Olds 403 Exhaust Gaskets

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Posts: 1
Joined: Tue Jan 14, 2014 8:54 pm
Membership No: 14-A364
Year: 1979
Model: Trans Am
Engine: 403
Name: Dan
Location: Lymm, Cheshire
Location: Lymm, Cheshire

Olds 403 Exhaust Gaskets

Post by danielcwright » Thu May 19, 2016 9:15 pm


I’m kind of a newby to all this, so apologies if I’m posting this in the wrong section.

I bought my ’79 trans am a couple of years ago, and since then my Dad and I have had many enjoyable hours rumbling around Cheshire in it. There’s nothing around here that sounds like my trans am!

Recently, however, the car’s been off the road after failing its MOT. It’s been in a garage for nearly two months and I am getting very stressed about it.

It went to this garage about 45 minutes’ drive from here (near Manchester) to have an MOT and any subsequent word done on it. The garage was recommended to us as being good for American car repairs, and, having read a few good reviews on the internet, my Dad and I decided that it was the place to go to. However, as I said, the trans am failed its MOT. All the required work has been completed… except the exhaust blowing in a couple of places.

The mechanic is having trouble obtaining the gaskets for where the headers attach to the Olds 403 engine. He thinks it’s one which matches the exhaust headers and is therefore round in shape. I have been searching the internet for suitable gaskets, but the results come back with a rectangular port. It appears from the two images attached that the headers are round.

I should say that these pictures were taken quite a while ago: for one reason or another, neither my Dad nor I have been able to get to Manchester to get a better image of the troublesome gaskets.

Does anyone think that it’s had aftermarket headers fitted or does the circular head pipe suddenly turn rectangular where it attaches to the engine?

I would be very grateful if anyone can shed some light on this because the car has been off the road for over two months and it isn't doing it (or me!) any good. A link to suitable gaskets would be brilliant.

Many thanks,
Dan W.
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Davy J
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Re: Olds 403 Exhaust Gaskets

Post by Davy J » Thu May 19, 2016 9:57 pm

Hello & Welcome to the forum Dan. You could try talking to Robin at Autopontiac who may be able to assist. His contact details are on the Sponsor's page.
Dave. Vice Chairman & Publicity Manager

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Re: Olds 403 Exhaust Gaskets

Post by bhm1712 » Sat May 21, 2016 11:05 am

The flanges on a 403 olds are rectangular and not round. The tubes are round but the flange shape is definitely rectangular.

to be honest I would loosen off the header that's leaking and put some clear silicone into the area where it's leaking. Despite what you think it will not melt or set on fire and will seal the flange!
Ian Hopkinson - Membership Manager & Forum Administrator
Northern England & Midlands Rep


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