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Hi, I purchased a holley TBI of ebay cheap. Had a strange Part #, but all the sensors matched. It has the 2" butterflies but they won't open if I mount to intake since intake has 1.75" holes. Do I buy a throttle body spacer with 2" holes, or get the intake machined out to 2"? What would be best route? I plan on upgrading heads soon, that's why I jumped on this deal. So one I add vortec heads I could do a new intake. Anyway let me know what you think please?
Interesting^^^tapered gasket. On a buddies car that I was working on, he already had a 1" spacer and I noticed the Holley 670 on there. Couldn't help shining a flashlight down the throttle bores to see if there was a mismatched lip. To my surprise, the spacer itself was tapered. I saw no benefit to running it this way and never bothered to adjust AE for the bigger throttle body. Anyhoo...I've done the 2" bore TBs by using a spacer that centers the bore over a spreadbore/quadrajet intake. I didn't care for the Holley injectors. They told me it flowed 80#s but I think that's bc Holley flowed them at 28 psi. Injector kept going static when trying to tune it w 12.5 psi. Ended up swapping entire injector pod with OE GM 61#s.
Seem to recall one web search the person had the proper tooling to bore oe manifold to 2" and another person that used a boring bit going really slow. That must've been a chore!!! Oh, one more thing there's seems to be some issues with the IAC passages. Need to make sure your gasket covers the passages completely and the other thing was with the shared passages with the MAP causing issues.
Thank you both. That makes sense. I read all the bad holley stuff after I bought it. Lol. Figured I would buy and play around with prom. If no improvement tear it back off. I did order one of the tappered spacers for$ 38 bucks. If I dont get close to no "up to 25% increase in HP" like holley states. Haha. I'll put it all back on ebay and let someone else mess with it, Maybe or put the GM pod on it like you said, Just look at those stock small bores in TB and think, how's that going to ever make decent power? Maybe I can just get heads now too. I think that's the last piece missing. I appreacite both of you. Thanks !!
There's two kinds of Holley fuel injectors for those aftermarket TBI units. The early style has rubber caps over the top of the injectors. Those were replaced later by injectors that did not have the rubber caps. Supposedly, the second design were the injectors to have.
There's two kinds of Holley fuel injectors for those aftermarket TBI units. The early style has rubber caps over the top of the injectors. Those were replaced later by injectors that did not have the rubber caps. Supposedly, the second design were the injectors to have.
here is a picture, not a great one but it's currently pouring out. The part # ends in 5389. I been searching that on here and I believe there 60lb. But I might need to find that post about the holley injectors again. Thanks for the input, much appreciated. I did order a TBI tappered aluminum spacer. I can at least make sure this thing works. The guy I bought it from knew nothing about it. Then said maybe 90's truck, a friend gave him a box of parts. So I like to make sure it works with the spacer. If tuning goes OK, it works good, maybe I'll have the intake bored out. One step at a time I guess. If it don't work I'm out $160. But as long as it works, I can resell if needed. I just took a chance at this. Figured it would be a test. Will I see any improvement, especially with a tb spacer, most likely not. Lol. The unit is pretty clean but these castings are a mess on the outside.
Last edited by JeepYJv8; Jun 12, 2023 at 05:29 PM.
There's two kinds of Holley fuel injectors for those aftermarket TBI units. The early style has rubber caps over the top of the injectors. Those were replaced later by injectors that did not have the rubber caps. Supposedly, the second design were the injectors to have.
I have the rubber caps on my TBI, can I purchase new injectors or do I need to invest in complete TBI?
Very easy to retrofit a stock injector pod on to a Holley TBI. I prefer that route actually. Cheap and reliable. The GM injectors rarely fail.
Thanks for your reply. I wasn't sure if a Holley Throttle injector was a different size to a GM injectors. My Holley TBI system is very old, purchased it around 1998.
Whatever you do when you go to install it do not use the port I marked with a Red "X" for the MAP sensor. That will cause cold start flooding and a rich/rough idle as that port is shared with the IAC. Instead pull the vacuum for the MAP
off one of the full manifold vacuum ports on the front of the TBI unit.
