Birmal and Dunn Heads - ZR-1 Net Registry Forums

Dynomite · 08-11-2018

Is there a difference in air flow rate between left Dunn and Right Birmal Heads on a 95'?

Paul Workman · 08-14-2018

Cliff,

IIRC, there likely is some slight differences as result of (reported) improved port matching and some other minor internal dimensions. Sources I've read claim as much as 20 hp improvement over the Birmal heads, yet the expense of re-certifying the HP was prohibitive in light of the fact the motor was to be discontinued. So! The "minor" HP change was never published. And, according to HOTB, some motors left MM with one of each heads - as you apparently have??

However, as you know, with only minor porting any flow differences are erased, FWIW.

P.

08-11-2018	#1
Dynomite Join Date: Aug 2009 Location: South Dakota/California Posts: 3,815	Birmal and Dunn Heads Is there a difference in air flow rate between left Dunn and Right Birmal Heads on a 95'? __________________ Clickable links On Iphone Touchable Links -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 08-11-2018 at 11:23 PM.

08-14-2018	#2
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	Re: Birmal and Dunn Heads Cliff, IIRC, there likely is some slight differences as result of (reported) improved port matching and some other minor internal dimensions. Sources I've read claim as much as 20 hp improvement over the Birmal heads, yet the expense of re-certifying the HP was prohibitive in light of the fact the motor was to be discontinued. So! The "minor" HP change was never published. And, according to HOTB, some motors left MM with one of each heads - as you apparently have?? However, as you know, with only minor porting any flow differences are erased, FWIW. P. Last edited by Paul Workman; 08-14-2018 at 07:43 AM.