Plan B - Holley HP ECU and old Pro-jection 4D Throttle Body
So I tried and failed to get a Megasquirt to work on my 496 BBC. So I went back and tried a series of carbs that got my car on the road which is what I really wanted. The problem is streetability... I am tuning with both a WBO2 sensor and vacuum gauge and cannot get the idle circuit to operate due to low manifold vacuum at idle. This is totally my fault as I selected an aggressive mechanical roller with lots of overlap to try to bring down my dynamic compression. Well, shockingly enough lots of overlap does not lead to much vacuum at idle.
Now I have a little more time and experience and am taking another run at EFI. I got a Holley HP ECU and the harness kit designed to be used with the old 4D TB. I plan to drill the boss on the TB to support an IAC. The TB that I have already has 85lb/hr injectors so I don't see a need to change anything on the TB except add the IAC capability.
I have taken measurements to determine where I think I want to put the passages in the top and bottom of the TB. I am now waiting for the IAC to arrive, hopefully on Friday. In the meantime I am off to the junkyard tomorrow to find a trashed Chrysler with TBI to get that IAC and disassemble the unit to get the pintle out and with my trusty drill and lapping compound use it to smooth the surface of where the pintle seals off the vacuum leak. The Holley TB was designed to use either the GM or Chrysler IAC, U just need the correct shape of the pintle to make sure the new one seats.
In the interest of full disclosure here is the link to my megasquirt endeavour. Follow this thread at your own risk.
Pictures to follow...
1969 L78 SS396 (Engine Long Gone)
BBC 496, TKO600, Beautiful Stock 12 Bolt Posi (maybe the only stock thing left.
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