gear ratio quandary

[Slow Ride]

I'm going to be changing my rear gear ratio shortly and am having a hard time finding the optimum ratio for my application. Here are my specs...

'90 S-10 2dr 2wd Blazer
probably 3600# race weight

'97 L29 454 big block 9:1CR
cleaned up stock heads
ZZ502 roller cam 224/234@.050 .527/.544 lift
RPM Air Gap intake
3310 750 vac sec carb
1 3/4" long tube headers
3" exhaust thru Dynomax Ultraflows
alternator,waterpump,powersteering

TH350 with shift kit and a few other tricks
Hughes GM25 converter supposed to stall around 2800-3000 behind the BBC
ProStick shifter

Currie 9+ rear curently has 4.11 gears from when it had a SBC
leaf springs and lakewood slapper bars

I will probably run 28"+ radial tires on the street and could switch to a 26" slick at the track. This a mild street cruiser I hope will run a decent number at the track. I am in the process of preparing for PowerTour and would like to make the long haul. I've been tossing around going with anywhere from a 3.00:1 all the way up to staying with the 4.11's

I don't think the engine will like being buzzed at high RPM for thousands of miles from my home here in WI all the way to FL and back. I also think that the torque of the 454 will be forgiving at the track if I err on the safe/low side for gear ratio. What ratio sciences out best for my torque curve?

DD2000 says I'll have 550lb-ft all the way up to 3500rpm and 450hp@5000 that should make for some tire shredding fun no matter what ratio is in the rearend. As you guys can probably tell I'm getting excited to get this thing on the road soon. The BBC swap took WAY longer than I had anticipated, but I'm in the home stretch.

PLEASE HELP!!!!

[1SLO5.0]

3.55s would be a nice highway gear

[lazyass]

i agree, iam putting in the same ratio, well close to it, but 355 is a good one, iam going just a lil bit higher

[BLUE66]

3.55's would be a good choice in your application. With your short tire heights it should be a good all around gear. With the setup you have you need no lower then that. People would be surprised how little rear end ratio affects ET's @ the track.

[jdsgallops]

Don't fear the gear! Put an OD in it. Even 3.55's with a direct drive top gear are going to turn close to 3K on the interstate at 70mph. That makes a long, loud, expensive, and slow cruise for 3000 miles.

[UPdragracer]

Yeah 3.55's for the street / strip and 3.73 strip/street unless of course you run Nos. then the 3.55s would be the ones to use :wall:

[bohn]

Put a gear vendor in it. Spend some of that money you got !!!! That or put that 700R4 back in.

[Slow Ride]

I wish I could afford a GV unit. I am a little leary of a 700R4 behind a big block. Besides I'd have to spend a good chunk of change to get the converter and shifter for the OD tranny. I'm kind of leaning towards a 3.50 gear set and some 31" tires for the street then use my old 26" slicks at the track. My concern is having my cruise RPM below the stall speed of the converter. Will that cause too much heat buildup in the tranny and cook it? I just wish I would've built a real motor this time around instead of screwing around with factory junk. I can't even really use the gears I have now at the track because the engine will give up at 5800 RPM. Someday I'll be rich and famous so I can be fast like all of you guys.

[1SLO5.0]

I wouldn't worry about cruising below stall speed. That used to be a concern years ago but with new technology it is not really an issue anymore. Just make sure you use quality parts (converter, valve body, trans cooler, etc.). My car has a 4500 stall converter and cruised at about 3200 rpm or so at 65mph. The transmission ran 170-175 degrees consistently while cruising. The only time it got hotter than that was when I was in town screwing around. My old transmission always over heated on the highway. The problem there was the valve body. It was an Art Carr transbrake and the fluid flow through it wasn't sufficient for prolonged highway use. I fought with that transmission for a year before I figured out the problem. Lesson learned....

Spend the money once and buy quality parts!

[Slow Ride]

I have a Brommo built long tail shaft TH350 with a standard pattern valve body and a deep cast aluminum finned pan. I have the biggest tranny cooler in the Summit catalog too. Hughes says that the converter I have has about 3-5% slippage. I think I might invest in a tranny temp guage that I could hide under the dash or something.

[jdsgallops]

I am a little leary of a 700R4 behind a big block. Besides I'd have to spend a good chunk of change to get the converter and shifter for the OD tranny.

The money you have to spend on the shifter and convertor will be partly made up with the gas mileage savings on power tour alone. You are looking at close to if not a little more than 3000 miles on that trip alone. Figure 12.5 mpg and you are looking at roughly $500 just in gas if the price holds to an average of $2 a gallon. If you need to use premium your looking at even more. That doesn't include hotel rooms or anything. Simply by going to 17mpg, somewhat realistic I think, you save about $150. That should pay for the shifter.

I have made the WI to FL trip 5 times now driving by myself. I can tell you that you want as low of an rpm as possible to keep your sanity that long. Not only for fuel mileage reasons, but noise level in the car.

You have a 9" rear don't you? You should be able to find someone with a center section with 2.73's or 3.00's to borrow just for the trip if need be. Then you can put a strip friendly gear back in it when you get home.

[cevan]

3.90's.................

[Slow Ride]

I am looking for a program for estimating ET based on actual engine specs and gear ratios. I have a very old DOS base one that works OK, but is pretty optimistic for engine power. I want to get an idea how much gear ratio changes will affect my ET without having to try a bunch. I am looking to possibly switch from my 4.11's to possibly 3.33's but I want to see if a 3.15 or maybe a 3.50 is better based on my engine/vehicle combo.

[lazyass]

you have a program that tells you ET's? if you do , i want to know mine, and the gear i recently put init

[Timmy2Step]

I would either go with a 3:55 for the street with nitrous. But am leaning toward 3:73, they are a good set up in your combo. I beleive I have both sets. and would probobly be willing to sell if interested. Depending what spline the axles are I have both a mini spool which I ran on my nova, including on the street. Or I have a detroit locker

[Slow Ride]

I finally got some reliable flow data for my cylinder heads and I am seriously ☺☺☺☺ed. The engine is going to give up completely by 4500RPM with a peak HP of about 350@4000 and shitloads(550++) of torque down low. I'm thinking I need like a 3.00 gear just to get all the way down the track now. I ran a simulation using my current gears and it got to 450ft and was out of revs. All this work and I will still be in the 13's ☺☺☺☺!!!!!

[BLUE66]

What heads are you using?
are you using the heads that came on that engine?
If so they were only designed for torque and low rpm.
Small ports and small valves.

[mistowomofo]

Are you running the stock peanut ports?

I've got 3.55's and 26" tires on my buick and the 350 hates it on the hwy. With a taller tire i'm sure the 3.55's would be great.

[camaro1]

that kind of torque is awsome, ask nos2go, he would shift his pontiac at less than 5000 rpm and run high 11 sec 1/4 miles with a 3.08 gear, keeping the revs low will make for an engine that will last a long time

[jdsgallops]

Sounds like it is time to step up to a real cam. That 224 intake duration on a big block just isn't enough.

[nos2go]

try some 3.08's or even 3.23's...you built a TQ motor so use it as that, it should pull like a frieght train!!

[Slow Ride]

The heads I am using are factory large oval ports. Everywhere I looked when I was building this engine told me they flow like 702's only better quality due to tumble and swirl. I later found a couple of website that gave rediculously crappy flow numbers and I finally confirmed the true shittiness of these heads. I'm kind of pissed at Competition Products, Goodwin Competition and everyone else for telling me these heads were a good choice for a 450hp, 5500-6000RPM engine.

These are the sites:

http://users.erols.com/srweiss/tablehdc.htm#BBChevy

http://www.strokerengine.com/GMBBC.html

just scroll to the L29 cylinder head data.

As for the cam, yes it's small but, it fit my budget. I would've had to spend another $1000 to go to a higher lift hyd roller and it seems to work pretty well in the ZZ502.

[BLUE66]

Finish it and take it to the track, you may be surprised how fast you can go without twisting the tach. And it will run forever. Or get it chassis dynoed first then you will know where your peak numbers are. I have some 049's, new guides and cut for 2.19, 1.88's but they are bare. I think I have some assembled 049's or 781's pretty much the same thing. I would have to go look which #'s they are. Those heads you have were designed for one thing.....low end tq.
Anyway, you wanted to run the power tour, so put in the highway gears and your set, and it should still be respectable at the track. If your not happy with it....change it, thats how you learn.

[jdsgallops]

As for the cam, yes it's small but, it fit my budget. I would've had to spend another $1000 to go to a higher lift hyd roller and it seems to work pretty well in the ZZ502.

Maybe to true but the 502 doesn't have peanut port heads on it either. Being a SBF fan I am quite aware of restricted port heads on "large" CI v8 engines. The stock Ford heads are notorius for that. What do you have to do to a stock headed SBF to get to run decent(besides a ton of port work)? Yep that would be over cam it. You will end up with a peaky engine but it will make decent power in that narrow rpm range. You also shouldn't need to spend 1K on a different cam. Cams are roughly $300 and make sure to match the springs. Then again this is why the next motor I build will have a solid flat in it.

[Slow Ride]

I would have to buy new hydraulic roller lifters though for the higher lift and better roller rockers/ pushrods/ valve springs/ valves/ retainers/ locks etc... After you exceed .550-.560 lift the factory lifters come out of the bores too far and bind so you have to get aftermarket lifters. Sure I could have put a monster cam in there, especially since I lost the power brakes due to valve cover interference, but I was stuck with flat top pistons so 9:1 is all I could get with the 100cc chambers. I really hate engines with soggy low end torque like the last small block I had didn't may peak torque until 4500 RPM and peak HP at 6000.

I guess this is just a learning experience to not trust anyone and not try to use factory parts to go fast. Hopefully my next engine will be better and I can come up with the $10-12K to build a real engine like some of the quicker guys around.

[mistowomofo]

You can use factory parts to go fast.
Check this out: http://www.pontiacstreetperformance.com/psp/rebuild455jh99.html
Jim hands 4100lbs '71 GTO wagon
Factory block, crank, and rods, TRW forged flat top pistons, a ram air IV replacement cam, home ported #64 D-port heads, Performer RPM intake, and a Q-jet! The car has 3.55 gears and he dosen't run n2o.

With this engine the car was running 11.80's shifting at 5500 rpm.



(Damn! I've got this same engine set-up in my formula, maybe I should get it running.)

[mistowomofo]

http://www.pontiacstreetperformance.com/psp/rebuild455jh00.html
Here's the car with the new 473 short block.
The car now runs 11.30's


The link you gave says your heads flow 226cfm @ .500" which sounds pretty shitty for a BB but look at what all the BOP heads flow. The heads Jim Hand has (64) would have only flowed 215cfm @ .500" and with minor porting they still only flow 254 @ .550.


I say get higher gears, screw around with your heads ,and get a better cam.

[nos2go]

I say its built..run it..its should pull good with different gears..if not there is always the blue bottle, you said you want to cruise it anyway....off topic..but there is a ZZ502, complete carb to pan for $4500 OBO in the new buyers guide.

[bohn]

I agree...run it, thats the best way to see what you got. In the future you can upgrade to a better set of heads, and cam. Or you have an option to go buy an engine already done. Take it down and have it dynoed to see if your numbers campare to real world numbers. Then take it the track and see what it runs. If you have to lift at 1000ft, then lift. Atleast then you know that you'll need different gears. I wouldn't spend to much money on stuff till you actually drive it and see what it does.

[Slow Ride]

well I'm taking the 9" center section in for gears tomorrow. I've decided on 3.25's with a 29" tire they are about the same as the 700R4,4.11's and 26"tires

I'm hoping I'll pick up some ET and MPH. It would pull really hard out of the hole even on the tiny street tires and then give it up when it got into the revs