Hi !

A friend (member : 88´TransAm) has problems with his 88 Firebird 305 cui TBI.

He uses a ´94 Z28 LT1 camshaft, a EP-241 TPI fuel pump, a fuel pressure regulator at 18 PSI, a ported TBI with standard injectors, upgraded intake manifold (46 mm bores) and the matching EBL-ECM.

After all modifications and adjustments he started the engine and we could hear something sounds like knocking from engines passenger side.

So he had a look to the valve adjustments again. He also changed the spark plugs (AC Delco R45TS - ok, original is R46TS but a little bit colder should be no problem). The old one were a little bit black.

The BPC value of the EBL-ECM has been modified to 18 PSI.

Ignition is adjusted to 6° BTOD. Further distributer adjusts made no goal.

Any idea ?

P.

 

Knocking sound will be something mechanical or exhaust?.

For the tuning the stock federal ebl bin should work fine to start out once fueling settings are adjusted for higher fuel pfressure.

I would start with 0°. Or you need to adjust it correctly in the bin.

 

I remember the LT1 cam digest thread says to set the distributor somewhere about 8° advanced or more? 0° is stock tbi cam timing and will imho most likely stall the engine off-idle after an lt1 cam swap..

 

You only need to move the base dist degrees if you need to widen the physical upper limit of degrees. Mine was at 6 so I used 6 in EBL. Then the dist moved a bit so I put the new value in ebl. What determines SA is the SA tables and off coarse all the 10 or more other % changes based on choke, temp, etc.

I do not know what the physical constraints are for a stock distributor, but EBL max SA is 41.8. What you need to verify is what SA - Idle State SA is, if the bit to use that value at idle is on(Option Word 2 - Bit 1 - IdlSa) and that SA - Initial SA is set to the physical degree value you see with a timing light with that one plug disconnected for timing.

 

That advance is probaly to get it running with the stock tune and ecm, as starting point. But could be interesting to test if there is a difference by having advance set at the distributor and adjusted in the bin.

 

Ok, Patrick and me found the problem. It was just a leak on the passenger side header. Cylinder 2. Now, i am happy and the engine runs very nice.
Now, i adjusted the ignition to 4° BTDC.