I don’t think it’s excessive at 3” , but running anything bigger would be. Why not twin 50mm pipes. I’m running that now on a L24 .My numbers on the dyno don’t look bad and  don’t have any evidence it would better with less exhaust. Then again maybe it would have had more torque with less? 

In the end it wasn’t wasn’t about getting the biggest exhaust for me, it was about having duals, so 2” pipes was readily available . I’m with Charles that going past the area of 3” is probably overkill

3 hours ago, jy.s30z said:

Thank you very much for the help and encouraging words on my build. 

I just looked up the ISKY cam and it is 290 adv. duration and 242@.05".  From my understanding, advertised is taken at 0.006" most of the time.  So for my cam, the advertised would be 311 duration and 254@.05". So, my cam is bigger than the ISKY with slightly less lift at only .480 vs .490.

I'm going to search through ur builds for reference.

Thanks for clarifying . I’m not surprised a Racer Brown cam has the bigger duration . Racer Brown has a great rep and would love to run one of his cams. I’ll be curious what PVC numbers you get. 

1 hour ago, madkaw said:

I don’t think it’s excessive at 3” , but running anything bigger would be. Why not twin 50mm pipes. I’m running that now on a L24 .My numbers on the dyno don’t look bad and  don’t have any evidence it would better with less exhaust. Then again maybe it would have had more torque with less? 

In the end it wasn’t wasn’t about getting the biggest exhaust for me, it was about having duals, so 2” pipes was readily available . I’m with Charles that going past the area of 3” is probably overkill

What were your dyno numbers and what does your build consist of?  Did you run a single exhaust and switch to duals?  I'd like to get others opinions on the single vs dual debate before I decide for myself.

Duals was a matter of a personal quest of mine for looks and sound and something different . It’s a lot of work and things get really tight under there when you start running two pipes. There’s some nice systems out there for both options.

My numbers were from two separate dyno’s - roughly 155 /150 on a chassis dyno.

That was with triples .

Check out Madkaw's video on youtube.  One of my all time favorites.  3rd gear chirp. 

 

12 hours ago, madkaw said:

Duals was a matter of a personal quest of mine for looks and sound and something different . It’s a lot of work and things get really tight under there when you start running two pipes. There’s some nice systems out there for both options.

Sounds great madkaw!

Do you have pictures underneath your car showing your set-up? 

Anyone else have experience with single exhaust and switching to dual or vice versa? 

Here's another good one.

 

Edited August 8, 20186 yr by siteunseen

5 hours ago, jy.s30z said:

Sounds great madkaw!

Do you have pictures underneath your car showing your set-up? 

Anyone else have experience with single exhaust and switching to dual or vice versa? 

You don’t want my exhaust - you would be changing too many things . Google dual exhausts Datsun . Check vendors on this site . 

3" is not too big and you won't lose anything by doing so. I never did do a single vs dual comparison though.

http://forums.hybridz.org/topic/81941-exhaust-tube-sizing-i-did-your-arithmetic-for-you/

Has anyone with a higher compression (10:1 or greater), N/A & hot cam set-up have done a dyno comparison of a 2.5" set-up and a 3" set-up and seen any difference?  I'd like to stay 2.5" max for ease of fitment and I am assuming 3" will be louder which I don't want that.  However, I don't want to leave hp/tq on the table.

Your engine build sounds great. I built a similar set up for my z. 

F54 L28 block...stock bore

P79 .080 shave...mild porting on the intake runners

Web camshaft regrind...260 duration, 238 @.050 

Roundtop SU's with SM needles and k&n filters

6-2-1 header with 2.5" exhaust

My setup made 181hp/184tq on a dynojet dyno.