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jrichards
01-20-2010, 08:46 PM
Doc D or anybody else out thier have a set of stainless steel risers with a 4 1/4 square bolt pattern. Thanks :nilly:

Dr. David Fleming
01-22-2010, 12:32 PM
jrichards,

Your engine should have come with stock cast iron exhaust manifolds that have a riser bolted to them. Some aftermarket cast manifolds have a riser. CMI E-top headers have a tailpipe. Harden and Lightening tube headers are one piece.

I think you need to be more clear about what you are talking about.

Also, the movie I told you about, I gave the wrong title, it is "The Eliminator." You can see the race part of this film if you go to the "Videos" section of the Donzi Registry and look under the selection "classics race a ZX" which is taken from U-Tube.

Need more information on you headers and what you are doing.

Dr. David Fleming
01-23-2010, 02:57 AM
jrichards,

Ok kid, I went to Hardin website and checked out the headers I think you are fooling with.

The Merc HP500 racing engine from 1998 - 1999 had a four barrel Holley intake system and the exhaust was GIL manifolds with a stainless riser. This was a bad setup for Mercury as the manifolds reverted water into the engine when it was running. To solve this Merc developed a sheet metal "turbulator" which was a little strainer device to kick the water that condensed in the manifold out the exhaust. You are not suposed to use this engine with out the "turbulator."

This setup was pretty "lame" at best so the new Merc race engine in 2000 was the 500EFI came with CMI tubular E-top headers. Problem solved.

Well what about the GIL manifolds on the "lame" ,manifolds on the Merc HP500? Hardin made a stainless tubular header to replace the manifolds that would use the existing Merc Racing HP500 risers. Sort of an "ass backwards" set of headers.

If you go to Hardin website and look under GIL exhaust systems you will see the header risers in several styles.

The other Hardin headers are the Hurricane one piece headers and this is the way most all headers are. Most header setups use a "tailpipe" not a "riser." Risers are on exhaust manifolds.

By the way who keeps trying to sell you on all this performance stuff? Seems like you are always talking about "used" take-off equipment that is sort of odd and left over?

Barry Eller
01-23-2010, 10:38 AM
jrichards,

Ok kid, I went to Hardin website and checked out the headers I think you are fooling with.

The Merc HP500 racing engine from 1998 - 1999 had a four barrel Holley intake system and the exhaust was GIL manifolds with a stainless riser. This was a bad setup for Mercury as the manifolds reverted water into the engine when it was running. To solve this Merc developed a sheet metal "turbulator" which was a little strainer device to kick the water that condensed in the manifold out the exhaust. You are not suposed to use this engine with out the "turbulator."

This setup was pretty "lame" at best so the new Merc race engine in 2000 was the 500EFI came with CMI tubular E-top headers. Problem solved.

Well what about the GIL manifolds on the "lame" ,manifolds on the Merc HP500? Hardin made a stainless tubular header to replace the manifolds that would use the existing Merc Racing HP500 risers. Sort of an "ass backwards" set of headers.

If you go to Hardin website and look under GIL exhaust systems you will see the header risers in several styles.

The other Hardin headers are the Hurricane one piece headers and this is the way most all headers are. Most header setups use a "tailpipe" not a "riser." Risers are on exhaust manifolds.

By the way who keeps trying to sell you on all this performance stuff? Seems like you are always talking about "used" take-off equipment that is sort of odd and left over?


I always thought it was the camshaft profile that caused reversion in the HP 500.
I have the GIL Exhaust, but with the Dry Offshore Pipes. No reversion problems with them.

MOP
01-23-2010, 10:52 AM
Reversion is strictly a camshaft issue, as Barry stated it is the over lap on higher performance cams. How did this get here all the guy is looking for is 4-1/2" pattern risers, note I have seen guys elongate the holes on 4" to make them fit. It works and does not have any issues as the S/S risers are a dry joint.

Walt. H.
01-23-2010, 10:55 AM
I always thought it was the camshaft profile that caused reversion in the HP 500.
I have the GIL Exhaust, but with the Dry Offshore Pipes. No reversion problems with them.
Barry is correct, I was just discussing this topic about an hour ago with another member by e-mail and reversion happens because of valve overlap: when the exh valve is still open as the intake starts to open at the same time.

WH

Walt. H.
01-23-2010, 11:00 AM
Opp's Phil,
I need to type faster or waited another 3 minutes to see your post written first.

Dr. David Fleming
01-23-2010, 12:07 PM
jrichards,

Ok so now we have to be "politically correct" about this.

The stock manifolds were developed by Mercruiser to handle most exhaust system needs that the general boating public has. This is low maint., high durability and low cost setup. They are compact and easy to work with. The drawback is the high performance of the engine is limited and they are HEAVY, 150lbs worth of heavy.

High performance exhaust manifolds are available from several companies the best I hear is Stainless Marine which makes a cast manifold that works about like headers. These have inner passages that duplicate the individual pipes of a header system. Tyler Crockett who is a major engine builder in USA tells me they produce power equal with headers and he considers them a legitimate performance option.

Mercury Racing went this way in 1998-99 with the GIL manifold setup which I am sure, because of its choice by Merc., was a good setup for manifolds. They did have problems with "reversion" and solved it with the "turbulator." The reversion was caused by the race camshaft in the engine and the design of the GIL exhaust setup. The whole problem made Merc look bad as some folks had a lot of trouble with these engines in stock production boats - 1999 Donzi 33ZX Daytona had this duel engine HP500 setup for example.

Merc Racing walked away from the GIL manifolds in 2000 and went with CMI E-Top headers.

This does not mean that GIL made a bad setup for manifold design as they really work for some folks who don't want headers. Dana also makes a high performance manifold setup.

Harden makes a bolt on set of headers for replacing the GIL manifolds and retaining the exhaust system which I am sure is great for some folks with continuing problems with the Merc Racing HP500.

My 502MAG MPI has the E-top headers which Tyler Crockett talked me into using. I also talked to Chris Cxxxxxx the Donzi chief engineer for the ZX hulls and he was the one that said "do CMI and K&N air filter, it makes a real difference."

These are the areas that Mercruiser cut quality on the design of their stock high performance motors - cheap GM valvegear, and stock heads and valves. The exhaust system is a good stock setup but was not a racing setup. About everything else on the stock engine is first class.

The GM valve gear is ok for a car running most of its life at low speed. Most mechanical failures in the Mercruiser engines are in the rocker arms and pushrods. The Merc Racing engines all use Crane roller rocker arms, lifters and pushrods. Even better is to go to racing valves and springs. Headers are always the premium exhaust setup.

The stock Mercruiser engines are excellent as a marine motors, and some of us just like to keep tuning them to make them better.

Walt. H.
01-23-2010, 02:23 PM
jrichards,

ok so now we have to be "politically correct" about this.

??? WtF ???

The Hedgehog
01-23-2010, 06:07 PM
There is nothing really wrong with Gils. I have seen some dyno results comparing Gils, CMI's SM's and the like. No big differences. There were some reversion issues. That is solved with better risers or turbulotors. Run the short risers on Stainless Marine or Dana and you will have the same problem.

I thought that the Gils were aluminum.

You don't really need true headers until you are pumping out some big hp.

I went with CMI because they have good quality and are pretty. I doubt I have any real advantage over Stainless Marine in the HP department.

I have seen dry Gils like Barry has with some BIG hp applications.

Barry Eller
01-23-2010, 06:16 PM
There is nothing really wrong with Gils. I have seen some dyno results comparing Gils, CMI's SM's and the like. No big differences. There were some reversion issues. That is solved with better risers or turbulotors. Run the short risers on Stainless Marine or Dana and you will have the same problem.
I thought that the Gils were aluminum.
You don't really need true headers until you are pumping out some big hp.
I went with CMI because they have good quality and are pretty. I doubt I have any real advantage over Stainless Marine in the HP department.
I have seen dry Gils like Barry has with some BIG hp applications.


Here is some information on GIL Dry Offshore Systems....Hardin Marine has acquired GIL Marine. They are not for the faint of heart...read "LOUD". If you are in a noise restricted area, not a good choice unless you hang mufflers off the ends. My camshaft profile warrants use of these, but I run on Pensacola Bay. I'm not as loud as the Blue Angels!!!

http://www.google.com/imgres?imgurl=http://www.marinemanifold.com/PARTSPAGES/gil/IMAGES/mar.gif&imgrefurl=http://www.marinemanifold.com/PARTSPAGES/Corsa/GIL4.htm&h=225&w=282&sz=37&tbnid=Z5xm7bl7L3SWfM:&tbnh=91&tbnw=114&prev=/images%3Fq%3Dgil%2Bmarine&usg=__uawhrTyY2qZpmxBfjoSrji73NZo=&ei=Z5BbS_G8Cc-Xtgf58smaAg&sa=X&oi=image_result&resnum=7&ct=image&ved=0CCYQ9QEwBg

mrfixxall
01-23-2010, 06:27 PM
Heres the scoop! the man is looking for a 4 1/4 from center of bolt hole to bolt hole risers. He has gil 4 1/2 from crnter bolt hole to bolt hole..He is looking for a set of risers for his hurracane exhaust headers..

Does anybody have a set for this man measuring 4 1/4'' ???????

The Hedgehog
01-23-2010, 06:36 PM
Heres the scoop! the man is looking for a 4 1/4 from center of bolt hole to bolt hole risers. He has gil 4 1/2 from crnter bolt hole to bolt hole..He is looking for a set of risers for his hurracane exhaust headers..

Does anybody have a set for this man measuring 4 1/4'' ???????

Awe come on Mike, don't get us back to the subject. It would be more fun to debate that pros and cons of different exhaust.

Got split top CMI's yet?

MOP
01-24-2010, 07:23 AM
The dissertations are good eye exercise!

Barry Eller
01-24-2010, 09:37 AM
The dissertations are good eye exercise!

LMAO:jestera:

BigGrizzly
01-24-2010, 10:41 AM
I am staying out of this one. I have tested too many hedders from merc to CMI. I can tell you this, with my Criterion engine that CMI E tops ARE almost as good as The tube type, so close that on the water there is NO difference. My third choice is Stainless Marine. I went with tube type for looks and any advantage I could get, beaised I had to drive to CMI to have them custom fit.

mrfixxall
01-24-2010, 07:21 PM
Awe come on Mike, don't get us back to the subject. It would be more fun to debate that pros and cons of different exhaust.

Got split top CMI's yet?


Nope! no split tops yet..he is hard to get ahold of..soon tho :)

jrichards
01-24-2010, 08:16 PM
Haven't been on in a few days. I found some risers. I needed 4 1/4 square bolt pattern. Your right about hardin and gil. The ones i bought are 21 inches long gils. Better than the short ones I had. They were gils but with 4 in square pattern. Doc D don't get mad when I tell you I just bought a blown motor for my boat and a Latham hyd full steering system. 650 hp that should step things up.

Dr. David Fleming
01-24-2010, 10:14 PM
jrichards,

Well I guess your zx grew up! Let us know what you are doing and how fast the little demon runs.

jrichards
01-25-2010, 09:44 PM
I will Doc. I did see that movie clip. It was neat to watch :eek:

The Hedgehog
01-26-2010, 08:17 AM
Haven't been on in a few days. I found some risers. I needed 4 1/4 square bolt pattern. Your right about hardin and gil. The ones i bought are 21 inches long gils. Better than the short ones I had. They were gils but with 4 in square pattern. Doc D don't get mad when I tell you I just bought a blown motor for my boat and a Latham hyd full steering system. 650 hp that should step things up.

Good man. Enjoy and keep us posted. We will need pics.

VetteLT193
01-26-2010, 09:05 AM
jrichards,

Ok so now we have to be "politically correct" about this.

The stock manifolds were developed by Mercruiser to handle most exhaust system needs that the general boating public has. This is low maint., high durability and low cost setup. They are compact and easy to work with. The drawback is the high performance of the engine is limited and they are HEAVY, 150lbs worth of heavy.

High performance exhaust manifolds are available from several companies the best I hear is Stainless Marine which makes a cast manifold that works about like headers. These have inner passages that duplicate the individual pipes of a header system. Tyler Crockett who is a major engine builder in USA tells me they produce power equal with headers and he considers them a legitimate performance option.

Mercury Racing went this way in 1998-99 with the GIL manifold setup which I am sure, because of its choice by Merc., was a good setup for manifolds. They did have problems with "reversion" and solved it with the "turbulator." The reversion was caused by the race camshaft in the engine and the design of the GIL exhaust setup. The whole problem made Merc look bad as some folks had a lot of trouble with these engines in stock production boats - 1999 Donzi 33ZX Daytona had this duel engine HP500 setup for example.

Merc Racing walked away from the GIL manifolds in 2000 and went with CMI E-Top headers.

This does not mean that GIL made a bad setup for manifold design as they really work for some folks who don't want headers. Dana also makes a high performance manifold setup.

Harden makes a bolt on set of headers for replacing the GIL manifolds and retaining the exhaust system which I am sure is great for some folks with continuing problems with the Merc Racing HP500.

My 502MAG MPI has the E-top headers which Tyler Crockett talked me into using. I also talked to Chris Cxxxxxx the Donzi chief engineer for the ZX hulls and he was the one that said "do CMI and K&N air filter, it makes a real difference."

These are the areas that Mercruiser cut quality on the design of their stock high performance motors - cheap GM valvegear, and stock heads and valves. The exhaust system is a good stock setup but was not a racing setup. About everything else on the stock engine is first class.

The GM valve gear is ok for a car running most of its life at low speed. Most mechanical failures in the Mercruiser engines are in the rocker arms and pushrods. The Merc Racing engines all use Crane roller rocker arms, lifters and pushrods. Even better is to go to racing valves and springs. Headers are always the premium exhaust setup.

The stock Mercruiser engines are excellent as a marine motors, and some of us just like to keep tuning them to make them better.

There is more to the story than this.

One is Merc bought CMI.

The other is the cam profile changed between HP500 carb (the ones with Gil) and the later HP500 EFI. If I remember right they went from 110 Lobe Separation in the HP 500 Carb to 114 Lobe separation in the HP 500 EFI. The HP 500 Carb with CMI E-Tops WILL revert if the idle is too low.