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View Full Version : Question: Exh. Restrictors On HP525 EFI



Carl C
05-01-2009, 09:57 AM
My service manual is showing a need for "exhaust restrictors" in the coolant hoses on the headers. It does not show what they look like or give part numbers. Can anyone shed any light on this. Besides keeping the headers at the right temperature they may be needed to help prevent reversion which I am concerned about since I will be running short tails to accomodate the Q&Q. Also I don't believe I will be running a lower coolant port on my tails. Is this motor running what would be considered an agressive cam? In other words is it on the ragged edge of reversion? The CMIs on my 496 did not use any kind of water restrictors. The manual does warn not to use the Q&Q above 2,500 rpm (the neighbors are really going to love me now). Getting close to the engine install and need to know this. Thanks.

Air 22
05-01-2009, 10:21 AM
http://www.custommarine.com/contact.php

Call: 920-720-4225

Carl C
05-01-2009, 11:43 AM
http://www.custommarine.com/contact.php

Call: 920-720-4225

OK but I will wait til I have the motor set in place and know if I will need new tails. Are you running restrictors in your 500?

Air 22
05-01-2009, 12:24 PM
No.... Your CMI Header and tail set-up is different than mine..CMI engineer's it, they build it...call them.!

Carl C
05-01-2009, 12:57 PM
OK. Nice high res pic BTW.:thumbsup:

BigGrizzly
05-01-2009, 07:32 PM
Sorry it seams pretty plane to me. Make the restrictions from aluminum bar stock or get a tune the right is. The reason id the motors run hotter on one side then the other, and they are trying to keep the water in the pipe longer. This is a very old thing even old big inboards especially closed cooling had a valve to adjust the heat of the engine byregulating with a valve.

Carl C
05-02-2009, 10:27 AM
Thanks Grizz, I'll probably just order some though since they shouldn't cost too much (yeah, right). I like the idea of dumping a little less water into the exhaust stream too. Heard too many reversion horror stories.

BigGrizzly
05-03-2009, 08:38 AM
Now you have the idea. Remember you really don't need that much water to cool. BTW if you look at the size they total more than a 5/8 water hose. and its cold water.

Dr. David Fleming
08-10-2009, 10:52 PM
Chris C,
Have followed a couple of your threads on the CMI exhaust and caught a couple of nice pics of your boat. I see you boat on Lake St. Clair with me. Would like to know what kind of transom tips your CMI is feeding into.

I have the Donzi 22ZX with 502Mag Mpi. Talked to Chris Collier who was chief engineer at Donzi. Told me the 502 ran great with CMI E-tops. Have a couple off of a 500EFI with the CMI silent choice setup. Am feeding it into the stock Corsa transom tips. No water on the plugs but low speed running sure seems to surge like its kicking water around in the header. The 500EFI used a 5/8 hose from the thermostat housing to the collector as well as a water manifold along the spark plugs. Water take-off was at the D ring into the exhaust pipe and sprayed just ahead of the diverter.

How did your restrictor plugs work out? Wonder if they used them in the 500EFI? Thought I might try some different exhaust tips. One Fountain with 500EFI and silent choice had strait tips with a pneumatic valve on the back of the boat.

Look for me at Jacks or on the Detroit river.

Dr. D

Carl C
08-11-2009, 08:06 AM
Assuming that "Chris C" was a typo, I am running straight through tips with internal flappers. I do have a set of clamp on Gibson mufflers that I hate but I use them on the local lake to keep the performance boat haters happy. I also was able to keep the silent choice with special tails. This gives the water an additional route out the engine and should help keep water from entering the motor while at rest because any water that get past the flapper can run down the down tube. Anyway, finishing my exhaust turned out to be complicated and costly and my mechanic Brian (Brian41 here) had to relocate my exhaust tips and fit the cool new tails. Yes, he also installed the restrictors. I have had no evidence of reversion:crossfing:. I have not had any experience with your version of the 502 or the 500 EFI version. Unless you have installed a more agressive camshaft I don't see why you would have excessive back pressure with the stock Corsa mufflers. Personally I don't like mufflers. It's hard to get a good pic of my tails but here are a few snap-shots. I will keep an eye out there for you but I boat week-days. I will be running to Put-in-Bay tomorrow, may have a couple other boats going; Want to join in?

MOP
08-11-2009, 09:39 AM
Carl give some thought to a relief valve, block pressure will go up more with restrictors you don't need to have weeping head gaskets!!!!

Dr. David Fleming
08-11-2009, 03:31 PM
Carl,
Thanks for the comback - I also am a weekday boater, my schedule varies. Can't get the donzi Wednesday because Island Harbor Marina in SCS is shut down for the "handicap childrens fishing tournament" which they do once a year. Should be back on the lake Thurs and Friday. Would like to see your little classic run. 525 sure is a great motor internally. Doug at CMI was telling me about your type transom tips, wasn't sure if you had the flappers. Who is Brian, am looking for a good Merc tuner.
Dr. D

Carl C
08-11-2009, 04:37 PM
Brian Orlandis Newport Michigan (downriver area). Phone 734-586-0448. He did a lot of the work on "hot shot" Mick's boat and is working on "RoadtripSE" Todd's boat. I like him. Might overnight at PIB so will be out thursday too if I do. See you around.

hot shot
08-12-2009, 09:20 AM
It's well worth the trip to newport mi. It's just off I-75 ( just north of monroe ). Brians done alot of work for myself and quite a few buddies and he does great work as a matter a fact his dyno cell will be up and running by next week for complete service including break in, check for leaks and also tune up as well... the cell itself is a work of art so keep all that in mind when making your decision on were to take your stuff here in mich.. Good Luck Mick

roadtrip se
08-12-2009, 01:35 PM
Straight shooter, capable, does it right or just won't do it. He has pointed out every short cut, and is addressing all of them, from when I did the work myself the last time!

You stop in over the next few weeks, and you wil get to witness his work on my beast. Coming together, and nicely, I might add...