Factory exhaust manifold project/ Porting and clean up with pics

[RaycinSS]

With Covid- 19 and stay at home in full play I seem to have way more time than money right now. To keep myself entertained Z/28 style I thought I'd take on a little project just for kicks and with a little luck hopefully I found a cheap pony or two.

I am about to put some TSP CNC ported heads and a TSP stage 2.2 cam in my car. Future plans are to add some American Racing long tube headers to take full advantage of those mods but current situation means the headers will have to wait.

Since I have my factory manifolds off the car right now I thought I'd do a little CNC (Covid Nineteen Controlled) porting of my own and see if I could make the most of what I have now.

I've seen a few questions concerning the factory tri-Y manifolds and thought I'd share my project and findings here.

I fully realize there's gonna be a few folks say that I'm completely wasting my time and there's not a single pony's worth of difference in what I'm doing and I welcome the spirited debate. I believe I haven't hurt anything and may see some small benefit because ultimately it's about making the air pump more efficient.

I'm going to have to do this in several post but it's a start.

Here's an inside look of one of the factory LS7 exhaust manifolds off of my 2015 Z/28

[RaycinSS]

There are some areas I have pointed out here that are darker from the exhaust that create a ridge and narrow the opening. Not by much but easily 1/8" to almost 1/4" in some areas and the entire circumference of the port.

This is a ridge that seems to impede flow and bottle neck the exhaust right where it comes out of the cylinder head. Just an eyeball guesstimate I believe it could be easily between a 5 and 15 percent blockage.

I'm removing this blockage as best I can and also getting inside and trying to open it up just a little and straighten some of the curves.

[RaycinSS]

Here's a couple of pictures with some of the ridge removed, opened up a little bit and some work to smooth and straighten as best I could with an air compressor and die grinder. It's not major in the whole scheme of things but I do believe it will make a slight difference and flow better than before.

Let the comments begin!

[SIM GhostrdrZ]

Originally Posted by RaycinSS

Here's a couple of pictures with some of the ridge removed, opened up a little bit and some work to smooth and straighten as best I could with an air compressor and die grinder. It's not major in the whole scheme of things but I do believe it will make a slight difference and flow better than before.

Let the comments begin!

Looks good. How where the bolts to remove, any troubles. Are you putting stock bolts back in or?

[RaycinSS]

Originally Posted by SIM GhostrdrZ

Looks good. How where the bolts to remove, any troubles. Are you putting stock bolts back in or?

For now the stock bolts will be reused. I didn't take the manifolds off so I can't comment on how difficult the bolts were to take off. Hopefully someone who has done it will comment. I can also let you know when I do take them off myself to install headers in the near future. I am considering changing to aftermarket bolts at that time and welcome feedback about it.

[olblue75]

All your work can’t hurt that’s for sure.

[VOIT]

BRAVO!
Blueprint/port matching your exhaust manifolds in quest to find free HP.

[pat_t]

Great work. I think you'll definitely see an improvement!

[joelster]

Won't pick up much at all. Maybe 1-2hp, and that could be dyno error from run to run. The restriction is the catalytic converters, not the manifolds. If you could fab up an off-road pipe the bolted to the back of the manifold to the factory catback you'd pick up 15+ hp, which is what you'd get by going to aftermarket long tubes without cats.

[Yessa]

Originally Posted by joelster

The restriction is the catalytic converters not the manifolds. If you could fab up an off-road pipe the bolted to the back of the manifold to the factory cat back you'd pick up 15+ hp, which is what you'd get by going to aftermarket long tubes without cats.

Yes. But the horrid smell of gasoline is a huge turnoff not to mention it's arguably bad for your health like in your garage upon start up.

[ariZona28]

Originally Posted by Yessa

Yes. But the horrid smell of gasoline is a huge turnoff not to mention it's arguably bad for your health like in your garage upon start up.

Try a W-31 spec cam (not a lot of lift but plenty of duration and 82 degrees of overlap). Pair that up with a rich running Holley 3310 carb and it will set off the CO detectors in your neighbors house. I love the smell of hydrocarbons in the morning. Smells like...VICTORY.

[DasBaldDog]

Originally Posted by ariZona28

Try a W-31 spec cam (not a lot of lift but plenty of duration and 82 degrees of overlap). Pair that up with a rich running Holley 3310 carb and it will set off the CO detectors in your neighbors house. I love the smell of hydrocarbons in the morning. Smells like...VICTORY.

I had a '72 442 clone painted in a Chrysler Gray with a dark gray center stripe.

Bought it as a non-runner because the guy reused his 350 starter and warped airhorn Quadrajet.

Replace the starter and carb and boom, fired right up.

[macalot]

Originally Posted by ariZona28

Try a W-31 spec cam (not a lot of lift but plenty of duration and 82 degrees of overlap). Pair that up with a rich running Holley 3310 carb and it will set off the CO detectors in your neighbors house. I love the smell of hydrocarbons in the morning. Smells like...VICTORY.

Reminds me of the time a some years ago I was sitting in my '69 Z/28 (with the off road race cam in the 302) at a redlight just thumping away. A Prius pulls up behind me real close as she was bz with her phone. As soon as she gets a whiff of my exhaust she tries to back up but is jammed by another car. She was really upset to say the least...hand/face gestures and all. I gave her a good shot before I pulled out to let her know I was glad she was driving a Prius so I could have more gasoline to burn in the Z! Most youngsters it seems don't give a crap about their driving skills or much else for that matter, unless it infringes upon their narrow views.

Oh, we port matched the original intake to the heads on the '69 way back when. It made all the difference in the world. Of course back then things were factory assembled without any real concerns to air flow.