Exhaust Dilema

topcatcustom · Post by **topcatcustom** » Thu Nov 19, 2009 8:41 am

Right- so now I know where I'm at as the engine is in, and its not the best place to be at!

Basically I have about 100mm for the manifolds, and thats being generous and includes trimming 5mm of the flange off the inside chassis rails. I think a pic would explain better:

The metal that is taking up the room isn't the inner wings- its the big boxy chassis rails (or whatever the proper term is when they're there!) so I dont really want to be chopping them around. As I mentioned before the most I think I can do is 5mm to make the gap 100mm, you can't see the tape but it shows 95mm, and is exactly the same on the other side (phew- means I got the engine in the middle!!!)

The pipes are going to have to exit down infront of the bulkhead (not enough room on the drivers side to go through by the bell housing as starter is in the way) and exit between the front wishbones, going behind the wheel and under the body that way. Not ideal but there is no space!

Because of all this there will be no space for curly equal length primaries which I'm gutted about, and whilst cast manifolds would just about fit, the exhaust ports in the heads are bigger than those in the cast manifolds, and I'm not going to be attempting to open up a cast iron manifold with my die grinder! Anyone got any suggestions as to how I might be able to get near equal length primaries in or shall I just accept that it aint gonna happen?!

What isn't obvious in the pics is that the ports are level with the top of the box rails, and to remind you the ports face down so the pipes can't come up over the chassis without having a nasty kink in them.

bones · Post by **bones** » Thu Nov 19, 2009 9:47 am

the 302 manifolds measured from the outside of flange are 105mm, but you could lose between 10 and 15mm by cutting the pipes back and adapting to fit the rover heads, the manifolds look about 1/2"difference to heads but you could make them fit , a pic of the part you could cut down to 95mm or less as they are square,

kiwicar · Post by **kiwicar** » Thu Nov 19, 2009 11:15 am

Just remembered this is a blown engine, less critical on exhaust tuning length wise but you need to get nice big diamiter primaries in there and good sized secondaries. cant you make up somthing similar to the existing cast manifold but in 1 5/8 or 1 3/4 tube if the standard one will fit?
Mike

topcatcustom · Post by **topcatcustom** » Thu Nov 19, 2009 3:50 pm

Mike, I'm planning on using some chevy manifolds of Rich's which are 1 5/8 so should be perfect size- I'm not going to get race quality pipes and this is supposed to be a fun car so will just go for it with a grinder and welder!

bodger · Post by **bodger** » Thu Nov 19, 2009 3:58 pm

what about some MGB block huggers ?
they turn quite tight

or these , yum yum

http://www.fastcarsinc.com/headers.htm

mgbv8 · Post by **mgbv8** » Thu Nov 19, 2009 7:26 pm

I reckon block huggers will fit in there Tom!!
And their quite lightweight, so easy to tweak

JJMclure · Post by **JJMclure** » Fri Nov 20, 2009 8:53 pm

any good to you?

http://www.summitracing.com/search/Depa ... Asc&RC=100

ian.stewart · Post by **ian.stewart** » Fri Nov 20, 2009 9:02 pm

What about TVR reverse manifolds, cut the silly collectors off and route them individually down and under each engine mount.

topcatcustom · Post by **topcatcustom** » Mon Nov 23, 2009 9:31 am

Bodger they are very nice looking!!! I'm still not over keen on huggers and I can fit something slightly better than them in there- the other prob I have discovered since getting under the car again is that I can't run the secondary pipes down the middle of the car very easily without them hanging quite low, they will be a lot happier at the sides running along side the chassis rails. This unfortunately means I wont be able to fit in my X pipe system

but will it really matter?

bigaldart · Post by **bigaldart** » Mon Nov 23, 2009 7:42 pm

TC,

I doubt very much you will miss the slight torque increase from an X pipe on your motor

Give it enough fuel and air, let it eat, and you will never lose the grin

Alan

14500rpm · Post by **14500rpm** » Mon Nov 23, 2009 8:02 pm

topcatproduction wrote:Bodger they are very nice looking!!! I'm still not over keen on huggers and I can fit something slightly better than them in there- the other prob I have discovered since getting under the car again is that I can't run the secondary pipes down the middle of the car very easily without them hanging quite low, they will be a lot happier at the sides running along side the chassis rails. This unfortunately means I wont be able to fit in my X pipe system but will it really matter?

This is what was done on my car, it does warm your ankles when getting out.

Drivers side wheel arch:

topcatcustom · Post by **topcatcustom** » Mon Nov 23, 2009 8:52 pm

Can I assume your name is Andy??! And that this is the car??? http://freespace.virgin.net/bob.carter/Mazda_mx5_V8.htm

14500rpm · Post by **14500rpm** » Tue Nov 24, 2009 11:41 am

topcatproduction wrote:Can I assume your name is Andy??! And that this is the car??? http://freespace.virgin.net/bob.carter/Mazda_mx5_V8.htm

Guilty as charged

topcatcustom · Post by **topcatcustom** » Tue Nov 24, 2009 1:02 pm

Got ya!

So guys, how does 4-2-2 compare to 4-2-1 on each bank? I'm assuming 4-2-1 has to be a bit better? If I kept 4 pipes all the way like Andy's one I could put bike cans on hte rear and have 4 mufflers

topcatcustom · Post by **topcatcustom** » Wed Nov 25, 2009 9:25 am

Come on Mike! I know your begging to tell me the cons of running twice as many smaller pipes! Also should the left bank not be linked 2+6, 4+8 or is the right bank that should be done like that?