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305 or 350?...


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I had a 'friend' sell me a 305 for $150ish, but he told me it was a 350. After I started tearing the thing apart, I noticed the 5.0L (LB9 setup) on the block. By then, it was too late. So, here is my question. Being a very poor college student, should I finish the 305, have fun with my 78 280Z, or wait and find a 350 block to transfer over the 305 internals (of course I will need to buy new pistons.) Will my 305 being fuel injected with MS, paired with a T56 to a 3.9 R200 be a huge let down and not worth the extra $500 or so to go to a 350? I guess my real question is, how much of a extra kick in the seat is 80 hp in a 280Z, and is it worth it. I know I am going to get a lot of "well, it depends", but if I already knew what side of the fence I was on, I would not be posting this.

 

I guess I am looking for a justification to spending more cash...

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Depends how much money you have. I personally wouldn't compromise on something so critical, when a 350 can be had so easily... get your friend to buy you a block!

 

Isn't it more than just the displacement lost? I am no Chevy expert, but I believe the main difference is a smaller bore, which in turn means smaller valves.

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Ok, here is the deal on the 305. It does have the smaller bore and smaller valves. It does not have a good following because if you fit better flowing, larger valve heads, you will have to notch the block for the valves to clear, not to mention you will be adding 15-20 cc's to chamber volume which will make the compression pretty dismal. Combine the asthmatic breathing with the long for displacement stroke(3.48" same as 350) and you have a pretty torquey, but low rpm engine, teamed with 3.9 rear, and this thing will be awkward to drive.(a lot of shifting!!)

Now that that's out of the way, depending on your plans, build a nice induction, get your headers and such, and go forward with the 305 on stock internals. I say this so that you can build the 350 that you get later. When the 350 is finished, the front dress and all the peripherals from the 305 will transfer to the 350. All of the external dimensions are the same.

I'm not trying to scare you, you will probably have a good time with the 305, I'm just making sure you realize that it is less than optimal for performance.

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Driving it is much more fun than looking at it. I ran a 305 for quite a while and was happy with it. If I wouldn't have blown it up I'd still be driving it. You'll have time to plan and build the next one. Now I have a 383, 2x the horsepower 2x the fun. You'll always want more power. Keep in mind you can't put your intake on centerbolt heads.

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I have a 305 in my ZX and it's pretty zippy. I'd say (being a poor college kid also) just finish your swap with the 305 and save up to build a 350/383 or whatever small block you want then swap the 305 out later. It'll only take a day or two for the actual swap since all the wiring, hoses, exhaust is going to be pretty much the same.

 

What intake are you using with the FI?

 

Edit: I forgot to say, this is exactly what I'm planning on doing. Since mine in carbed it will literally take a day to change engines. After that it's another half day tuning the carb/ shake down cruse.

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I ran a 305 for 2 years in a '78 280z

After a complete rebuild with flat tops, head work, and a cam swap I ran it for 500 more miles before I pulled it out and sold it. Save the greif and the $$$ go for the 350. Besides if you ever get a lil more hunger you can turn it into a 383, not an option with the 305.

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Chevy High Performance magazine did a build-up of a 305 TBI motor:

 

http://www.chevyhiperformance.com/techarticles/148_0409_chevrolet_305_ci_engine_build_ii/index.html

 

"257 ponies--which translates to 330 at the crank (allowing for the same 22 percent loss factor we used in Part I). Torque-wise, we stayed right where we were before, coming in at 294.96 lb-ft of torque, which translates to a mind-boggling 378 at the crank."

 

Cam was a 210/214 at .050, .510/.520, 114° LSA.

 

Choices, choices.

 

Best -- Gary

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I had a 305 with the bigger 1.84 valve "ho" heads, a performer intake, and a 212/212 comp cam, hooked to a TH350 and 3.54 gears. It was useless. It had a little more low end torque and no top end. I liked the L6 better, I replaced it with a flat top, vortec headed 355. At least twice the power. Don't waste your time on the 305. Go rough up your "friend" to get you a 350, or your money back.

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Well, seems as though I have some mixed responses, but... Sounds like I need to be bad on the budget. I found a real 350 and a T56 for $300. Herm, thanks for the feed back. And you would still be rid of the 3.9 R200 for something geared lower despite the T56? Heck, I could see how cheap they are selling an LS for...

 

Anyways, thanks for your feed back. And know anyone looking for 305 parts

:wink:

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Come on guys, while a 350 will make more power than a 305, determine what the total project goal is. 305 is not a bad choice for a budget street Z. The 235 hp TPI motor with 5 speed is actually a killer Z car motor. Should easily put a 240 in the 12's and knock down 30 mpg.

 

If you have to completely rebuild it, don't mess with the 305, but if it is in good serviceable shape, run it and work on the rest of the car.

 

I've used my buddies car as an example quite a bit. He got a free TPI 305 from his dad with only 6k miles on it. With an SLP flat tappet cam and headers, it ran 13.90's in his '74 'vette convertible (a 3700# car). The car returned 27 mpg on the highway with 3.08 gears.

 

If you want to build a race car, don't even consider the 305. But just bashing 305's because is passe. We had an '81 Jimmy that got 250k miles out of the 305 and a '78 Malibu wagon that got over 200k.

 

If max output is the goal, why run a traditional small block at all? Just score an LS1.

 

You found a 350 AND a T56 for $300 and you haven't bought it yet why?

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I hope you bought the 350 & T56 combo. With a T56 you could easily run the 3.90 rear end. If you don't like the rev's you could easily swap someone on this site for a 3.54 unit. I had a 94 Formula with a t56 and 3.42 gears. The car needed more gear. Good Luck on your project.

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the screw up that had you aquire the 305 may actually be a semi blessing in a weird way ,by the time you finish the total project the cost of upgrading from that 305 to a 350 or even a cheaper version of a 383 in the car, the cost differance between them will be reasonably minor. I seldom build even 350s any longer as the cost differance to build a 383 vs a 350 is almost meaningless but the extra 45-50 hp/tq the larger displacement gives you is almost free as it comes from the displacement increase and the ease of getting a bit more compression with less piston dome height, over a similar 350. PLUS a 383 operates about 400rpm lower so its easier on the valve control issues. If I was bucks down (and TRUST ME I USUALLY AM...BEING RETIRED AND ON A PENSION) Id do the least work I could do too the 305 sbc and get the car drivable and depenable so you have transportation and can work out the other bugs in the swap process with the smaller engine , like the exhaust, trans,mounts,cooling,oil pan,etc. and get the car up,functional, dependable first. install a better radiator, get the trans and shifter correctly adjusted, work on getting a decent baffled oil pan, a free flow low restriction exhaust, a high flow aluminum water pump, etc. just don,t put much money into the heads,cam,short block ETC,then at the same time Id be keeping an eye out for the parts Id need to assemble a 383 or 396 SBC so that at some point I could spend an afternoon swapping out the 305 and in that serious performance engine while KNOWING almost all the potential problems have long since been worked thru.......think of the 305 as a test mule that only in thier to work thru the bugs and don,t put much money or effort into that long block assembly, but take the time and effort to build the replacement 383-396 SBC too far better standards ,than you could ever do swapping a few components at a time onto a running street car. do the necessary research, build the dream engine slowly and correctly rather than throwing parts at a car that you need for transportation.

ID keep the 3.90 rear and the EFI and get good at tunning that, Id spend a good deal of time researching the parts list for the ENGINE COMBO Id need to assemble a 383 or 396 SBC and in the long run the test mule 305 will be a reasonable and cost effective step too your having a killer car thats dependable

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a 350 with a T56 for $300 sounds way too good to be true.

 

I agree. I'd check it over extremely well before dropping $300 on something that should cost much more in theory.

 

Dan Juday has the nicest Z with a 305 that I know of on this board. His car does very well with the 305 and he has not replaced it yet, even years later.

 

Davy

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