Exhaust port flow

[Warp Speed]

Small exhaust ports/ valves make more power than large. The reason [theory]: A secondary combustion chamber is developing in the exhaust port which is creating reversion. (I.e. more exhaust gases going in the exhaust port than going out). This creates a secondary combustion process that makes reversion and a cool flame out the exhaust. The flame is confirmation of unburned air/fuel going thru the motor caused by the reversion pulse.

[moparian]

1.76" 270 cfm.
1.70" 220 cfm.
Maybe that is not the correct flow numbers, you double check everything in the flowbench? Before and after.

"maybe i should go back to the original size valve?"

Maybe you should go first in the dyno and then go back to the original valve size. If it needs to go.

I spoke to the customer about the heads and he is happy to try it and see what the dyno say's, it has been on a dyno before so we kind of have a base number's i will post what it make's old numbers and new,the engine only got a freshen up same comp and a little bigger cam .

[moparian]

Small exhaust ports/ valves make more power than large. The reason [theory]: A secondary combustion chamber is developing in the exhaust port which is creating reversion. (I.e. more exhaust gases going in the exhaust port than going out). This creates a secondary combustion process that makes reversion and a cool flame out the exhaust. The flame is confirmation of unburned air/fuel going thru the motor caused by the reversion pulse.

Maybe that was what he was thinking,i think i will re flow it with a pipi and see what it does just to rule out error.How long should the pipe be? and size 2 1/4 pipe then step to 2 1/2 thoughts?

[PRH]

What did it make for power before, and what kind of gains were you hoping for with the rework?

If it makes the power you want, it doesn’t really matter what the flow numbers are.

A 14:1 580” B1 motor with intake ports flowing 450 should easily be in the 1000hp range.

[SpeierRacingHeads]

I have some data from the B1 heads I did for Koffel on the engine that went to EMC if your interested.

It was a huge head on a small engine and struggled.

[PRH]

I have some data from the B1 heads I did for Koffel on the engine that went to EMC if your interested.

It was a huge head on a small engine and struggled.

Is that more or less what you would have expected in that type of “racing” format?

[SpeierRacingHeads]

I have some data from the B1 heads I did for Koffel on the engine that went to EMC if your interested.

It was a huge head on a small engine and struggled.

Is that more or less what you would have expected in that type of “racing” format?

It was less. It was a 433. I have a dyno sheet, let me find it. From start to finish in 10 days, LOL. Poor Scott worked his butt off. Old rusty block to complete engine. That alone was pretty amazing.

[PRH]

I meant “fundamentally”.
Big heads, small-ish cubes....... run in a competition with a limited power band and where making good TQ numbers right at the beginning of the pull pays dividends.

For me, intuitively that doesn’t seem like it would be the hot ticket.

I was wondering if while you were doing the heads if you had suspicions that’s how it might play out....... that the combo, as you put it, struggled.

I would have thought some B1-BS heads might have been better on that sized motor in that environment.
What was the scored rpm range that year?
Looks like it’s just getting going at the end of the pull.

The tq numbers actually look better in the middle there than I would have expected.

[Elroy]

I have some data from the B1 heads I did for Koffel on the engine that went to EMC if your interested.

It was a huge head on a small engine and struggled.

Is that more or less what you would have expected in that type of “racing” format?

It was less. It was a 433. I have a dyno sheet, let me find it. From start to finish in 10 days, LOL. Poor Scott worked his butt off. Old rusty block to complete engine. That alone was pretty amazing.

I am going to assume that the circled number was the EMC score. Just did some searching on the google machine and saw 1st place had a similar score. Was this a second place engine then? Or is the top of that field that tight? I didn't see a big block Chrysler in there but I could have missed it.

[SpeierRacingHeads]

That sheet must have been on Koffels dyno. Everyone was happy and excited, but it was wounded on the competition dyno. (No excuses)

[SpeierRacingHeads]

I meant “fundamentally”.
Big heads, small-ish cubes....... run in a competition with a limited power band and where making good TQ numbers right at the beginning of the pull pays dividends.

For me, intuitively that doesn’t seem like it would be the hot ticket.

I was wondering if while you were doing the heads if you had suspicions that’s how it might play out....... that the combo, as you put it, struggled.

I would have thought some B1-BS heads might have been better on that sized motor in that environment.
What was the scored rpm range that year?
Looks like it’s just getting going at the end of the pull.

The tq numbers actually look better in the middle there than I would have expected.

They were big before I started. If epoxy would have been allowed, it would have been a different story.

[Elroy]

That sheet must have been on Koffels dyno. Everyone was happy and excited, but it was wounded on the competition dyno. (No excuses)

Too bad you couldn't have brought that dyno with you. I love to see a BBM running well.

. If epoxy would have been allowed, it would have been a different story.

For everyone.

[PRH]

Are the flow numbers for those heads top secret?

Or can they be shared?

[SpeierRacingHeads]

Are the flow numbers for those heads top secret?

Or can they be shared?

2.250/1.680

[RevTheory]

What are you guys looking for velocity on exhaust ports? In Don's interview with Darin Morgan, I think he mentioned 280 in some applications and 310 or something on others.