Dellorto Trumpet Length On Pinto

[Guest Brokey12]

Hi , I've recently put a set of 40s on my pinto along with a kent race cam , the duration of the cam is 3500 to. 8000 . Just wondering what length trumpets I would need on a 3 inch manifold to get the best performance

[richardm6994]

Generally speaking, the longer the better...but more importantly is the shape of the trumpet and making sure their opening is tight up against the chassis etc...causing a restriction.

 

Try going for big rolled lips as these make a big improvement over standard trumpets.

 

Edited July 25, 2014 by steamer

[Snapperpaul]

The calculations are complex, engine size, valve size, port size, cam duration etc come into play

I got someone on Turbosports forum to crunch the numbers for one of my builds and I got several options depending on the wave reflection harmonics.

The exhaust numbers were helpful

Inlet tract was less so with a measurement of 332.5mm

Not clear if this is measured from the valve to the end of the trumpet of the manifold face.

 

What is probably more important is that you air filter is large enough and free flowing.

 

Here's a diagram of trumpet shapes for your perusal, this may have more effect than length

 

[Snapperpaul]

He's nicked my photo

Or nicked the one I nicked

[richardm6994]

He's nicked my photo

Or nicked the one I nicked

 

lol....whenever one of these useful diagrams pop up on forums I always save them for future use

[Guest lotusPaul]

Brokey12.

 

Hi.im new to thus forum but ive been playing with engines for a fair few years. Basically Steamer and Snapperpaul are correct. There are simple equations you can follow but the result is sometimes hard to achieve.

Essentially the length is from the valve to the entrance of the ran pipe. By following the maths you will get an ideal length based on where you want the pulse tuning to hit revs wise.

The longer the path the lower the power will be.

Fit the biggest filters you can get in depth wise. Then give 25mm gap from the filter head and meassure.This will give you the length of ram pipe. The 25mm gap is really the least you should aim for or entrance to pipe will suffer.