69 Heat Riser Install Questions

[Michael C.]

I'm attempting to reinstall the heat riser on my BB after purchasing a replacement flange donut (Fel-Pro) from a local parts store. Using the same studs that I removed months ago I don't get enough exposed threads to attach the nuts. Unfortunately I discarded the old donut so I can't compare the thickness of the old with the new. My first though was that the new donut is too thick. It's listed as 5/8" (.625") thick but actually measures .662". Seems like that's not enough to cause my issue if the original was 5/8".

Can anyone tell me what the thickness of the donut should be?

Should the studs be tightly seated into the exhaust manifold? I don't see any information in the AIM or service manual regarding stud tightness. I did back the studs out a couple of threads, but still not enough to get the nuts attached properly. Of course I don't want to back the studs out too far.

Any suggestions.

Thanks
Mike

[Mark E.]

Re: 69 Heat Riser Install Questions

Are you sure you're using the same studs? Studs for the RH manifold are longer than the LH because of the heat riser.

Also, if the studs came out, consider installing new ones. They become brittle with heat cycles and corrosion, then snap the next time you do this.

And yes, the studs should be fully threaded into the manifold.

[Michael C.]

[Mark E.]

Re: 69 Heat Riser Install Questions

If judging points are not a concern, consider stainless steel hardware with high-temp anti-seize.
You'll thank me later.

[Joe L.]

Re: 69 Heat Riser Install Questions

I'm attempting to reinstall the heat riser on my BB after purchasing a replacement flange donut (Fel-Pro) from a local parts store. Using the same studs that I removed months ago I don't get enough exposed threads to attach the nuts. Unfortunately I discarded the old donut so I can't compare the thickness of the old with the new. My first though was that the new donut is too thick. It's listed as 5/8" (.625") thick but actually measures .662". Seems like that's not enough to cause my issue if the original was 5/8".

Can anyone tell me what the thickness of the donut should be?

Should the studs be tightly seated into the exhaust manifold? I don't see any information in the AIM or service manual regarding stud tightness. I did back the studs out a couple of threads, but still not enough to get the nuts attached properly. Of course I don't want to back the studs out too far.

Any suggestions.

Thanks
Mike

Mike------

The original exhaust pipe packing was, nominally, 5/8" in thickness. The difference you measure is insignificant.

The right side studs should be 3-1/6" in length.

As Mark mentions, I recommend only stainless steel studs for this application. They are available in original configuration.

[Michael C.]

Re: 69 Heat Riser Install Questions

I found some studs of the appropriate lengths at a local parts house I can use temporarily until I can get the ss version. They fit fine.
Thanks folks