Hi all. My 72 Skylark has a buick 350 engine and TH350 trans. The rearend is an open 2.56 ratio, which is good on the freeway. But sometimes she be a bit of a dog at low rpm. Tires are 255/60/15. I could/should go smaller but love the look of the big ones. I had it timed and they have the total timing in a 3000rpm. I have heard that could be 2000? I have the 4bbls opening what seems just right. But the engine must be lugging a bit because of my gear/tire combo. I have headers and 2.5 inch pipes. I love the low ratio on the freeway , but would like more take-off power. Go figure.. I saw some mention of the "power band" Am I way out of it? Main question is this, do I have any options to keep both? A special torque converter? A 2 speed rearend? An add on overdrive? What would you do? Thanks for any help.
A 200-4R is a nice option. (Re: What are my options? I have a 2.56 rearend.) Dear Jason and V-8 Buick cruisers, It isn't cheap, virtually all cars these days use an overdrive transmission to solve the problem you are describing. For Buicks, the 200-4R tranny is a particularly attractive swap because it can be swapped for a TH350 with minimal modification. The final drive on the 200-4R is 0.67. So you can go with a much shorter rear-end and still maintain your highway engine RPM. It is worth crunching a few numbers to decide how you want to set up any option you consider. The lower your engine's freeway RPM, the better your gas mileage. If you enjoy cruising, a little planning might reduce visits to the gas pump. Cheers, Edouard :beer
A 2 speed rearend??? I haven't heard of that since the Ruxtel rearend of Model T days It all depends on what you use the car for most of the time and how much money you want to throw at it. Going with a 200-4R is a complete waste of money unless you plan to change the rear gear. Cheapest route, keep the th350 and go with a 3.23-3.42 rearend. If you do more highway driving then go with a 3.08. Best but most expensive would be a 200-4R and a 3.73-4.10. Either way, stepping up on the converter will always help but that alone probably won't accomplish what you want.
So theres not much difference in 1st gear between the TH350 and the 200r4 I take it? Yeah for sure expensive to go changing both tranny and rear! Most shows I go to are an hour or more freeway drive. I cruise with it too. You think I'd notice a better take off with w 3.08, and not have a lot higher rpm? Sustained 70mph for example. Thanks guys!
No,not much difference,2.52 vs 2.74,if you went with a 700R4,the 1st gear is 3.06,with this gear you will definetly feel the difference. But you would have to shorten the driveshaft,use an adapter to bolt it to your Buick engine,and have to move the cross member back,and hook the TV(throttle valve) cable to your carb,making sure it fuctions properly.(TV cable on the 200R4 also) A 700R4 would raise your 1st gear multiplication to 7.833:1,and a 1.792:1 final drive ratio in OD,from your T350's anemic 6.451:1 1st gear multiplication,and final drive ratio of 2.56:1.If you wanted to optimize the 700R4 later,all you would need is a 3.08 gear,and get a 9.425:1 1st gear multiplication,which would be close to a 9.5 optimal street/strip 1st gear multiplication ratio,and a 2.156 final drive ratio. A 200R4 would have a 7.014 1st gear multiplication with 2.56 gears,and a final drive ratio of 1.715,and to optimize this one,it would need a 3.42:1 rear gear,and get you a 9.37:1 1st gear multiplication,and a final drive ratio of 2.291,if later you wanted to change the rear gear. If your engine is set up with a low RPM power range(stock) the 700R4 would be the better choice,if your engine doesn't start making power until 2,000 or more,the 200R4 would be better.
Thanks. So I'm reading all this thinking theres alot of dollars needed for this stuff. What would be the effect of just throwing those dolars at more power for my 350. (Which is stock inside) Its a 69 block with 72 heads oiled thru TA's adjustable pushrods. Essentially would more power pushing on a 2.56 rearend be more prone to damage a rearend because of the torque it takes to turn it?
If your 72 has the stock 10 bolt in it, it's an 8.5, and that is a good strong rear, plenty strong for your 350. I would first post a picture of the rear cover, and rear u-joint to make sure you have the 8.5. If so, parts are available virtually anywhere. I would just install a 3.08 ring and pinion. The 3.08 is a nice compromise between acceleration and economy.
I initially went from a 2.56 rear to a 3.08 for the same reasons you mention. If you change the gears you might want to consider going a bit higher to get the performance off the line you are looking for.
Is this engine totally stock or have you upgraded any items on the engine? How many miles on the motor if stock? What stall do you have now? Jim
So I would probably look for a 3.23 as something more then 3.08? Reading around looks like not much diff in fuel economy even going fast? I know there are 10 bolts in the cover of my rear. I can take pics just gotts remember... The converter is stock. Engine miles unknown. Doesnt use oil. The engine is an all stock inside 1969 block and guts with 72 heads oiled thru TA's adjustable pushrods, running the 69 rocker assembles. It was a 2bbl 350. Now has the TA stage 1 intake, 4bbl Qjet, Hooker headers and 2.5 inch exhaust with X pipe and flowmaster 40's. Still stock cam that was in the 69 2bbl. Has the lectric limited breakerless ignition in it instead of points. http://www.lectriclimited.com/mainpage.htm
No,usually people upgade there engine first and are disappointed,because they pick a cam that is in a higher RPM range,and makes it even doggier of the line until its in its power range. The best way to go about upgrading a car would be start with rear gear and work your way forward.If I remember correctly,you wrote that your car was originally a 2bbl engine,and upgraded with a 4bbl and free flowing exaust.Did the last guy upgrade the cam? Those changes alone slowed your car down off the line,by moving the power in a higher RPM range.Upgrading the engine further will make it worse off the line if you don't add more gear,and or a trans. If you want better off the line performance,without changing the rear gears,or trans, you should go back to the 2bbl setup,and make sure it has a low RPM power band camshaft(some where around stock). This will restrict the airflow,and the cam will create more low RPM cylinder pressure and give you more low end torque to get your car moving.So yes there is something you can do with your engine to give you more power off the line(but its at a sacrafice to the upper RPM power range). Even the headers probably slowed it down off the line,by raising the torque peek. Its all a compromise,and how you want the car to run. I have a 72 Skylark that had a 350 2bbl,and 2.56 gears with stock exaust manifolds and duel exaust with turbo muflers. It seemed to get off the line halfway decent for that setup. Of coarse,I will chose to change all of that,but thats my choice.I would start with a rear gear change,and work my way forward to the trans,then the engine,if the car wasn't on my rotisserie right now. If I had your car,I would go with the 3.42 rear gear fisrt(so what,you'll lose a couple mpg,it will still be fine on the freeway),and decide how I would build the engine(cam,head work,compression ratio..so on...have a plan ready),and when funds are available,I would do a 200R4 with the stall I would need when I got to the engine. Then the engine,this one needs the most $$$,and more down time,but in the mean time I would enjoy it with what ever upgrade I had in it.The 700R4 is a good option also,because you can set the engine up in a lower RPM range for an even better mpg,but the drive shaft needs to be shortened,and an adapter is needed to bolt it to the engine.If you decide to go with the 700R4,a 3.08 gear is a good choice.(read above post)On second thought I would go with the 700R4 and build the engine in the lower RPM power range,because Buick engines make excellent low end torque,and will still pull hard at 6,000. And with this choice you could go either way,do the gear first,or the trans.(but if you do the trans first,your final drive gear would be 1.792:1 with the 2.56,would be great going 70mph,and give you even better mpgs,but you should leave it in D for street driving) I hope all this helps,this hobby is not cheap,but there's none better!! Have fun.
Nope, stock 2bbl cam. I heard the 200r4 also needs a difference crossmember and torque converter lockup switch, etc. I suppose I could experiment with the 2bbl carb again. Probably needs cleaning from sitting. Could I put it on the 4bbl intake? I am thinking change the rearend, but I dont have the funds do to rearend trans and engine, the engine runs good I was hoping to avoid tearing it apart and spending money in there. So...3.42, any idea the mpg difference I can expect, running 65-70 mph on a tank?
The cam does not differ between OEM 2 and 4bbl 350's. Same cam. ---------- Post added at 09:11 AM ---------- Previous post was at 09:02 AM ---------- I disagree. The cam determines power range. Power range is the same. The smaller primaries of a q-jet will make it snappier at low RPM, but the 2.56 gear will hold you back launching from low speed or stop at WOT. You can compensate somewhat with a better torque converter, and getting the mechanical ignition advance in quicker, but the best solution is to change the rear gear.
I figured getting the total timing in at 2k would be best, (instead of 3 where it is). Also look for a 3.23....or would you thinkg 3.42? I still would like decent mpg/rpms. Dont we all.
No free lunch. I think 3.23 at most. The only way to get the best of both worlds is with an overdrive. That gets expensive. I opted for the Gear Vendors Overdrive. Figure on about 3000.00 with everything. Or you can get a 2004R. That will be cheaper because of the 350, but it still needs to be beefed up some. For the street, a stock one would probably last awhile if it wasn't raced or abused. A fully prepped 2004R with all the good stuff will run you around what the GV costs when all is said and done. www.gearvendors.com
If you're worried about gas mileage and still want to be able to cruise at 70 I wouldn't go any higher than a 3.23 gear if you're staying with the T350 trans. That's the setup I have in my '69 and with the stock 26" tall rear tire I'm pushing about 3300rpms at 70mph. When I had the 2.73 rear gear I could run 70mph and still get about 18-19mpg, now with the 3.23 I get about 13-14mpg because of the higher rpms. It also gets a little unnerving running for long distances at that high an rpm.
Did not know the cam was the same,thanks for letting me know,good stuff.Did the 2,and 4bbl cars get the same converter from the factory? Well anyway,I think the 4bbl cars got at least a 2.73,or a 3.08 rear gear if I remember correctly.And I disagree(unless the higher power 4bbl cars got a different cam) with the "snappier" at low RPM,because of the free flowing exaust with headers WILL still raise the power range into a higher torque curve,thats why the 4bbl cars got bigger gears.If I remember correctly,the 2.73 cars had single exhaust,and the 3.08 cars were duel exaust from the factory.(4bbl cars) Ok,I dug up my 1967-1973 Motor Auto Repair manual,there are 6 different 350 power ratings for 1972; 1)350 2bbl 8.5 comp.,h.p. 150 @ 3800,lbs ft torque 265 @ 2400 2)2bbl,8.5,155 @ 3800,270 @ 2400 3)4bbl,8.5,175 @ 3800,270 @ 2400 4)4bbl,8.5,180 @ 3800,275 @ 2400 5)4bbl,8.5,190 @ 4000,285 @ 2800 6)4bbl,8.5,195 @ 4000,290 @ 2800 As you can see,the power range was raised on the bottom 2 of the list,and that was with exhaust manifolds,with headers the range will be even higher.I would agree that a torque conveter will help,but not as much as a set of gears would. The bottom 2 of the list probably came with a 3.08 gear sets.With headers,a 3.23(a good compromise between 3.08,and 3.42) would be a minimum I would go if I didn't want to swap out the trans,or get a converter,and just wanted to be able to pull out into traffic,and still get decent mpg on the freeway.(trying to save you some $$$,and you could go either way with a trans if in the future you wanted to do that)JMO Even cheaper would be to buy a 2.73 used gear set for peanuts,that will still work on your 2.56(2 series carrier)or a gear in the 2.90 range if there is such a gear.(with a gear in the 3s,you'll need a 3 series carrier also) And yes you could use a 4bbl intake to 2bbl adapter,but the 2bbl manifold would match the 2bbl carb better with higher velosity ports.(smaller) Ported heads,and intakes increase flow,but reduce velosity,which raises the power band in a higher RPM toque,and HP range.
Well my engine is a frankenstien as mentioned. 2bbl 1969 inside except for heads, lifters and pushrods which are 72. I had a dyno once because it was on ly $60 for 3 runs. Best it did was 180 hp at the wheels...that was 150 mph with this rearend. Before the timing was set proper too. This increase is can only be due to the stage 1 4bbl intake, headers, and 2.5 inch dual exhaust with x pipe. I had a thread a while back where I tried to estimate engine hp backwards but it was really guesses. How about getting really wild. Leaving the rearend as is and looking at what 5 speed bolts up to the Buick 350.... I always wished it was a stick. Maybe there is a car I can swipe clutch and trans from? ---------- Post added at 04:31 PM ---------- Previous post was at 04:10 PM ---------- Pics of my rear, lol It was mentioned to put a 3. something where a 2. something was would mean changing the carrier?
