Manifold design

[jay28]

The main reason Im doing this is that my exhaust that I have on the car now was the one that came with the first rusty Z I bought, its only a 1 3/4" which is too small, I was told it should be al least 2 1/2".

So I thought I might aswell do the manifold while im at it.

Compression ratio.........I dont know, I asked on loads of threads and got no answers, I dont know what cc my chambers have since the head was skimmed 2mm, its around 10/1

Dellorto's are 40's and not been properly jetted jet, another reason to get the exhaust sorted.
The ports were only cleaned up so no real headwork worth talking about.
The Cam is a Schneider, 290, 495.

I dont drive like a mad man but I do like to "Drive" the car, im rarly below 3k rpm.

What the placement of the last collector about? do tell!

Thanks

Jay

 

[SKiddell]

What the placement of the last collector about? do tell!

work done in the past by various parties from all over the globe places the final collector back along the gearbox almost at the shifter for good mid to top end power and torque, poor placement will hamstring an engine, however most owners dont know this as they dont have the benefit of comparative data and to many people an exhaust is just a bit of pipe.

Your carbs are ok for the setup you have but possibly wont flow well enough to justify a 1 3/4 header design... particularly if you are considering moving to a stroker setup....most big power L series's run 45's, 48's or even 50's. The L series loves cam overlap which allows scavenging to take place (the assisted removal of spent gases by the inetia caused by the pressure drop of preceeding exhaust pulses) of course too much overlap can cause reversion, (exhaust gases being dragged back up the inlet tract) polluting the fresh charge, creating lumpy idle and affecting cylinder pressure at lower rpms. if your gas speed is low due to a large (or to small) primary then this vital scavenging process can be affected and upset, finally the cam you have is the Schieder stage 4 which doesnt have large lift on overlap, coupled with a possibly modest compression ratio means that maintaining a high gas speed via strategic use of primary sizes will be important....

Getting back in my box now...

 

[moggy240]

Hi All.

Reason I dont want to make the collectors is Ide need a proper saw to cut them, an angle grinder would be too messy and there would be alot of trial and error, I have pipe benders, tig and everything else I need in the garage apart from the saw.

Cheers for the advice guys and keep it coming.

you could try simpson race exhausts as they list 3 into 1 collectors on their website and

 

[SeanDezart]

Or more simply put - use 1 3/4" primarys (int dimension) and bigger carbs or forget about the new crank !

 

[jay28]

Ok lots of info there, most I understand ..........Yeah I was expecting the carbs would be too small for a stroker.

Which collector goes further back?, how would moving one collector further back make a difference, surly you would have to move both of them back? So the primaries for say cylinders 3-6 would be much longer for the first 3?

I thought the idea of a tuned header was to have all primary lengths identical?

 

[jay28]

Or more simply put - use 1 3/4" primarys (int dimension) and bigger carbs or forget about the new crank !

Well im nopt going to make a manifold with 1 5/8 primaries now and then come along a couple years down the road with a strokewr and find they are too small........The 1 3/4 primarys may not be the best for my current engine but will still be alot better than my current system and still be suitable for a stroker.

 

[jay28]

you could try simpson race exhausts as they list 3 into 1 collectors on their website and

Thanks for that Moggy, I'll look into it.

 

[samuri-240]

Sounds like the 1 3/4" Nismo I am about to fit is not the best choice for my DJR short stroke 2.6 then !!!

 

[jay28]

Sounds like the 1 3/4" Nismo I am about to fit is not the best choice for my DJR short stroke 2.6 then !!!

Any chance of some close up pics?

 

[samuri-240]

Any chance of some close up pics?

Yep can do pm me your email address & I'll send some over the weekend, its a shame you did not live nearer you could have borrowed it to take your diamensions.

 

[jay28]

Yep can do pm me your email address & I'll send some over the weekend, its a shame you did not live nearer you could have borrowed it to take your diamensions.

Yeah its a pity, any 240/260'z over here are all standard so ive nothing to go off really, but pics will be a huge help,

Thanks alot

 

[samuri-240]

Hi Jay just remembered I still have a GDS manifold here & a Janspeed aswell would you like some pics of them ? Which manifold do you have at the mo ?

 

[jay28]

I have an MSA 6-1 manifold at the moment, I think pics of the NISMO manifold will do, I'll concentrate on that one I think.

No rush with the pics whenever you get a chance.

Thanks again!!
Jay

 

[SKiddell]

Which collector goes further back?, how would moving one collector further back make a difference, surly you would have to move both of them back

As in my post....the final collector (there are three)
After the 2 groups or banks of 3 have been "collected" (which is approximately at the base of the back of the sump just before it nips under the passenger footwell) they merge into 1, this is the final collector and most systems, GDS, Fourways, MSA etc collect this too early almost half way up the ruddy firewall, killing the gas speed......15 -20 hp on the dyno says so.

So in short, collector 1 and 2 (primaries) merge approx at the back of the sump (not half way up the engine) with the final one at the back of the gearbox some 2.5-3 feet futher on (not at the bottom of the firewall).

 

[SeanDezart]

Sounds like the 1 3/4" Nismo I am about to fit is not the best choice for my DJR short stroke 2.6 then !!!

Why not ? If your engine is going to rev.....it's going to need to breathe - what carbs have you, what comp ratio ?

DJR and I are having 5 made ( 1 3/4") - 3 are already spoken for, he's probably keeping one for a future engine client, that leaves one to be sold on the open market in stainless steel............

 

[jay28]

As in my post....the final collector (there are three)
After the 2 groups or banks of 3 have been "collected" (which is approximately at the base of the back of the sump just before it nips under the passenger footwell) they merge into 1, this is the final collector and most systems, GDS, Fourways, MSA etc collect this too early almost half way up the ruddy firewall, killing the gas speed......15 -20 hp on the dyno says so.

So in short, collector 1 and 2 (primaries) merge approx at the back of the sump (not half way up the engine) with the final one at the back of the gearbox some 2.5-3 feet futher on (not at the bottom of the firewall).

Im putting a twin system on mine.........So I wont be using a third collector.

Its going to be similar th the system below

 

[SeanDezart]

Mine - with an expansion box in the middle and another at the rear (note where the two down pipes connect) :

 

[Nigel Brook]

Any chance of some close up pics?

Think I put some/one on a thread somewhere.

 

[SKiddell]

Im putting a twin system on mine.........So I wont be using a third collector.

So the back box has two completely independant and isolated tubes running through it with no gas cross over.

 

[jay28]

So the back box has two completely independant and isolated tubes running through it with no gas cross over.

Yeah both pipes are independant they dont rossover anywhere not even in th rear box. is this a good or bad thing?

Thanks for the pics I see now what you meant by the 3rd collector