Totally custom.

Energy Suspension "short wide" polyurethane mounts.

Removing the center of the "U" bend of the rear tube would weaken the cradle, and allow the rear mounting flanges to flex/shift under load, which was one of the problems with the first V8 cradle fabricated by another shop.

http://home.earthlink.net/~jimlab/pi...ine_cradle.jpg

I no longer have the SLP headers, I sold them to someone else because they would have required more work to correct than I was willing to do at the time.

No, the main problem is that the car cannot travel to the fabricator, and the fabricator must therefore come to the car. Otherwise, we have to guess by fabricating headers on a mock-up engine and hope they fit, and then correct them when/if they don't. The ideal solution would be to fabricate headers on the actual engine, in the car, which would require some expensive welding equipment to do the job onsite and a lot of time. The other option is to use some off-the-shelf parts to avoid the cost of having to fabricate so much.

 

That's one of the options I originally mentioned. Phil Tobin is using this style of header on his 10-second NA Corvette. I was concerned that the runner length was too short for a street car, but didn't want to go the opposite direction with longer runners and be stuck with 1 5/8" primary tubes.

 

I don't agree with that. The exhaust gasses are constantly cooling as the pass along the exhaust system, from over 1200F at the port to maybe 300-400F after the muffler. Gas volume is proportional to temp, so a 3 inch Y-pipe near the engine is seeing much hotter gas and therefore more CFM than a 3 inch tailpipe behind a 3-1/2 muffler. The farther you can go before downsizing the less power you'll lose.

If your 396 is above 500 hp at the flywheel, you could choke off 20% or more of that thru one 3 inch system. You might need to spend at least 10% of your engine's cost to keep from losing that 20% power. That seems like a reasonable cost/benefit to me, and for high-dollar engines, that's probably a high %.

My $.02.

 

Did you look at the picture that I posted? A U bend doesn’t have much inherent strength without bracing, if you cut it out and replace it with a straight section like the red line I added to the picture you will end up with a stronger cradle and more room.

Well, I’ve already said that in that case what I would do is just use a cheap mig, tack them, take them off and take them to his shop. It will run you $200. For that matter, the only 2 guys that I know of that I would trust to do this kind of work both have multiple mobile rigs (one has 2 complete trailers setup to ‘fix’ race cars at the track). Really, if I needed it I’d use it as an excuse to get a nice tig setup and do it myself, my welding skills are sufficient, my equipment is lacking though, maybe a plasma cutter also.

FWIW, I’m in total agreement with OldSStroker (I’m starting to see a trend here, haven’t I typed that sentence before? I think that you said something about us thinking alike first…), as exhaust gasses cool they take up less volume, and for the most part, you want to keep exhaust velocity up to prevent any reversion or other flow problems in the exhaust. Every car I own and a few others that I’ve setup are built with smaller tailpipes then collector, down pipes, intermediate pipes… I’m a big fan of 2 3” pipes, a Y into a single 3.5, ending up with a single 3” tailpipe or possibly twin 2.5 or even 2.25” pipes. On a street car you don’t loose any thing but noise (if it’s a race car, why are you running all those pipes, they’re just extra weight ). You just want to make sure that the transitions are smooth.

 

Yes, I did. I took your red line to mean that you were advocating eliminating the rear center section altogether, because putting a cross bar in where your line was located would mean running it through the sump of the Canton pan.

http://www.torquecentral.com/attachm...=&postid=96248

A perpendicular bar could be added just in front of the sump, and would add a little room to pass the exhaust under the pan, and from what I now understand you were discussing, would retain the strength. I don't believe that the U-bend is by any means weak, however.

Sounds like good advice. Clearance is an issue that may dictate the use of smaller diameter tubing, however. We'll see.

 

Jim, have you consider using oval tubing for the header-back exhaust? Ovaltech makes some nice 3" oval tubing, which would probably let you run duals tucked up under the body somewhere.

If you have issues with muffler clearance, you could probably run them into a dual-in, single-out Dynomax Ultraflow-type muffler. Great performance, not too loud, and it would probably fit too!

 

We've been looking at the oval pipe for going under the pan and keeping ground clearance at maximum, but haven't started looking at the rest of the exhaust yet. I was planning to run a Borla XR-1 in the mid-pipe (where the main catalytic converter would have gone) but I don't know if there are any ready-made 3.5" mid-pipes available. I'll have to check.

The exhaust for the rotary (aftermarket) was a 3" downpipe to a 3" mid-pipe to a 3" cat-back along the passenger's side of the transmission. The slave cylinder on the T56 is in the way of running anything along the driver's side of the car, unfortunately, and there wasn't that much room there to begin with, even with the smaller OEM 5-speed.

 

By in the way, do you mean that things would get so close that you’d melt the frp cylinder or do you mean completely in the way?

If it’s too close it would be a simple matter to adapt an aluminum, girling race style cylinder, and if it’s completely in the way you could always convert to an LS1 style front plate and throwout cylinder which would completely eliminate a slave hanging off the side (it fits around the input shaft on the LS1, completely in the bellhousing)

 

I mean completely in the way. This car was never intended to have a T56 in the transmission tunnel. Here's a couple comparison shots with a stock RX-7 5-speed...

http://home.earthlink.net/~jimlab/pi..._back_view.jpg
http://home.earthlink.net/~jimlab/pi..._side_view.jpg

The stock exhaust was on the passenger side (all of a rotary's exhaust ports are on that side) so it was never intended to have exhaust on the driver's side. As such, there's no room in the transmission tunnel for it, especially with the increased bulk of the T56.

Since I'm having trouble finding an aftermarket solution for a slave cylinder anyway (the stock pre-bled setup won't work on my car, so I have to run an aftermarket or OEM master cylinder from another application anyway) I've been looking into a hydraulic throw-out conversion. That would mean that I'd have to sell my LT1 Street Twin, of course, and get an LS1-style version instead, I assume.

However, then I could use the McLeod SFI-approved "universal" bellhousing (which doesn't have provisions for an LT1-style slave cylinder, apparently), which would solve two problems at once. I happen to like my feet and I'd like to keep them on the end of my legs, if possible.

 

Looks like I'd need the following:

8710-05 - McLeod LT1 T56 modular bell housing
73010-07 - McLeod LT1 push-type hyd. T/O bearing conversion kit
63050-00-07 - McLeod LS1 Street Twin, aluminum flywheel

And now I need to know if the Corvette lightweight starter for the LT1 will work with a 168-tooth flywheel. Anyone know? Otherwise, I'll need a CSI (or whatever) aftermarket starter.

 

even tho the stock GM unit is "prebled" you can take it appart, and put it back together then rebleed.. fyi.

 

I know, but the master cylinder won't work in the FD, so people have been "converting" the slave cylinder with -04 braided line to use with a GM full size pickup master cylinder or Wilwood master cylinder instead. It's sort of a hack, though. I'd rather have a well-engineered system, and I think that converting to a hydraulic throw-out solves a lot of issues.

 

Trey? Dynatech pictures??

 

I'm sorry Jim,
Last weekend was a clutter ***
I got ZERO done on anything due to an unfortunat chain of unplanned events. Would some low Resolution pics of the headers in the vehicle suffice for now?

 

Sure.