1500 Exhaust

[Blueghost]

1978 Midget, originally had Cat converter right off exhaust manifold. Several years ago I eliminated that cat (it was totally empty and can shape couldn't be good for flow). P.O. added custom exhaust system many years ago. He used same routing as O.E.M., but added a new Cat just aft of forward pipe, and he eliminated 1st muffler just behind left wheel. Only has muffler behind gas tank. Also he used 1 3/4" OD pipe. This system is at least 10 years and 30,000 miles old, but is in reasonable condition. I would like to get rid of this Cat.

I have a parts car with useable O.E.M. pipe and 2-mufler system. I'd like to install this system, but just found OEM pipes are 1 3/8." Obvious advantage - get rid of Cat; disadvantage - 1 3/8" pipe instead of 1 3/4." I don't have factual information on internal condition of Cat or donor muffler. Any thoughts on which might be best? Thanks, Blueghost.

 

[Blueghost]

Also, this is not a performance car. But it does OK for a 1500. If there is an affordable better performance system that bolts on aft of the 1st pipe, I'd be highly interested. Moss/Monza looks a little overkill and expensive. Almost always better breathing means better performance, and by good luck, better economy, and sometimes, less emissions. Thanks, Blueghost.

 

[JPSmit]

Seems like you have a few options -

1. get rid of the cat in the existing system - replace with straight pipe. Advantage is it is cheap and quick and the larger size already installed. Disadvantage, the rest of the sytem is getting older.

2. Install other system. Advantage is it is all there and convenient, disadvantage is smaller pipe (probably not that big a deal taming those 55 or so screaming horses!)

3. A fresh start. I bought a header for Miss Triss and a Harley take off muffler (remember Ms Triss is now chrome bumpered, so the "side mounted" 1500 bumper was no longer an option.) At any rate, I took it to a muffler shop and had them install a stainless muffler - 2" if I recall, lovely sound, a little more expensive (but not too bad) and it will outlast the car.

Not sure there is a right answer here, time and money and your personal desire for a project seem to be the determining factors.

 

[Jim_Gruber]

JP did you install a muffler in addition to the Harley or just the Harley Muffler?

 

[SaxMan]

I don't think the 1500 cranks out enough to notice the difference that 3/8ths of an inch in diameter would make. I'd stick with the OEM system with no cat.

From what I recall from hanging out with the "car guys" back in high school and college, a more open exhaust may give you better breathing and more usable horsepower, but you lose some degree of torque in using a more open exhaust. For a small car like the Spridget, I'd take the torque over the horses.

 

[JPSmit]

JP did you install a muffler in addition to the Harley or just the Harley Muffler?

just the Harley. I haven't punched it out like Billy tells me I should, sounds just right, performance is not really an issue with a stock 1500 and for the environment I think it actually has a cat.

 

[Blueghost]

1st, I agree this motor isn't going to do much no matter what I do. But,I don't want to go backwards.

Believe I will try local muffler shop and get estimate on 1 3/4" pipe, no Cat, and single muffler. If reasonable, I'll have new system, and best flow. Can't do until at least next week end.

SaxMan, your right about torque versus HP. But with the low gear ratio of the 1500, torque is not a problem. And 3/8" difference between the two pipes looks small at first. But, percentage of area difference between 1 3/8" and 1 3/4" is more than I thought at first. 1 3/8" Dia equals area of 1.48 sq in. 1 3/4" Dia equals area of 2.40 sq in. Area of 1 3/8" is only 62% of 1 3/4"; conversely, 1 3/4" is 1.62 times greater than 1 3/8". The big question is, "does any of this matter?"

When I searched this site for info on 1500 exhaust, most comments were about tone and volume. That may be way more important.

I'll let you know how things shake out in a week or so. My guess is there won't be much (if any) change. Thanks, Blueghost.

 

[Guest]

When I searched this site for info on 1500 exhaust, most comments were about tone and volume. That may be way more important.
.

Volume or velocity? Volume effects velocity and that's what you need to worry about. A stock pipe with a punched baffle Harley muffler gives you both good flow and velocity. IIRC my stock pipe is 1 1/2", not 1 3/8 on my '79.

 

[Jamie]

I'd go no cat, smaller pipe. I have both a 1.5" and a 1.75" system for my '78. Both are from a 4 into 1 header to straight pipe to muffler by tank. 1.5" is to 1275 latest muffler. The 1.75" is to glass pack type bullet muffler. The 1.75" is too loud but mostly it gives away too much bottom end torque, the 1.5" is much better all around road system. Remember that the carb 'sees' whatever you do beyond the exhaust port. Use a Colortune or check your plug colour to make sure you don't go too lean.

Best mods I ever made to my 1500 from stock:

Remove the front bumper, cut down the stock spring height. Cooler running engine, looks better, weighs 75 pounds less, spring rate is higher.
Gut the cat, remove the air pump, richen up the mixture a turn or two. Way more power.
Replace the cat 'can' with a 4 into 1 header. More power.
Chop about .080" to .100" off the head, clean up the back of the gunky valves, add stem seals. More power again. Not your anemic 1500 any more.
Ditch the 'log' manifold and go to dual 1.25" SUs with manifold. No wait, they're too small for the 1500, go to dual 1.5" SUs from Spitfire 1500. I have both, the 1.5" just aren't on yet.
Remove rear bumper, install chrome one. 50 pounds lighter.
Cut the frame stubs out of the front grille area, install a proper Midget surround and grille.
Lay up a lower rear valance from a Sprite to fill in the missing body metal under rear lights. Have the mold made, just have to make the part.

 

[Blueghost]

Update from a week ago. I installed the O.E.M. 1 3/8" which eliminated the Cat and went to smaller diameter pipe. Great improvement. Throttle response 1,500 to 5,000 RPM sitting at curb (no load) is VERY fast. I have to be careful not to over-rev. This engine has mild cam and 9.1:1 pistons with Weber.

Actual performance is much improved. Pulls much better from 2,000 through at least 5,000 RPM. Didn't even think about it, but even shifting is noticeably improved, especially down shifting. I am guessing this is because I can more quickly match throttle response with load-unload-load.

Still has the 1,500 Speed limitation for late model 4-speed. Anything above 70 MPH sounds like it wants to blow up. Just more fun getting there.

For all you east coasters, it's been bitter cold here in Oregon - down into the lower 40s. Also had to shovel nearly half inch of rain.


Thanks, Blueghost

 

[recordsj]

Blueghost,

I have a similar setup (9:1 compression pistons in a 1500 MG Midget with Weber DGV) and over in the Portland Oregon area like you (down 99W in Dundee, OR).
I have a Harley muffler I installed last summer, did you end up going with the Harley muffler also?
What jets and and such do you have with your Weber carb?

Jason