I thought the same thing when I saw my 8.1L starter shared the same case as a 3800 starter. The larger diameter flex plate/flywheel does give the starter more leverage, though and the little starter had no problem cranking it. I had some questions about this but never posted up here. The 2003+ starter is a different style and it seems the block itself must have changed to accommodate.
Unlike LS engines, the nice thing about the 8.1L is it has the staggard bolt pattern and same ole 168 tooth ring gear GM has used for decades. Any starter from decades of BBC’s or SBC’s with the staggard bolt pattern and 168 tooth flywheel will work. Don’t feel obligated to spend crazy money to use an “8.1L” application starter
From page 1 of this thread:
- The L18 8.1L has the same foot print as older BBC engines and will bolt in the same as any other older SBC and BBC. In fact, the L18 will accept any exhaust manifold or header from older BBC engines. The starter motor from any older SBC and BBC for use with a 168 tooth flywheel will also fit the L18. Any transmission from an old PowerGlide, TH350, TH400 to Allison, to NV4500, etc. will bolt on to it as well.
I like to run Denso 281-8002 starters on everything. The Denso starter on my Suburban’s 8.1 is the same exact starter that was on the TBI 5.7L before the swap. These starters aren't cheap but they will be the last one you ever buy. This is the starter UPS uses where it lives up to their punishment of starting hundreds of times a day. It will turn ring gear teeth into razer blades long before the starter wears out as the Rockwell hardness of the starter drive gear is harder (55) then the ring gear on the flywheel/flexplate which was around 35. Us guys would probably never see the ring gear teeth get worn down like they do.
I think the shrouded nose of the Delco style vs the open gear of the Denso style was throwing me off. I have a aluminum inspection cover and not the stamped steel one that came with 8.1L trucks, but I suppose as long as the nose diameter is the same, they will interchange. It's just weird that the Denso style isn't listed as compatible for anything before 2003 and not studying the pictures I just accepted that.
went and looked at a 2001 3500HD std cab today . she has 80,xxx miles on the od and the nice 8.1 / nv4500 combo . told him i would take it for his asking price of 2500 bucks . going to keep it as a work truck for my self . Pics to come soon .