Holden 355 compression on NZ fuel

[Deuce]

Hey all,

Has anyone built and tuned a 355 on NZ pump fuel with decent compression?
It seems like 11:1 is pretty normal on the great western island running on BP98, but machinist's in NZ all get worried over 10.5 with alloy heads and pump fuel.
I've been asking in a few places, but still hoping to find a kiwi running high 10's on iron heads that can share cam specs etc so I can get an idea of dynamic compression etc.
I know one person running low 11's on avgas, and spoke to another a while back that was high 10's (he thought) but I didn't enquire cam specs etc (and won't bump into him again until sept drags).
Any experience you can share is appreciated.

Hopefully ordering pistons in a few weeks based on my decision.

[vlad01]

Pretty much depends on the cam specs. The bigger the duration and the tighter the LSA, the more comp you need.

I know it's not a 355, but I run 10-ish on my V6 with a very mild cam, but my LSA is about 109. It's on 98 petrol, and I know it's not knock limited at all as I had wayy too much timing initially, turns out the timing for MTB drops like a tank when you have high comp and a mild cam, it never saw any knock whatsoever.

I want to run 11-11.5 for my all out engine, but it has a cam with 260 duration and 106 LSA, so it really will need it.

Also, having good squish will do wonders for allowing more comp without knock.

[VK_3800]

I have a 355 with cast iron early heads around 10.3:1 static compression with a 242/252@50 cam. In hindsight I wish I'd bumped the compression a little more, it has no issues running on 91 octane with the right tune.

[Jaso74]

I have a crow 4503 with 10.2 :1 , 355 , cast heads, and I have had to gut my timing to stop pinging. It still goes great on 98 , super responsive but it appears my cylinder pressure might be a tiny bit much with that cam . I wondered if as the weather cooled a little it might have been a bit less prone with cooler under bonnet temps etc but it has not . Tune wise mine seems to be pretty close to the mark and I'm mostly happy with it minus the occasional under load ping , afr readings are good, very fine tuning only left.
I did aim to run as much cylinder pressure as possible in my build as I wanted instant torque low in the revs for fun lower speed street driving , not so much loose you ticket higher road speed shit.

[Deuce]

I have a 355 with cast iron early heads around 10.3:1 static compression with a 242/252@50 cam. In hindsight I wish I'd bumped the compression a little more, it has no issues running on 91 octane with the right tune.

This is exactly the info I was after from a NZ member. Thank you (I actually started flicking through your build to see if I could find info before posting the question).

I'm considering 11:1, 242/248, alloy heads on NPD100 fuel. Your combo gives me confidence.
What is your intake closing degrees?

[Deuce]

I have a crow 4503 with 10.2 :1 , 355 , cast heads, and I have had to gut my timing to stop pinging. It still goes great on 98 , super responsive but it appears my cylinder pressure might be a tiny bit much with that cam . I wondered if as the weather cooled a little it might have been a bit less prone with cooler under bonnet temps etc but it has not . Tune wise mine seems to be pretty close to the mark and I'm mostly happy with it minus the occasional under load ping , afr readings are good, very fine tuning only left.
I did aim to run as much cylinder pressure as possible in my build as I wanted instant torque low in the revs for fun lower speed street driving , not so much loose you ticket higher road speed shit.

Interesting. Thank you.
My current 355 is around 9.2comp with 4502 cam and torque was so great at idle that I fitted larger diameter headers and intake to shift power up the range. (That's why I'm building another 355 - to take advantage of all my good induction and exhaust system)

I'm impressed that the compression/cam worked together. Does it start okay (slow cranking?).
You are on Aussie fuel, correct?

What squish/quench are you running? I've read tightening that up might help your ability to feed it more timing, although it will also increase compression.
Maybe a slightly larger cam would've been the ticket.

[VK_3800]

I'm considering 11:1, 242/248, alloy heads on NPD100 fuel. Your combo gives me confidence.
What is your intake closing degrees?

If it were me that seems reasonable. If you run my numbers through a dynamic compression calculator it's on the low side, 11:1 static would bring it back up and alloy heads don't hurt.



In hindsight I feel the split duration is more than necessary for a Holden, I think they do it because it's a common thing on Chevy small blocks for longer duration. No problems with torque though, still trying to de-tune it for better street manners down low and it makes plenty of vacuum for brakes. Manual gearbox, of course.

Jaso's combination would probably see pretty big benefit from a small increase in cam to something more like 230/230. Would wake it up with no loss of driveability and help the pinging. The old Crane 286 seems overdone these days but it really is a sweet spot for a mild Holden V8.

[Jaso74]

I have a crow 4503 with 10.2 :1 , 355 , cast heads, and I have had to gut my timing to stop pinging. It still goes great on 98 , super responsive but it appears my cylinder pressure might be a tiny bit much with that cam . I wondered if as the weather cooled a little it might have been a bit less prone with cooler under bonnet temps etc but it has not . Tune wise mine seems to be pretty close to the mark and I'm mostly happy with it minus the occasional under load ping , afr readings are good, very fine tuning only left.
I did aim to run as much cylinder pressure as possible in my build as I wanted instant torque low in the revs for fun lower speed street driving , not so much loose you ticket higher road speed shit.

Interesting. Thank you.
My current 355 is around 9.2comp with 4502 cam and torque was so great at idle that I fitted larger diameter headers and intake to shift power up the range. (That's why I'm building another 355 - to take advantage of all my good induction and exhaust system)

I'm impressed that the compression/cam worked together. Does it start okay (slow cranking?).
You are on Aussie fuel, correct?

What squish/quench are you running? I've read tightening that up might help your ability to feed it more timing, although it will also increase compression.
Maybe a slightly larger cam would've been the ticket.

Yep slight bit more cam prob what mine needs ultimately to get timing back into it. Runs pretty dam good though, love the fast throttle response and instant torque . I'm also in need of more exhaust size being I haven't touched it and on a single 2.5 inch system still with pacemakers. The 3k stall is spot on right in middle of torque when you stand on it .