TheSamba.com :: View topic

Fri Mar 07, 2014 9:59 am

I'm getting an 1776cc motor from a guy that is doing an trade with me. What I need to know is will 1 1/2 header with stock heater boxes work fine for this engine or do I need to get 1 1/2 heater boxes but will require to buy 1 5/8 header?

Fri Mar 07, 2014 10:02 am

What size valves does it have?

Fri Mar 07, 2014 10:11 am

I'm not exactly sure. I can ask him but he is very busy. The heads are single port and from what he said that mild port works are done to it. That's the best info I can give right now.

Fri Mar 07, 2014 10:18 am

That exhaust will be just fine, my 1776 dual port with 40x35 valves has a 1-1/2 header

Fri Mar 07, 2014 10:21 am

Alright thanks, for now I'll put j tubes because I don't need them for the summer. I just want to make sure I'm going in the right direction without choking the engine.

Fri Mar 07, 2014 11:08 am

With SP heads, 1 3/8" would be optimal and best matched to stock heater boxes, but you could use 1 1/2" if you have one already.

Fri Mar 07, 2014 11:13 am

The guy that built my motor recommends 1 1/2 header which I'm going to get. Mostly just the question was if stock heater boxes will be ok with this type of motor I'll be running.

Fri Mar 07, 2014 11:19 am

Rule of thumb, If stock heater boxes are used the heads must use stock size valves. Dan

Fri Mar 07, 2014 11:27 am

Dan Ruddock wrote: Rule of thumb, If stock heater boxes are used the heads must use stock size valves. Dan
Ok then I'm better off buying 1 1/2 heater boxes? I don't see any those available to fit 1 1/2 headers only 1 5/8 headers.

Fri Mar 07, 2014 11:49 am

Regardless of what your engine builder says, SP heads with stock sized 32 mm exhaust valves with or without port work will work just fine with stock heater boxes and a 1 3/8" exhaust. You don't have to step up to 1 1/2" until you bump up to 35.5 mm exhaust valves.

Fri Mar 07, 2014 11:54 am

Seriously - this is a street car - a 1 3/8" header is really a better choice. With a header, bigger is not better. A larger header diameter will hurt your low end torque a lot. I run up to a 1955 with stock heater boxes and a 1 3/8" header. And this is with middle of the road performance heads. And the same setup works beautifully with a mild 1600. If you are concerned with max power over 5000 RPMs, then its a different matter.

Lots of write ups on this and Hot VWs did an article on this maybe a year ago.

Something else to think about - a perfect header will have the same resistence to flow on each cylinder. Pretty much all will have the same primary tube diameter. Running larger or small tubes on one pair of cylinders compared to the other pair is not really a good idea.

Fri Mar 07, 2014 1:13 pm

I went from 1 3/8 to 1 1/2 on my 1641cc dual port engine in my 71 bus and it made it stumble on take-off it was difficult to back out of the driveway with it. Once it warmed up good it was ok. I did notice some increase in top speed (about 10mph) on the highway but that was partly due to the 1.25:1 Ratio Rockers I put on it.