500 exhaust manifolds

[77Lac]

lookin for some 500 exhaust manifolds for my 77 425.

[Nashalac]

We just got a few in.
MTS

[~JM~]

Will they fit ?

I seem to recall that there is a large suspension bolt that is in the way. Whether or not that bolt can be removed & replaced in the other direction to provide clearance I don't know. Maybe the excess threaded section on the end can be cut off.

Is this car subject to emissions testing where you live?

The old fashion way to better performance still works well if you can do it.

In the simplest form. The engine is an air pump. Anything that can be done to allow it to move larger amounts of air through it without resistance will improve power. Anything that can be done to reduce the internal friction of the moving parts will release power.

Used to be that the first thing was exhaust. The engine needs to be able to exhale freely. This helps in several ways. A couple of which are to reduce pumping losses & help promote scavenging. Dual exhaust with 2.5" pipes, an X-pipe and a pair of mufflers that will flow as much as your neighbors ears will allow. Don't let anyone tell you that a street engine needs some back pressure. That is one of the most rediculous statements I've heard. There is something to be said about sizing the exhaust correctly to maintain gas velocity though.

Once the engine can exhuast more efficiently. Now you can feed it more with a better intake system. Same thing applies. Least amount of restriction to the intake charge. You should also look at trying to duct fresh, cool, outside air to the engine instead of hot under hood air.

Do you know the basic principles of how the 4 stroke engine operates & what each of the 4 cycles are? If so... Good! Now see if you can find anything about the Fifth Cycle. :confused:

[Nashalac]

A arm stud needs to be trimmed near the front of each manifold and the 500 ones fit

[77Lac]

Unfortunatly the car is subject to emissions testing so I’ll have to put cats in the dual exhaust.

I Know the engine is just a big air pump and I’m familiar with the four stroke im just a noob to the whole carburetor and timing stuff

I got my adjustable vac advance and curve kit in the mail yesterday (thanks MTS) and picked up a remanufactured carb off ebay so im going to dive in this weekend and see what happens

[~JM~]

I don't want to get in the way of a sale... but you might want to check all the exhaust manifold bolts that are on your car right now to see if any have snapped off. Especially the rear most bolts. I'm not sure if the 425's have the same problems with broken exhaust manifold bolts that the older engines had. If you're lucky all the bolts will be fine & you won't need to use an easy out.

Be very careful removing the manifold bolts. If you're not gentle & slowly work them back & forth when you remove them, you will snap them right off at the head. I was surprised at how easy it was to break them. I usually like to "ping" them first with a straight on strike with a small ball peen hammer. I've never done this while they were still in the car though.

Other than headers, I think you are on the right track with the larger exhaust manifolds from a 500. Do yourself a favor & open up the mounting holes a bit more before you bolt them up. There is speculation that there needs to be more room for expansion/contraction in the bolt holes to prevent snapping the bolts. See if Marty at MTS has a set of new bolts & what he might recommend for a high temp anti sieze.

The 500 manifolds have a lot of room inside to grind the outlet to a larger diameter. I think there is information on this board about hogging them out. Try the search feature & see what you can find.

Good luck & let us know how it goes.
~JM~

[djcwardog]

which came from MTS as used parts - but never installed. I know they come and go as to availability so this is offered just in case Marty has run out and you need some fast. You will likely need to trim down the suspension bolt on the passenger side as the 500 manifolds are not "dimpled" (and therefore should flow much better!) like the 425's are.

[djcwardog]

...so they may go on my "new" Cadillac!