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09-26-2002, 11:29 PM | #1 |
Post Whore
Join Date: Feb 2000
Location: Rose Hill, KS, USA
Posts: 12,684
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Question about header flange flatness
How flat should the flange be where the header bolts to the engine?
I just got a set of Dynomax Cermacoated headers for my 454 and I put a straight edge against the flange and it is not as true (flat) as I would have expected. I understand the gasket will be there, but I'm just a little concerned.
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1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14 |
09-26-2002, 11:37 PM | #2 |
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Join Date: May 2002
Location: Olathe, Kansas
Posts: 929
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I wouldnt be concerned really. Those tubes and the flange will give per each cylinder port. It's not like a rigid manifold that wont give and warpage causes the gasket to go.
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09-27-2002, 01:40 AM | #3 |
Gotta Startem Early
Join Date: Oct 2001
Location: Amarillo, TX, USA
Posts: 364
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After you put them on, just snug up the bolts every 3-400 miles for about the first 1500-2000 miles. With good gaskets you should see no problems.
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09-27-2002, 08:12 AM | #4 |
WTF
Join Date: Jul 2000
Location: loganville, Ga.
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An old timer once told me if you cut the flange down the the center and let them have a little give they will seal better. Though I could not see my self cutting a set of ceramic coated headers.
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09-27-2002, 08:32 AM | #5 |
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Join Date: Dec 1999
Location: Austin, TX, USA
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They SHOULD be as flat as the manifolds, but seldomly are. Buy gaskets that have the steel inserts and DO NOT use the bolts that came with them. Buy a set of bolts that came with reduced diameter lock washers. After switching to these, I did NOTHING to the headers on the Jimmy for 8 years.
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09-27-2002, 09:11 AM | #6 |
Post Whore
Join Date: Feb 2000
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I've heard the suggestion about cutting the flange but was very hesitant with the finish and I'm sure that would void the warranty.
Mike, I have the Percy Deadsoft gasket's and I did buy the special header bolts. The Percy's ought to take care of it, right? I was like a dang kid at the candy store last night when I was opening all the boxes. I've got quite a task on my hands!
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1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14 |
09-27-2002, 09:50 AM | #7 |
Senior Moment
Join Date: Mar 2002
Location: Pittsburg Ca
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Please let me know how they work out. I'm thinkind about a set myself. Do you have AC ? I need to know if they will work with AC. Last ? How many $$$$$$$$$$$$$$$ and whats the reasoning for the ceramic coating.
Thanks Steve
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09-27-2002, 10:19 AM | #8 |
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No AC. Got these for the big block for $209.99. My understanding is the cermacoating helps with decreasing the underhood temperature a bit and supposed to be a rust protection. They are coated inside and out. Guaranteed for life, but I'm always sceptical of guarantees!
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1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14 |
09-27-2002, 11:01 AM | #9 |
Senior Moment
Join Date: Mar 2002
Location: Pittsburg Ca
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Thanks. Not a bad price, let me know how they fit.
Anybody have any Idea if they make headers for use with Factory AC ?
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1970 CST LS 1 6 speed Ford 9 inch Detroit Tru Track, Dakota Didgital, Vintage Air, QA1 Coil Overs Front & Rear Lots of FUN 2013 GMC PU, Oldest Son 71 GMC LWB. QA1 Suspension, Angry SB. Youngest Son 2019 GMC Diesil Dually. Youngest Son 2017 Toyota SUV Daughters car 2018 Traverse , Wife’s Ride Pittsburg Ca 94565 |
09-27-2002, 12:25 PM | #10 |
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Join Date: Jan 2002
Location: Lemon Grove, California
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This has worked great for me-on non coated headers-I run
Hedman Hedders. 1.Cut header flange. 2.Use copper high temp silicone sealant. 3.Use Mr. Gasket ultra seal header gaskets of choice. 4.Apply copper sealant to both side of gasket. 5.Assemble using high quality American made bolts like ARP stainless and washers. 6.Keep those header bolts tightened after several heat/cool engine run cycles. Never had any gasket blowouts or other problems that you always hear about after doing this.Pretty common fix with the weekend road warriors.I've been to cheap to buy a pair of coated headers,maybe someday,though I get a long life out of my good' ol Hedmans. |
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