbo route & look for sizeable gains I'd suggest a bulletproof short motor & just use the heads you already have, also those ex manifolds they supply look like a fairly low mount, how will it go for engine bay clearance?

If you do go for boost be sure to keep us updated & have lots of fun with it all......

visit my shed
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My current 308 has ported and polished B cast heads decked with over size valves race bread head gasket the pistons are also none standard but we did not pulled them out when we did the top end a couple of months ago as the motor has a very tight bottom end with good compression and no smoke or blow by so cant tell you what pistons they are.I will be adding roller rockers so as not to bend the top end.I think I will have to have a look at the fuel delivery as well as I currently run standard fuel pump with 600 holly. I'm a little concerned about space under the hood but then it is a race car so I don't need to worry about rego so I'm sure we will work it out.I also run a rev limiter to save the engine from my right foot !Its an interesting project though so when I get MY SHED up I will post pics as we go.

Ditch the rev limiter if going turbo, you'll pop it quicker with one fitted to a carbed turbo engine than without it.

visit my shed
>E-mail Me

OK you got me! Y will the rev limiter be a bad thing? wait hear that sqeeking ?Thats my slow cogs turning. is it because the turbo would continu to produce unwanted boost? or is there somthing other than that?

Yeah pretty much, a limiter will kill a cylinder at a time whilst the thing is still being fed under pressure ,then you end up with lots of fuel in each pot for the next firing = pop at some stage. I've seen a 350 die this way after the advice was ignored....& a few head gaskets ona 308 (my learning curve...)

That is only for a blow through carb system, you can program an injected engine to limit successfully .

visit my shed
>E-mail Me

Whatever you choose to do remember there is no such thing as cheap horsepower, let alone cheap boost on an engine that was never built for it.

You could go about 5-6 psi on a stock bottom end with mild cam and head porting but thats about it.

Even though 5psi would be ok for a street car that is driven normally most of the time and occasionally thrashed, i think you are kidding yourself if you believe a 5psi/stock bottom end motor will last in a circuit car that gets the bejesus revved out of it for an hour at a time... let alone 10psi (did someone say "melted piston").

Figure out how much you are prepared to invest in your toy. Then get all that money and spend it on the best bottom end you can afford. Put on your current cam/top end and go racing. You can worry about the boost later.

Having your pride and joy sitting broken in the shed is annoying, even more so when it was you taking shortcuts that put it there.

just put in one of these and be done with it.

[http://gallery.oldho...|355 engine]


My mates and i have had trouble with COME cranks, they were bloody good in thier day but now we believe they're resting on thier laurels.(bad machining in some cases, had to send them back)
Harrop are damn good but for unbelievable reliability i'd go for Auscrank. Just my 2 cents from experience but your cash so your go.
PS: Arias pistons for boost.

last three that i used had the rear bob weight around 15 degree's out.

Eagle steel cranks coming soon.

Harrop too flamin expensive.


Eagle stroker hits are already here mate, looking into it myself. Can be ordered now from Rocket or most speed shops Id say, and the cranks retail for half the price of a Harrop at around $530!!

Scat cranks will be coming out later this year too and are rumored to be dirt cheap aswell.

VhBunky - All tow no go!

VhBunky - All tow no go!

the first shipment crashed upon landing.

they were recalled.


I e-mailed the guy on e-bay and asked him st8 out (are these cranks any good as I have been told they are not balanced very well) FUNNY he has not replied ! I guess I will take that as NO.I picked the car up from Phill at head world today and look forward to getting out to Oran Park next week for testing. We still need to do some tuning after putting a new cam in the old girl so fingers crossed I might see some more hp yet.

For what its worth i would just build a QUALITY NA engine rather than cheating through turbo- 350hp should be easily achievale with quality parts, a stroker kit and quality bolt ons. i would reccoment to look at prostrokes range of stroker kits

looking at doing a twin turbo setup on my vk carbie 304 any kits about???????