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Hey guys, been awhile. iI need some help, some might know, I have a 1977 Chevy nova. 350 v8, mild cam. So I have taken a brake from it. But I'm ready to start working again but im not sure what to do. Its old school, 4 barrel carb BTW. So basically my engine starts and runs. But the engine hesitates when I rev it. My teacher (whom I'm not fond of, he is not SAE certified) says it hesitates because of the altitude (7,200 feet) it sounded reasonable to me and I didn't argue the point. So, the engine, when driving is very slow. It won't accelerate fast what so ever. A slight tapping sound can be heard when the engine is turned on. So I decided to adjust the rocker arm lash. Due to poor teaching and frustration, I can't do a 15 minute job. So I put it to this side for now. Any ideas on why the engine is running poorly? Only thing I can think of, is that the valves aren't opening/closing properly.But quite frankly I'm upset. And I'm ready to send it in to get it fixed somewhere. 400$ later it should be done. What should I do? Im not to sure what to do . I certainly don't have the money . thanks for reading
 

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Acceleration is a function of Torque. If your engine is not making as much torque as you want (and installing a cam takes away your bottom and mid range torque and shifts it higher up in the RPM band beyond where it does you any good on the street) you will have to change your rear gear ratio.

That semi truck next to you at the stop light has a little in line six cylinder diesel engine that displaces four hundred and fifty cubic inch engine and makes 350 horsepower flat out to push air out of the trucks way. It also makes 925 foot pounds of torque to accelerate 40,000 pounds of truck and load by way of seven forward gears and rear end that has a really high number. Over the road trucks have small motors and lots of gears to shift to multiple what little torque the engine makes while sipping fuel. There are quad turbocharged V12 engines under the stretch hood on some of those Peterbuilt tractors but they are not exactly economical to operate (most of those V12 Cats are installed in train locomotives.

I don't know what your gear is now but it is probably a two series ten bolt. If your '77 Nova left the factory with a V8 it will be a 8.5 ten bolt. If the 350 you have now was put in place of a six cylinder your Nova will have a tiny 7.5 inch ring gear ten bolt designed for the fly weight Chevy Vega with a four cylinder. Makes a difference so you ned to look to figure out what you have. You want to see this rear end when you bend down to look.


This is a ten bolt posi 8.5 inch rear gear marked by the squared off lug cast on bottom lip on both sides of the case. You can tell it is a posi by looking at the springs visible when you remove the inspection cover to change the fluid or count the gear teeth to see what gear ratio you have.

Here is the ten bolt 8.5 inch rear gear with the inspection cover in place:



This is what you don't want to see.



This is an open rear end with a 7.5 inch ring gear. It has the square lug with a three quarter inch drill bit run through the lug to yield a "C" shape.

Big Dave
 

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Hesitation in motor:
1. Carb: Too fat versus too lean.
2. Wore out valve springs can cause hesitation in the motor. Usually solid lifter high revving motor with big cam, but a motor with lots of miles could have issues.
3. Distributor: coil, wires, plugs, pickup, cap, rotor
4. Fuel pump/regulator

Can change jets to account for altitude.
 

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Acceleration is a function of Torque. If your engine is not making as much torque as you want (and installing a cam takes away your bottom and mid range torque and shifts it higher up in the RPM band beyond where it does you any good on the street) you will have to change your rear gear ratio.

That semi truck next to you at the stop light has a little in line six cylinder diesel engine that displaces four hundred and fifty cubic inch engine and makes 350 horsepower flat out to push air out of the trucks way. It also makes 925 foot pounds of torque to accelerate 40,000 pounds of truck and load by way of seven forward gears and rear end that has a really high number. Over the road trucks have small motors and lots of gears to shift to multiple what little torque the engine makes while sipping fuel. There are quad turbocharged V12 engines under the stretch hood on some of those Peterbuilt tractors but they are not exactly economical to operate (most of those V12 Cats are installed in train locomotives.

I don't know what your gear is now but it is probably a two series ten bolt. If your '77 Nova left the factory with a V8 it will be a 8.5 ten bolt. If the 350 you have now was put in place of a six cylinder your Nova will have a tiny 7.5 inch ring gear ten bolt designed for the fly weight Chevy Vega with a four cylinder. Makes a difference so you ned to look to figure out what you have. You want to see this rear end when you bend down to look.


This is a ten bolt posi 8.5 inch rear gear marked by the squared off lug cast on bottom lip on both sides of the case. You can tell it is a posi by looking at the springs visible when you remove the inspection cover to change the fluid or count the gear teeth to see what gear ratio you have.

Here is the ten bolt 8.5 inch rear gear with the inspection cover in place:



This is what you don't want to see.



This is an open rear end with a 7.5 inch ring gear. It has the square lug with a three quarter inch drill bit run through the lug to yield a "C" shape.

Big Dave
Since when does a 10 bolt have 12 bolts to hold the inspection cover on? :confused::confused:
 

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That is a Pontiac/Olds rear end I believe. It is an 8.5 corporate ten bolt behind that 12 bolt cover; but it doesn't use C-clips as it has press-on axle bearings like the old Salisbury rear ends.

Sorry I was keying on the square shaped identifying lugs cast into the housing not the inspection cover when selecting this photo from the thousands of shots I have stored.

Big Dave
 

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That is a Pontiac/Olds rear end I believe. It is an 8.5 corporate ten bolt behind that 12 bolt cover; but it doesn't use C-clips as it has press-on axle bearings like the old Salisbury rear ends.

Sorry I was keying on the square shaped identifying lugs cast into the housing not the inspection cover when selecting this photo from the thousands of shots I have stored.

Big Dave
Thats kinda what I was thinking that it was, NO I'm not saying I knew thats what it was (no experience with BOP) but I was looking at the mounts and had to think about it and was thinking BOP!

Like my sig says. Not screwing up once in a while, your not doing anything!

Happy Holidays Dave! (and everyone else!)
 

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Cullin what has been done to the engine? If it has been apart the timing gears may not have been installed correctly. That will make it a dog with just one tooth off. Valve lash adjustment can also affect performance by not opening the valve all the way or not allowing it to close all the way. Initial timing settings as well as the distributor curve need to be set up properly.

The changes of gear ratios and converters can be addressed once the engine is running well.

On the 10 bolt with the 12 bolt cover, it is an O type Olds rear. No C clips and corporate 8.5" internals do not fit.
 

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Discussion Starter #12
Cullin what has been done to the engine? If it has been apart the timing gears may not have been installed correctly. That will make it a dog with just one tooth off. Valve lash adjustment can also affect performance by not opening the valve all the way or not allowing it to close all the way. Initial timing settings as well as the distributor curve need to be set up properly.

The changes of gear ratios and converters can be addressed once the engine is running well.

On the 10 bolt with the 12 bolt cover, it is an O type Olds rear. No C clips and corporate 8.5" internals do not fit.
Well Phillip, it was a fresh rebuild it has 50 miles or so. At first I thought maybe the canwwasn't broken in yet by the guy who owned it before me, and I've been trying different solutions. I have done the fuel/air mixture on the carb and I set the timing to the best of my abilities. It was still tapping. I bought some thicker/higher head gaskets hoping to raise the covers so that they don't tap anymore but that doesn't fix the problem. I doubt that the tapping is reducing the acceleration that much. I'm just not sure what to do at this point. Also, it seems like a lot of water got into the heads. I left it outside and they froze over. Should I pull the heads and clean them or will the water go away?
 

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Water inside the engine is not good. It promotes corrosion and thins the oil. Unscrew the drain plug a bit so that water can wick out along the drain plug threads, but the thicker oil stays in the oil pan (this is one way a SAE 30 weight beats Zero weight oil all hollow as zero weight is the viscosity (ability to flow) of water.

Big Dave
 

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By heads do you mean the valve covers?
That was my interpretation.

Classic junk yard scenario where something on an engine is opened up to the weather and the hood or similar sheet metal isn't placed over the remains to save what is left of the engine for future use.

I want to remind everyone they haven't made a new SBC motor in twelve years, there are fewer and fewer entering bone yards now, and they will soon be as frequently found as a flat head Ford V8 (they were as common as dirt in my youth). So protect what you don't use for others.

To give you an idea of how scare a SBC will soon become look at how many BBC there are available now (last one was made twenty two years ago). I would buy up every 350 I found in the yard and hoard it the same way the 12 bolt was hoarded when they went out of production in 1972. Of course I have a pretty good size barn in my back yard (360x120 feet) to store things out of the weather. If you live in an apartment on the third floor you might not want to drag a SBC up those stairs to place in your living room as a coffee table (no really dear; we just put a sheet of glass over it and it will be a great talking point!)

Big Dave
 
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