L31 Vortec 350

[lowbucktrucks]

There seems to be some confusion or contrversy as to whether rams horns will work on L31 vortec. Has anyone used vortec log manifolds on our trucks?? Just wondering if they will fit our frames?? Thanks

[harpo231]

On the L31 Vortec heads, the exhaust ports are not centered on the bolt holes. This results in a mismatch of the exhaust ports of the heads with any manifold or header other than the L31 manifolds. Really not sure why GM did this.

[B. W.]

pic 1: L31, 2.5" corvette rams horns

pic 2: stock manifold with L31 exhaust gasket

[truckster]

Yep. thousands of swaps have been done using the L31 and the rams horns or headers. I haven't heard of any problems (except the typical leaking header problems).

[AK49Watson]

I run headers. They barely leak. A couple pinholes, that's it. Can't even hear or feel it.

[lowbucktrucks]

Will it work with factory rams horns or does it have to be corvette 2.5 inch??

[Jrainman]

Originally Posted by harpo231

On the L31 Vortec heads, the exhaust ports are not centered on the bolt holes. This results in a mismatch of the exhaust ports of the heads with any manifold or header other than the L31 manifolds. Really not sure why GM did this.

Harpo is correct the exhaust studs are set lower and not centered as in the older gen1 sbc head , just hang a set of sbc gaskets on and you will see this so ,there will be a small amount of interfearance at the top of the ports , will the rams horns fit yes they will and any gen 1 sbc exhaust manifold or header will fit, some guys say you want to use round hole gaskets and headers in stead of the oval/d port gasket and headers , I did some grinding (porting) and a little gasket moding to my headers so there was no interfearance issues on my vortec heads, also the rams horn might be close to your spark plug boots and cause issues . If you are staying with manifolds if I remember rite the best ones you can use for the vortec heads are out of a vortec year 3500 series truck I think ,I could be wrong but I know that there is a certain stock manifolds that is is highly prized for there flow on vortecs by the circle track racers being thety have to conform to stock manifolds those would be the people you want to ask.

[B. W.]

Originally Posted by lowbucktrucks

Will it work with factory rams horns or does it have to be corvette 2.5 inch??

If it's 4wd you can run either stock or the larger ones. The corvette's only come int straight dumps I think. If it's 2wd you're better off with the stock angled exit for clearance, though some guys here have made the straight dumps work.

I have a stock L31 manifold so I compared it with the rams horn manifold using an L31 specific gasket (MS16093):

[truckster]

Originally Posted by B. W.

I have a stock L31 manifold so I compared it with the rams horn manifold using an L31 specific gasket (MS16093):

Interesting. It looks like the rams horn is a better match to the gasket than the stock manifold.