47-55.1 Cast header question

[51 3600]

I went to AutoZone and purchased a new starter for a 2010 LS3 6.2. Bolts right up and gives me the clearance I need for the header flange with no heat shield on the solenoid. Even with a shield I think it would work.

Still, looking at the pics below I'm not comfortable with whether the starter would actually function properly and I don't really want to jump it in place as pinion gear might get scarred preventing me from returning it.

Oddly the new starter pinion gear seams to be the same diameter and tooth dimensions as the stock 2001 LM7 5.3 but the new has 10 teeth and the stock 11. That does not make sense to me. If they were different diameters I could understand how 10 vs 11 could work. But as it is I hesitate to use a LS3 starter. I have read that a LS3 flex plate is different than a LM7 plate but I don't know how it is different.





Unless someone on here can confirm that the LS3 starter will work, I think I'll go the safe route and clearance the frame boxing plate (have to do that either way) and grind the starter side of the flange and dimple the heat shield.

[62c30]

I checked the clearance on my starter to header, turns out my starter is off. So I guess I'll probably have the same issues. Let us know which starter you go with.

[51 3600]

I think I can stick a fork in this header project other than painting, powder coating or ceramic coating the headers. Once I relieved the boxing plate on the frame I gained enough room to barely (by 1/16") clear the solenoid heat shield using the stock starter. For some reason the stock location of the heat shield is on top of the solenoid. I might try pivoting it down 45 degrees to be more between the header than the engine block.





Viewed from above.


Thanks to all for the help, ideas and suggestions, all invaluable to me. Now onto the next episode with this truck. I'm sure I'll have more ???.

[Rickysnickers]

Question, is that slot going to give you enough clearance for engine movement when it's running?

[dsraven]

my question as well. a bigger slot is easier now than later. good thinking outside the box.

[51 3600]

"Question, is that slot going to give you enough clearance for engine movement when it's running?"

"my question as well. a bigger slot is easier now than later. good thinking outside the box."

That is a good question and a concern I posed earlier in this thread. The height of the slot is 1-3/16" and the flange thickness is 5/8" which I've ground down to 1/2" where the flange protrudes into the frame. The flange is centered in the slot. Is the slot big enough? I don't know because I don't know how much to expect the engine to move when running. How much clearance to allow would be good to know if someone has that info. Engine mounts have a hard, puck shaped, rubber cushion.

[dsraven]

how about if you simply bend the edges of the cut inward so if the engine does move some- a mount fails or whatever-the manifold flange has a ramp to work with instead of a squared off hole. it would suck if it moved doing a burn out or something and the manifold stuck in the hole, that could break the flange possibly.

[leegreen]

Can you get the downpipe and donut on there? Looks tight to me, but hard to tell from photos.

I think I'd make that hole rounder & little larger then use torch and BFH to dimple the edges inwards a healthy amount. The dimple will keep the plate stiffer

[51 3600]

Originally Posted by dsraven

how about if you simply bend the edges of the cut inward so if the engine does move some- a mount fails or whatever-the manifold flange has a ramp to work with instead of a squared off hole.

Originally Posted by leegreen

Can you get the downpipe and donut on there? Looks tight to me, but hard to tell from photos.

I think I'd make that hole rounder & little larger then use torch and BFH to dimple the edges inwards a healthy amount. The dimple will keep the plate stiffer

I can get the down pipe on and planned on grinding the donut on one side. It’s somewhat smaller than the header flange to start.

Consensus says make the hole bigger. I like the idea of doing that then heating the edges and dimpling them. Because there’s so little space in which to work, using a torch and BFH would necessitate pulling the engine which I REALLY hate to do because I just put it back in. Arrrrgh!

Two questions: How big of a hole can I make without compromising the purpose of the boxing plate? Won’t most of the potential engine movement be in a vertical direction when the engine is under torque?

[dsraven]

if you can slip something in behind you could bend it into a cone shaped hole with a home made die, like a short socket, and use a bolt and a thick washer, that loosely fits inside the socket but is bigger than the hole, to suck the metal into the socket enough to dimple it. maybe no heat required that way so less chance of buring something that you wanted to keep the paint on, lol.

[leegreen]

yeah it is going to move up and down, not front to back.
Just a gut feel, I'd want at least 1/2" all around with the flange, donut all in place. And I'd probably go for more than that, if it is hitting when you get it on the road you'll wish you cut more now.

The boxing plate looks like it will be plenty strong even with a hole in it, I don't see anything welded to it nearby. I'd make the corners of the hole as round as possible to avoid concentrating stresses. Dimpling the edge will add back any stiffness the plate loses due to the hole, probably make it stiffer than it was before you cut the hole. dimples / beads in a sheet metal part make it a lot stiffer than just flat sheet.

[51 3600]

My plan is to enlarge the hole along the redlines in the drawing below. This will accommodate the flange and the donut with 1/2"+ for movement. Weird shape of the hole is because the flange and donut are at an angle but as a whole it will move vertically with the engine. The upper portion of the hole would cut into the top of the frame when keeping the 1/2" tolerance but I don't want to cut into that. Should be ok because that's also where the flange tapers toward the bolt holes for the donut.

Also rather than dimple the hole edges of the 3/16" boxing plate, I'm going to bend some round or square bar into a frame to match the hole and weld it on the inside of the hole. That's easier for me and I think will accomplish the same purpose.

Now to get the engine pulled....AGAIN.

[dsraven]

welcome to "mock up" stage. it's always install, remove, install, remove. always nice to install for the last time. marking the spot and removing the engine will get you a better job that you will like a lot more and it will look a lot better. post up some pics of the process.

[leegreen]

If the top of hole is tight, consider a healthy bevel to the hole/welded in frame there so if the flange does hit it is a gradual pinch rather than a sudden hard stop that might break your header. I think dsraven suggested that above

[leegreen]

and think about your exhaust design, it appears that the downpipe on that side might need to get angled up into that hole before you bolt it on. So if the final exhaust is a tight fitting Y or X pipe you might need a slip joint or band clamp on one side to allow the two manifold connections to be lined up or disconnected one at a time.

[51 3600]

Originally Posted by dsraven

welcome to "mock up" stage. it's always install, remove, install, remove. always nice to install for the last time. marking the spot and removing the engine will get you a better job that you will like a lot more and it will look a lot better. post up some pics of the process.

This is all I've been doing last 3 months or more. Mostly fixing work done by others that I discovered wasn't right. Then each of my fixes points to other problems needing a remedies. Frustrating as these constant interruptions are to my plans I've learned to hark to the words of C. S. Lewis:

“The great thing, if one can, is to stop regarding all the unpleasant things as interruptions of one's 'own,' or 'real' life. The truth is of course that what one calls the interruptions are precisely one's real life -- the life God is sending one day by day.”

Back to the wrenching life. And thanks dsraven and leegreen for the help.

[Kermitt47]

Here is another solution for the exhaust clearance I borrowed from the YouTube site of the Idaho Fabricator. On his 53 Chevy frame he used a piece of pipe in the boxing (think C notch only running top to bottom) to give the clearance and not give up any strength.

[dsraven]

pic shows a great idea of also having the pipe flange bracket installed on the manifold for mock up. that way you remember there is more to it than the manifold and also have some idea of how much room that other stuff takes. a vertical or angled pipe cut into the boxing plate could also be used, as noted above. it would mean cutting into the frame flanges though, most likely, unless you have some decent metal skills and can make up a custom bubble shaped part

[leegreen]

I can't say I am in love with that idea. The pipe welded into frame as shown creates clearance but reduces the cross section of the boxed rail. Unless you compensate for that somehow you have created a significantly weaker spot with clearly defined borders. I'd much rather see a clearance hole in the boxing plate.

if you want a dished shape to weld in and don't want to pound your own out of plate you could buy a weld on round pipe cap (expensive) or cut a piece out of a condemned inert gas cylinder, or......

These cast LS headers are often sold with an option of ductile steel, so you could slice the flange off, weld on a pipe to bring the flange down past the
obstructions and weld a flange on again. Quite a few people modify factory LS truck manifolds the same way so those castings may take a weld Ok as well.

[51 3600]

Originally Posted by Kermitt47

Here is another solution for the exhaust clearance I borrowed from the YouTube site of the Idaho Fabricator. On his 53 Chevy frame he used a piece of pipe in the boxing (think C notch only running top to bottom) to give the clearance and not give up any strength.

I've watched a lot of his YouTube channel and his truck is a fantastic piece of work. Well worth watching. Unfortunately the Big C took him out before he could finish it.

Originally Posted by leegreen

These cast LS headers are often sold with an option of ductile steel, so you could slice the flange off, weld on a pipe to bring the flange down past the
obstructions and weld a flange on again. Quite a few people modify factory LS truck manifolds the same way so those castings may take a weld Ok as well.

When the time comes I'll ask the shop I'm gonna use for the exhaust system to look into that possibility.

Got busy this afternoon, pulled the engine and started cutting out the hole.

Started with drilling pilot holes in corners using original layout.


Enlarged those holes with step drill and connected dots with new tape.


Using die grinder and angle grinder cut from hole to hole. Shorter distances had to be taken out in small pieces as length of cut was less than diameter of cutting disk.


Final result.

[51 3600]

Thought about welding a u-shaped plate as depicted by the blue tape in the pic below to strengthen the frame but I don't have the space for that. I could put the plate on the inside of the frame and plug weld it in place. Not sure if that would be worth the effort. Opinions?

[whitedog76]

I don't think you need to do anything. The boxing plates basically just give you a place to weld your IFS to and a flat spot for motor mounts. The 3600 truck is 3/16 steel vs. 10 gauge in the 3100 trucks. The 24 or 30 inches of boxing plate it way overkill to begin with.

Grind it and paint it, call it done.

[dsraven]

you could chamfer the edges of the hole on the outside face and weld in a round bar on the inside face perimeter if you so desired. that would strengthen the holes edges and not leave a hard corner for a stress crack to form. probably not gonna need it though, bevel both edges so they arent sharp and carry on

[dsraven]

tip: on the ends of the cut where the zip disc is too big to fit you can try a jigsaw spaced off the work with a piece of wood or whatever so it doesn't hit the blade on the outside part of the frame behind, or use a hacksaw blade without the hacksaw frame and with tape on the part you will grip. a row of holes drilled with a small bit makes short work of that and then a die grinder with a burr cleans up the poor cut down to the proper finished edge. a pneaumatic cut off tool also works well. I have an assortment of the zip discs and also cut off tool discs that are used but not worn out and they come in handy to get closer to those corner style cuts, but they don't make it all the way in.

[51 3600]

Originally Posted by whitedog76

Grind it and paint it, call it done.

Concisely put, the goal this afternoon.

Made a little plywood buck that fit the hole better than the pic shows.


Bent some 3/16" round bar to fit the buck. Open section goes at top of hole against underside of top of frame so no room for the round bar.


Tacked the round bar in place. Clamps didn't work well on the round bar so used strips of masking tape to hold bar in place.


Welded it all in place and ground it smooth. Painted it but didn't take a pic.


May not have needed to do this but I had it in my mind to do and had the materials so what could it hurt. Abandoned the idea of the extra plate. I think I'm done with this (I know, famous last words). Headers are getting ceramic coated so can't check my work til next week sometime.

Again, thanks to all for your input. I learn every time get on this forum.