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What to do - rebuild?

Discussion in 'VR - VS Holden Commodore (1993 - 1997)' started by Dean1985, Feb 25, 2020.

  1. Dean1985

    Dean1985 New Member

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    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.
     
  2. losh1971

    losh1971 Well-Known Member

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    Probably a stupid question but are you running 98?
     
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  3. Dean1985

    Dean1985 New Member

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    Yeah mate 98. My wallet loves it.

    Its that borderline the slightest quality difference will make it worse.
     
  4. VS 5.0

    VS 5.0 Well-Known Member

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    Change the cam to suit the compression ?
     
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  5. woteva

    woteva NEED 4 SPEED

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

    Sandman Challenge Accepted

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

    _R_J_K_ Well-Known Member

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    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?
     
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  8. Dean1985

    Dean1985 New Member

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    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
     
  9. Dean1985

    Dean1985 New Member

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    Shes definitely a ping, i just described as rattle for readability sake.
     
  10. losh1971

    losh1971 Well-Known Member

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

    gtrboyy Well-Known Member

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    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.
     
    Last edited: Feb 26, 2020
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  12. Dean1985

    Dean1985 New Member

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    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.
     
  13. Vin999

    Vin999 Active Member

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    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.
     
  14. Dean1985

    Dean1985 New Member

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    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.
     
  15. EYY

    EYY Well-Known Member

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    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.
     
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  16. Dean1985

    Dean1985 New Member

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    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?
     
  17. someguy360

    someguy360 Well-Known Member

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    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.
     
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  18. EYY

    EYY Well-Known Member

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    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.
     
  19. gtrboyy

    gtrboyy Well-Known Member

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    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.
     
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  20. Vin999

    Vin999 Active Member

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    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.
     

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