373 gears or 355s?

Doing rear ended gears. Thoughts on either 373s or 355s. I've got a low compression rebuilt 350 4 barrel. 8.5.1 I guess or I'm told. It's got 1100 miles on it. I plan to do intake, cam, heads.
Thinking about low budget perf increase for rest of this season and wanna change out highway gears. Will turn 3200 at 85-90 mph now on highway. I want some more power around, quickness around town.
Thoughts on either one? Leaning towards 373 being a lower HP motor

 

Also has a 3 speed that was on column from factory. Switching to four speed I have soon as I locate a 11' inch flywheel

 

The issue you have is you set up is putting less than 200HP to the rear tires. Transplant in a Buick 455. It will cost a lot more to get the same HP and TQ out of a Buick 350.

I have run 3.08 3.23, 3.42, 3.55, 3.64, 3.90, 4.10 and 4.78 gears on street cars. I would stay away from higher numerical gears. I suspect the carrier would need to be changed for you to go there anyway. You are going to spend a lot of money you could use on a 455 transplant.

To do the 4 speed set up correctly will cost north of $3K. It will be fun but not as fast on the street as an automatic.

 

Wait. My engine is brand new rebuilt 350. I understand it will need some head work, cam and intake to make about 280-300hp but just scrap it?
Why will it cost that much to swap trans? I own the 4 speed and have the clutch. Only need the flywheel that applies to the car.
Will i not have a slightly quicker car putting in 355 or 373 gears going from the stock highway gears?

 

I am giving you the total price that it costs to do the conversion to factory specs. If you have some parts deduct accordingly. The list of parts is set forth in past threads.

 

No disrespect I assure you. The vehicle came with a fully operational 4 speed period correct trans and new matching clutch. Prob im having is 11 inch flywheel. However back to original question, will 355s or 373 gears improve my vehicles acceleration around town?

 

If the person that did the rebuild bought the jobber "stock replacement" 8.5:1 pistons and skipped the deck milling(odds are they did to save $$) and then used .040" compressed thickness composite head gaskets instead of the .020" thick steel shim head gaskets that the factory used because the composite gaskets cost less. I would say your compression is more likely closer to be 7.8:1, could even be less if the even cheaper jobber 8:1 pistons were used!

If your have plans to swap to a 200R4 later in a year or 2 then get a set of 4.10:1 rear gears and have even more fun! Even with the planned engine mods you should be able to run a good used 200R4 trans behind that engine without having it rebuilt. Do a search for the right code to get when you look for a trans.

What plans do you have for heads? If you have the heads you have milled about .060" and use the steel shim head gaskets you can probably get the compression up closer to 9:1. You will need shorter pushrods if you have the heads milled. You'll want more compression with a 4 bbl intake for better responsiveness anyway.

TA hasn't came out with aluminum heads as of yet so the only choice is still the factory cast iron heads. All year heads flow around the same unported and have about the same combustion chamber size and shape from the factory. The older heads are rumored to be better for porting, the '68 to '72 heads but are more prone to cracking.(but not that bad)

Most higher performance cams will also want more compression or you'll be VERY disappointed if you go to big with a cam with a low compression engine. The big cam will kill the off the line get up and go you just added with the better rear gears!

Build the driveline as a matching combo and you'll be better off. Plan out what mods you want to do before hand, you're doing it right by starting with a rear gear swap and working your way forward. Get the gear for the trans you want to run, I highly recommend an overdrive of some sort. A 200R4 will basically bolt right in with only moving the cross member back a few inches, no driveshaft shortening required.

When you swap in the trans you'll want to match the torque converter to the cam that you'll eventually swap in that will match the compression ratio that the engine will be increased to. The torque converter can be added later after the compression upgrade or the engine upgrade can be done first so you'll know what the compression can be raised to when the heads come off and you can measure what you have to be able to better chose a good cam.(not as hard to do as it may sound)

Feel free to ask any questions you may have. GL

 

Took to long to write my post, didn't know about 4 speed getting swapped in, the phone rang while I was writing.

Anyway, what Larry said in post #8.

You can disreguard the 200R4 info, unless you sell the 4 speed and go that way? The engine advise is still good though but won't get you to 280 HP, maybe 250?

You'll either need different pistons and better machine work to get to the 280 to 300 range with the 350 but like Flyn-B said a 455 is easier to make power. You could just drive the 350 like it is and build a 455 to swap in later or build a different 350 to swap in later. You can always sell the low miles 350 to recoup some cost of a better engine? Dealers choice.

 

I like the idea of doing the gears, swap to four speed and running the 350 as is...look for a 455 in mean time. After dust settles, swap engines and sell the 350. The engine was done by Titan Engines in Fla however they sourced out the work and got from another party. was told "shallow dished pistons"?. Told me it was strong engine but not huge HP...reliable. Getting kinda bumped out but car is super solid with 41k original miles so Ill take it slow...runs great now just not the power im looking for. Great cruiser and smooth...ive owned too many fast cars. Couldn't pass up deal on great condition car with very clean interior and solid metal panles. Where I live if was a chevelle would have cost 25k

 

I also feel the build quality of this buick is better then the numerous Chevrolets Ive owned. From the door closings to the interior fit and finish. Reminds me of old BMWs and MB from late 80s...HOWEVER...I didn't know engine was as soft as Im learning. I was told it was rebuilt and provided paper work...so that was selling point. I figured it need some tuning.

 

I had 3.73s in my 350/200-4R powered 72 and it was an amazing difference from the 2.73s I had prior. I went to 4.11s and was disappointed. The increased highway rpm was not worth the small acceleration improvement.

3.73s are the sweet spot with 26" tires and an overdrive trans.

 

Thank you for input..Ive got a 3 speed manual but its super long so im thinking equivalent to a OD auto trans

 

ok...now I have to ask...what else to I need to swap my gears? just the new ring and pinion gasket? I haven't done since I blew up a 68 Firebirds rear end and had to shim it all out...took a weekend.

 

Ya need to figure which rearend you have. Then you need to decide if you want to leave the rearend open or go posi . Either way you may also need a 3 series carrier , either open or posi . This depends on what carrier and gears are in the rear now.
Jim/Rott

 

Ah ok. I was going off a summit web site. Part Yukon gear YGA-24505 373 GEAR fits 10 bolt 8.2 rear end GM.

 

Im missing something indeed

 

You didn't mention which 4 speed you have---wide ratio or close ratio. Close ratio might be happy with the 3.55 or the 3.73, but a wide ratio could be better with what you have now.