Manifold to Head Alignment

[trikesrule]

Hi guys. This 1200 Corolla Speedway car I'm working on has the manifolds off at the moment and I'm just finished puting studs in instead of the traditional bolts. One thing I noticed when I was checking the manifolds port alignment and fit over the studs was that that both manifolds are quite a bit larger than the ports. Now this class has a NO PORTING rule but what I'm wondering is there an advantage in off setting the manifold one direction so that the port floor lines up (or may be another). I read somewhere a while back that it was all important to have one line up but as it was so long ago I don't remember which............trikes

[JohnD]

trikes,
I haven't seen that suggestion before but it is a good point. If the port/manifold join is on a bend, the edges at the outside circumference of the bend should be lined up. The fastest flow should be there.
John

[Notso Swift]

Yes, the long side

It says no porting, but what about adding something... liquid metal or some similar epoxy to reduce the manifold to a smooth transition to the head.

[trikesrule]

The long side. Thanks I'll give that a go. Rules also stipulate stock appearing. Basicly if your head must pass tech at every meet. She's a strict class for sure but 35 cars running 4 - 5 wide and not touching each other is good watching

[phoenix]

But do the same rules apply to the manifold?

As Noto Swift suggested, I would modify the manifold to match the head. Any step down will cause undesirable turbulence which should be avoided if at all possible. A smooth taper in the manifold will get round this problem and may even improve torque at low to mid engine speeds.

[trikesrule]

Had to sit down and reread the engine section in the rule book looking for gray areas regarding manifold(s). The good book says ' Inlet manifold and exhaust manifold must bolt on without any modification to either head or manifold(s)'. Definately a gray area don't you agree. I think I carefully need to speak with a scrutineer or tech guy here.............trikes

[terence]

. The good book says ' Inlet manifold and exhaust manifold must bolt on without any modification to either head or manifold(s)'. Definately a gray area don't you agree.


I would have read ANY modification as being the diffinative guide to that paragraph.

[GordonG]

How about: Dont modify the head or manifold, but create an additional piece that is sandwiched between them that provides a shape extending into the manifold that smooths the transition. If you were to get an exhaust gasket (or laser cut steel plate in the shape of a gasket) that matched the head port shape, you could then use chemical metal (or something) to add onto the gasket a shape that blends into the manifold.

It might be as simple as bolting the gasket onto the manifold, smearing the inside of the manifold with grease to prevent the epoxy from sticking, and just laying the epoxy in there with a lolipop stick! If we're talking about the exhaust side it's unlikely that anything would drop into the engine if it did come loose - more likely to be blown out the tailpipe.

If chemical metal etc wont handle the temperature, you might have to use plaster, wax or something to make a buck then cast the shapes in iron. Or something.

The "gasket" then comes away from the manifold. Neither the manifold nor the head have been modified. You're just running a high performance manifold ;-)

On a related topic, why would a manufacturuer produce a manifold that so badly matches the head? I know there are prodiuction tolerances, but I've seen manifolds that are totally different shapes from the head port, and that's jsut wrong.

G

[Chris Y]

Originally Posted by GordonG

How about: Dont modify the head or manifold, but create an additional piece that is sandwiched between them that provides a shape extending into the manifold that smooths the transition.

That's a very good point, the regs say the manifold should 'bolt on' without modification - it doesn't say what it should bolt to!

[coln72]

Dont ask, just do it and argue about it later But have an unmodified manifold on hand just in case.

Be careful with the studs as it can be very tight getting the manifold on and off if they are too long.

I know there are at least two different port sizes in Corolla manifolds too. A quick look around the wreckers may help.

[trikesrule]

Gordo I love it thats cheeky enough for me to just about be able to get away with that. I reckon KB Weld would work well enough as Motoman uses it in the inlet tracts and I've actually used KB for making 'stuffers' in the bottom of two stroke crankcases. Yeah I reckon that may just work a treat - thanks Gordo I'll do a before and after on the dyno to see if it was worth while. Got two cars on the dyno on the 9th..........trikes

[coln72]

Another option could be finding an early Corolla head. These have much bigger ports so they should line up with your manifolds better. They are identified by a welch plug in the rear of the head instead of a bolt on plate.

[trikesrule]

Thanks coln I'll have a look in the spares bin..........trikes