Sounds like you may have a brake hose that is suffering from separation inside preventing fluid from returning when pedal is released. I have seen...
I would also like to see a detailed write up on the stock EFI for a 4.0 head on a 258 since I already have the 4.0 head installed for over 20 yrs...
Looks like a very nice project.
I want to clarify my earlier post about the comparison between EFI and old style carbeuretors...make no mistake...EFI is superior in almost all...
I have a 390 Holley on my 258 using an Offy Dual Port along with a 4.0 head, has worked very well for 21 years. This combo delivers better mileage...
For the same money there are several GPS speedos available, no changes required for tire size..
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