whats the best exhaust for my 1641?

[beetletom]

will be running 36 webers, 120 cam...

i've got an RX, would that be ok? 
what about a dual quietpack? and whats the best header?

i love the sound of turbo mufflers, but don't like the look...

[Peter]

quietpacks look cool

[beetletom]

yep!!

what exhaust and header gives the most power though?

[Neil Davies]

Depends if you want heating!

Ditch the heater boxes and go for a full merged 1 5/8" Bugpack  with twin quiet packs would be my recommendation, but if you want to keep the heaters then it'd have to be a regular 4-into-1 and dual QPs. I couldn't recommend a make though - I got my first bug in March 1995 and took the heaters off before the end of the season to run a merged header - never had heating since...

[beetletom]

deffo no heating!!
as i want the heater channels to last when they get redone! 

[Torben Alstrup]

I´d go for a 1½" merge header. Bettter overall power. The 36 mm carbs can not supply enough air to benefit from a 1 5/8" IMHO
T

[nicolas]

i'd use a 1 1/2 as well and not bigger. with those 36's i would even opt for a smaller 1 3/8. i have seen a nice SS merged one that you can use with either the heaterboxes or J tubes. i would go with that and J tubes. they looked like a seventies exhaust (the bends and form) and then a single or dualpack. bigger isn't always better for exhausts.

i had a 1 1/2 SS for my type 3 and that worked good with the 40x35 heads, but with stock heads and 36 IDF's i would use the 1 3/8

[beetletom]

cheers guys!!! 

[Neil Davies]

I suggested the 1 5/8" exhaust for ease of buying - I don't know of anywhere in the UK that sells the smaller merged headers!  Tom, don't forget to block off the ends of the heater channels under the car, or water will pour into the inside of the channels!

[qubek]

i'd use a 1 1/2 as well and not bigger. with those 36's i would even opt for a smaller 1 3/8. (...)
(...) but with stock heads and 36 IDF's i would use the 1 3/8

The 36 mm carbs can not supply enough air to benefit from a 1 5/8" IMHO

I have a similar problem at the moment.
The point is, that with my 36 DRLA's I can use 26mm vents as well as 34mm ones. So how can you tell that "with a 36's I would ..."? I don;t have experience with that, but IMO knowing carb's model is not enough information, is it?

[Rick Meredith]

1.5 is gonna be too big... car is gonna run like crap. I have a 1 3/8 on my 1776 and it ran pretty good.

[louisb]

Check this out. Price is pretty good too.

http://www.cbperformance.com/catalog.asp?ProductID=1634

--louis

[Torben Alstrup]

i'd use a 1 1/2 as well and not bigger. with those 36's i would even opt for a smaller 1 3/8. (...)
(...) but with stock heads and 36 IDF's i would use the 1 3/8

The 36 mm carbs can not supply enough air to benefit from a 1 5/8" IMHO

I have a similar problem at the moment.
The point is, that with my 36 DRLA's I can use 26mm vents as well as 34mm ones. So how can you tell that "with a 36's I would ..."? I don;t have experience with that, but IMO knowing carb's model is not enough information, is it?

Hello. When chosing venturi size in a certain carburettor (In this case Dellorto) there is the "85%" rule to be guided by. That means the venturi should be no larger than 85-88% of the throttle bore size. With 36´s that means 32 mm venturi. - the next thing to consider is, how high does it rev, how many cc´s, are you chasing max hp or max drivebility. going 1 # up or down can make a huge difference in how the engine responds

 Now the 85% rule is a good guideline for street cars. - That doesnt mean that you cant go beyond that. But then you run into jetting problems. The sweet spot gets significantly harder to hit. And is generally not recommended, unless we are talking race.

 A 32 mm venturi in a 36 mm carburettor is sufficient for up to about 120 hp within reason. Assuming your engine is a 1600 cc. you will "hit a wall" at about 112 hp. From thereon up it gets complicated. I have pulled 117-120 hp on 1776és and slightly modified 36 Dells several times. But it takes a little detailing to the carb and a well breathing engine.

On a 1600 cc stock to mild engine, I normally chose 30 mm venturies for best all round performance. On hotter setups I use 32 mm.
With some carefull selected parts and good heads, it is not so difficult to get 100 hp out of a 1600 cc.
T

[qubek]

i'd use a 1 1/2 as well and not bigger. with those 36's i would even opt for a smaller 1 3/8. (...)
(...) but with stock heads and 36 IDF's i would use the 1 3/8

The 36 mm carbs can not supply enough air to benefit from a 1 5/8" IMHO

I have a similar problem at the moment.
The point is, that with my 36 DRLA's I can use 26mm vents as well as 34mm ones. So how can you tell that "with a 36's I would ..."? I don;t have experience with that, but IMO knowing carb's model is not enough information, is it?

Hello. When chosing venturi size in a certain carburettor (In this case Dellorto) there is the "85%" rule to be guided by. That means the venturi should be no larger than 85-88% of the throttle bore size. With 36´s that means 32 mm venturi. - the next thing to consider is, how high does it rev, how many cc´s, are you chasing max hp or max drivebility. going 1 # up or down can make a huge difference in how the engine responds

 Now the 85% rule is a good guideline for street cars. - That doesnt mean that you cant go beyond that. But then you run into jetting problems. The sweet spot gets significantly harder to hit. And is generally not recommended, unless we are talking race.

 A 32 mm venturi in a 36 mm carburettor is sufficient for up to about 120 hp within reason. Assuming your engine is a 1600 cc. you will "hit a wall" at about 112 hp. From thereon up it gets complicated. I have pulled 117-120 hp on 1776és and slightly modified 36 Dells several times. But it takes a little detailing to the carb and a well breathing engine.

On a 1600 cc stock to mild engine, I normally chose 30 mm venturies for best all round performance. On hotter setups I use 32 mm.
With some carefull selected parts and good heads, it is not so difficult to get 100 hp out of a 1600 cc.
T

We're going slightly off topic here, but that is interesting.
Actually my situation is that I have 1915cc and Eurorace F grind cam (link to timing chart - >http://img249.imageshack.us/img249/5851/euroracegn2.jpg)
Originally, the engine was supposed to have stock heads, not-merged 1 3/8 exhaust and 30 vents in 36 drla's
I finally ended up with 40x35,5 heads and that doesn't match the rest of the combo. The carbs are not a big problem - I have 34 mm vents that I can use (which can make carbs hard to tune, so maybe I will end up buying either smaller vents or 40 DRLA's). The problems is with the exhaust. I'm afraid that the one I have may cause overheating. I should probably get 1 1/2 or 1/5/8 one. I'm loosing control over this project :/
As for venturi choice, there are rules, but sometimes, they just seem not to work
I use 30 vents in 36 DRLA's in my girlfriend otherwise stock, small valved 1600 and it seems to work fine, although we're considering trying smaller vents. But how does a 85% or 80% rule apply to the fact that the most common vent size you can find in 40 DRLA's is 28mm and in 36 DRLA's - 30 mm? Those are factory settings for Alfas.

[Torben Alstrup]

Going to 28 mm venturies on an otherwise stock 1600 typically moves the powerband down by 2-300 rpm. And it definitely stiffles the top end.
WRT your 1914 with larger valves. You need to go 1½" all the way through. If you use stock heater boxes you will heat up #1 & 3 cylinders 30 - 50 degrees more than 2 & 4 under load. That´s too much and results in cracked heads pretty soon. I learned that the hard way many years back.
36 Dells on a 1914 will work. You need 32 mm venturies and most likely something like 0,58 idle, # 2 E tube, 170 main air and 135-138 main jet. I dont know that cam, so I dont know how much port vacum it makes.

Yes most Alfa´s came with 30 mm venturies. The later ti´s came with 32mm and the early 1,7ti had 40 Dells and 32 mm venturies.
T

[qubek]

Going to 28 mm venturies on an otherwise stock 1600 typically moves the powerband down by 2-300 rpm. And it definitely stiffles the top end.

In this case I have some spare vents so I can experiment without bearing any cost other then my time. I'll have to look into this carbs anyway, because they last time they were tuned was about 2 years ago. They still run as good as then though From what you say, I will probably have to go back to current setup after all, but I'd like to see what the difference will be by myself
This engine was a new mexican longblock, so it comes with smaller valves then normal 1600 and (i suspect) lower compression ratio. The way it's driven, it does not use top end most of the time - no one races this car. I would like to improve the low end though, because I thing that it might be a little bit better then it is at present. Maybe the change of distributor would help (it uses centrifugal advance Mallory) but I don't trust vacuum advance distributors - I don't know how to make sure that they work properly with a non-stock carb setup without access to rolling road.

WRT your 1914 with larger valves. You need to go 1½" all the way through. If you use stock heater boxes you will heat up #1 & 3 cylinders 30 - 50 degrees more than 2 & 4 under load. That´s too much and results in cracked heads pretty soon. I learned that the hard way many years back.

Thanks, I wouldn't like to repeat your lesson. I thought about that before and that's why I was looking for an exhaust system that would have aftermarket, larger heater boxes which match the size of the header. The problem is that little people seem to care about this and no one is really sure what is an internal diameter of such heater boxes. I don't even know where to find them, especially in Europe. Anyone have a good, full 1,5 inch exhaust system with heater boxes for sale?
Actually I gave up and at the moment hesitate between Sidewinder(no one sells them here) CSP Python (pricey) and VW Speedshop sidewinder copy - good price but comes only in 1 5/8 size and this may be to big (?)

36 Dells on a 1914 will work. You need 32 mm venturies and most likely something like 0,58 idle, # 2 E tube, 170 main air and 135-138 main jet. I dont know that cam, so I dont know how much port vacum it makes.

32's I would have to order from someone (dellorto co uk) because I only have a set of 26s, 30s and 34s. As for main jet's I always used a "vent size times 4 plus a safety margin" rule and I would end up with slightly smaller size then your recommendation. Thanks for advise, it's always faster and cheaper not to have to order additional set of jets. Other thing is that I use stock 180 airs, so what you recommend is bigger mains and smaller airs.
As for idle jets, the 1600 I mentioned above needed bigger ones at the beginning, first 1000km or something like that, and then I had to change to smaller ones, once the engine settled in

[airstuff]

Get yourself merged 1 1/2 merged header.If you can find it,this system would work the best on that combo.I had it.

[Torben Alstrup]

CSP has 1½" heaterboxes at the same price as stock. If the Python is a little too much for your wallet, get a regular 1½" large flange header and the muffler you "want" and use that for starters. then if you want to improve the set up, you can save up for the Python or similar. Personally I really like the Python, but for a daily I would build myself a better (read more silent) muffler system.
T

[Jim Ratto]

I ran the S&S Rally muffler on my 1641 in the 1980's.... sounded like a Porsche
Looked, well..... "eighties"   

A friend of Sheep's once said "Jim's car MUST be fast....he has four stingers."

[qubek]

CSP has 1½" heaterboxes at the same price as stock. If the Python is a little too much for your wallet, get a regular 1½" large flange header and the muffler you "want" and use that for starters. then if you want to improve the set up, you can save up for the Python or similar. Personally I really like the Python, but for a daily I would build myself a better (read more silent) muffler system.

I like the Python too, but I've only seen it on the pictures, like the most of the other systems I'm considering. This does not help.
The problem with "regular" merged headers is that most of them stick out too much at the rear, which  reduces ground clearance a lot. I've seen to many cases when someone lost his exhaust on a kerb or underground parking lot. Heaving a header like that means that you need to think about it all the time, be careful and even than - sooner or later - I would damage it. It's not practical in my situation and on Polish roads. That's why I was thinking about "sidewinder type" of exhaust systems.
Second problem is that most of the systems tend to disintegrate very quickly. That's why I was thinking about stainless steel and that's why I started to look at vwspeedshop systems. They aren't expensive and are stainless steel. I wonder what's the catch, because good things doesn't come cheap. One obvious downside is that they don't do merged systems smaller than 1 5/8 (is it really too much for me?), their 1.5 header is not merged type.
That's why i envy Americans - they can go and see everything, check how the part looks in the shop, check how the part looks on someones car after some time of usage, compare everything. In most cases all I have is internet and magazines, where 95% of parts are described as great even if they're not, or as "crap" because someone don't like the man who sells them.