What's the simplest way to tell if I have a stock size exhaust manifold and stock diameter exhaust system on my 62 327/300?

I'm trying install a 2/5" heat riser and was told that I have only a 2" pipe. The installer want to cut the pipe and expand it to 2.5" to fit the riser. I just want to make sure he's on the right track?

Joe

 

Is it possible you are missing a donut sleeve?

Look at the ZIP site

http://www.zip-products.com/Zip/dept...1619956C5F4C62

just my 2 cents.
Craig

 

Since '62's had only two sizes of pipes, 2" and 2 1/2" If the 2 1/2" heat riser you're trying to slide over the three studs appears too large, you have the 2" manifolds. That's the easy way but certainly not the only way.

Both sizes of pipes were same diameter all the way to the doughnut flange. No expanding or resizing.

 

This doesn't sound right.

Do you have the original engine in your car?

1962 Corvettes came with 250, 300, 340, and 360 HP engines. The 250 came with 2" manifolds. The 300, 340, and 360 came with 2.5" manifolds. The last 3 digits of the part numbers cast into the 2.5" manifold were 901 and 902. That is also how those manifolds are referred to.

The heat risers in both sizes are still sold by Chevrolet and the parts vendors. You can't make a 2" heat riser fit 2.5" manifolds and vice versa. I'd be very doubtful that you can expand or shrink the diameters of the front pipes to make one fit the other. You fit the heat riser to the manifold and then the front pipe to the riser.

 

No, I put a donut sleeve in there but it slips up into the exhaust manifold.

 

Mike and Chris;
Thanks for the advice. I'll measure the distance between the manifold studs and see if the heat riser is the correct size. You've helped by clarifying that the pipe itself should be 2" for the all the engine styles.

I'm pretty sure that the guys at the muffler shop don't know what they're talking about and that they can just bolt in the heat riser.

One problem I'm expecting is when the hear riser is attached, the pipe will drop about an inch and hit the frame. I guess they can chop off the bell (flare) and re-flare it an inch shorter.

Cheers!

Joe

 

Something is not right here. This should be a put in bolt up all done job

 

"Both sizes of pipes were same diameter all the way to the doughnut flange. No expanding or resizing"

This statement could be confusing. This means that the 2" pipe for example, is 2" from one end to the other and not swelled or reduced along it's length. Likewise, the 2 1/2". As Chris said, the 250 hp engine used the 2" system. The other engines used 2 1/2".

I don't know how you've been running without a heat riser unless you have two left side manifolds and custom pipes on your car.

 

Mike, Piper;



GM Exhaust Manifold RH 3781802

Here are some photos and more info.

I'm told the block is not original. I don't know if that means the whole engine or just the block. It's a 327/300 Carter AFB and everything cosmetic looks pretty stock for a 62 C1

The 2 donut gaskets in the photo measure 2.5" and 3.0" OD.
ID is 2.0" and 2.5"

On newly purchased Heat Riser, distance between center of stud to center of stud is 3.0"

The larger donut fits the chamfer of the new heat riser and the smaller donut can easily drop into the heat riser and interfere with the butterfly valve.

The exhaust pipe is 2" dia. with 2 small graduating expansions near the flare. I'm not sure of the max diameter of the pipe just below the flare, but I bet its between 2.25 and 2.5".

Joe

 

One more photo.

 

BTW, the new heat riser does fit on the studs of the exhaust manifold. Problem is that the flared end of the exhaust is small enough that it's going to either........

1. slide into the larger donut seal and rest against the butterfly valve, OR
2. if I use the smaller donut, the donut itself will sit inside the heat riser and interfere with the valve.

3. If I have the exhaust pipe flared larger to mate with the larger donut, the I have the problem of the driver side exhaust donut being of the smaller size.

Let me know if this is too confusing for the forum and I'll take the car into a specialist in Culver City.

All the best;
Joe

 

if i understood what you said, it sounds like you have different sized exhaust manifolds on each side of your car...

my understanding of the stock exhaust system is that even if the exhaust manifold outlet is 2-1/2", the exhaust pipe will be necked down to 2" shortly after coming out of the exhaust manifold because the rest of the exhaust system is 2"...

so, if you by some strange chance have a 2" & a 2-1/2" exhaust manifold, then they exhaust pipe is going to end up be 2" anyway... strange, but workable...

Bill

 

Yeah Bill, but aren't I better off trying to get this thing back to original?

 

sure....

if you're not trying to be OEM 'original', then i suggest you buy another 2-1/2" manifold (or the pair for about $145 + shipping) on ebay. they're made in China but look and work good. the word "China" is cast on the inner face of the manifold and can't be seen, but you can grind that off if it bothers you.

a single OEM manifold is going to cost you over $200 at somewhere like Paragon.
Bill

 

I'm sorry. I've got at least average intelligence, and I can't understand your question.

All I know is:

1. The manifolds, heat risers, gaskets, donuts, and front header pipes only come in 2 sizes - 2" and 2.5".

2. One size will not fit the other, and can't be made to do so.

3. You buy the first thing in one size, and then buy everything else to fit that size.

What's being changed? Buy the size to fit what's already there. Or, change everything to fit the size of the thing you just bought. This is the reason I like stock parts and the stock configuration. If I use the parts Chevy used, I know it's going to fit.

This is a bolt on installation. You should not be having this trouble. Is the front pipe stock? What did you have in there before you decided to put a heat riser in?

Some observations. Use brass nuts and anti-seize paste. Use anti-seize on the exhaust manifold bolts. Somebody will thank you 40 years from now. You'll need to tighten them up at least once after a few hours use. Don't overtighten to deform the donut. Consider double nutting the brass nuts. You need the riser or the FI spacer in there, or the alignment of the right side header pipe is off.

 

Chris, Bill;
Got it clearly now.

Manifold is 2.5", Riser is 2.5" and pipes are 2". I'll just change the exhausts to match the manifold/riser.

Joe

 

Chris, Bill;
Got it clearly now.

Manifold is 2.5", Riser is 2.5" and pipes are 2". I'll just change the exhausts to match the manifold/riser.

Joe

 

The only difference in the 2" and 2.5" systems are the 2 front header pipes. After the 2 front pipes, the 2 exhaust systems are identical. Mufflers, tailpipes, "X" pipes - all the same for both the 2" and 2.5" systems.

I believe the vendors sell exhaust systems as system. That is, they don't sell the individual pipes, but only the whole system. But shop around. Corvette Central has some shipping deal on exhaust systems. Most of them are made by Allen. Don't bother with stainless steel. Aluminized will probably outlast us all. Don't try to install it yourself unless you have a helper and can put the car up on a lift. I tried to do mine for a few hours sliding back and forth on a creeper. Adjust one thing. Move to the next. And the first thing goes out of adjustment. Much sliding around. The expert I brought mine to spent 2 hours adjusting it. Doesn't rattle. (I hate rattles.)

When you go to buy the system, you can get it with and without a cross-over pipe. Chevy put cross-over pipes on the 340 and 360 HP versions. Not sure about the 300 HP version. Hot rod magazines report HP gains with cross-over pipes. Modern cars have cross-over pipes. Some people report that they like, and some people report that they don't like, the sound change that the crossover pipe makes in an exhaust system.

If you have to also buy mufflers, you can get regular production oval mufflers. Or, the smaller, rounder, "off road" mufflers. The "off road" mufflers were an RPO. The "off road" mufflers are louder. Most people report that the sound they make is louder, but in a good way. Not unpleasant.

 

Chris;
Great info and advice.
I know exactly how to proceed now.

Joe