77 Gremlin V8 swap questions

xGremlinx wrote:

So I've spent a lot of time looking but I haven't found a definitive answer. What AMC vehicles have "free flowing" exhaust manifolds? I understand there are larger and smaller outlets (2" vs 2-1/4") as well. What vehicle(s) and years can I source the larger free flowing manifolds to put on the 401 going into my 77 gremlin? Thank you all again!

xGremlinx

The only reason they are called free flow is because they were designed by AMC to be high flowing and that is the nick name we use to describe them. Truth is... they are some of the best stock exhaust manifolds available from any manufacturer during the time period they were available. The larger ones were off the Rebel Machine but you will most likely pay through the nose for those. I got a set from a standard set from a guy for 20 bucks.. so the deals are out there. And since you can port them or even have a machine shop port them for pennies on the dollar vs. buying a Machine set.... the stock manifolds off of a Matador or a old Jeep will work just fine.

The Machine set might work out better if you think your 401 will operate at high RPM often.. and if that is the case.. then yeah... you'd probably be better skipping them and going with the long tube header... but if you are primarily street cruising and going red light to red light... then the stock set of free flows will be fine.

I probably wasn't clear enough in my previous response... ANY AMC vehicle with a V8 will have them after 1970... just don't look at the manifolds from the Full Size Jeep that has the axle Cabbage head on the drivers side... stay away from that manifold and any other log type manifold... like in the picture above... they don't flow as well.

The high flows can still be purchased brand new from Amazon... so.. not hard to find... try to get a good deal though... save every penny you can... like I said.. I have a free flow set for 20 and I got a small car pass. log manifold from 35 shipped from a salvage yard in my home state. At the time I thought I needed the log style for the small car.. then later on a found out I could get away with the free flow style too.

Go to car-part.com... look up an 1973 Matador or a Javelin... select Exhaust manifold... punch in your location and see what you can find... I used the North West section of the state and found them each going for $35-$45...

You can also buy them from Auto Zone, EBAY or Amazon... draw back to buying them new is that they can be expensive... upside... they look new. Draw back to buying used.. they look used and will need to be cleaned up... upside initial cost...

New

Amazon Pass. side:
https://www.amazon.com/Jeep-Exhaust-Manifold-Passenger-Side/dp/B01K2KJ7SS

Ebay
http://www.ebay.com/itm/5-0-5-9-304-360-AMC-Jeep-1972-91-New-Exhaust-Manifold-Set-/372053961867

USED

Ebay

http://www.ebay.com/itm/JEEP-CJ5-7-8-WAGONEER-CHEROKEE-304-360-401-AMC-V8-72-91-EXHAUST-MANIFOLD-SET-/122637959131

This is the one you want to STAY AWAY from... the pass. side v8 small car looks exactly the same except its design is of course orientated to the pass. side...

http://www.teamgrandwagoneer.com/exhaust-manifold-w-gasket-v8-360-401-gw-1974-1991/

Edited by 1982AMCConcord - Aug/25/2017 at 7:14am