CMI E tops/ Imco power Flow pro and cons
 

The 502 in my Velocity VR 1 is being bored to 540 and rebuilt. Horsepower will be north of 600. My original exhaust is CMI E tops. Problem is that they are the model that doesn't use tail pipes, just a rubber connector from the elbow to the through hull tips. Builder is recommending either CMI E tops with tails or IMCO Plowe Flow with SS riser. As I had some cylinder damage with the original (non-stock) 502 he wants the water introduced further back then my old CMI without tails. He is OK with either choice.

Besides the fact that the CMI is prettier and the IMCO are less expensive...What are the other pros and cons. I do wonder how changing spark plugs are with the IMCO. I am not as limber as I used to be.

Thanks for the help, deciding.

Padraig

Go with the CMI Elbow Tops. They look great and last forever!!!

I have the black (powder coated) Imco power flow plus manifolds ....Attached to 572 cu. in. tall boys ~ back in 2018 (2) sets of black manifolds & 30* risers
cost $5,199.98 from CP performance. I can get under them to change spark plugs easily.....

Thanks Skippy. Any idea of how the Power flow and power flow plus are different?

Padraig

Same here... mine have been on the 311 (TRS tails) for over a decade in salt water and not one issue. I pressure test with air and heat every other year... still going strong.

550 hp would be border line for the Power Flow manifolds ...above that, I would go Power Flow Plus reason being their ported to flow better for above 600 hp
Also, the tail pipe accessory is different than the "plus"....https://www.cpperformance.com/c-436-...ock-chevy.aspx check out the differences between them.

Might want to check into extending the one piece E tops you have. Have a good welder make them like the older CMI Unitops
https://cimg2.ibsrv.net/gimg/www.off...5f2a6f359a.jpg

I thought boosted engines did not usually have water intrusion from reversion. Griff's comment above, ^^^^ makes the best recommendation with probably the best cost too.You are likelt only looking at a few hundred vs several thousand $$.

Cmi look cool. We had issues with bad welds. Stainless marine ftw

With E-tops or full long tube?

Sorry I am getting back late....been traveling.

Jason did check with CMI about modifying my existing headers and they couldn't or wouldn't.

Need to decide soon as we need to get them in as I would hate to have a rebuilt engine and have to wait for the exhaust.

Padraig

Not boosted

Padraig

Ah, my mistake, I thought post #7 was your engine. Thanks for the clarification.

From what I’ve read, CMI will not work on or repair any headers that are more than 5 years old.

We've had no issue with sending much older stuff than that. Perhaps because we're a dealer, not sure. Nevertheless, they didn't feel his elbow tops could be converted.
99% of CMI's issues are on the Mercury 525-700 headers which were built to Mercury's spec, not CMIs. Thinner metal plus the lack of a flex flange. The CMI genx sweeper replacements are 10x better as are their E-Tops.
All your options are good Pat, we wouldnt recommend anything but a good plan :)

Thanks! I know both of your options will work well...just trying to decide which i like better. Leaning toward the CMI . They don't take up as much room and are pretty. LOL I know...not very logical. LOL

Padraig

That is my old 525SC showing the older style CMI Unitops

Just to let everyone know...I decided to go with the CMI elbow tops. Prettier and easier to work around IMO. Jason has all the parts ordered and delivery looks good. Now that I have made up my mind on the exhaust, we are all set. Saris is great team to work with.

Thanks for the help!

Padraig