[Mister L]

I just did an engine change on my 03 auto Mach with 200,400 miles on it. My replacement engine was from eBay and is an original, NEW, old stock manufactured short block, pn XR3Z-6009-BA dated Jan 2008. It was a short block only and this is not a reman but an original production block. Of course, following the fitment guide on eBay said it wouldn't fit but running that part number against Fords website said otherwise.

Here are the issues when changing from a 6 bolt cast crank to an 8 bolt forged crank in the Ford 4.6L engines we have. You have to change the Flexplate to an 8 bolt unit and I bought mine from Summit. It is an ATP Z-346, 8 bolt, 164 tooth, neutral balanced and it fit perfect and cost was 38 bucks. You must also use auto flexplate bolts to attach it as the 8 bolts for a manual flywheel are too long and will bottom out in the crank flange. You should replace the flexplate bolts and I bought mine from Ford p/n F1AZ-6379-A for 1.97 ea. Additionally, the torque converter bolt pattern for this flexplate is 11.44" and your stock converter is like 10.5 so it won't fit.

I picked up a rebuilt torque converter from Blumenthals Transmissions here in OKC that had the 11.44 bolt spacing and fits perfectly in the 4R70W transmission and matches the ATP flexplate. It is a Dayco F60 according to Blementhals and is industry standard. It is larger than stock dimensionally but fits well in the bellhousing and is equivelant to your stock converter. This new engine is not built for racing but dependability as a daily driver so a high stall converter was not what I was after. I likewise replaced the torque converter nuts which are self locking, p/n -378941-S441 (package of 4). I also changed the input shaft seal p/n F2VY-7A248-A since I was changing the converter.

Coolant crossover O-ring p/n -391533-S100

I bought a set of motor mounts from NAPA and they were annotated as w/o Appearance Package and compared to the old ones were about 3/4 inch too tall. Their other option for 4.6s had incorrect block attach points and I was then told that all the local shops will not use aftermarket mounts becuase of poor fit. So, if replacing motor mounts, get OEM. I decided not to change mine.

FWIW, I have the 4.6l Hot Rodding book by Sean Hyland and in his book he talks about harmonic balancers. I personally spoke with him yesterday and he confirmed the use of the automatic harmonic balancers from a Mach1 to be used with either the cast 6 bolt or forged 8 bolt crankshafts in a 4.6 with Autotrans. It was likewise his comment on the flywheel bolts bottoming out if you use them with a flexplate. Use the shorter bolts.

Engine is being installed in the car today but I thought I would share my experience with this change while I still had data. And yes, out the bottom, not out the top in my garage! Hope this helps anyone considering this change.