I just got through swapping my 3.31's to 4.10's, a 25% increase and boy was i disappointed. The car is definitely short legged and I don't feel like i picked up any performance. With my 331(327+0.030) and 216/228, 454/480 cam and ported stock heads with 7.8 DCR and 9.4 SCR, I thought i would feel a big difference, NOT! I cant even smoke the tires on my 12 bolt posi. I'm running a performer intake 1 5/8" headers, dual exhaust and 200-4r transmission and this thing still feels like a dog. The thing sounds great, nice little lope. What am i doing wrong? I've tried my q-jet and a 650 VS holley and i am still dissapointed.

with the overdrive transmission,and lower first gear I think you went too low. Do you have timeslips to compare before and after? the butt dyno often lies ;)

Sounds like low cranking compression. Right off I would look at more initial timing. You will have to take it out of the mechanical probably also. Look for 36-38 for start total. What is your initial timing now?

I think Bob is right.

Example, a guy at my local track has a 12.1 E.T. 72 Chevelle, with a 4 speed auto, and 4.10 gears.

He said "First Gear is rediculously low", and he started leaving in second.

I switched from 3.08 gear to 3.90 gears with a Turbo 350, in a 327 powered 68 back in college, and the difference was huge. Guys who used to beat me from the light, didn't anymore.

You didn't mention your rear tire overall diameter b/c you can switch to say a 27" or maybe a 28" tall tire from a 25.5" or maybe a 26" and gain some of your old gear back which just might put you where you think you should be in low gear??

I ran really tall Mud and Snows at one time, (29 to 29.5" from a stock at about 25.3" to 25.5"), and my car was a dog off the line but boy, from the midrange of second to the top end of third gear really enabled me to catch cars before the end of the quarter line..

I used to love the look on a guy's face that had 3.73's or 4.11's after he beat me out of the hole about 2 to 2.5 cars and I would motor on by him before the end!!!

pdq67

I'd venture to guess that there is something wrong if you're having trouble spinning the tires with that.

My 6 cylinder, automatic with 3.08 gears can spin them with ease.

Personally, i think it would be an excellent idea to start methalogically checking and diagnosing every engine system, that is compression, ignition, fuel, and air.

You'd be surprised how many people never check to see if they are actually getting WOT, among other things taken for granted.

My 540 has the same problem... graemlins/clonk.gif

Thanks for the response guys. I dont have any timeslips as i have never had it to the track. I'm just going by the seat of the pants feel. I am running P235/75R15 uniroyal radials because I had them already. I like the look of the 15" tires over the 14" tires. They are 13" tall from the ground to the center of the hub. I measure them this way as the tire height can be misleading. The torque is being applied from the center of the hub down to the ground.

I think my timing is about perfect. 12 initial, 24 mechanical and 10 vacuum advance at 10 inch of vacuum. The car idles with 12-13 inches in drive and i have about 17" vacuum at 1000 rpm's.

I don't have a compression tester to check compression. The cam I chose says its range is 1500-5500 and you could really feel it kicking in around 2000-3000 rpm with the 3.31 gears but you can't feel it now with the 4.10's and it feels like the the car isn't free as it runs down the road, feels tight.

My 94 Chevy 4X4 extended cab half ton truck with a 350 and 700-R4 and 3.73 gears with 265/85R16's feels like it could blow the doors of my chevelle.

This is a prime example of how things can be misunderstood. The reason the car coes not spin the tires alot is you are getting the vehicle speed and the engine's torque peak to match very early in the acceleration curve. Your 331 engine with the 216 dur cam probably has a torque peak of about 3000 rpm and a HP peak of about 5200 RPM. 4.11's ususally work best with an engine that revs to 6500 rpm. The tires you are running are actually rather tall. The tire look shorter at sitting still but it is very tall from a performance standpoint. I would tell you to run it and enjoy the fact that it doesn't spin the tires wildly, a 331 is not supposed to run that way. You need to run your engine up higher in first gear before shifting and keep the rpms in the power curve. The big difference would show up at a track.

what do you mean when you say the car feels tight? you sure the gears were done right? the first gear in a 200r4 is only 2.75 compared to 2.48 for a th350, so i doubt that is the problem, especially with that tall of a tire. did you go from a 3.31 open rear to a 4.10 with posi? because if it wasn't hooking before and now it is, that could be the difference you are experiencing in the seat of the pants feel. SOTP feel really doesn't mean squat. ;)

I did a similar swap in my camaro before I switched to a 700r-4. Big difference. Now that I have switched trannies, its terrible. The 2004r's first gear should be OK, so I'd definately look elsewhere. I do have the same problem and I think you're right about the torque is happening too soon, but that shouldn't be your problem !

I've switched from 2.72 to 3.73 and (TH-400) and loved the increase in acceleration. My opinion greatest mod ever. Then I blew the rearend. So I went with 4.33's smile.gif (12 bolt 5 speed tranny) and I LOVE IT!!! 20 roll stomp on the gas and it's up in smoke for me ;) (all on 26.1" tall tires) Just thought I would share my experience.

first gear is going to be pretty useless with that rear gear. 200R4 first gear is 2.74, 2.74 x 4.10 is like 11.2 overall first gear. This would be similar to running a close-ratio Muncie with a 5.13 rear gear. First just won't go very far. You might have to make adjustments in the old SOTP dyno. Tall tires might help too. I've got a roller 406, TH200R4 and 3.73 posi in a 70 Chevelle and was disappointed at first, but later realiuzed that first gear is just short and it pulls like crazy in the other gears. Took some getting usde to. If I had it to do over I'd run a 3.36 or 3.42. Probably not what you wanted to hear, I know.

Tom

I expect first to be really short but I'm not fealing that hard pull in any of the other gears either. It may be accelerating but i don't feel it. I don't know what the speed is as I am missing a part on the 200-4r transmission speedometer gear housing. I haven't even been able to find one at the junkyard and my local chevy dealer said that he probably wouldn't be able to get one so I am going by the tach for now. When i reffered to a tight feel, I was reffering to how easily the car maintains momemtum when you let off the gas. It decelerates rather quickly with the 4.10's whereas with the 3.31's it tended to maintain its speed when you let off the gas. I'm confident the rear gears are set up right. Maybe not perfect but well within the acceptable range.

I need to find someone in WV who knows what the car should do and can tell me what I need to change. There isn't anyone at my local chevy dealer who probably ever saw a 327 let alone drove or had one.

mine also seemed a little sluggish and then of all things I readjusted my valves and gave them one half turn preload after the tap and it brought the engine to life
they were alot tighter to start and the car had dog power
afterwards that baby would tear up the street

Are your secondaries opening? Do you have WOT? If you have a qjet,you might need to adjust the air valve,and with a vaccum secondary carb,you might need a lighter spring..

Have you tried putting it in netural while rolling to see if the brakes might be overadjusted? I know that sounds too easy but stranger things have happened.

I used the turn the pushrod until you feel it and then add one 1/4 turn method at breakin because I wanted to err on the conservative side and not have the valves too tight. they didn't tap and I never checked them after that.

The brakes aren't dragging. I checked them. It's definitely a motor problem. I readjusted the secondary air valve and it didn't seem to make a difference. Maybe I need to loosen it some more. I think it is running lean. The tailpipes are black from where it ran rich with the 283. There is a brown residue on the bumper just above the tailpipe outlets which I am interpretting as a lean condition. It just started since I installed the Q-jet after removing the Holley 650.

you may want to recheck the valves to at least rule it out

You've got gears that want to run up to 6500+ and a cam rated for 5500 max rpm. I think that you were much better matched with the 3.31s I don't think that your torque max. is where you need it now. You blow right through peak torque on your engine with those gears.

torque converter .

My s10 with a 305/700R4 felt like a dog in 1st with the 700R4 first gear and 3.73 rear. I added more intial timing and that cured that problem. I only added 5deg too.

The motor is going to want to run through the rpm faster, so you need to start with a little more timing I think, to compensate to burn that rush of fuel better... or something.

Try more timing, it's easy.

You say you can't burn the tires from dead stop. A 200-4r they sometimes suffer from 2nd gear starts. Are you sure you are getting 1st gear? If you are keep searching.

Jim

A buddy in high school had the same problem. He had a '46 ford truck with the original rear end that ended up having about 5.10-1 gears. He had a built 289 ford (built to 306hp cobra specs) and a 3 speed truck tranny. 1st gear was useless...it wouldn't spin the tires no matter what, just slam you back in the seat, and then slam you into the dash if you didn't shift fast enough. He had to take off in 2nd gear, and in 3rd it would do 95mph max with the engine flat screaming. Sounds to me like too much gear for what is basically a torque motor. Sounds like a good candidate for a cam swap.

Clyde,

Just saw your post.

I'm a little surprised that your 327 won't turn the tires. With my THM-350, first gear is basicly all tire spin!

What stall converter are you running? I have a very similar engine to yours. I'm running a 2600 rpm stall.

Might be time to get a compression gauge and see where you are at. If that checks out, it's likely a valve adjustment or tune-up problem. Don't overlook the possibility that you aren't getting full batt voltage to the coil, and that your throttle is opening all the way.

If that all checks out, maybe someone was into the heads before you and hogged out the ports, killing your flow.

Mike

Originally posted by Clyde_Maston:
Thanks for the response guys. II think my timing is about perfect. 12 initial, 24 mechanical and 10 vacuum advance at 10 inch of vacuum. The car idles with 12-13 inches in drive and i have about 17" vacuum at 1000 rpm's.

I don't have a compression tester to check compression. The cam I chose says its range is 1500-5500 and you could really feel it kicking in around 2000-3000 rpm with the 3.31 gears but you can't feel it now with the 4.10's and it feels like the the car isn't free as it runs down the road, feels tight.

First off, it won't feel as free. Take the truck out of OD and see how it feels going 55. Same thing in the Chevelle. And when you let off the throttle , it 'snaps' off. And has less "momentum". That's gearing, pure and simple.

Your timing does seems quite correct, although with 4.10s you could have the mechanical come in a bit later.

Question, and as a caveat I'm purely a 'stick man' when it comes to Chevelles, what is the stall of the torque converter? One thing to bear in mind that reducing rear end gearing ( numerically higher), does just the opposite of throwing more torque through a torque converter, it effectively lowers the stall of the converter as its easier to move the mass forward through lower gearing.

As the man a few threads before said it so simply and eloquently " the torque converter ".

If it was a stock or near stock stall, could it be that with the slight reduction in stall and large increase in gearing that you have effectively 'locked-up' your torque converter? This would be especially true in your 1st gear ( 2.75 X 4.10)

My bet is that is exactly what it feels like now (ASSUMING you have no engine anomoly going on! All you changed is the gearset right!?). It needs another 1000 rpm stall is all. Then it'll smoke 'em at will. But again, caveat, I'm just a simple stick shift guy and have no personal knowledge as to it would effect the rest of the combination. 2800 stall should do it.

And as others have opined, that's a bunch of gear for a non-(solid cammed 6500 rpm zinger).

Let's see, 2800-3000 stall, knock the heads down .025" to bump compression, and swap to a .230/.236 )@.050 solid.

Heck assuming you have decent cranking compression now ( 150+ psi), you could probably go with a nice small solid cam asap and use them gears PROPERLY! ;)

I can't help myself, I a SOLID FLAT TAPPET missionary!)

Converter, I beleive, would be the correct response.

The '73 Vette I had was a 6000+ RPM small block. Only had 3:73's in it, but I did have a 2800 RPM stall conv. in it, it would lay down alot of rubber out the hole. These are typical expected responses. When you make one significant change, you often have to make a number of complimentary changes to make things work.

Absolutely , all about how the 'system' works in a balanced combination.

The torque converter is only slightly higher than stock. Around 1800 I believe, at least thats what I was told by the guy I brought it from. It was built by a shop up around Pittsburg, Pa. If I upgrade to a 2600-2800 rpm stall, what effect will it have on the cars driveability while cruising around town. I know that the 2600-2800 stall is when you nail it and depends upon how much torque you have. How does it act when you ease into it, just like a stock or will it rev up to around 1500-2000 before it starts to pull. I never had a high stall converter so I don't know

Originally posted by Clyde_Maston:
How does it act when you ease into it, just like a stock or will it rev up to around 1500-2000 before it starts to pull. I never had a high stall converter so I don't know Clyde,

You notice that it feels a little different around town, but after driving it a day or so you get used to it. When you ease into it it feels a little loose, but it doesn't rev. At least mine doesn't.

Clyde, you said " you were told by a man it's slightly higher than stock stall". That's pretty iffy. Wish I knew how to tell you to actually check your stall and not assume a durn thing about what you were told.

The cam is too small to use the extra gear. I think your motors power is in the 1500-4800 RPM range with the small cam so you don't stay where it makes torque long enough. I overgeared my stage one Buick G.S. once (4.66s) and it was only slightly faster than with stock gearing (3.42s) as it made very little power above 5000. You could blaze away from stop lights in second gear with street tires.

Around town you bearly fell the diffreance. I have a 2600 rpm stall tourque converter and if I let off the gas, it will start to move forward It doesn't free rev (like I used to think) to the stall speed, but rather "slips" to the stall speed. I'd agree with the higher stall speed. 2600-2800 is great. but I'd also agree with the fact that not being able to spin the tires is not always a bad thing. graemlins/beers.gif

a quick and dirty way to get an idea of your stall rpm is to stand on the brakes and push on the gas...when you start to spin your rear tires or push your car...or the motor doesnt rev any higher this is your stall speed...use this method spareingly as it is hard on convertors and creates a lot of heat...Steve B

The easiest way to get an unconfused torque converter flash is to try it in 3rd gear...

From highway speed, lets say 60 mph, floor it, and see where the tach instantly goes to.....this will give you an idea of your flash stall speed.

You need to do it at a speed that the car will not downshift.

..what Dave said..I've done this numerous times with my 70 SS454 with a 2400 B&M holeshot..it flashes at 2800

whoops

Your combo might not be perfectly matched. It could use more cam with more compresion and more converter to help the 327 wind up. The trani/4.10's would be a perfect match if the motors power band would hit 6,500! I sill think you should be able to roast the tires and outrun your truck! Something must be wrong with the engine or converter. Sounds like you adjusted the valves correctly, and trying two different carbs. should rule that out, how big is your dual exhaust? Maybe its plugged, what kinda muffs? The timing curve sounds great also. I wunder if it could still make that much vaccum if you had a couple plug wires crossed up? I have done that b4 and it took me a 1/2 mile of driving to figure out what was wrong lol. Also I wonder about the condition of yur cam. Did install it yourself? Maybe its not installed correctly!?

The cam is installed correctly. I degreed it when I installed it and it was right on the money, degree for degree. The exhaust is 2 1/4" mandrel bent and the mufflers are dynomax turbo's.

Anyway, the 4.10's are history. I replaced them today with the original 3.31's. I didn't like the high RPM's all the time. Even with the overdrive, it was too high for my liking. If anyone's interested, I put them in the classified section for $100 including the spacer and bolts. They have less than 100 miles on them.

Thanks everyone for your help. Its obvious that I have some tuning to do. I think I'm going to try timing it by ear rather than the timing light and get some bigger jets for the q-jet. My friend had a 283 that he built really similar to my old 283 and wasn't happy with the performance when timed by the timing light so he ran the RPM's up to 2000 and adjusted the timing until the motor smoothed out and sounded the best. He said it really runs good this way. Heck, what have i got to lose.