Exhaust manifold swap - need help to solve a gap
 

My new L31 vortec hasnt been broke in and I have decided to swap out the headers with ram style manifolds. The distance between the new flange and the existing exhaust needs to be connected somehow now be it temporary or longer lasting just so I can break in the engine in the garage by revving up to 2000 rpm for 20 min or so and swap out the oil and filter and then take to a shop to fabricate whats needed. Anyone have advice on what I should do here?

Here are pics of the headers and the new manifold. The tape line shows about the length of connection I need.

Re: Exhaust manifold swap - need help to solve a gap
 

Correct me if I'm wrong, but doesn't the L31 come standard with a roller cam?
The 2000 rpm, 20 minutes was more to break in a flat tappet cam.

Re: Exhaust manifold swap - need help to solve a gap
 

I bought some exhaust tubing from JEGS. I just got a couple of curved pieces and a straight piece and welded them in place. Since I'm not planning on putting the headers back on, I just cut the collector where it was the same width (2 1/2") as my new exhaust tubing.

And Matt is correct - there's no break-in required for a roller cam. Just drive it somewhat conservatively for the first 500 miles so the rings can seat and you'll be good.

Re: Exhaust manifold swap - need help to solve a gap
 

It was.
But what about enough oil splash on the cam lobes and lifters, the pushrod tips, the rockers, the valve tips and pistons and pins.
All things that need rpm to get enough lubrication.

Re: Exhaust manifold swap - need help to solve a gap
 

As for exhaust you don’t need the ram’s hooked up to fire it up.
If you’re worried about flames out the flanges just slip in some sheet metal deflectors. Cookie sheets work well.
Don’t tell the wife you borrowed them though!

Re: Exhaust manifold swap - need help to solve a gap
 

I really dont know much about engines but I dont mind being overcautious at this point with the money and time ive already spent to do the break in. The front of the truck is still in the works. No body panels or wiring at all yet just getting it set up to be ready for firing up. I was hoping to break it in while its still in the garage at the house and not have the sound levels and carbon monoxide on the high side. Ive got a few shop fans that ill set up to circulate the air out and fresh air in, but I thought if I can temporarily connect the manifold to the existing exhaust I would think the engine would run better and not have my neighbors too mad at me.

Re: Exhaust manifold swap - need help to solve a gap
 

Just make sure you prime the oil system, longer the better. Once you start driving it, follow GM recommendations with no full throttle runs for 500 miles and changing the oil.

Re: Exhaust manifold swap - need help to solve a gap
 

:lol::lol: my poor wife...:lol::lol:

Re: Exhaust manifold swap - need help to solve a gap
 

And wash all your car parts in the dishwasher. People love that.

Re: Exhaust manifold swap - need help to solve a gap
 

Oh and the transmission in the tub - Lead balloon.

Re: Exhaust manifold swap - need help to solve a gap
 

Just run the headers until you get it to the shop then have them install the ramhorns and exhaust tubing. Hope those are 2.5" ramhorns otherwise you'll be choking that vortec.

Re: Exhaust manifold swap - need help to solve a gap
 

I bought these, says 2.5!

https://www.summitracing.com/parts/SUM-G9200S

But I have yet another issue. I took the exhaust manifold and tried to put it in place on the drivers side and the brake lines I ran are needing to be closer to the frame to clear the central connector. Always something. :mad:

Re: Exhaust manifold swap - need help to solve a gap
 

The options are go back with headers or redo the brake lines. The clearance is not far enough I would think with the ram style without redirecting the lines toward the firewall 4 inches or so and then backtrack in the frame and drop to the connections I have already.

Re: Exhaust manifold swap - need help to solve a gap
 

Redo the lines and run them on the outside of the frame rails....

:mm::mm::mm:

Re: Exhaust manifold swap - need help to solve a gap
 

Even with headers the lines seem pretty close. Couldnt find any clear pics of the original set up. I did have to add a 3rd line for the proportioning valve that the PO never had going on the front disc rear drum set up which isnt helping for space.

Re: Exhaust manifold swap - need help to solve a gap
 

I didnt consider that, I thought the inner fender would not allow a gap for the lines. Currently I have no body panels on the front yet to give me room to work.

Re: Exhaust manifold swap - need help to solve a gap
 

Just trim the inner panel to clear the lines outside the chassis....

Even with the headers, those lines would have been cooking, unless some sort of shield was placed there...

Outside the chassis is best place for them....

On later series, the proportioning valve is on the front of the chassis cross rail, under the radiator....

:chevy::chevy::chevy:

Re: Exhaust manifold swap - need help to solve a gap
 

Here's a pic of my 72. The inner fender has a cutout to clear the brake lines.