Ported or home made manifold

[scottmcguinness172]

Hey all has anyone here modified a 5 litre manifold like ported it or made a twin throttle body manifold as I'm looking at doing it to mine?

 

[ephect]

Have seen dual arts on the 5L manifold, was another throttle body housing welded on the other side. Standard pointing right, additional pointing left.

Benefits? No idea, but I would suggest porting would be more benefitial than just adding another throttlebody.

 

[scottmcguinness172]

I was going to mill the top of mine off and mill the guts out and make a new top and put a second throttle body on it

 

[pjdm1980]

Probably better off just buying a low rise manifold and a 1000cfm throttle body. I don't know much about the standard manifolds but I think they're pretty rubbish for any engine that likes to rev.



PJDM1980

 

[scottmcguinness172]

I was thinking that and making up a snout for the throttle body on it what about ports for the injectors?

 

[Deuce]

Benefits? No idea, but I would suggest porting would be more beneficial than just adding another throttlebody.

I thought the reason 304's didn't make anymore power after about 5000rpm was because the standard throttle body physically could not flow enough air to a full 5litres at that sort of RPM? That is why so many gains can be made from switching throttle body's or fitting larger ones (70mm bolt on, or even 90mm on mildly modified intake)

if you enlarge the intake runners wouldn't you slow airspeed at low RPM and kill off a little torque? Whilst of course improving flow at high RPM, but to no advantage as your throttlebody can not keep up??

I think you should fit larger or multiple throttle body's and don't touch the internals of the bananas. IMO

just my thoughts, someone please feel free to prove me wrong.

 

[ephect]

adding a larger throttle is different to adding an additional one, its all about maintaining airspeed throughout the engine.

Its all about matching your mods for the greater gain, so say adding dual smaller throttles keeping airspeed at a max will help it more than dumping on the largest throttle available. same with exhausts, it will run like **** dropping on 4inch pipes.

porting/polishing is free and you can achive great results. yes u may lose a little airspeed if the throttle area hasnt bee matched or taken into consideration.

there is always a down side: unless your consistant with ur machining/porting it can be difficult to keep every runner/port flowing the same amount. so one cylinder could end up running leaner or richer, so you may burn out 1 or 2 plugs quicker than normal

 

[Deuce]

That seems to make sense, cheers Ephect

 

[ephect]

No worries, glad it made some sense

 

[pungent]

I have done a basic clean up of a few standard manifold's a couple of years ago.

You can clean up the elbow A lot just by smoothing it out and also taking some out of the inside of the elbow so the air can get sucked straight into the manifold.

Also I got an extention on the die grinder and cleaned up all the runners as high as the extension could reach. I stress the clean up part, take out any dags etc not make any larger. Create extra flow without loosing air speed.

I have noticed on A few different manifolds that the port to runner alignment on number 5 and 7 are terrible. Up to 5mm + out of alignment.

With an injected manifold you can smooth everything out as much as you can and will increase air flow unlike A carby manifold where you need to keep the surface A little rough to help the fuel and air mix together.

My current vehicle is basically A standard engine with A crane 276 cam. Factory style extractors and my own custom tune, just putting A 70mm throttlebody and high flow airbox top on made A huge noticable difference.