What to do - rebuild?

[Dean1985]

Hi all.

Long story short: here goes.

(This could also serve as a lesson to others, i really just need to be nudged in the only direction im scared to take.)

I went through the process of a rebuild of my 304 V8 just over 18 months ago now.

I took my time asked the questions i thought were important to the cam supplier and engineer and came up with a combination.
Crane H268
10thou off heads/block/bore (she was a well looked after engine)
Flat top pistons.
Convert rear main to two piece neoprene seal.
Dynamically balanced with new balancer.

Got it to a tuner (good bloke, did his absolute best) but we cant get the ping out of it. Knock sensor fitted and activated as well.

Turns out the compression which we believe has ended up close to 10:1 is just too much for the cam profile.

So mr tuner has had to dial the tune back quite substantially. It still rattles at different times (cold nights where air is dense and humidity is low). If i give the accel a little stomp the car gives a decent ping and then takes off. Will rattle up inclines etc etc.

So im in a painful spot.

After talks with Mr Tuner it goes like this.
Roller rockers - higher ratio, maybe that will give the cam the extra lift to bleed some chamber pressure.
No, it would be piss all difference.

Thicker head gasket?
No. It would reduce compression but by how much? Not an ideal solution. Longer push rods required as well.

Drop base timing and cut my losses and know im driving a detuned waste of time and money.

Engine out. Strip down. Replace pistons with standard dish top, retune, mr tuner can then dial back in some advance and id have what i was originally after.

Any options ive missed?

Cheers peoples.

 

[losh1971]

Probably a stupid question but are you running 98?

 

[Dean1985]

Probably a stupid question but are you running 98?

Yeah mate 98. My wallet loves it.

Its that borderline the slightest quality difference will make it worse.

 

[VS 5.0]

Change the cam to suit the compression ?

 

[woteva]

Change the cam to suit the compression ?

Just what I was going to say. The Crane H268 looks to be only a step or 2 over stock.

 

[Sandman]

+1 get a cam of similar specs which likes more comp.

 

[_R_J_K_]

we cant get the ping out of it. Knock sensor fitted and activated as well.

The knock sensor setup is garbage on the 5L because the block was developed in the 60s before they existed and they were added as a bit of an afterthought 'feature' in the 90s. It's pretty common to just unplug the knock sensor and deactivate it when doing any kind of cam work because of the amount of false positives that the sensor gives. It's really a situation where a knock box and headphones is far more accurate.

You're still using a Delco ECU, yeah? Does your tuner do a lot of 304s? Nowra seems about the same distance to Sydney and Canberra, if you feel like getting a second opinion there's obviously a few good shops in Sydney (would start looking at Ace Performance tuning), while in Canberra there's Gentech and Profection, both shops have really good 5L support.

And the rattle - pinging or does it sound like oiling/tolerance issue?

 

[Dean1985]

Thanks for the replies guys.
(I forgot to add originally)
A larger cam was also a suggestion from Mr Tune however it would require a stall converter. I never intended to go that way as its a daily driver and fuel use and drivability are a big factor.

Mr Tuner is from Sydney and appears in the forums .
Like i saod i tried to do it properly. A bag of research, questiondd the cam supplier, engineer. Hooked up a tjner before i commited to make sure it was possible to still tune a delco.

In hindsight a tuner was probably the only person i should habe asked to determine the best combination.

Can anyone comment on the attitude of a h286 and stall converter in a daily scenario?

Cheers kindly fellas

 

[Dean1985]

The knock sensor setup is garbage on the 5L because the block was developed in the 60s before they existed and they were added as a bit of an afterthought 'feature' in the 90s. It's pretty common to just unplug the knock sensor and deactivate it when doing any kind of cam work because of the amount of false positives that the sensor gives. It's really a situation where a knock box and headphones is far more accurate.

You're still using a Delco ECU, yeah? Does your tuner do a lot of 304s? Nowra seems about the same distance to Sydney and Canberra, if you feel like getting a second opinion there's obviously a few good shops in Sydney (would start looking at Ace Performance tuning), while in Canberra there's Gentech and Profection, both shops have really good 5L support.

And the rattle - pinging or does it sound like oiling/tolerance issue?

Shes definitely a ping, i just described as rattle for readability sake.

 

[losh1971]

I can provide a partial answer, a stally is fine for DD. I have a 3500 (IIRC) in my V6.