Roadkill's 1983 Chevy Z28 - (Work Starts on Page 5)

[Roadkill]

Welding the flexi was, I quote "a bitch" as it's made up of multiple paper-thin layers of stainless . . . .



Now begins step 2 . . . . . The exits . . . .

[Roadkill]

Oh, and Titsy : NO CHEMICAL METAL THIS TIME !!!

[Cunning Plan]

It's beginning to look like a stock aircooled VW exhaust

[EDGE]

where are the exits going?

[Roadkill]

Quoting: EDGE

where are the exits going?

At the ends, which are currently open.

They'll channel back into a 90 degree / 2.5" pipe section . . . unfortunately, as before, I have to aim them forwards, towards the front of the car before U-turning them back again due to the SFC/clearance issues.

I briefly considered notching the SFC's to make the exhaust path more direct but the amount I'd have to notch would mean that they'd be doing nothing, even with plating.

[EDGE]

ah

[Roadkill]

This was the old arrangement . . the flow path is not dissimilar but I'll hopefully gain around 40mm of ground clearance . . . .

(Old pic)

[EDGE]

are you sure the exhaust isn't overheating because of all the U bends?

[Roadkill]

Difficult to say, to be honest.   We've run it for maximum of around 15 minutes or so . . . . Yes it got hot but I'm not sure how we could measure that.

It certainly seems to be running well . . . can't speak for the gases, though.

I do appreciate the gases flowing into the new oval section are going to be hitting the back of it like meteors into Russians . . .

Without making a highly complex fabrication utilising said section I'm a bit stuck.

EDIT -

I've got some heat-bandage that I intend to wrap around it to protect some areas under the car it runs close to (gearbox) . . .

[ianjpage]

that cross over looks very nice now

[Roadkill]

No progress over the weekend . . . . .

At all . . . . . .

I opted to take Saturday off and spend some time with Sammy and Jensen (as I'd left early and been late home from work every evening and missed seeing Jensen entirely one night), plus it was Vicky's party in the evening - it made sense.

Sunday I felt achy and feverish all day and my hands were shaking alot of the day . . . I decided using an angle grinder was unwise in such a condition (silly Health & Safety head) . . . .

It means that this week will be punishing in order to get it all done !

[ianjpage]

Quoting: Roadkill

Sunday I felt achy and feverish all day and my hands were shaking alot of the day . . . I decided using an angle grinder was unwise in such a condition (silly Health & Safety head) . . . .

Wierd, that almost sounds flu-like symptoms, hope it ain't anything like that tho

Quoting: Roadkill

It means that this week will be punishing in order to get it all done !

More so than usual !!

[Roadkill]

Got about 2 hours on it last night . . . .

The first exit cut and ready for welding.

Mocked up in place :



And, as before, showing all the work (cutting the pipe section was a tad scary at times) :



Hope to somehow get the other side done today so it can go back off for welding tomorrow . . . .

[Incursus]

Certainly looks the biz

[Roadkill]

I've got a stainless Lambda boss and plug arriving this week which will be added (only for short-term testing).

Also think I'd benefit from a little notch at the top of the cross-over to allow breathing room for the gearbox - but won't know for sure without a test-fit.

EDIT -

Good progress made on my lunch hour . . . should be finished the other outlet tonight/tomorrow morning.

[Titsy]

Isn't the ledge as it transitions into the exit piece going to cause a lot of turbulence...?

[Roadkill]

The gas is going in the opposite direction so I hope it's minimum, but yeah, I know what you mean.  

It will be tapered a little once it's tacked into place (there's only so much I can do with it loose).

Plus, a little turbulence is probably acceptable considering the rest of the system is theoretically free-flowing.

There's no silencers or mufflers . . . . only a straight-through cherry-bomb style glass pack on each side pipe to try and kill some of the higher pitched noises.

[ianjpage]

That looks very nice!!

[EDGE]

it looks like you've got at least 2 stall points in there where the gasses will just be pounding in to a flat wall.  

Could you not at least open up the oval and weld in some angled baffles to help the gasses turn.  It looks like you're going to end up with a huge build up in the box with the pressure of the engine having to force it down the side pipes rather than it flowing at all.

Have you considered the distance of the "H" from the headers?  It looks awfully close.

I don't know what the underneath of your car looks like to be fair but I would have thought that the headers could reduce to 2 lengths of flat oval pipe, to about the tail of the trans.  A flat oval cross could be fairly high at that point as the tail is narrow and then the rest could exit as an where there's space over the axle.

Or is the compromise because you want the side pipes?

just playing devils advocate,

[Roadkill]

Quoting: EDGE

Have you considered the distance of the "H" from the headers? It looks awfully close.

It is.  No choice really . . I could move it back another 40mm but then I'd hit the trans mount.

On my reading it was said numerous times that you want the cross-over as early as possible . . . ?
I agree the cross-over they had in mind probably didn't look like mine but -

Quoting: EDGE

I don't know what the underneath of your car looks like

Here's some pics from last night's test fit :

Quoting: EDGE

I would have thought that the headers could reduce to 2 lengths of flat oval pipe, to about the tail of the trans. A flat oval cross could be fairly high at that point as the tail is narrow and then the rest could exit as an where there's space over the axle.

The "stock" position for a third-gen is to run a 3" pipe through the trans-tunnel.

This was the original plan and I even got an off-set upper panhard arm to increase the clearances for the pipes near the axle.

The T56 trans mount and the tubular torque arm's cradle mean that you couldn't even get a single 2" pipe through the gap, now !

Quoting: EDGE

Or is the compromise because you want the side pipes?

No.   I actually don't think sidepipes look "right" on 80's cars (I actually discussed making the sidepipes out of square section to keep more "in keeping" with the lines of the car . . . ) . . . I DO like side exits but the pipes are where they are because that's the highest point to position them.

I'm stuck, really.

With Long Tube headers I can't take the normal path for my cross-over (behind the sump and before the flywheel).

Another option is to forget about the cross-over altogether and literally just put a 90 degree turn on the headers and dump them out each side (ground clearance wouldn't be an issue, then, but it would be a) VERY loud and, b) What would I loose by not having a cross-over of some description ?

[EDGE]

It's probably worth finding out exactly where the cross over should be by using the wax crayon method.  Once you now that you can actually make it where it needs to be.

Have you thought of going to a rear exit exhaust, I imagine that you could run 2 flat ovals ticket up beside the subframe connectors, cross them over behind the trans, then bring them both over the axle where you could use a larger muffler.  

This would probably require some bending but you could easily mock it up with tack welds and slits under the car.  You may even find someone selling plastic oval that you can use for mock up.  

You can get the whole lot coated so it won't cook anything under the car too, that's probably an ideal solution.

[Roadkill]

Quoting: EDGE

Could you not at least open up the oval and weld in some angled baffles to help the gasses turn

Just re-read that bit - actually I'd been thinking similar earlier.

I had considered adding something before the "pods" were welded on but was "to the wall" with time so they got forgotten.

I am considering insert a 32mm wide strip of stainless flat . . . . If it was long enough it could be tacked into position at each end before the exit tubes were added which then avoid the need for it to be cut open (cutting and re-welding now would cause too much distortion - it banana'ed last time but we managed to heat it and flatten it back out).

Anyway - I could bend radii into the flat to encourage the gas to flow, like you say . . .

------v---v------

It would look like the above in plan, slide into the oval tube and be tacked at each end . . . theoretically it may resonate a little bit but it's highly unlikely you'll ever hear it !

[Roadkill]

Quoting: EDGE

cross them over behind the trans

So this would be O.K - as the articles I'd read said that the sooner the better for the cross-over ?

That said it wouldn't help at all as any path under the car is too low.  Which is why GM run the pipe in the trans-tunnel.

If I can't join them between the sump and the flywheel I have the same issue everywhere.

[EDGE]

So there's no room at all under the car? How deep do the subframe connectors sit?  There's always a way. Can you get the car up on a 4 post to have a proper look?

[Roadkill]

Quoting: EDGE

So there's no room at all under the car?

To run pipes front-to-back they'd have to be oval (like the ones Martyn showed).

Quoting: EDGE

How deep do the subframe connectors sit?

They're nominally 30mm deep.

Quoting: EDGE

Can you get the car up on a 4 post to have a proper look?

I've spent an accumulated 10+ hours under the car - much of it when it was on 4 high axle stands.

A 4-post lift would be better but not readily available . . . .