What to do - rebuild?

[gtrboyy]

Knock sensor is junk,most tunes end up having them disabled for various reasons.

How did you you work out 10:1 compression ratio? Got pics of piston in bores? Cam timing?

Pistons would need to be flush with the block,most sit down bore without decent deck skim unless been machined before or perhaps using chev pistons or something weird.Something amiss.

But yeah baby 268 not much more than standard so if comp is hiked up a decent amount it wont like baby cam/banana combination....most do the opposite cam too big for stock low compression

A good stally won't hurt drivability at all...2800 lockup & 3.45/3.7 diff gears would make nice all-rounder

Cam wise you'd be looking at 284 or better yet modern day version of it from camtech

Off the shelf tunes only work well when it's tried & true combination that's been done a million times otherwise if done something wrong or tried to be different then road/dyno tune &/or troubleshooting required.

I'm surprised you were sold the 268 when even a 276 is tad small for stock 304,just sounds nicer.

 

[Dean1985]

The engineer said its somewhere between 9.5 - 10:1.

I definitely didnt measure it.

I am told the flat top pistons would make a decent difference?

I am to believe the block and heads were virgin material and the engineer only ripped 10thou off them.

A stally and cam would cost more than ripping it down and putting in dished pistons after what i saw last night

The car was dyno tuned and then live tuned around town and on the highway by a bloke from Sydney. (Dont want to use names or businesses as i havent asked permission.)

The decision to do something about the pinging occurred when i broke down the other day.according to the codes the TPS was "stuck open". When limping the vehicle home (fluctuating idle and terrible gear shifts) the code for "TPS voltage too low" was also logged.

Things just getting worse i decided its time to pull it off the street and fix things for good.

 

[Vin999]

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

Sounds like your Mr Tuner was your Mr Engine Builder, if not, speak to a good engine builder and head porter first, forget the rest. Your comp ratio seems funny. Flat top piston depth in bore ? deck height ? spring heights/pressure ? pushrods ? gasket size ? heads/cc ? distributor ? exhaust ? stall etc there's more to it that just comp and a tuner.

Would'nt hurt to just put back a set of clean ported stock heads for that 268 cam and ecu, cheap improvement to your situation. Cut your losses .... If your going to rip engine apart, go do the proper 355 stroker combo with a good engine builder and the 286 cam or a camtech will suit better with a head port job.

 

[Dean1985]

Nah Mr Tuner is reputable and well known.

The engineer was from the south coast.

What would head porting achieve?

Valve springs were upgraded with the cam as a package from Outlaw Speedshop. LT1 valve springs or something. Pushrods std. Rockers std.

 

[EYY]

No massive loss - lucky it’s an easy fix (provided you don’t drive it anymore and do serious damage).

I’d expect compression to be between 9.5 to 9.8:1 with those mods. Crane 284 would be great and still easy on a relatively stock valvetrain. If you’re willing to spend a little more on roller rockers then consider the 286.

Without a histall and diff gears, I’d definitely choose something along the lines of a 284.

268 is too small - I’ve got that cam in my 304 and absolutely no way I’d run it with flat tops. Don’t bother with porting or pulling the whole thing apart. Just work with what you have. You’ll be pleasantly surprised with the difference the right car makes.

 

[Dean1985]

No massive loss - lucky it’s an easy fix (provided you don’t drive it anymore and do serious damage).

I’d expect compression to be between 9.5 to 9.8:1 with those mods. Crane 284 would be great and still easy on a relatively stock valvetrain. If you’re willing to spend a little more on roller rockers then consider the 286.

Without a histall and diff gears, I’d definitely choose something along the lines of a 284.

268 is too small - I’ve got that cam in my 304 and absolutely no way I’d run it with flat tops. Don’t bother with porting or pulling the whole thing apart. Just work with what you have. You’ll be pleasantly surprised with the difference the right car makes.

Thanks for the reply, Eyy.

So in your opinion, youre saying a 284 would potentially sort my dramas without the need of a stall converter? Borderline?

 

[someguy360]

284 without a converter with ok compression will be drivable on the streert.

I'd probably go some taller diff gears if you get the chance down the track, that will help pull it into the powerband quicker will retaining drivability.

I've just gone from a 268 to a 276 in mine, and after driving both I can definitely see how the 268 would have been crippling an engine with that kinda comp.


I'm building an engine at the moment with very similar specs to yours and I'm going to be going the 284, it's a really good all round cam for both drivability, sound and power.

 

[EYY]

Thanks for the reply, Eyy.

So in your opinion, youre saying a 284 would potentially sort my dramas without the need of a stall converter? Borderline?

If you MUST stay stock stall, you can and it’ll be fine. But if you want to make the most of the new engine, it’ll really need a histall and 3.45-3.9:1 diff gears.

 

[gtrboyy]

Don't have to do stally & gears it just might push on the brakes at idle in gear & feel a bit doughy light throttle.

My 304 has come cam that is closer 276 specs,reco lpg motor from wreckers..sitting at lights you can feel it push against the brakes.

Gears & stally just compliment everything else done to make them nicer to drive + added performance.

 

[Vin999]

If you MUST stay stock stall, you can and it’ll be fine. But if you want to make the most of the new engine, it’ll really need a histall and 3.45-3.9:1 diff gears.

Very good advice EYY
Hey Ian have a chat with this guy 0414 174289 he's good with 304 motors and heads, worth getting advice on combo.