V8 Swap (Page 1/1)
Watsonjay JUL 08, 10:44 PM
When bolting my sbc to trans there is about a 5/8 inch gap which makes sense since the adapter plate is about 3/4 inch thick. My reading says gap shouldn’t be more than 1/4 inch. I am guessing everyone else that has done this swap has had same problem but i cant find anything on it. It is stock th125c.

Thanks in advance.

Jason

[This message has been edited by Watsonjay (edited 07-08-2020).]

fieroguru JUL 09, 06:51 AM
What kit are you using to bolt the two together? Archie and Zumalt? It sounds like you are using the Zumalt as the Archie kit uses a much thicker adapter plate.

With the Zumalt kit, you have to cut the starter pad off the engine to clear the 125C transmission. Even doing that, things are very tight inside the bellhousing. When I did a 4.3L/4T60 swap using a Zumalt based kit, I added spacers to made the overall adapter thickness about 3/4" so the crankshaft to flexplate bolts would clear the torque converter body.
Watsonjay JUL 09, 01:19 PM
I bought a kit from jimmies in canada and it was crap so I didn’t want to spend that much more for stuff I already had. I bought another from street dreams by Ross. It sounds like the zumalt. I did have to cit the block. It uses a 280z starter.

What spacers?
Watsonjay JUL 09, 01:21 PM
My problem is there is too much gap between flex plate and torque converter
fieroguru JUL 09, 05:24 PM
Like this?



I welded spacers to the flex plate to fill the gap:



While checking measurements, I also noticed that the protruding torque converter would keep the transmission from fully meeting the adapter plate, so I used some large washers at the bellhusing bolt locations to space the transmission from the adapter plate to get about 3/4" from engine bellhousing face to transmission bellhousing face.



Start about 3/4s the way down this page for a lot of info. Granted this was a 4.3/4T60 swap, but there will be a lot of similarities:
http://www.fiero.nl/forum/A...0314-2-087174-2.html
Dennis LaGrua JUL 09, 05:53 PM
It looks like you are doing a terrific job of mating the SBC to the TH125 three speed. It should work out well but be advised that without some internal modifications, that automatic trans is not real strong. The good news is that they can be built stronger by adding a HD clutch pack, and shift kit. We built one a while back and it held strong at WOT with 250 hp engines. The other option is the 4T60 transmission that is stronger. Good luck on the project.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
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Watsonjay JUL 09, 08:07 PM
Thanks for the responses. I will probably just do the same thing with the washers. I just figured this would be a common issue and couldn’t find anything. Thanks for the heads up on the tranny. My v8 estimates around 350hp so the tranny probably won’t last long. I do have a th440 that i plan on doing eventually. Just want to get up and running for now. Been a long time on project.