Right, discussion time, well i hope so and not a one answer closed subject.

Example.

Standard head, the known norm is that there only good for 400bhp, but what about torque? i.e can you chuck more boost at it to create a much larger punch\torque lower down, i.e like a resistor on a turbo, and then bleed the boost off at high RPM. Or will this cause serious surge issues.

I.e T4 on a standard head, or a GT30 on a standard head.

I know one of Karls fav conversion is the t4 standard comp setup (i think)

so how far can the envelope be pushed? I guess what im getting at is the thing karl\stu\mike was discussing about pushing a standard engine

 

oh come on people

 

I would like to know the boffins opinions on this as well,as i am tempted to see how far i can push my motor without going headwork etc...

My motor is just rebuilt virtually standard with the only difference being lower comp(7.8:1)

Come on chaps...........

Discuss.....

 

Wouldnt mind knowing this myself

 

What do you want to know, as the answer is in the question. Once past 400bhp its hard to get more power on a std head. Obviously this means if you choose to achieve 400bhp at lower rpm and high boost then yes the torque will be high but ultimately will tail off as the air flow potential is at its max and hence cannot increase to maintain torque and hence bhp.

 

so basically cancels itself out unless you building a sprint car. i.e point to point speed.

Karl, whats the limiting factor on a standard YB head?

simply Port size?

or is that being crued?

 

ryan its all in the primary use of the vehicle, thats it how to spec the engine correctly you need to be able to make use of what youve got but there is ALWAYS a compromise you cannot have your cake and eat it

 

my std head had a 38psi peak

 

The single limiting factor on a standard YB head is the SHOCKINGLY poor valve seat profile and throat shape.

My stage 1 head for example resolves this issue but maintains standard port sizes and can be used to create a comfortable 420bhp with a T4. 450bhp is about the max I go with this spec head.

Stage 2 sees an increase in port sizes to match the revised valve seats and throats and can be used in engines up to 600bhp. Essentially this head has extra flow potential due to the increased port size.

Stage 3 is taking the stage 2 head to the max port size on both inlet and exhaust and is good for 650bhp.

Stage 4 is my latest evolution of head and utilised the stage 3 porting, but I have had the std cosworth valves remade in to std specification but with 1.5mm oversize heads. These heads are good for 750+bhp.

Hence in summary the std head is choking up beyond around 360bhp but will struggle on to 400bhp with the right turbo. Reprofiling the valve seats and throat area can achieve up to 450bhp. After this power level enalrging the ports is necessary but the degree to which this is done is dependant upon the rest of the engine spec, rpm band etc etc.

 

so with mildly enlarged ports, knife edged etc etc, and with the throat shape redeveloped 500-550 bhp is easily achievable as long as all the other engine bits are right for the task?

Karl, thanks for your input, i miss the days when there used to be excellent topic discussed on the board with yours and others input.

Has unforunately become a rarity

 

What you thinking Ryan?

Slapping a "smaller" engine together in the meantime?

I'd love that std engine greys T4 conversion - a lot of power for not too much outlay by the looks of it.

 

550bhp is not "easily" achieved but yes it can be done with the correct head spec without the need for huge ports.

 

yes pon thats bascially it.

A well spec'd 400 bhp engine, i.e with a worked head, and ring its neck for the mean time till i get the car finished and setup and then think about where i want to go, if anywhere.

i.e that power in the car might be perfect with everything else that is there.

I.e pretty similar spec to marco's apart from a different beam and arm setup.

 

yeah sorry, the use of easily was a bit hasty, i meant "is" acheiveable.

 

Karl, have you ever worked on an SR20DET head from a Pulsar GTi-R ? If so what are they like in standard form ?

Cheers

James

 

I think that's a sensible idea.

Will be seriously quick in that spec anyway!

 

Hi,

No I have'nt worked with that engine so can't comment on it's power potential in either std or modded form.

 

possibly not the most sensible no.

but aslong as its setup probably i cant see much difference?

Other than surge?

 

ryan soooooo many people go all out for the 'big' engine spec , then fit it to a fokin piss poor chassis , go with your plan

 

exactly why i've left the engine till last.

only trouble is my house has swallowed up all my budget, damn over spend

My engine is now "the granite worktop" in the kitchen

 

Get some looms bought folks,this man needs a motor...

I`ve just ordered mine...

 

I know they good for over 400bhp on standard head. Cant remember what exact numbers ive seen barring about 420bhp.
Tho im sure i recall some crazy numbers, 500+

 

i do mate, im actually working at the moment making coilpack looms.

I'm fookin broke and crimbo is looming, excuse the pun

 

I have seen quite a lot over 400hp on a standard head.

 

Fantastic bits of info there Karl.

Thanks for sharing that, really interesting stuff