"You" frequently hear of folks supposedly using a lighter Holley secondary spring in the Autolite 4100. I've never seen anything definitive that the springs would actually fit.
I've got an Eelco plate on mine. It opens the secondaries pretty aggressively even in the "mid" position.
Display MoreRight on Dan Case!
4100 flow rates posted are pretty close to what we saw at JBA back in the day.
OP needs this monster 1.23 prototype for his 347
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The content cannot be displayed because you do not have authorisation to view this content. What is a 1.23 prototype , first i have seen one.
I got it off eBay. Listed as coming from the estate of an Autolite engineer. It's supposedly a carb intended for paxton applications.
Right on Dan Case!
4100 flow rates posted are pretty close to what we saw at JBA back in the day.
OP needs this monster 1.23 prototype for his 347 
289HD, aka GT40 heads-
There's an "early' and "late' design with regard to the spring pockets. (Early as in like the 289HP spring pockets, late as in machined in look/change in the head casting).
They used the close tolerance pushrods slots like the 289HP. The combustion chamber CC numbers are larger than the 289HP. The intake port is superior and the exhaust port
is far superior as compared to the 289HP. The only exhaust port close to that of a 289 HD would be those on the 302TP. They use GT40 valves, which are larger diameter than 289HP. (i.e.: 1.875 and 1.625....... pretty sure some were raced with 2.02's also)
Your brain-trust on these things would be Craig Conley, Randy Gillis, Jay Cushman and I'm sure a few others on this forum.
Yes I know, not 289HP.....
Anyone know current pricing on these things?
(Service block D1ZE-BA, date code works out to March 26, 1974
New, standard bore, main caps present, not molested. Sonic
checked, good shape)
Thanks.
The "K" booster was also used on the 1962 221 carburetor. (C2OE-N & C2OE-R)
I've used those more than once on 1.12 carbs on small blocks. It does fix the unresponsive idle mixture screw issues, is a legitimate "replaced by" booster in the hipo carburetor lineage and provides correct performance from that carb.
I've never checked the bushing size though.....
Please merge 66GT289
TIA
Couldn't find the Username 66GT289, do you remember which email you used back then?
BR,
Niko
DELETED FOR PRIVACY REASONS.
Please merge 66GT289
TIA
