Rebuilding 1275 for a little performance...

[lbc_newbie]

OK, so I was talked into pepping up the 1275. I'm going .030 over with a performance cam. It will still have the Weber 32/26 DGV down-draft carb. One question is will I need to increase my exhaust from 1.75 to 2.0 inches? Is there any re-jetting necessary? Eventually, the ignition will be updated to an MSD type ignition. Open to thoughts, experiences, and catastrophies...

 

[Trevor Jessie]

I'd think 1.75" is more than adequate.

 

[bill_powell]

Your quest for knowledge lies here:

https://www.amazon.com/Tuning-Engine-Defi...6828&sr=1-5

Get yourself <span style="font-style: italic">The Book</span>, and you'll be one happy grasshopper.

Seriously.



...gratuitous photo:

 

[Gray_Cat]

Be sure to have the rotating parts balanced while you're at it. Crucial to longevity and adds a bit of performance as well!
Roy

 

[GeeBee1]

1.75 s/b fine, the most performance gains for the buck are in the head.

Pat

 

[theleisure]

Hey Pat,

Can you elaborate on that a bit, please. I'm going to be redoing a 1275 soon and the limiting factor in my rebuild will be money.

 

[Dadandson]

According to Mr. Vizard, all performance enhancements begin at the top of pistons. While have new main, rod and cam bearings can reduce friction, paying closer attention to the cam, valves, porting and polishing of the head and intake manifold will give you the most HP for the dollar. Buy the book! Borrow the book! Even steal the book in you need to! It will set you on the right direction before you start buying parts!

 

[GeeBee1]

According to Mr. Vizard, all performance enhancements begin at the top of pistons. While have new main, rod and cam bearings can reduce friction, paying closer attention to the cam, valves, porting and polishing of the head and intake manifold will give you the most HP for the dollar. Buy the book! Borrow the book! Even steal the book in you need to! It will set you on the right direction before you start buying parts!

Pretty much says it all.

Pat

 

[John Moore]

Hey Pat,

Can you elaborate on that a bit, please. I'm going to be redoing a 1275 soon and the limiting factor in my rebuild will be money.

The simamese ports on the A & B series engines are restrictive. Here is an article that Sean Brown wrote about the Port & Polish job he did on my MGB head. Different engine, but similar design and idea. The result was impressive.

I know Hap does this work on A series heads, I would imagine that Sean does too.

https://www.flowspeed.com/board-week.htm