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Cadillac & LaSalle Club Forums => Technical / Authenticity => Topic started by: grantatx on October 02, 2017, 09:50:27 PM

Title: Headers for a 1970 Deville convertible
Post by: grantatx on October 02, 2017, 09:50:27 PM
Hi All,

Finally found a nice '70 Deville convertible to bring home. The exhaust manifolds are pretty much shot and I'd like to go with headers. I've seen a few offerings out there - Sanderson, MTS and Also the cheapie block hugger headers on Ebay for around $100, but looking at them though I doubt they'd fit even though the sellers say they do. Has anyone had success fitting headers to a '70 Deville convertible without modification and if so what brand/model were they?

Thanks in advance,

Title: Re: Headers for a 1970 Deville convertible
Post by: chrisntam on October 03, 2017, 06:41:19 AM
My understanding is that the chassis is different on a convertible than a coupe or sedan.  I can't answer if they would fit or not or how difficult to install or a good brand.

How do you intend to use the car?

I got my car about 3 yrs ago and also toyed with the idea of headers.  I spoke to MTS, they asked why I wanted headers, told them for better air flow through the motor, performance, etc.  They advised that the manifolds do pretty well and just add dual exhaust if I wanted.  I had them build the motor, 10 to 1 compression, mild cam, mild port work on the heads, electronic ignition, etc.  I do regret the compression choice, it forces me to use premium fuel and it's not a race car.......

I did not install headers, I'm using factory manifolds and am glad I made the choice I did.  I had my manifolds ceramic coated, they still look new after 3 years (as they should).

I've come to find out that these Cadillacs are better cruisers than performance vehicles.  The main reason is weight, approx. 5000 to 5500 pounds.  The motor is plenty powerful, more than enough for what I need.

I recommend you make it a dependable cruiser and get a lighter car if you want to go fast.

Additionally, from the factory, there were no gaskets between the heads and manifolds.  If you have a leak, be sure the exhaust hasn't eaten away the mating surfaces.  MTS supplied the gaskets, nary an exhaust problem since.

That's my $0.02.  Kind of a long reply and I didn't even answer your question...............

And since you just got the car and are new to the forum, please post pics!
Title: Re: Headers for a 1970 Deville convertible
Post by: cadillacmike68 on October 03, 2017, 07:51:40 AM

There are very few chassis differences b/w the Coupe and Convertible, especially up front. I don't think there are any forward of the firewall.

I would second the idea of adding dual exhaust.

The convertible had a curb weight of 4,600 lbs not 5,000-5,500 lbs, but still it's not a lightweight.  These case had great acceleration for their day, but they can't compare to the 5 or 6 sec 0-60 cars that are around today.

As for your high compression, just add some 110 octane race fuel to the tank.  It will rocket down the road without knocking.
Title: Re: Headers for a 1970 Deville convertible
Post by: "Cadillac Kid" Greg Surfas 15364 on October 03, 2017, 09:50:43 AM
The easiest thing of course would be to replace the manifolds.  They are however getting pricey.  The headers MTS sells will fit your car and any good muffler shop can make the connections.

What I have shown here is my MTS headers which I've modified for performance to help my 5000 pound '73 Coupe deVille get into the 12 second neighborhood. The main reason I am showing them is to show how VHT paint looks and lasts.  The paint on the original (upper 1/2) of the headers is several years old, and the lower half where modifications have been made to incorporate electric cut-outs and extend the headers to "long tube" is fresh/. Very little difference. Point being, the ceramic coatings sold as an extra are not necessary unless you like "pretty".

I suggest calling MTS and talking to Paul about your needs.
If you want to go with original manifolds, I've got the pair off my '73.  PM me.
Greg Surfas
Title: Re: Headers for a 1970 Deville convertible
Post by: George D. Mukalian CLC # 10047 on October 03, 2017, 02:08:17 PM
I purchased exact fit headers for my 1969 Convertible.
I had no issues with them.
Attached is the company I bought them from.

Title: Re: Headers for a 1970 Deville convertible
Post by: grantatx on October 03, 2017, 09:53:36 PM
Thanks guys for all your responses, they're all very helpful!

The manifolds on the car at the moment are in bad shape and causing leaks at the join between the manifold and pipe, so rather than try and find good used ones for big bucks I figured I'd just go down the header route provided I can find some that are a direct fit. And it sounds like both MTS and Sanderson do make direct fit headers so I'll give them a call.

I'll definitely be going dual, I guess 2 1/2 all the way back. At the moment the car is going to be a cruiser but next year I'd like to build up a fresh engine and warm it a little.

I'll definitely post some pics soon, just struggling with a turn signal replacement tonight!

Thanks again!
Title: Re: Headers for a 1970 Deville convertible
Post by: grantatx on October 14, 2017, 12:09:11 AM
Hi All,

I ended up purchasing headers from Sanderson, the CAD700 model. installed them tonight and they look and fit great! And what a sound!

I needed to unbolt the engine mounts on both sides (one side at a time) and jack the engine slightly to tilt it so I could get the headers between the block and chassis. The passenger side went in from underneath the car, driver's side from the top.

Thanks everyone for all your input!