Hi,
My B16 head is going for servicing soon, and I figured it could benefit from a little extra care. I was searching around and found what supposedly Honda did to the ITR/CTR heads: "Valve seat angles changed to 30-45-65 degrees (instead of 30-45-60) and the seat throats were opened 0.25mm."
The idea for this build is to squeeze every horsepower from a stock block and stock head (stock cams and valvetrain), kinda like an N1-spec engine. So, are those specs really what is found on a ITR/CTR head and will they benefit my build? Or maybe they are plain wrong will actually ruin the head flow? Any advice is welcome, and keep in mind I don't have access to other cams or a bigger block.

 

Definitely pointless to try adjusting this on a bone stock B16 head. The ITR/CTR heads were made with the larger ports and different angles with their more aggressive camshafts in mind. The tiny B16 cams won't benefit from this.

 

Thank you for replying. So there are no gains to be had anywhere in the head with stock cams? I'll use a thinner head gasket so milling the head will not be useful. I know this is off the original topic, but is there any work that can be done to the intake manifold regarding porting/polishing? I'll be running the stock TB bored to 64mm as it has been tested to gain about 4hp/2ftlbs from 6k and up and its not big enough to hinder velocity at low rpms and lose power. Just trying to get the most from what I already have and learn in the process, as I don't have any access (and a liberal budget) to get performance parts. Head work, machining and etc is far more accessible in my position.

 

Port matching the TB to intake is always good, polishing the intake manifold is also a good maneuver. Besides that though there's not much you can do to a stock 1.6L engine to gain power without swapping out internal parts and bolt ons.

Can try to clean up the exhaust manifold and remove all the carbon deposits which may not really bump power but would be an added "clean" step.

 

Great, I'll definitely match the TB to the manifold. As with polishing the intake, the objective is to get rid of any casting marks and getting the runners as smooth as possible, right? Is it a good idea to also match the intake manifold ports to the head ports? (using the head as a reference, not the gasket).

I'll probably get the exhaust manifold ports bigger than the head as an anti-reversion step.
Regarding the setup it will basically be a 3" short ram, 64mm TB, 10.5:1 compression, Adjustable Cam Gears, DC JDM 4-1 header, 2.5" Exhaust, FPR and a set of Bosch injectors. Will be tuned on a chipped P30 using HTS. Hoping for 180hp at the crank on a freshly rebuilt engine and a little more on E85 down the road.

 

ITR-heads factory portwork is little overvalued, basically they just made finishing from seatmachining to port by hands, Quite basic stuff.
Full radius seats are good proven modification which improve the flow also small valve lifts. But because sealing width is narrow, they won't last as long like traditional seat cuts.

Polishing is usually just cosmetic (and placebo), after prescribed surface quality is achieved, there is not much affect for laminar layer thickness anymore. If something (like casting imperction) affect shape of the port, it should be removed. It is ok if intakemanifold port is slightly smaller than in head, the step is from smaller to bigger. Manifold and throttlebody aren’t your bottlenecks anyway. 62mm ITR tb works well in 190-200hp (at crank) setups.

I recommend cold air intake or somekind airbox with that short ram, sucking warm (less density) air from engine bay reduce your gains. Even then, 180hp at crank from basically stock engine with just header/exhaust is hardly realistic, even when finished and fine tuned well.

 

You can always toss the B16 head and swap a stock Type R cylinder head on! cams manifold and all.. you will have a beefed up B16! not going to be close to a CTR unless you install CTR pistons.

 

Unfortunately, there are no ITR/CTR heads available around here and getting one from other country wouldn't make sense money-wise. That's why I said I'm restricted to OEM cams and pistons, with close to stock compression.

 

You can turn the B16 into a Type R head. the difference is just the extra bowl smoothing in the valve chambers. Of course the camshafts are different. But you don't have to get rid of a B16 head to get a Type R head

 

I see. So there isn't any difference regarding the valve angles and seat throat width between the B16 and the Type R? Interestingly, the ITR service manual states the same 30-45-60 angles, but I couldn't find any info regarding the seat throats.

 

No, they did not change any of those angles. The only thing that was changed for the camshafts, the sets of dual valve springs oh, and the additional Bowl work. That's all that they changed. Honda likes to keep things as simple as they possibly can, and only makes changes when they feel it's absolutely necessary

 

These are pics of my crate B18C5 Type R head brand new! this is straight out the box from the dealer! you can see the bowl work is very minor the port work is very minimal in my opinion!