Hi!
I drive a stock 1988 Camaro 305 TBI.

I would like to modify the engine, initially starting with the TBI. I have thought about modifying the stock unit but think it may be easier and probably cheaper to go with an aftermarket unit.

After much searching on the web I keep finding the Holley 670 cfm unit, although it appears to be for trucks only.
I emailed Holley to ask if the unit would fit my engine and they said no as the EGR would hit. I however see that a lot of third gen owners seem to use and support the Holley unit.

Does the Holley TBI directly replace the stock unit with no modifications? or would the EGR need to be altered/removed. I am really confused and would appreciate any suggestions.

 

Do a search for "holley 670 stock intake". It'll bring up everything you would want to know about the unit.

 

I have the holley unit on my 305 and I did not have to do any mods to fit it

 

Re: 1989RS comments.

Does it even come close to the EGR valve? how much clearance is there?
What Intake manifold are you using and have you ported the intake manifold bores to match the larger TBI bores?

More importantly, what sort of performance gains did you get?

cheers!

 

JFYI: The 670 holley unit is exactly the same demisions cast as the stock 11/16" bore units. The only time there was any clearance issues was with one of holley's intake manifolds. I don't remember if it was a carb intake with EGR or if it was TBI. It would be imbarresing if it was their pro-jection intake manifold that didn't clear the IAC.
If anything you'll have slightly more room for the EGR valve with the holley unit on a stock intake. The reason for this is the thick tapper gasket used to funnel the 2" bore of the 670 into the 11/16" bore. I wouldn't invest the money into the larger bore TB until you've already tried the stock unit, done the ultimate TBI mods (tech section links from the main page), AND gotten a larger intake which would accept the TB with just an adaptor plate (carb intakes).

 

I have a holley intake w/ a 4 bbl adaptor plate so i have no egr but when i had the egr it bolted up fine. as for performance gains, i picked up a bunch of bottom end and not so much top end to my dissapointment but overall performance gains were
2/10ths of a sec in the 1/8 th and 2mph

 

What I intend on doing is getting the Holley 670cfm unit and also the Edelbrock performer intake manifold.
I would port out the manifold bores to match the Holley TB but leave the runners at Edelbrocks factory standard.

This I hope, would let a lot of air in, then accelerate it through to the valves. I should be able to reuse my EGR valve and from what people have said it should not hit!

cheers!

 

you might want to consider getting a 4 bbl intake instead of the tbi piece it would be easier to swap intakes if you get an adaptor if you ever plan on doing so. I did that and it works great with the adaptor

 

I am also planning to run a carb on mine because my engine has reached the limits of effectively using the tbi and im looking for more top end. Im told that swapping to a carb will greatly improve my top end performance