SBC TPI 0411 24X conversioin

[evilstuie]

Hey Mikey,
My problem is that I'm in Australia, we had one maybe 2 cars that have a Chev Small Block in them (HT I think) and they were back in the 70s with a carb. Everything they tune here is a LSx and there might be maybe a handful at the absolute most of other people here in Australia that have done a 24x conversion.
All the shops I've talked to about tuning it don't have a clue what I'm talking about when I explain the setup, which doesn't instil much confidence.
My main concern is without them knowing about the 24x conversion and just trying to tune the tables like they would for an LS1, they'll
1) Not be able to do it
2) Spend a lot of hours ($$$) trying to tune it
3) Damage the motor
4) Hand it back to me no better and with a 1K+ bill.

If tuning is as simple as doing a run on the dyno, taking the readings and adjusting spark and fuel until the maximum power is obtained, and then extrapolating the values measured into the areas of the map that weren't measured using smoothing or calculations, then it will be fine I guess, so long as he uses the base tune LRT has configured for me, and doesn't start from scratch with a base tune and miss out things like bank assignments etc.

If it requires knowledge and understanding of the differences in the SBC spark requirements and timing then it may be problematic.

There's also the risk of "tuners" just using a library of LS1 motor tunes that they charge an arm and a leg to flash a generic tune which won't come anywhere near what mine needs.

[evilstuie]

Hey Mikey,
My problem is that I'm in Australia, we had one maybe 2 cars that have a Chev Small Block in them (HT I think) and they were back in the 70s with a carb. Everything they tune here is a LSx and there might be maybe a handful at the absolute most of other people here in Australia that have done a 24x conversion.
All the shops I've talked to about tuning it don't have a clue what I'm talking about when I explain the setup, which doesn't instil much confidence.
My main concern is without them knowing about the 24x conversion and just trying to tune the tables like they would for an LS1, they'll
1) Not be able to do it
2) Spend a lot of hours ($$$) trying to tune it
3) Damage the motor
4) Hand it back to me no better and with a 1K+ bill.

If tuning is as simple as doing a run on the dyno, taking the readings and adjusting spark and fuel until the maximum power is obtained, and then extrapolating the values measured into the areas of the map that weren't measured using smoothing or calculations, then it will be fine I guess, so long as he uses the base tune LRT has configured for me, and doesn't start from scratch with a base tune and miss out things like bank assignments etc.

If it requires knowledge and understanding of the differences in the SBC spark requirements and timing then it may be problematic.

There's also the risk of "tuners" just using a library of LS1 motor tunes that they charge an arm and a leg to flash a generic tune which won't come anywhere near what mine needs.

Well I've still got some misfiring issues I think. Going to hit the exhaust ports today with a laser thermometer and see if I can find a cylinder that's not firing.
I also bit the bullet and bought the HP tuners suite and scantool to help diagnose and tune. I installed a fuel pressure gauge, wideband and vacuum gauge, and can now see i've got between 7-11" of vacuum that bounces around wildly, and with the XR270HR cam in a 400SBC, it should be more around the 15-20" and very steady, so I have to go exploring after the misfiring is fixed to see what's causing it.

My next best guess is either a vacuum leak on the intake gasket, or something more sinister like a cam lobe being wiped, collapsed/spun lifter, valve seal or something else mechanical.
From what I've read there's also the possibility the low vacuum is because the valve timing is wrong. I've checked for vacuum leaks outside the motor, so maybe it is in the motor.

[Mikey G]

Well I've still got some misfiring issues I think. Going to hit the exhaust ports today with a laser thermometer and see if I can find a cylinder that's not firing.
I also bit the bullet and bought the HP tuners suite and scantool to help diagnose and tune. I installed a fuel pressure gauge, wideband and vacuum gauge, and can now see i've got between 7-11" of vacuum that bounces around wildly, and with the XR270HR cam in a 400SBC, it should be more around the 15-20" and very steady, so I have to go exploring after the misfiring is fixed to see what's causing it.

My next best guess is either a vacuum leak on the intake gasket, or something more sinister like a cam lobe being wiped, collapsed/spun lifter, valve seal or something else mechanical.
From what I've read there's also the possibility the low vacuum is because the valve timing is wrong. I've checked for vacuum leaks outside the motor, so maybe it is in the motor.

Looking to see if you're firing on all cylinders with a temp gun is very useful - correct if required
Check your initial and total timing. Engine can sound quite good but have a low vacuum.
How are you checking for vacuum leaks? What intake you using? - Perhaps a missed open port somewhere? (I've been fooled at least half dozen times )

Let me know,

Mikey G