Installing Headers
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New User
Joined: Apr 2021
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From: Garland, TX
Installing Headers
the 84 302 i recently purchased had no exhaust aside from the headers. One of the first things we did was take it to go true duals with flowmasters. The shop explains that things still sound bad due to what seems to be a manifold leak. Easy enough diy fix right?
okay, so on the driver side there were only 6 of the 8 bolts attached and 4 of the 6 were barely finger tight. It's all making sense until i attempt to add bolts to the #5 and #6 cylinder. these Hooker headers make a pretty tight turn that will not allow the bolt enough clearance to be installed unless they're done first with the other more accesible bolts brought on later.
would you A) try a shorter bolt or B) remove header and install with correct bolt length? my case for A is that it's all pretty tight on space so it all has to be done with a spanner, box wrench or socket isn't an option.
okay, so on the driver side there were only 6 of the 8 bolts attached and 4 of the 6 were barely finger tight. It's all making sense until i attempt to add bolts to the #5 and #6 cylinder. these Hooker headers make a pretty tight turn that will not allow the bolt enough clearance to be installed unless they're done first with the other more accesible bolts brought on later.
would you A) try a shorter bolt or B) remove header and install with correct bolt length? my case for A is that it's all pretty tight on space so it all has to be done with a spanner, box wrench or socket isn't an option.
Tuned
Joined: May 2014
Posts: 311
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From: MD
the 84 302 i recently purchased had no exhaust aside from the headers. One of the first things we did was take it to go true duals with flowmasters. The shop explains that things still sound bad due to what seems to be a manifold leak. Easy enough diy fix right?
okay, so on the driver side there were only 6 of the 8 bolts attached and 4 of the 6 were barely finger tight. It's all making sense until i attempt to add bolts to the #5 and #6 cylinder. these Hooker headers make a pretty tight turn that will not allow the bolt enough clearance to be installed unless they're done first with the other more accesible bolts brought on later.
would you A) try a shorter bolt or B) remove header and install with correct bolt length? my case for A is that it's all pretty tight on space so it all has to be done with a spanner, box wrench or socket isn't an option.
okay, so on the driver side there were only 6 of the 8 bolts attached and 4 of the 6 were barely finger tight. It's all making sense until i attempt to add bolts to the #5 and #6 cylinder. these Hooker headers make a pretty tight turn that will not allow the bolt enough clearance to be installed unless they're done first with the other more accesible bolts brought on later.
would you A) try a shorter bolt or B) remove header and install with correct bolt length? my case for A is that it's all pretty tight on space so it all has to be done with a spanner, box wrench or socket isn't an option.
Lead Driver
Joined: Apr 2007
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From: Houston
Hard to say, some headers are curved quite tightly against the bolts where you have to start them through first then place up and thread them on. Now the question is do you actually have header bolts installed or just plain bolts? if plain bolts then I strongly recommend you install header bolts, they have a smaller head which allows for easier clearance on close fitting tubes.
Lead Driver
Joined: Jun 2013
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From: Tolland, CT
Agree, B do it right the...second time. Get the correct header bolts, new gaskets.
After they are heat cycled a few times check them for tightness. I seem to recall that was a thing back in my day...1974.
After they are heat cycled a few times check them for tightness. I seem to recall that was a thing back in my day...1974.
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Joined: Apr 2021
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From: Garland, TX
the bolts i have are 1" and am considering the 3/4" bolts to help with some of the tight clearances. and if it's worth doing right it's worth overdoing so new gaskets and some copper RTV are just a quick trip to the parts store away.
original post was the cliff's notes version of a readers digest story so yeah, i don't blame the shop for not doing any more than they did. The owner and I have a decent enough rapport over the last 20+ years he's my shop.
original post was the cliff's notes version of a readers digest story so yeah, i don't blame the shop for not doing any more than they did. The owner and I have a decent enough rapport over the last 20+ years he's my shop.
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Joined: Jan 2001
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From: Virginia
Just making sure you are using header bolts with the very small head? Allen head bolts (called socket head) would probably work also.
Headers are sometimes not worth the few extra HP they give you after you battle the fitment issues.
Headers are sometimes not worth the few extra HP they give you after you battle the fitment issues.
Lead Driver
Joined: Jun 2013
Posts: 5,668
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From: Tolland, CT
If the bolts don't thread in far enough you risk pulling the threads out of the head when you tighten the bolts.
That is a standard grip length of engagement. One of the Engineers will know that number. I'm just an Assembly Tech that told Engineers their idea wouldn't work. But they did always have the final say.
That is a standard grip length of engagement. One of the Engineers will know that number. I'm just an Assembly Tech that told Engineers their idea wouldn't work. But they did always have the final say.
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From: Garland, TX
ain't that the truth. if they hadn't been there when i bought the truck they wouldn't be there today.
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Lead Driver
Joined: Jun 2013
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From: Tolland, CT
Socket head cap screws.
But I'd use 12 point header bolts. ARP will have them.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Same goes for the 12 point as I have yet seen a 12 point open end wrench.
The small head (3/8?) header bolts you can get a open end wrench on and do a 1/8 turn flipping the wrench after each turn.
As said use new gaskets, think it is the copper Remflex or something like that are the best.
And yes pull the header get the hard ones started then fit the others, thats how its done.
Yep got to love headers!
Dave ----
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From: Angier, NC
As old as I am I have had my share of header installs mostly on race cars & 4x4 trucks.
I only have 1 street car project that has headers, that how I got the car, and they are thin in areas and leak at the heads.
I have a set of shortlies to install,hope they fit, but that is low on the "to do list".
Dave ----
I only have 1 street car project that has headers, that how I got the car, and they are thin in areas and leak at the heads.
I have a set of shortlies to install,hope they fit, but that is low on the "to do list".
Dave ----
Post Fiend
Joined: Feb 2008
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From: St Albert, Alberta
If the bolts don't thread in far enough you risk pulling the threads out of the head when you tighten the bolts.
That is a standard grip length of engagement. One of the Engineers will know that number. I'm just an Assembly Tech that told Engineers their idea wouldn't work. But they did always have the final say.
That is a standard grip length of engagement. One of the Engineers will know that number. I'm just an Assembly Tech that told Engineers their idea wouldn't work. But they did always have the final say.
But to be absolutely precise an analytical calculation including a finite element analysis would need to be done
But none of that will give you an answer that you can use day to day in a pinch or in in the field.
Basic design on a piece of equipment should ensure that a bolt breaks before the threads strip out of a tapped hole.
And that is the goal of having an easy-to-use rule of thumb that can be used in pinch and will satisfy the above basic design philosophy.
The minimum thread engagement in a tapped hole in material the same strength of the fastener should be the same depth as the greater diameter of the fastener (obviously).
But rarely are we stuffing bolts in the same strength material as the bolt itself. And this does not take into account some of the courser and proprietary thread pitches. But it will always apply to NF and the fine-thread metric pitches. But I digress
Regardless we need some sort of rule of thumb that can be used in the field and in a pinch.
So the off-the-cuff rule of thumb is a minimum thread engagement depth of 2 times the diameter of the fastener.
This is supposed to apply up to and including materials as soft as aluminum as the base tapped material.
But personally, I like to see a minimum of 2.5 times the diameter of the fastener worth of thread engagement in softer materials like aluminum.
For example, a 5/16" fastener should be seeing a minimum of a full 5/8" thread engagement in ferrous materials.
In nonferrous materials like Aluminium, the 5/16 bolt should be seeing a minimum of 25/32"s of thread engagement.
Lead Driver
Joined: Apr 2007
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From: Houston
Those work great if you can get the wrench on them. I havent tried installing my 86-96 F150 shorty headers but it looks like the bolts should be able to be easily accessible with a wrench like that. I mainly went with these headers as it appears to keep the sparkplugs open to a plug socket unlike some out there.