304 Supercharging a COME 355 stroker questions

[Forcedvp]

Hi all, Im in the process of rebuilding/stroking my 304 to a 355 with a Yellaterra whipple supercharger on top.
I contacted the boys at COME performance regarding the 355 stroker kit which will cost about $2300. I told them that i will be fitting a whipple s/c with just standard boost (about 8-10 psi i think). Im not looking to drag or do 1/4miles just a good street car that ill give a good squirt every now and then.

They told me that the kit would not work for forced induction as they say the crank and pushrods could break and that i would need special lower comp forged pistons too. They said that they do a kit for forced induction but thats $5500(billet crank,Hbeam rods etc).

The kit i was looking to buy was their 355 forged piston stroker kit for $2300 as stated above. It consists of
:Iron crankshaft
robe forged flat top pistons(not sure what the compression ratio will be)
:4340 forged steel "I"beam con rods
:all bearings and piston rings
:ARP studs/bolts
Its out of a VP Calais so only 2bolt main caps

I have read on hear of some guys s/c or turboing stock and mod 5l on reasonable boost and the motors seem to handle it fine. But dont know what type of pistons and what ratio the mod ones are using.

Does anyone know if this 355 stroker kit will be fine for the just street use and a squirt now and then?

I dont mean or intend to rubbish the guys at COME as i do have alot of respect for their work but i feel like they just want the extra $ out of me for something that will never see a drag strip/ 1/4 mile. I mean if guys on here are F/I on mild to high boost on relatively stock 5l with no problems. Then surely the kit im looking to buy should easily handle mild boost?

Thanks in advance

 

[mr j-man]

definitely upselling!!

if you only plan on running 8-10 psi and not spinning it much more than 6000-6500 rpm
Run a scat crank, either a forged I beams or Standard H beam.
A forged piston....(CP Carillo pistons).....this kit would set u back approx 1600 bux maybe more for the forged I beams....the I beams will weigh less than the H beams.
With running low boost you don't want the compression too low as it will be doughy down low.....How much comp have you been advised to run??...id say around 10.0:1

Youll want a cam to suit a blower...with 112-114LSA
What bore size are you going to end up with 30 over, 40 over??
What cc are your heads??...being a VP Block im guessing 61cc
Run a .041 thou head gasket and bore size to suit cylinder

Once you know those, then you can work out what size valve relief or dish you need in the piston
0 decking the block is essential for good quench/squish .... and then you offset the comp ratio with the piston relief.

Heres an example
Bore: 4.030 (30 thou over)
Stroke: 3.48 (355)
Heads cc: 61cc
Valve Relief / Dome (cc's): 0 for flat tops
Gasket Thickness: .041
Gasket Bore Diameter: 4.030
Deck Height: 0

will give you 11.45:1 CR

add a 12cc dish top piston instead of a flat top youll end up with 9.9:1 CR....prevailing everything else stays the same

pretty sure theres a few dudes on here with blower so they may chime in later

 

[Forcedvp]

Mr j-man, thanks for your input on this. Much appreaciated. I havent been advised on comp ratio other than your suggested 10.0:1 which is about what i was thinking. Either 8.4:1(stock 5l inj) or around the 10.0:1.

The bore size will be 30thou over
Heads will be stock vn/vp not sure of CC's for these heads
Cam will be small not decided on lsa yet so open to suggestions there too. Around 114 as you stated.

Was a bit taken back by the boys at COME performance. Was going to send my block to them for a full machine an clearence etc, cam, oil pump an was considering buying their heads too. So they were going to get a bit of money out of me anyway. So now i need to find a good machine shop in Sydney area to get the block work done. So if anyone can let me know of any good shops would be appreaciated.

 

[Vs hsv manta]

10.0:1 is way to high man

Keep it in the 8s it's a screw blower there won't be any gutless down low and 8-10 psi in a 355 won't be any slouch

I had 7psi with a vortech and made 380rwkw and was a weapon

You can run the risk of not using a forged crank of you want but there is a really really god reason why come is telling you there is a risk they can break

So many say you don't need to but so many have snapped a cast crank as well

If you want power it's expensive especially in a holden motor unfortunately

Cheap reliable fast, you can only chose 2

Flat top pistons won't work, you need some dish pistons, myn has 31cc and I belive I have 58cc heads and 40 thou cosmetic head gasket that comes in at 8.5 comp

Anyone running boost I say

Forged crank H beam rods forged pistons and a girdle or 4 bolt and grout fill it if your goin to jam boost down a 355

Lots have done the cast crank with boost and it's mixed results so really it's up to you but I went forged

It's not the power that will break it, it's the torque

 

[Forcedvp]

Thanks Manta for your input. I have alot to think about and more research to do and wether to go down the blower route at all. I guess it all comes down to how much money i want to pour into this project. Its easily creeping up to the 20k mark and thats without headers/exhaust and the rest of the running gear.

 

[Vs hsv manta]

Yes it will easly

Unless you get second hand stuff there is no way you build it for under $20k

Quick look

Blower kit $6-10k depending on what you get
355 stroker long motor $11k absolute minium I would think more like $13-14k unless you cheap out witch will most likely end up costing you double plus more
Fuel system minium $1000
Gear box stally or clutch will be $4-6k
Exhaust and extractors $2k
Ingition system $1000 with MSD or ice cdi ingition, coil, leads plugs
Tune $1000+
Anyone that pay to do anything g can blow out real bad $$$$
The endless little fittings bolts wires sensors can be anywhere from $500 to $10grand depending if you want a basic engine bay or a show engine bay

And most of these will blow out to be more then that

Or could stick with 304 with a basic freshen up forged pistons girdle rods small amount of head work with some rockers and blower

This be much cheaper and stick to 330 rwkw mark as in the end it's power that cost money and blowen 355 starts to make power and then every thing needs to be bullet proof and that's the expensive part

Or just buy a wrecked ls1 2 or 3 car and drop that motor box in, you then have a m80 diff as well witch is stronger that you can use

 

[delcowizzid]

you can do 330rwkw on a dead stock 304 with cam and turbo kit peice of cake.but to be indestructable youde go the forged stroker doesnt make sense to spend all that money on cast cranks etc and machining to do it all over again when the crank takes a ****.

 

[Vs hsv manta]

^^ yep very true actually

 

[Forcedvp]

Thanks everyone for great answers, opinions, suggestions. Its a real big help. So much to consider. Not as straight forward as i was hoping. But thats cars for ya. Looks like i will have to sell an arm/leg and possibly a kidney too, to get this project over the line. Thank god i have kids for that I will post updates on progress should anyone be interested.

On a side note. Anyone have any opinions on Kalmaker street pro3 ecm's or Pcm Delco Hacking hard/software? I like the fact that you dont need a piggy back system attatched and that you can keep alot of the cars original settings( such as A/C and thermos) as well as real time tuning etc. I understand that SP3 only works on old laptops(win98) in dos and TunerPro RT works on any laptop I will search this forum now on this subject. Thanks again everyone

 

[Vs hsv manta]

Look up (holden 355 ) on face book

There is a 355 with a yells terra top mount for sale for $6500 got vid of it running in car

Need to get on this quick as it will sell fast