Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.

New Posts Contact us

Just Commodores Forum Community

It takes just a moment to join our fantastic community

Register

355 vs 304 high rpm?

Rydermiller2002

New Member
Joined
Mar 25, 2023
Messages
3
Reaction score
0
Points
1
Age
21
Location
Western Australia
Members Ride
Hz ute 304,vs statesman 304,vu ss 5.7
Im wondering what maximum rpm I can expect for a 304 and a 355?

I have a 304 with a 288 solid lifter cam, ported heads, a port matched Harrop single plane intake with a 650 Holley carby on top and an msd ignition system with a 6000rpm limiter on it.

Should I stroke the motor to a 355 or leave it alone? How would it affect rpm and what sort of rpm can I somewhat safely run it out to with each set up?

It's got a manual 4 speed Saginaw box behind it in a hz ute. This gearbox used to have a 355 Infront of it previously. Cheers.
 

Deuce

Super Stock
Joined
Feb 5, 2012
Messages
4,475
Reaction score
4,692
Points
113
Location
Snobs Rock (or so the locals say)
Members Ride
'94 VR SS V8
It's all about bottom end (main caps) and oil system (modification) with these blocks.
My 355" does 6400 every now and then.
In theory all things being equal, 304 could rev higher.
But I would say go 355 for the extra torque, and build the bottom end well so it is safer at rpm than your current setup.
 

Rydermiller2002

New Member
Joined
Mar 25, 2023
Messages
3
Reaction score
0
Points
1
Age
21
Location
Western Australia
Members Ride
Hz ute 304,vs statesman 304,vu ss 5.7
It's all about bottom end (main caps) and oil system (modification) with these blocks.
My 355" does 6400 every now and then.
In theory all things being equal, 304 could rev higher.
But I would say go 355 for the extra torque, and build the bottom end well so it is safer at rpm than your current setup.
I'm thinking I might stick with the 304 and spend a bit on the bottom end as it doesn't need much more torque in the ute, I can hardly get it to hook up as it is.

What can I do to the bottom end and oil system to make it a bit safer to rev out to what the intake and cam can support? (7000-7500)
I don't plane on reving that high for long but I'd like the peice of mind to know the bottom end won't just let go and it won't starve for oil.
Also do I need to do anything with valve springs to make sure they're closing back up quick enough. Like dual or bigger springs or something like that?
 

keith reed

Well-Known Member
Joined
Sep 26, 2010
Messages
1,289
Reaction score
5,973
Points
113
Age
76
Location
Raceview Qld
Members Ride
1983 vh v8 sle 2000 vs v8 ute 2012 ve11 redline
I got beehive springs from Comp Cams. Get in contact with someone like them with all your specifications and they will advise on what spring to use. There is a spring maker who's name eludes me that people say not to use. Perhaps someone on the forum will know their name.
 

Immortality

Can't live without smoky bacon!
Staff member
Joined
Apr 15, 2006
Messages
22,556
Reaction score
20,278
Points
113
Location
Sth Auck, NZ
Members Ride
HSV VS Senator, VX Calais II L67
Look up some video's from a guy called RVK355.

A 304 will turn 8000rpm. Making it live at 8000rpm is where the skill is at.
 

Deuce

Super Stock
Joined
Feb 5, 2012
Messages
4,475
Reaction score
4,692
Points
113
Location
Snobs Rock (or so the locals say)
Members Ride
'94 VR SS V8
I'm thinking I might stick with the 304 and spend a bit on the bottom end as it doesn't need much more torque in the ute, I can hardly get it to hook up as it is.

What can I do to the bottom end and oil system to make it a bit safer to rev out to what the intake and cam can support? (7000-7500)
I don't plane on reving that high for long but I'd like the peice of mind to know the bottom end won't just let go and it won't starve for oil.
Also do I need to do anything with valve springs to make sure they're closing back up quick enough. Like dual or bigger springs or something like that?
I'm not the expert, but I believe over 7k is 4bolt main cap territory.
Single pipe oiling mod, or #1 crossover mod to even out oil flow when it counts. And shim and blueprint the pump, plus larger sump I think should sort you for the occasional 7k blip. For anything serious you would best go further with oil mods (circuit or burnout comp etc).

The heads are non-interference so soft springs will stop it rpm-ing rather than break stuff if that is a concern.

How much comp are you going for to suit the cam?
 

Rydermiller2002

New Member
Joined
Mar 25, 2023
Messages
3
Reaction score
0
Points
1
Age
21
Location
Western Australia
Members Ride
Hz ute 304,vs statesman 304,vu ss 5.7
I'm not the expert, but I believe over 7k is 4bolt main cap territory.
Single pipe oiling mod, or #1 crossover mod to even out oil flow when it counts. And shim and blueprint the pump, plus larger sump I think should sort you for the occasional 7k blip. For anything serious you would best go further with oil mods (circuit or burnout comp etc).

The heads are non-interference so soft springs will stop it rpm-ing rather than break stuff if that is a concern.

How much comp are you going for to suit the cam?
I've got no idea of the compression, it's already in my hz ute and goes like f**k, I just want to know my bottom is good to handle it.
It's also handy to know the heads are non interference, cheers.
 

Deuce

Super Stock
Joined
Feb 5, 2012
Messages
4,475
Reaction score
4,692
Points
113
Location
Snobs Rock (or so the locals say)
Members Ride
'94 VR SS V8
I've got no idea of the compression, it's already in my hz ute and goes like f**k, I just want to know my bottom is good to handle it.
It's also handy to know the heads are non interference, cheers.
Unless you know the bottom end has the mods to safely support more rpm, I would advise that you assume it doesn't until proven otherwise.

If you end up taking it apart to add 4-bolt mains etc you can do the math on the compression ratio then.
 

keith reed

Well-Known Member
Joined
Sep 26, 2010
Messages
1,289
Reaction score
5,973
Points
113
Age
76
Location
Raceview Qld
Members Ride
1983 vh v8 sle 2000 vs v8 ute 2012 ve11 redline
The real issue is how much are you willing to spend to get the results you want. 355 = more power at less revs.
 

Immortality

Can't live without smoky bacon!
Staff member
Joined
Apr 15, 2006
Messages
22,556
Reaction score
20,278
Points
113
Location
Sth Auck, NZ
Members Ride
HSV VS Senator, VX Calais II L67
I think 2 bolt with main studs and a girdle will do on a stock stroke deal. Probably some better rod bolts wouldn't hurt.

Ask @Smitty what his bottom end has in his race car.
 
Top