Any HP gain for early 1.7 heater boxes and Bursch muffler vs late 1.8 system? Options

[914rrr]

I have a 75 1.8 with the OE heater boxes and a Bursch muffler w/o cat.

Is there any HP gain if I were to switch to an earlier 1.7 heater boxes and Bursch muffler?

Another alternative is to use a Supertrapp muffler with the late 1.8 heater boxes.

[brant]

If you have the late style where the short header points to the front of the car and then does a 180 turn to go out the back

That 180 is resrictive

The 1.7 being straight to go back is less restrictive and will give you a couple of hp

The 2.0 (or SSI brand for a 1.7) has bigger diameter tube and will give a couple more hp over a stock original heater box

[914rrr]

Thanks! Are we talking 2 HP add or 8 HP added, worst case to best case system?

That also begs another question:

Is the early system lighter than the late system? If so, by how much?

[bdstone914]

1974 1.8L stock heat exchangers have the same size pipes as the 73-74 2.0L.
SSI all use the larger pipes. In theory yes. How much? Had to be tested. I would not expect much difference on low HP engines

If you switch go with SSI or 2.0 73-74 or 1974 1.8 stock. I am not a fan of SSIs. Especially with the Dansk Kuality.
They were better when made in California

[rick 918-S]

The other issue is heat from the case manifolds. Harder on the heads from heat cycling. At least that is hypothesis. (IMG:style_emoticons/default/idea.gif)

[Dave_Darling]

The official power figures are the same for the 74 1.8 and the 75 1.8 . I don't buy that, personally.

On the 2.0 cars, the 75 has 7 fewer HP than the 74 does. 95 HP -> 88 HP. The 75-76 2-liter cars used exactly the same exhaust as the 75 1.8 cars did. I would expect between 4 and 7 HP difference on the 1.8 motors (the 74 1.8 was rated for 76 HP), but I don't have any actual data to back that up. Or, come to think of it, any back-to-back experience.

--DD