Topic: Stock heads restrictive?

[Sam Green Racing]

Yes !  what was it again ? 

Sam

[MRieck]

We were on 15/46 with the old motor..3.06...it peaked in top gear at the end.

It never came up or spun with Chris on it, it spun even in third with me on board.

I hate to think what it would do with me on it now

Sam.

I personally wouldn't recommend a 15 front secondary to chain engagement issues . I'd think something around 2.7  to 2.9 would let you use all the engine. I'm not second guessing you Sam. You run well secondary to great torque for sure. I'd just let that #$%* rip in all gears. I don't know....it's easy to second guess sitting in a seat 3,500 miles away.

[Sam Green Racing]

Dragman836 Dennis was running 12 or 13/52. Knowing that ours peaked in top on 15/46 useing 9,000rpm in each gear, what must Dennis have been reving his to ? 

Sam.

[puppytrax]

To get back somewhere near on-topic...   

I recall reading in the cycle magazines at the time, that when the 500 Four first came out [1971], the 500 Four head was redesigned (from the prototypes/pre-production samples) because it out-performed the 750 and Honda worried that it would cut into sales thereof...

(This post subject to CRS syndrome; YMMV)   

[MRieck]

To get back somewhere near on-topic...   

I recall reading in the cycle magazines at the time, that when the 500 Four first came out [1971], the 500 Four head was redesigned (from the prototypes/pre-production samples) because it out-performed the 750 and Honda worried that it would cut into sales thereof...

(This post subject to CRS syndrome; YMMV)   

The 550 ports are better than the 750's for sure. They are straight to begin eith and the intake floor is a better shape. The 650's are even better except the intake guide boss has a lot of extra material. The chambers of both engines are much better than the 750's too (once again secondary to straight ports).

[TwoTired]

MRieck<
Are there pictures somewhere of stock port vs. one of those smoothie jobs?  Would be interesting to see them side by side.  Or, did I miss that post?

Cheers,

[MRieck]

MRieck<
Are there pictures somewhere of stock port vs. one of those smoothie jobs?  Would be interesting to see them side by side.  Or, did I miss that post?

Cheers,

Yes sir...I have the natural, bead blasted pics etc, etc. Reducing has been a problem lately. I can show the difference but even in this thread you see, between my avatar and the pic, the difference between stage 3 and stage 2. Plus... no disrespect intended...my wife thinks I'm a bit abrasive sometimes ( she is looking over my shoulder while I type this and bustin my B's over something else).
  Mike

[mattcb350f]

I'm going to hijack this thread for a moment,
MRieck, Have you perfomed any head work on the smaller fours like a 400 or 350? The reason I'm asking as I plan to port my 350F head shortly and was wondering if there is any no-no's I should know about.
 Matt.

Do not cut the floor of the exhaust port. Just clean it up. Stick to removing material from the guide boss and cut into the area just behind the guide (the bowl) on the intake port. Blend the floor of the intake into the seat so it's a smooth transition. There...now you are an expert.

Thanks a Million Mike! Thats just the advice I was looking for. When I actually start to get some work done (Job in the way again)  I'll post some pics. 
 Matt.

[sparty]

MRieck<
Are there pictures somewhere of stock port vs. one of those smoothie jobs?  Would be interesting to see them side by side.  Or, did I miss that post?

Cheers,

TT,
Look at my build page and you will see the stock ports vs. the Stage 3 port job.
http://www.basd.net/staff/aentz/CB750/CB750_page.htm

Sparty