1.5 inch primaries

[Simon]

is this too small for a standard (ish) 302?
Thanks

Simon

 

[Keith]

I think that 1 5/8ths inches is about right for a mild 302, 1 3/4" for a stroked higher capacity modified ( around 350 cubes) and 2" for an all singing big block, 427 and up...!

That was my experience anyway, unless someone knows different - which they invariably do around here....

 

[Brett James-McCall]

Didn't Kalun_D do a long thread on the best size to use along with length?

Brett

 

[Ian Anderson]

Simon

My memory says the originals had 1.5 inch primaries!

But with modern engines and better breathing they may now be "too small"

IAn

 

[Gordon Levy]

If you have a basically stock 302 the 1.5" primaries will work fine. They will help torque but cost top end power. On a built engine they would just choke it and cost a lot of power while promoting minimal torque gains.

 

[Scott Calabro]

Simon,

Read this thread...

"Primary pipe length formula"

Seems like 1 5/8 is perfect.

Cheers,
S

 

[kiwi ka]

Whilst we are on the subject of pipes, is there any source of information regarding back pressure or the lack of. I have been trying to prove / disprove what I have built for the Rover 3.5 that I have built. I have made all the primary pipes the same length and arrived at 1 5/8 pipe size, but there are many experts...

 

[Russ Noble]

Russell,

I thought we covered this subject earlier, however off the top of my head "Scientific design of exhaust and intake" by Phillip H Smith. It's not a new book but IIRC it covers what you are talking about.
I used to have a copy but I lent it to someone and haven't seen it for years!

Cheers

 

[kiwi ka]

Yes I kind of thought we had untilI went to a club night at a leading muffler shop. When they told us all about their expertise and knowledge, I was floored by the fact that they had no technical data and relied totaly on what looked right and a drive round the block.. I suppose I am looking for some reassurance that what I have done is right before I throw some paint on them. All the primary`s are the same length and size was down from a set of high performance headers as I will not be making that much.
Suffice to say when I asked them how do they spec their systems they were lost.
Cheers

 

[Russ Noble]

I suppose I am looking for some reassurance that what I have done is right before I throw some paint on them.
Cheers

Russell,

What you have done is right! Get the paint out!

Cheers,

 

[kiwi ka]

The paint is out.............

 

hey russ, look after that crook thumb, and no deep inhaleing while on the job eh !! stweve. ah a welsh steve