Rough head exhaust surfaces, gaskets, and avoiding leaks.

[Ranchero50]

I won't get into the quality of the build because it serves no purpose at this point... That they didn't surface the exhaust flange is just bad though...

A very important consideration is the flange thickness, more for selecting headers vs. anything else. The 5/16" or 3/8" flange is much better at not deflecting vs. the typical 1/4" flange. same for the tubing gauge. 14ga is great, 16 is ok and 18 is junk.

Personally I don't use gaskets, just a nice bead of Permatex Ultra RTV to glue the flange to the head.

Another tip is to get the longest header bolts you can. Most kits come with 3/4" bolts, knock 1/4" off for the flange, 1/8" off for the gasket and you only have 3/8" of threaded bolt going into the head. Nominal threat strength is threaded length = 1.5 x diameter of the bolt. So a 3/8" bolt should have 9/16" of thread going into the head, not going to happen with a 3/4" bolt... 5/16" flange, 1/8" gasket = 7/16 clamped = 9/16" threads in the head so you will be ok. Buy the 1" bolts and use the permatex to glue them in (locktight releases over 200`). I also use the nordlocks in this application to self lock the bolts in place and they work great.

Jamie

[robroy]

Thanks very much for replying Jamie!

I won't get into the quality of the build because it serves no purpose at this point... That they didn't surface the exhaust flange is just bad though...

Yeah, I might have to agree on this one.

A very important consideration is the flange thickness, more for selecting headers vs. anything else. The 5/16" or 3/8" flange is much better at not deflecting vs. the typical 1/4" flange. same for the tubing gauge. 14ga is great, 16 is ok and 18 is junk.

Thanks for this advice! I think the headers I picked out has good specs in this arena. I picked out Hedman 89810's, which have 3/8" flanges and 14 gauge tubes.

Personally I don't use gaskets, just a nice bead of Permatex Ultra RTV to glue the flange to the head.

Okay, it's good to know that this is a real option. I'm guessing that that the RemFlex gaskets might help in my situation though, since the exhaust surfaces on my heads aren't so great.

Another tip is to get the longest header bolts you can. Most kits come with 3/4" bolts, knock 1/4" off for the flange, 1/8" off for the gasket and you only have 3/8" of threaded bolt going into the head. Nominal threat strength is threaded length = 1.5 x diameter of the bolt. So a 3/8" bolt should have 9/16" of thread going into the head, not going to happen with a 3/4" bolt... 5/16" flange, 1/8" gasket = 7/16 clamped = 9/16" threads in the head so you will be ok. Buy the 1" bolts and use the permatex to glue them in (locktight releases over 200`). I also use the nordlocks in this application to self lock the bolts in place and they work great.

In this case I think I'm OK! The headers came with 1" bolts, thankfully. Thanks for the tip on the Permatex for locking the bolts in, and as for the Nord-Locks, I'm sold on those things--I'll definitely use them here!

Thanks very much Jamie!
Robroy

[robroy]

Another tip is to get the longest header bolts you can. Most kits come with 3/4" bolts, knock 1/4" off for the flange, 1/8" off for the gasket and you only have 3/8" of threaded bolt going into the head. Nominal threat strength is threaded length = 1.5 x diameter of the bolt. So a 3/8" bolt should have 9/16" of thread going into the head, not going to happen with a 3/4" bolt... 5/16" flange, 1/8" gasket = 7/16 clamped = 9/16" threads in the head so you will be ok. Buy the 1" bolts and use the permatex to glue them in (locktight releases over 200`).

In this case I think I'm OK! The headers came with 1" bolts, thankfully.

You know, I got to thinking about this again.

I measured the thickness of a Nord-Lock and it's about 3/32". The flanges on my headers are 3/8", and the gasket is 1/8". That means that I'd only have 13/32", or about 3/8" of thread going in to the head! 1" - 3/8" - 3/32" - 1/8" = 13/32".

In order to have 9/16" of thread in the head, I'd need to have bolts that were 1 and 5/32" long, or maybe 1 and 1/8" long since the gasket will probably squish down a little from its original 1/8" measurement.

I can use any kind of bolt I want for the headers, as long as the bolts are strong enough, right?

Thanks again Jamie!
Robroy

[Ranchero50]

The trick is getting small head grade 8's. I've never noticed header bolts longer than 1". I did stud my aluminum headed 302 in the Mustang. Stainless ARP studs keep the bolts from going crossthreaded but are more difficult to put together, but they don't leak either...

Jamie

[fomocoguy]

The Remflex gaskets have a 50-60% crush rating. That is why they are so thick, and that is also why they work so well. When you tighten them up they will get down to about 1/16 inch in the tight spots, just like normal gaskets.

As for bolts, when I did mine I just got some regular grade eight bolts and they worked just fine. I didn't have any trouble with the head size.

[70_F100]

Actually, the length of the threads that go into the head only has to be equal to the diameter of the bolt. Learned this MANY years ago.

What I was told in engineering school makes good sense.

Think about it. Generally, the thickness of a nut is equal to the diameter of the bolt it screws onto. Why would you need it to thread into a hole any deeper than that? Maybe add another 1/16" to cover the small taper on the first thread, but that's the maximum strength you'll get.

[robroy]

Jamie, FoMoCoGuy, and 70_F100, thanks for replying!

The trick is getting small head grade 8's. I've never noticed header bolts longer than 1". I did stud my aluminum headed 302 in the Mustang. Stainless ARP studs keep the bolts from going crossthreaded but are more difficult to put together, but they don't leak either...

I like the idea of those studs! But I probably won't go that route just because I'm not sure if I'd find a the ideal thread length in those studs.

As for the small headed bolts, I know just what you mean. Indeed, the bolts supplied by Hedman have small heads. They're flanged bolts. The flanges are 9/16" and the heads themselves are 3/8".

I went out to look at the headers, and looked around the area on the heads, and can't see any reason why these small headed bolts are required. It looks like there's lots of room around there for regular bolt heads, but I might not be seeing the whole picture for some reason!

The Remflex gaskets have a 50-60% crush rating. That is why they are so thick, and that is also why they work so well. When you tighten them up they will get down to about 1/16 inch in the tight spots, just like normal gaskets.

As for bolts, when I did mine I just got some regular grade eight bolts and they worked just fine. I didn't have any trouble with the head size.

Thanks for the advice FoMoCoGuy! It's interesting to know that the RemFlex gaskets crush down a little. It's also good to know that the head size wasn't an issue in your setup.

What make/model were your headers? And were you putting them on a 390 also?

Actually, the length of the threads that go into the head only has to be equal to the diameter of the bolt. Learned this MANY years ago.

What I was told in engineering school makes good sense.

Think about it. Generally, the thickness of a nut is equal to the diameter of the bolt it screws onto. Why would you need it to thread into a hole any deeper than that? Maybe add another 1/16" to cover the small taper on the first thread, but that's the maximum strength you'll get.

Now this is very interesting information. I can imagine this being true in a way, but my imagination is rarely an accurate way to measure how strong something is; it's notoriously wrong when it comes to mechanical stuff.

Jamie, I remember hearing from you that the threads should go in at least 9/16". Do you have a response to this new info posted by 70_F100?

I measured how deep the threads are in the heads, and it looks like they're about 11/16" deep. So 9/16" is possible at least as that's concerned.

In order to get the 9/16" thread depth though, I'll need to use 1 and 1/8" bolts. While I can buy those from McMaster, they're expensive ($1.23 each) due to their unusual length.

Thanks very much!
Robroy

[cep62]

[quote="Ranchero50"]The trick is getting small head grade 8's.[/quote

The only problem with grade 8'S is if you ever break one in the future they are harder to drill out.

Another head choice is a Allen or Socket head bolt they can be easier to get on especially with a ball end Allen wrench.

[70_F100]

99% of allen/socket head bolts are Grade 8...

[fordman]

even if i use original manifolds i am going to use stainless bolts. it just sounds like a better advantage to not have to drill a regular bolt out for one reason or another.

[robroy]

Welp, I just talked to RemFlex on the phone. They said that RF3050 gaskets were made to fit my exact Hedman headers (89810), so that's the one I should use.

They added that with the gaskets, they'll send me a material sample so I can squish it and see how easily the stuff compresses. It seems that a while back, they were recommending that folks use the factory torque specs with these gaskets, but they ran in to problems because the RemFlex gaskets are so soft--they'd get squished with the factory torque. So they now include a torque range on the package for each gasket they make.

They also added that after I initially torque the gasket, I shouldn't re-torque it. But if I have to for some reason, I should take great care to make sure no part of the gasket squishes down to less than 1/16" thickness.

I also heard that they're 100% guaranteed, even if I break them during installation or anything. They'll send me new ones.

I'll post detailed photos when they arrive!

Thanks very much to Convincor and FoMoCoGuy for recommending these gaskets! They seem like they'll do the trick for sure.

Robroy

[thebannister8]

"It sounds to me like they tried to cut corners, and now they got "caught with their pants down" and are making excuses."

.... at minimum ...... and bad excuses .....jettison these clowns

[robroy]

Hey TheBannister8! Yeah I can see how things seem that way, based on what we know. I have a feeling that I may have just misunderstood his explanation though. Maybe next time I call for something I'll bring it up again to see if there's something I missed.

It's kind of hard for me to believe that a place that seems to have unanimously great reviews could have messed up this badly--I don't get it.

Robroy

[Ranchero50]

Thread length rule of thumb as I was taught is good advice. 70 is right about the nut only being one diameter thick, it's also ironic that fastenall suggested using grade 2 nuts with all grade 5 hardware in the plant so the nut threads would give before the bolt failed...

The 1.5x diameter helps alot where thread loading (heat cycles, vibration, shear) can damage the threaded hole or the bolt threads. It won't help if the bolt itself fails, but it will help keep the darn bolt tight. The only thing that concerns me about a gasket that will compress easily is the lever action of the header on the flange. It's probably not a big deal on a truck 390 setup where the bolts go in the top and bottom, but I think it helps the 302's leak where the bolts are side by side...

Jamie

[70_F100]

By all means, if you have the length in a threaded hole, use it.

Like Jamie said, 1.5x diameter is a good idea in the case he describes.

The more threads you have engaged, the less chance of the bolt working loose. It's not really any stronger, but the loading of the additional threads also translates to friction, which will help keep the bolt from moving.