TBI305Camaro

title says it all...i was wondering how hard it would be to adapt a holley 670cfm TBI to a zz4 crate motor? im pretty sure the crate motor comes with a vaccum advanced distributer...ill have to change that right? i think ive made up my mind to just go ahead and get all my suspension changed up, rims, stall, new driveshaft, hood, and start saving for a 350...i could probably go carb easier with the new motor but id like to have the reliablity of the TBI but if carb would be better i might go with that

Z28 Boy

it wouldnt be that hard. just look at what you have on your motor now, and it is all the same components.

you will need a different distributor...you can reuse your stock one. the ZZ4 has a roller cam, and so does your motor, so you will be ok as far as the distributor gear goes.

other than that the rest of your ignition will work.

you will want a free flowing intake, probably a performer RPM or equivalent. just get a TBI adaptor and you can use the 670 CFM throttle body.

other than that, just about anything else you would use on the 305 will bolt up...flexplate, tranny, accessory brackets, exhaust.

-brian

Z28 Boy

in all the above stuff, i am just talking about the physical "what will fit" stuff.

other than that, you will need a lot of computer calibration, and tuning.

-brian

TBI305Camaro

i was talking more on the lines of the computer...i figured it would take alot to get that a 305 lo3 computer to work right on a zz4

Z28 Boy

physically all thej computer, etc. will hook up. you will just need an EPROM burned. that's all i meant by computer work.

-brian

TBI305Camaro

that probably wont be to bad...i havent decided wether to get a new motor this summer or another car...id like to get a l98 TPI z28 and keep mine now so ill have a car to drive while the other is down

BahamutRS

Talk to JPrevost! He's nuts about that PROM nonsense, eh?

JPrevost

Eprom burning for a speed density EFI system is like tuning a carb with jets and screws etc. If you think you can take a carb made for a 170hp motor and make it run on a bigger more powerful engine then try. The good thing is that with TBI you can change the fuel injector size and pressure but you still can't adjust the fuel and timing curves/maps unless you tap into the awesome resources stored in the eprom.
It's been done but use a vac. AFPR or you'll need to get a custom eprom.

91Bird305

won't it be most likely robbing a lot of power or should I say depriving a lot of power from that ZZ4 motor. They recommend a 750cfm carb and dynoed the engine with a 750cfm carb. Wouldn't he want to shop around for a 750cfm TB so that he knows he is getting all the hp/tq from that engine? Cause I am guessing that GMHTP probably had that 750cfm jetted when they dynoed that engine so that 750 was probably running as good as it could get. Just a thought though.

Z28 Boy

and a good thought at that...

-brian

Keith5

Well if they recommend a 650 carb with the 330 horsepower 350HO, and the zz4 just makes 25 more horsepower with another whole point in compression, the 670 should make power just fine on a zz4.

Mark305TBI

Thing about comparing flow rates between the Holley 670cfm throttle body (or any two barrel, for that matter) and four barrel carbs is that the throttle bodies are flow rated at a 3" pressure drop. The four barrels are rated at 1.5". It isn't really a totally fair comparison. It might not be correct to say that the 670cfm throttle body can the same engine as a 670cfm carburetor...

91Bird305

Damn, I think we need a Carb and FI expert in here to anwser this question. To many things are a factor, LoL. I hate that.

AJ_92RS

You are so right.

A 670cfm @ 3.0 inHg would only flow about 475 if flowed @ 1.5 inHg.

That's good for throttle response, bad for anything above 4500 RPM.

AJ

91rsrider

personally i would just go for carb.that ZZ4 is rated with a carb on it,and the TBI would just choke the hell out of that motor.then when you do get it running you gotta bust your *** to tune that thing to get it optimal.thats why im dumping the TBI when i get my 350 next summer.i dont care what anyone says,tuning carbs is a whole hella lot easier than dealing with a computer.i know,cause ive done it with a 403 olds motor with a fat holley 700 double pumper sitting on top.and all it took was a little rejetting and spark curve tuning,and now the car is an animal.oh yeah and that car is my buds 79 trans am.ran 14.9 stock before we changed the heads to 70 olds 350 heads,RPM manifold,big azz cam,and true dual exhaust.now its running a 13.7@107 with 2.46 gears!ahh cant wait till he gets gears in that thing.sorry for the long post,just thought i would get my $.02 in.later ya'll.