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Engine exhaust question

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Old 12-12-2006, 07:38 AM
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Default Engine exhaust question

OK, here's the problem. I'm building a mildly hot small block chevy motor. Engine has/will have 400ci bored .030 over with forged 9.8:1 pistons, roller top end, etc. I've been using a computer program to help select the cam (and carb). Since it's for cars, my exhaust options are :
1. Full stock
2. Open stock manifold
3. Small tube headers (w&w/o muffler)
4. Big tube headers (w&w/o muffler)

The problem is I want an upgraded exhaust and they form 2 types with a big price gap. They are:

Performance MANIFOLD with SS risers (Like S Marine)
Full header system (Like Lightning or CMI)

With all things equal, when I select manifold w/o muffler and when I select small tube header w/o muffler, there is a BIG difference (as much as 50hp at some spots).

So, is there really that much of a difference in the REAL world, or can I save $1000 or more and just get a performance manifold system. Also, I would like to hear peoples opinions on systems they like or don't like. The previous motor I had in the boat was built much the same, but I used a mercruiser exhaust and had water problems.

I know there isn't many SBC people around, but any help would be greatly appreciated.
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Old 12-12-2006, 08:07 AM
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Default Re: Engine exhaust question

I just decided to go with a cast manifold/SS riser for this spring, too many complaints on cracked welds on headers. I'll be looking at the EMI, Stainless Marine, and Dana systems.
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Old 12-12-2006, 08:31 AM
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Talking Re: Engine exhaust question

Quote:
Originally Posted by Indy
I just decided to go with a cast manifold/SS riser for this spring, too many complaints on cracked welds on headers. I'll be looking at the EMI, Stainless Marine, and Dana systems.
Why don't you stuff a cork in the tailpipes too.
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Old 12-12-2006, 08:54 AM
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Default Re: Engine exhaust question

So Kennyo, does that response mean that you think headers are THAT much better? I'm on a tight budget, and don't want to spend any more than necessary. Do you have experience that can help me?

My friend has told me that in a normally aspirated engine, the headers will function better and I WILL be able to notice a big difference, however he's a car mechanic.
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Old 12-12-2006, 09:45 AM
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Thumbs up Re: Engine exhaust question

General rule is always upgrade exhaust side first. If you put big carbs,cam and heads and don't let it breath your wasting time and money. Go search the forums for someone who's built a similar engine and go with what someone else knows works. The headers should be your first investment though.
By the way I run lightning headers and I believe they are the best bang for the buck!
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Old 12-12-2006, 10:52 AM
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Default Re: Engine exhaust question

I HAVE THE SAME SM DRY PIPES 12YRS BOTH THEM USE FROM BOB CHRISTY WHO WAS RUNNING A 26 SCARAB IN ACLASS HE WENT TO CMI'S AND TOLD ME HE WASTED THE MONEY BECAUSE THEY LOST TQ DID NOT GAIN ANUFF HP FOR THE SWITCH. YOU SHOULD GO WITH THESM OVER ANYOTHER MANIFOLD MY LATES SET UP IS 670HP TQ 637 WITH OLD PROP HIT 83.2GPS THIS SPRING LOOKING FOR 86. THATS A 88 240OL BAJA AND DRY YOU CAN HERE ME MILES AWAY COMING UP THE BAY AT 5900RPMS FRED AT TRICK OR SCOTT AND CATHY SPEED AND CUSTOM MARINE CAN GET YOU S/M OR CMI
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Old 12-12-2006, 10:53 AM
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Red face Re: Engine exhaust question

SORRY I BOUGHT THEM FROM BOB
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Old 12-12-2006, 11:07 AM
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Default Re: Engine exhaust question

Quote:
Originally Posted by kennyo
General rule is always upgrade exhaust side first. If you put big carbs,cam and heads and don't let it breath your wasting time and money. Go search the forums for someone who's built a similar engine and go with what someone else knows works. The headers should be your first investment though.
By the way I run lightning headers and I believe they are the best bang for the buck!
Let see those lightnings after 12yrs and I run a 509 with a 1050 nickerson mine breathes fine with the s/m and my buddy has 502 built runs all my old stuff with cmi's in his 24super boat but i still kill himon the top end boats are with in a 1,000lbs and i have alittle more hp better drive my b1 shortie his trs. he thought the cmis were going to put him over the top. and I know he will not get 12yrs out of his cmis,we only run sea water or near one riverbut still sea water. if you are in the lakes only the lightings might be the way to go, but if you see any salt water get the S/M..
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Old 12-12-2006, 12:48 PM
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Default Re: Engine exhaust question

What drive(s) are you running? I've got 300hp SBCs running through Alpha drives and cooling has become a problem. Seems the impeller doesn't pull/push enough water for the Gil header system.

Matt's Mobile Marine is welding dams in the exhaust to push water to the top of the riser at slow speeds. This could get even uglier, like aftermarket water pickups, sea strainers, dual hoses for cleaning (one for the drive and one for the motor), etc.

Good luck. D911
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Old 12-12-2006, 01:52 PM
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Default Re: Engine exhaust question

I was going to go either CMI or SM on a 461ci w/ 560hp.
I didn't want to deal w/ CMI headers cracking, wasn't going to spend big $ on Lightning, and liked the 5yr warranty on the SMs.
So i went the manifold route.
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