hartsmike

Looking at changing out the 305 and replacing it with a 350. Have the quadrajet system and am keeping it. What would I need? The 350 comes out of a typical 90 model Chevy.

Thanks Guys

hartsmike

Also, it's the 5 speed.

Apeiron

Just the 350 shortblock and probably a flywheel.

hartsmike

What about the PROM and computer stuff? Intake fit on the 350 just fine? Specialty flyweel?

Thanks.

five7kid

iTrader: (14)

No PROM changes needed.

'85 305 had knock sensor, you'll want to get a 350 knock sensor and module.

The intake will need the center two mount bolt holes on each side modified to the '87-up angle; or get an '87-up intake manifold; or put your 305 heads on the 350.

The flexplate is just a replacement '86-'92 f-body V8 piece. The rear main seal changed from 2-piece for '85-earlier to one-piece '86-later. The flexplate mounting changed with the rear main seal type.

Z2887

^^^ what he said. Unless your using the 350 intake.

PaPaROC

I'm also lloking at doing the same thing. 86 ROC,carb 305,5 speed. But to my understanding, the tranny can't handle the 350. There were a few 350 5 speed maros that were tested, but not put into production. What mods need to be done for the 5 speed to work.

Apeiron

Just be gentle with it.

PaPaROC

Im more of a cruiser guy tht likes to burn some rubber here and there, I'm not looking to go to any track. Just a car to have some fun with.

Hartsmike how your project coming along?

ATOMIC

iTrader: (1)

also change all the metering rods in the carb out for the ones for a 350 in truck of
about the same vintage. it'll run if you dont do this, but not great.

hartsmike

I'm thinking by the research I've been doing I'd be beter off going to an Fbody salvage yard a couple of towns over and getting a 350 from an 87 or 88 and using it instead. What do you guys think about that? I also wonder what will have to be done to beef up the tranny?

Apeiron

An 87 or 88 F-body 350 will be TPI. At worst, if you keep the TPI then swapping the whole computer system is a lot of work. If you keep it carbed, it's exactly the same as swapping the 350 from the 90.

There isn't anything that can be done that will significantly strengthen a T5 in the areas that it's weak.

hartsmike

Wasn't for sure how the manifold from the 305 would match up. No, I don't want the hassle and headache of changing everything over to TPI. After everything I read, they say what gains might be there for changing aren't enough to justify doing so.

hartsmike

So, basically all I have to do is pull the 305 and drop in the 350 but put the intake/carb from the 305 back on there and put a 350 knock sensor and that's it? Or, just keep the 350 intake and stick the quadrajet back on? Thinking of getting an aftermarket carb from Summitt. Think Edelbrock makes one.

Z2887

I would just keep the 350 intake, or get like a Performer or something. The T-5 trans will be fine behind the 350. I had one in my '84 Z28. It had a 350, with TFS heads, Lingenfelter cam, Holley 750, and Performer intake. It was a solid 12 second car. It lasted until I put sticky tires on the back. As long as you dont hook it up. It will be fine. Alot of it will be in your driving technique as well. Dont power shift it. Save up for a TKO or similar.

Apeiron

Pull the 305, drop in the 350 shortblock, put the heads/intake/carb from the 305 back on, and a 350 knock sensor (if your 305 has a knock sensor now, not all do).

Change the cam if you feel like it, and put some headers on while you're at it.

Z2887

Whats the difference in the intakes ? I was just thinking he wouldnt have to pull it apart that way. Now that you mention it though. The 305 heads would up his compression a little. Give him a little boost in power. Another question. Why not put a good intake and cam in there while your at it. As cheap as that is, and give you a nice performance increase. Still no PROM changes necessary or anything. You can find used intakes and cams CHEAP. Definately would be worth it. Especially if your going all the way to pull the heads and everything off. Performance is probably not the goal though since your keeping the quad. If thats the case though, why worry with a 350. Unless the 305 is shot. If your going to a 350 for the power. I would definately put a small cam, and intake on it atleast. because once you start getting more power. You just want more and more and more. Better to do it while its apart. Just rambling of things off the top of my head.

Apeiron

A 90 350 never came with a carb, so it'd be hard to put a Quadrajet on its TBI intake.

"Quadrajet" and "performance" are by no means mutually exclusive concepts.

Z2887

Oh yeah. lol. See told ya I was just rambling off the top of my head. lmao I would still put a Performer on it myself. lol Probably get one for 50 bucks

Apeiron

A Performer is too similar to the stock Qjet intake to be worth the effort. A Performer RPM would be an upgrade, but until some other things are done the intake isn't holding anything back anyway.

hartsmike

So, all I need for that then is to have an intake that takes a carburator? Was thinking of the quadrajet b/c it's already made for the vaccum hoses and plug for computer. Shoot, if all I need is an intake that will accept "any" carburator, I may as well get a good one. What about the computer running a major or lopy cam. Will the 350 knock sensor take care of that?

Apeiron

To mount a Qjet, you need an intake that takes a spreadbore carburetor.

With a carb, there's no worries about cam size and idle vacuum like there is with stock fuel injection.

Z2887

Thats exactly what i was saying. While you have it apart. With a carb you wont have any issues with that computer. It is mainly just emissions stuff. Are emissions a concern in your area ? If you ever plan on getting some good heads, I would do like he said and get a Performer RPM. If not I would just go with a Performer or similar. The one I had on mine accepted bot spread and square bore carbs. I may even have one if you need it. Your 350 shortblock will have a roller cam too. Since its newer than 87. If you can afford it,I would put a vacuum secondary Holley on it too. Thats up to you though.

hartsmike

That's what I'll do then. Got another question and don't know if I should start another thread on it. Got an LT1 with 189,000 miles on it. Would I be able to build it and find an intake to accept a carburator for it and if so, would it work?

Z2887

Yeah you could. I mean thats alot of miles, but if its in good shape it wont hurt anything. The 350 I was talking about up there with the TFS heads,ect, had like 147,000. Somewhere close to that anyway. When I put it together. They do make carb intakes for that.

hartsmike

Well, I was thinking if I built the LT1 it should have better performance but is there an intake that would use the heads that are on it but for a carburator instead of the fuel injection? Also, would the rear end out of a 94 Camaro or Firebird fit without major adjustments?

Apeiron

GMPP has an intake to put a carb on an LT1, don't know if it's spreadbore. It'll cost you a lot more than building a carbed Gen-I SBC, and without the LT1 induction system it's really just a glorified Vortec.

Z2887

Yes you can make the LT1 carbed easily. Using stock parts it may not be woth it though.The rear I dont think so. Im not positive about that. It seems like it will bolt in but its different length. So your wheels wont sit in the wells properly. I think they will stick out like 2 inches or something

Z2887

Whats the deal ? You have the option of building the 350 you mentioned or the LT1 for you 3rd gen, or you want to build both ?

hartsmike

Got the option for doing both. Thought if it was not much difference would build the LT1 and put it in.

hartsmike

Nevermind. Just researched it and it would be wayyyyy tooooo costly to even recieve any benefits.

Z2887

Yeah man. You will be better off just doing the reg. 350.

naf

iTrader: (7)

There's no reason not to re-use your existing intake, the standard performer is really no improvement over stock. The 85 manifold only needs the center holes wallowed out some to accept the bolts into the heads at a diff angle. Swapping the carb will also require swapping the dist as both are computer controlled and the ECM relies on each for input.

Your cheapest option is to re-use as much of your existing components as possible. An 85 should have a KS. Some have used methods to de-sensitize the 305 KS for a 350. Others claim the frequency is different and the KS must be swapped. The ESC module must also be swapped if the KS is changed.

A 90 truck motor may not have a roller cam or the provisions machined for a roller cam. An 87 or later car motor should have a roller cam. Roller is preferred.

Your current fuel system is designed around a block mounted mechanical pump. The truck motor will probably not have the fuel pump rod bore machined for the pump rod. A car motor may, or may not. Stock roller cams will likely not have the fuel pump lobe, aftermarket cams may. I'd check before you jump or be prepared to provide an alternate fuel supply method.

A 90 truck motor will likely have TBI swirl port heads. A 350 from a later Fbody should have better heads. I'd check the head casting number before purchasing. Anything could have been changed since 90 or earlier. A couple hundred spent on your existing 305 heads would be a good investment if combined with a 90 LO5 shortblock.

Save your money to replace the T5 at some later time.

Z2887

Sounds correct to me. Im not sure about the intake. Especially with stock heads. A performer may not be much if any better using stock heads. It did make a significant improvement on my old car, but I had better heads. On yours the heads are the choking spot, where mine was the intake. Good call on the fuel pump. Forgot about the roller not having that lobe.

Apeiron

His current 305 heads are about as good as anything that came on a later Fbody, and of course don't need the center intake holes modified.

naf

iTrader: (7)

Agreed.

Z2887

AFR

marcopasco39

Also agreed, I'm about to put my L69 heads on an L98 shortblock, w/ the q-jet. And I've got a 5 speed too.

hartsmike

Five, where is the knock sensor located? Where can I get one-Autozone?

naf

iTrader: (7)

right side block drain (next to the starter)