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Discussion Starter · #1 ·
I am new to cars. i got a 1982 el camino for my first car. 350 sbc with a th350 trans and a big cam.
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I posted a photo of the camshaft specs. im pretty sure it has a stock rear diff. i talked to a transmission shop and got them to build a custom torque converter for me and install it. so i dont think its the torque converter holding it back. anyways i will describe the issue. the car wont go to redline or close to it when in gear. in idle i can rev it to 5200 rpm with no issues, but when its in drive it will quickly rev to 2200-2500 rpm, then stop increasing, and then slowly increase in rpm as my speed increases. the faster i go the higher the rpm goes. the highest the rpm got was around 3300 and i was going 80 mph. not sure what could be causing this. I am stumped and really need some help figuring out whats wrong with it... any ideas?
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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To get the ball rolling...That cam and torque converter are going to need more gear. The stock gear ratios in the G body rear ends have ratios like 2.29, 2.41 and 2.56:1. That covers a very high percentage of what you may have. Decide on what you're intending to do with the El Camino and we can figure out a gear ratio to better suit the application. If you do more highway driving or want more in town performance.

The next step is determining what you have for compression ratio, heads, intake and carburetor. Find out as much of that information as you can and let us know. If this cam went into a stock lower compression 350, with a numerically lower gear (like the ones listed) those 2 mismatches alone can cause what you're reporting.

Fear not. Over camming an engine and other mismatches are as much a part of learning cars as falling when you learn to ride a bicycle. The folks here that really know their stuff can chime in and get you the best advice on where to go from here.
 

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Typical 1982 El Camino rear axle ratio is going to be something like 2.29 or 2.41....maybe 2.73. Performance awful....
Once the torque converter has reached it's rated stall, rpm can only climb as fast as the engine can accelerate the vehicle mass.

Other than sounding like it maybe only has 3rd gear and given that it has crummy rear axle ratio, it sounds pretty normal to me.
RPM flares up to converter stall speed quickly, then climbs slowly as it pulls the entire vehicle load.

Verify the trans has all three forward upshifts, and that you don't have something like a manual valvebody in it, which would make the "Drive" selector position 3rd gear only.

Shift it into manual low and take a test drive, see how the rpm climbs then.

Quick little math check shows 3300 rpm, 25" tall tire, 1:1 high gear in trans, 10% converter slip, and 80 mph comes out to 2.78 rear gear....

How much info do you have as far as what parts and features were used in the engine and transmission build??
 

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Good call on the manual low test drive, Ericnova. I didn't consider something like stacking shifts.
 

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Discussion Starter · #7 ·
To get the ball rolling...That cam and torque converter are going to need more gear. The stock gear ratios in the G body rear ends have ratios like 2.29, 2.41 and 2.56:1. That covers a very high percentage of what you may have. Decide on what you're intending to do with the El Camino and we can figure out a gear ratio to better suit the application. If you do more highway driving or want more in town performance.

The next step is determining what you have for compression ratio, heads, intake and carburetor. Find out as much of that information as you can and let us know. If this cam went into a stock lower compression 350, with a numerically lower gear (like the ones listed) those 2 mismatches alone can cause what you're reporting.

Fear not. Over camming an engine and other mismatches are as much a part of learning cars as falling when you learn to ride a bicycle. The folks here that really know their stuff can chime in and get you the best advice on where to go from here.
definitely more in town performance, as for the information i can try to figure it all out tomorrow. once i have it i will write back here. thanks for the info!
 

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Discussion Starter · #8 ·
Typical 1982 El Camino rear axle ratio is going to be something like 2.29 or 2.41....maybe 2.73. Performance awful....
Once the torque converter has reached it's rated stall, rpm can only climb as fast as the engine can accelerate the vehicle mass.

Other than sounding like it maybe only has 3rd gear and given that it has crummy rear axle ratio, it sounds pretty normal to me.
RPM flares up to converter stall speed quickly, then climbs slowly as it pulls the entire vehicle load.

Verify the trans has all three forward upshifts, and that you don't have something like a manual valvebody in it, which would make the "Drive" selector position 3rd gear only.

Shift it into manual low and take a test drive, see how the rpm climbs then.

Quick little math check shows 3300 rpm, 25" tall tire, 1:1 high gear in trans, 10% converter slip, and 80 mph comes out to 2.78 rear gear....

How much info do you have as far as what parts and features were used in the engine and transmission build??
I will try the manual low thing out and reply back. as for the other info i cna gather it all tomorrow. thank you for the reply!
 

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That cam is a little bit big but not so much it should fall on its face with the trans and gear ratios you have. That said more info as to whether this cam was just stuck into what otherwise is a low compression 82 SMOG motor which might be a 305 rather than a 350.

So a starting place would be ID’ing what this engine and head’s are?

Bogie
 

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Agree with Bogie. If someone just stabbed in a big cam on a stock 1982 small block, you probably just have a big mismatch. The 1982 small block had around 7.8:1 compression (advertised at 8:1 in many cars) but you need 10:1 compression to match that cam. It's possible it's a fully sorted combo, but might be just a cam.

I'll also ask... does the engine make a louder "waaaaah" sound when you are accelerating at full throttle? If your carb is running too lean it will sound great and run smoothly, but make very little power. Before tuning the holley carb on my boat it would actually start slowing down when you went full throttle because it wasn't getting enough fuel.
 

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Discussion Starter · #11 ·
Agree with Bogie. If someone just stabbed in a big cam on a stock 1982 small block, you probably just have a big mismatch. The 1982 small block had around 7.8:1 compression (advertised at 8:1 in many cars) but you need 10:1 compression to match that cam. It's possible it's a fully sorted combo, but might be just a cam.

I'll also ask... does the engine make a louder "waaaaah" sound when you are accelerating at full throttle? If your carb is running too lean it will sound great and run smoothly, but make very little power. Before tuning the holley carb on my boat it would actually start slowing down when you went full throttle because it wasn't getting enough fuel.
not sure what year the engine is. its not the stock engine as the stock engine was a 4.4 L v8. i was handed whatever info the previous owner had. i figured it would be a cool challenge to try and fix it up. not exactly sure how to find compression ratio without taking apart the engine. hard to determine what a waaaaah sound sounds like through text, but i can take a video and send it as im going home. i have a a/f ratio guage and at idle it reads about 14.5 and at WOT it goes to about 13.5. Maybe the video can help others determine what might be wrong. thanks for the response.
 

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Discussion Starter · #12 ·
Typical 1982 El Camino rear axle ratio is going to be something like 2.29 or 2.41....maybe 2.73. Performance awful....
Once the torque converter has reached it's rated stall, rpm can only climb as fast as the engine can accelerate the vehicle mass.

Other than sounding like it maybe only has 3rd gear and given that it has crummy rear axle ratio, it sounds pretty normal to me.
RPM flares up to converter stall speed quickly, then climbs slowly as it pulls the entire vehicle load.

Verify the trans has all three forward upshifts, and that you don't have something like a manual valvebody in it, which would make the "Drive" selector position 3rd gear only.

Shift it into manual low and take a test drive, see how the rpm climbs then.

Quick little math check shows 3300 rpm, 25" tall tire, 1:1 high gear in trans, 10% converter slip, and 80 mph comes out to 2.78 rear gear....

How much info do you have as far as what parts and features were used in the engine and transmission build??
ok so when i put the gear to the number 1, i assume thats what you mena by manual low, i can go WOT to redline with no issues. and then shift into 2nd and hit redline there too. its just third or the D on rhe shifter where it doesnt like to go to redline. but when it is in D it shifts so i dont think the drive is 3rd because i can feel hear and see the rpms drop as if shifts. I talked with my father because he is much more knowledgeable than i am and he said same as you. but he says if i want to raise the shift point then i can mess with the transmissions governer. So i think i was mistaking normal trans behaviour for a problem. my other car which is a modern **** eco car goes to redline just fine when i floor it but i suppose thats because its different tech. as i said before I will come back with as much info on parts as i can gather. Thanks
 

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I think I have a much clearer picture of what you're describing. You described it very well. I just didn't follow along correctly.

Setting aside, for the moment, the shift points (yes, your Dad knows what he's talking about). It sounds like both manual shifting and leaving the shifter in drive both arrive at the same little to no RPM increase situation in 3rd gear?
 

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So, how fast does it go in 1st gear? Also, how fast in 2nd before it shifts into Drive? This will give us an idea of your overall gearing.
For example, some cars will go 40 in first before they shift into 2nd. Then they will get up to 80 before shifting into 3rd. So when you hit 3rd gear, (also known as D) you are moving right along and breaking the speed limit in most places but Texas. So be careful for sure, but with this info and your rear tire size we should have a rough idea of your rear gear ratio.
 

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Discussion Starter · #15 ·
I think I have a much clearer picture of what you're describing. You described it very well. I just didn't follow along correctly.

Setting aside, for the moment, the shift points (yes, your Dad knows what he's talking about). It sounds like both manual shifting and leaving the shifter in drive both arrive at the same little to no RPM increase situation in 3rd gear?
yes that is correct, when i have it in manual 1st i can go to redline. when in manual 2nd i can go to redline, then when i shift into 3rd it goes down to about 2600 rpm. before i was guessing the rpm based on sound but now i was focusing more on the tach so 2600 is around where it sits before it slowly starts rising in speed and rpm consecutively.
 

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Discussion Starter · #16 · (Edited)
So, how fast does it go in 1st gear? Also, how fast in 2nd before it shifts into Drive? This will give us an idea of your overall gearing.
For example, some cars will go 40 in first before they shift into 2nd. Then they will get up to 80 before shifting into 3rd. So when you hit 3rd gear, (also known as D) you are moving right along and breaking the speed limit in most places but Texas. So be careful for sure, but with this info and your rear tire size we should have a rough idea of your rear gear ratio.
in 1st it will get up to 30 and in second it goes to about 65 then i shift in third. when i have it in drive (automatic mode) and flooring it, the rpm hits maybe 3200 then shifts into 2nd, then hits 2800 and shifts into 3rd. it hits like 10-15 mph before shifting to 2nd and then around 35-40 mph before shifting into 3rd. oh and the tire size is P295/50R15 105H
 

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yes that is correct, when i have it in manual 1st i can go to redline. when in manual 2nd i can go to redline, then when i shift into 3rd it goes down to about 2600 rpm. before i was guessing the rpm based on sound but now i was focusing more on the tach so 2600 is around where it sits before it slowly starts rising in speed and rpm consecutively.
Generally speaking there is likely a cross leak somewhere causing fluid to activate something along with the direct clutch in 3rd gear (low/reverse clutch or intermediate band). It gets more confusing if anyone installed a shift kit or had the valve body apart (check ball, shift valve, springs, gasket not correct). We could go for pages with the possibilities.

Other than checking the shift linkage or cable for binding and proper location...I can't think of anything externally causing this. Hopefully some of the more knowledgeable folks can chime in with other ideas that I'm missing. I'm thinking the pan has to come off for a look inside.
 

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Lets try to clarify if this is an actual problem, or is just the fact of poor rear axle gearing for performance.

We need to know what rpm you consider "redline"...

If you run it to redline of say 5500 rpm in manual low, shift to second and run it to the same 5500 rpm at redline, then shift to third and it drops clear down to 2800 rpm....then there is a problem.

Otherwise, what you are presenting is just the basic facts of low engine power and not enough rear axle gear to accelerate the mass of the vehicle.

Let me ask this.....you have indicated you have a functioning tachometer....does the speedometer also indicate the correct speeds when you drive, or is it incorrect?
What I'm poking at is to have you do a simple test for us, where you drive it at a specific steady speed in low gear and tell us what MPH you are actually going.
If the speedometer is reading correctly, we can use that info to tell you exactly what rear axle gear ratio you have....along with doing the necessary math for expected rpm drop from redline to "xxxx" rpm and figure out if you really have a problem in the transmission.

Say, 3500 rpm locked in low gear at a steady roll....what is the speedometer saying?
 

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It could be something as simple as the vacuum modulator needing an adjustment as well. When you use a hairy cam you reduce the amount of manifold vacuum the engine makes. Less vacuum means it has less effect on the modulator and can cause funky shifts.
 

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ok so when i put the gear to the number 1, i assume thats what you mena by manual low, i can go WOT to redline with no issues. and then shift into 2nd and hit redline there too. its just third or the D on rhe shifter where it doesnt like to go to redline. but when it is in D it shifts so i dont think the drive is 3rd because i can feel hear and see the rpms drop as if shifts. I talked with my father because he is much more knowledgeable than i am and he said same as you. but he says if i want to raise the shift point then i can mess with the transmissions governer. So i think i was mistaking normal trans behaviour for a problem. my other car which is a modern **** eco car goes to redline just fine when i floor it but i suppose thats because its different tech. as i said before I will come back with as much info on parts as i can gather. Thanks
It sounds like what you're describing is that it's not downshifting on its own. Normally when it's in 3rd and you floor it, it downshifts to second depending on your speed.

When you say you floor it and it shifts itself to second at 3200, that's an issue. It should go all the way to about 5500 before shifting There is little to no vacuum at that point so the modulator likely isn't doing anything. Governor could be the problem, or as someone mentioned an internal leak in the valve body letting pressure get where it shouldn't.
 
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