Anyone running Imco powerflow manifolds on ZZ502
 

Has anyone run Imco powerflow manifols with S/S risers with a ZZ502 and had reversion issues ? Has anyone had success ? Thx

Are you asking about the short risers used with silent choice?

Not sure about the cam profile on the ZZ502, but It could be a problem (silent choice riser?) because of the cam 110 lsa. I am running the PowerFlows W/silent choice SS riser on stock cam, 509mpi and have no problems but the cam is much smaller. A friend is running the 741 cam with the long risers and has no problems. Not exactly what you are asking but some similar comparisons for you.

Yes , short risers with silent choice . I've run the boat for 2 seasons with stock merc manifold/risers with no issue but uncertain of making this change without talking with you guys , I appreciate the help thx

If those work ok, I can't see how Powerflows would create any more reversion issues than stock Merc manifolds. I guess it would depend on the type of manifold & risers you actually have. The gill ones seem to be pretty good. Are the risers the cast iron type or rolled steel with a long reach?

Old risers are the cast iron really heavy ones . Imco ones are s/s they call Short SA

The zz grind is outside the gm marine grind box has a idle rumpity rump similar to hp500 ,if you have closed cooling you may be able to manipulate the idle water dump.to the minimum ,otherwise its going to be close if you want to put it together and forget it ,I did a zz dump at the tips cmi headers with 3rd overflow never reversion lots of idling and it was complicated .everybody will know its not a 502 mag when you start it .did I just read your zz502 went 2 seasons with cast manis and no problems ? You have aluminum heads on that ?

2 years on a zz502 with merc risers ? I was about to fall asleep . Awake now.. .you will get a power bump with imco's . If you have any valve seats left .

I'm running ZZ502 cam and have many members advise me to go with only the longest risers possible, and have posted pictures of what happens if you don't. It gets ugly.

Thx guys . Sounds like I'd be dancing with the devil eh ? I will re think this for sure ! What a difference in weight though ..... I was hoping the runners were long enough to get away with no reverson issues

Yes aluminum heads . I boroscoped inside the cylinders , no trace of reversion . Love the sound of the camshaft , iffy on the change

If your on to something here , I'm game . So far I have a zz 502 hooked to merc exhaust that has lived unscathed as is and you want to upgrade to the next stage cast aluminum dry joint risers and your wondering if this will introduce new issues with the reversion bullet that you somehow dodged . Nah . It won't . Just watch your water flow to exhaust at idle make sure the water exit and drop is right and now is the time to ask how warm those cast manifolds were getting on a long idle while while listening to that rumpety rump .if you had some rust clogged barely flowing Manis and didn't notice cause you had some aluminum head friendly closed cooling system with the deluxe triple dump exchanger yea your potentially going to put your engine in danger with what should be the right upgrade .it will sound better and make more power .but keep a close eye on it and make sure those new manifolds are not getting hot from the or a lack of water flow

Gotcha , thank you

I guess you are sure it is zz502 cam? I bought a nova with twin 350's. LT 1 hot cams supposedly. But flat tappett motors.

Yes , I bought it ,

Well keep us posted on the uncorking of your crate motor , if its not sucking water back at idle with merc centers and captains call thats what most would call a miracle unless your idleing at 1200 and crashboxing the drive or starting in gear .should pick up some notible power with exhaust upgrade .gotta be running full closed cooling on that bad boy to get this far . Just watch your raw water exchanger dump flow rate and you will be golden

Will do , I'm going to go for it ... Currently idle is set at 750 with raw water cooling . Thx for all the help . How can I adjust my raw water dump rate ?

I've run that cam in a 489 with stock 496 exhaust and silent choice, idle at 700rpm. No signs of reversion, and ran an O2 sensor in the riser all year. Just keep your initial timing low, and you'll be fine.

Awesome thx very much Alex . I actually called you on this the other day :) I appreciate your help as I'm a little worried ....

I prob wouldnt fiddle with it , other than maybe a off season leakdown test especially since you have the manifolds off just to confirm its all good .sometimes with lots of hp and water requirements you can have 2 exit ports to exhaust to control mani temps and rubber parts meltage , the extra goes through a 3rd line overboard .time consuming to dial but some motors can really floood the exhaust with the outbound water .heat exchanger styles with big cams in lighter boats benefit most it seems

So I finally got out on the water the last 2 weekends to try the Exhaust change . Success ! I had no reversion issues and definately a performance gain throughout the mid range . Sounds great . Thank you Alex