304 355 Stroker Kit Help

[304RR]

I am about to start the process of building a 355 stroker from a VR V8. The engine is for a Range Rover so it requires more low down torque than high horsepower at high revs. I have an open plenum manifold with an Impco 425 LPG carb, roller rockers and Commodore SS headers, the cylinder heads are standard.
There are so many different stroker kits available with different journal sizes, crank manufacturers, rod length/type and piston types I am not sure which of these would be suitable. The price of these kits also varies quite considerably. Which kits have people used, and which ones should I stay away from? Which kits would be recommended?
I am looking at a camshaft somewhere around a Crane H268 or H276 as I would like torque from as low as possible, and as its LPG, a compression ratio of 10.0:1. Ideally power in the 1000-4500rpm range would be good.

 

[EYY]

Single 425 will limit you - I wouldn’t bother with a stroker unless you were to run two of them really. But if you must, run with the 276. It’ll run out of air mid to upper rpm.

Go for a chev journal scat kit. Cheaper to rebuild down the track and you start with new rods too.

 

[Deuce]

Would you not be better off using the stock banana manifold? Makes great torque all through the low rpm.

 

[EYY]

Would you not be better off using the stock banana manifold? Makes great torque all through the low rpm.

OP wants to do away with fuel injection by going the 4 barrel impco gas carby it seems. If going mixer gas then the 4 barrel manifold is the way to go for ease of conversion and simplicity. Gas likes single plane manifolds too.

 

[304RR]

I do have a banana manifold which I could use. My main concern is which of the 355 stroker kits I should consider using, and those that are not so good.

 

[Deuce]

In regards to strokers:
- h-beams are for strength at a level above what you are aiming. Stick to I-beam for ease of clearnacing (VR block may be cast with sufficient clearance)
- scat crank with chev journals seem to be the go. Then you can use chev 383 stroker rod/piston combo with it and they are one of the cheaper options to come across.

Stock heads with 5cc dish piston give great compression ratio. Go a bigger dish if you want to tame it down a little.

Then cam it to suit the above choices.

 

[bevzan]

LPG can be difficult to setup, but once its running right, its awesome.
I have 355 come crank, chev I beams, chev pistons csbh-462 CAM, come heads with all the good bits, Eaton M122
Fuel system is. 2 X 80 litre tanks, 2 lines, 2 Vapour Convertors, 16 x 30kw vapour injectors running thru profire -T ecu.
Main limiting factor is flow, each vapo is rate at 240kw. When my car was dynoed the lpg pressure was set too low limiting mxax HP to 260kw at 4900rpm.

At 10.1 comp you will need a hi torque gear reduction starter as stock one wont spin it fast enough to start lpg. i run 9.5.1 and use a CVR protorque 1.9 hp and that works really well.
Beware of startup backfires with impco setups, my iac stuffed up and i had a backfire that bad it hydroed the motor long enough to dent the flexplate, resulting in a nasty ping noise on every roation on starter, once running it was all fine.

let me know if want up upgrade to injection, i still have heaps of bits lying round

 

[EYY]

Single tank and elec lock off limits you to around 200kw before it’ll start to lean out too much. Single impco 425 flows enough air for approx 150-160rwkw then can’t flow any more air so it sucks more lpg and richens up.

Twin tanks and lockoffs are required for decent power levels. Lpg injection piggybacks off the existing pcm and most only work with full sequential injection as the injector drivers aren’t adequate to fire all 8 injectors at once (despite being able to select it in the software).

 

[304RR]

If I reinstall the banana manifold how hard is it then to put all the injection gear on. I only need LPG injection not petrol, I have had no experience with this at all.

 

[EYY]

Then keep it simple. Single impco 425 with 4 barrel throttle plate and manifold. Basically a gas carby setup.