Derek The Great

So I've done my share of thread searching and haven't found anyone that's tried using the Holley direct TBI replacement unit. Here's what I'm looking at dropping in: http://holley.com/502-6.asp

Question is, will it fit? 502-5 is for the 305's but I eventually plan to do the the 350 TBI swap so I figured I'd just go with the 350 model. If it does fit, has anyone noticed any performance gains?

Thanks,
Derek

lozantius82

iTrader: (1)

The Holley version will bolt right up to a Holley projection intake but not on your stock intake. You need to bore the holes on your stock intake to 2 inches on both sides. As far as performance your 305 will run rich and loose performance. The Holley tbi is for a 350 and you will need to get a custom chip made. Your stock TBI is fine, put on a set of headers with 3inch piping. Buy a 84 camaro dual snorkal air cleaner, and slap some 3.42 gears in your diff. Call brian harris (TBICHIPS.COM) and get a stage 2 chip made after you complete that list of mods. Your fire chicken will run hard!!! A 350 is the hot ticket if you want to destroy foxbodys. Goodluck!!!

Derek The Great

Thanks for the reply, that's exactly what I wanted to know. I've been playing around with the idea of putting a posi unit in and whether or not I wanted to keep the 2.73's.. I end up on the highway a lot and although I'd love the opportunity to race its just never there. As it sits now the car has aluminum heads from trickflow, edlebrock performer tbi manifold, full msd ignition and a jet stage 1 chip (I have the link to tbichips on my desktop so I can have harris make me a custom one). The car is a lot of fun to drive now. I remember when I first got it it wouldn't even squak the tires from a stand still and wouldn't do a brake torque if you had the a/c on. Now I get plenty of rubber and it pulls hard after 70 mph..

Derek The Great

hell I need to go back to the track, 16.9's are terrible, I'd hope i'm at least low 15's now

ex-x-fire

Check out the ultimate tbi mods, including the salad bowl mod.

lozantius82

iTrader: (1)

3.42's will be perfect because your car will be very slow off the line with 2.73's. What kind of heads and how many cc's are they? 16.9 is very slow lol TRUST ME Brian Harris will tune it awesome just tell him your EXACT SPECS!!! You just need to stick to the right parts and not mismatch them either. TBI is all torque so match your componants from idle to 5000 rpm. Many people diss TBI but its the engine that sucks.

86firebird350

I'd say don't bother buying the Holley TB unless you've found a killer deal on one somewhere. They're extremely expensive brand new and won't offer that much performance gain over stock. If you really want a 2" tb, you can buy reman units from a member here (don't remember his name) on ebay. They're GM throttle bodies off of the trucks I believe so everything bolts up as it should unlike the Holley. You can always do the ultimate TBI mods as mentioned previously also to increase flow characteristics.

Basically I would suggest doing like everyone else mentioned; upgrade your exhaust and gears first. You'll get a much better bang for your buck and a good SOTP feel.

thomas1976

You have the TFS 175 heads? What did you do to fuel it? Trying to evaluate if it needs a bigger TB

UnderCover89TBI

iTrader: (25)

dctrumpet is his name. and for a 305 you deffinately dont need the holley. I am having trouble with the holley feeding my 355 with aluminum heads. but for the 305 you will see no gain from the tbi upgrade.

86firebird350

Is it too much or too little fuel? What cam are you running? I'm building a similar combo right now (350, 113 heads, LT4 hot cam) using the Holley TB and am just curious. By my calculations, I'm not going to have enough fuel. I'll need bigger injectors to reach its full potential.

BTW, what size adapters are you using for the fuel ports on the back of the TB? I was messing with mine yesterday and tried using the ones from the stock unit but they don't fit.

UnderCover89TBI

iTrader: (25)

I have too little fuel. I am running the holley injectors at 21 psi. I have a 25-30 lb spring but then I also have to modify my fuel system to run a VAFPR and then for smog I fail visual. I really need bigger injectors at less PSI. I am running a really mild cam, waaay smaller than the LT4 cam. 10:1 compression with edelbrock performer cylinder heads. I am debating on going to holley 4 bbl tbi with self tuning ecm...Have not decided if I wanna drop 2k... I did not buy the throttle body new. I bought it used and used the adapters that were on there. except for I added one of those long adapters to run a fuel pressure gauge. I think the stocker's should work..otherwise contact Holley and see what they say. any other questions feel free to PM me.