cylinder heads what works?

[TimTona]

i got a spare set of 3.0 heads whats the best way to get power outta them for the least money porting? 3-5 angle valve job? shave the heads?

[Ntrain2k]

For a budget build I would shave them just enough to make sure they are flat, good basic gasket match and port and polish, then a three angle.

Be sure to gasket match and port the intake and exhaust manifolds too.

[c2xejk]

Quote:

Originally Posted by Ntrain2k For a budget build I would shave them just enough to make sure they are flat, good basic gasket match and port and polish, then a three angle. Be sure to gasket match and port the intake and exhaust manifolds too.

To know if you have made progress, you really need a flow bench and velocity probes.

The stock intake port is too big and both ports are too big at the gasket surface... You can probably make mild improvements by slightly reshaping the short-side radius, but take too much material and you will kill flow...

If the intake port is too big, port velocity is too low and you have reversion... (exhaust gas going into the intake...)

As for the exhaust port, I have been working on a relatively cheap way to reduce the exhaust port exit area... So far so good, flow is up just slightly. Exhaust port velocities are much better. Surprisingly, the results are even better after I have ported the exhaust port.

Right now I am looking for somebody to dyne test them...

[Tim_K]

I remember reading somewhere around here a while back that the thing to do in the exhaust ports was to raise the roof (long side radius) some, in the area around the valve guide. Don't have any flow bench numbers on it, though.

I have a set of V6 heads that got some mild porting, and I took out some aluminum in the roof area around the guide and into the port a bit. It seems to open up a restricted part of the port some, but only the flow bench and dyno can tell for sure if it was a good idea.

What about using larger exhaust valves along with stock intakes, and 3 and 5 angle valve jobs? Is a 5 angle really any better than a 3 for the extra money spent on it?

[c2xejk]

So far I taken the exhaust port from 103 CFM to about 135 CFM on the stock valve...(all measurements were on my flowbench, other benches may yield different results.)

A larger valve would help exhaust flow. How much it would help hp is currently unknown.

I say that becasue, so far nobody (myself included) has determined how sensitive the motor is to improvements in the exhaust flow... That said, the E/I flow ratio is rather abysmal in stock configuration, so I tend to believe that the engine will be responsive to exhaust changes, but that is a guess at best and does not fully consider the multitude of other variables...

[Ondonti]

You have all my exhaust numbers right? (and how they compare to a stock head on the same bench).
I think my numbers are sort of hard to interpret or cross compare.
They show a healthier stock exhaust port with the same plateau but a stock intake port that doesnt move as much air and plateaus in the higher lifts numbers...not to mention the 13cfm difference between an good stock intake port and a stock intake port with lots of casting flash on the shortside.


Anyways, have you been able to help the low lift exhaust numbers? seems in the past and on my own that was not achieved. That seems to lead to the need for bigger cams which at least make use of the higher lift increases that are possible...and that bias would seem to create a conundrum when trying to turbocharge and limit exhaust reversion while helping the exhaust port move more air.

I guess I dont know what change in my heads even caused the higher lift increases. Also some of the work could have been very uncomplimentary to overall improvement.

Higher combustion pressures/densities from turbocharging might also make my exhaust ports behave very differently (either good/bad)

I guess thinking about that makes me wonder how useful exhaust port measures really are. many cylinders see 1000+psi pressure (and this # is still quite high when the valves actually open) and this great pressure + momentum of piston moving upwards after BDC has to fight against or be pulled by whatever is outside the exhaust valve. I am rambling...avoiding doing my last paper for finals :P

[c2xejk]

A good exhaust port is difficult to design on a flow bench... General, if you open up the flange area, bench flow will go up, but engine hp will go down... (ie. the same shape as the stock port...)

The reason, air velocity goes down... Hence I have been considering selling some exhaust port inserts...

As for low lift flow improvements, oddly the best way to improve low lift flow is to keep throat SMALL. Unfortunately, the stock throat is big to start with... So either you need to weld the throat or go with a larger valve and keep the throat as small as possible...

[Ondonti]

I find that weird as mr G. bell seems to think exhaust port diameter should be .9-1.0 the diameter of the exhaust valve.
The stock throat is about .55-.6 of the stock exhaust valve diameter from what I had measured on Franks cut up heads.

Anyways I didnt touch at least 1" from the flange area beyond removing casting flash.
I do wonder if deshrouding the exhaust valve hurt or helped. Apparently at least on some motors partial shrouding can help HP (I dont know about flowbench #'s though). I did a pretty massive deshrouding simply because there was plenty of room and the bigger valves sort of screwed up whatever was the stock shrouding. I figure it helped the low lift Intake numbers on the bigger valve but apparently not the exhaust.

The goofy "pockets" that the valves are seated in just complicate things when you go to a bigger valve because you need to remove lots of material just to get back to stock shrouding.

[TimTona]

how about diamante or montero cams is there any improvement in them or the valves?

[c2xejk]

Quote:

Originally Posted by Ondonti I find that weird as mr G. bell seems to think exhaust port diameter should be .9-1.0 the diameter of the exhaust valve. The stock throat is about .55-.6 of the stock exhaust valve diameter from what I had measured on Franks cut up heads.

You are measuring the wrong areas... The throat is the narrowest area under the seat. On a stock 3L head it is about .87 valve head. Doesn't leave much room for improvement. As a general rule of thumb, you want to keep it in the .85-.90 range. Smaller for street applications.

Push it much beyond that and you will think you have made a gain since high end numbers will go up. Unfortunately, you likely will have killed hp...

As for the port diameter. The rule of thumb is .8-1.0. For street cars, you will be much happier at .8. Going to 1.0 may yield top end gains, but hurt low rpm power... To realise the top-end gains, you will need to really be on your game and have other parameters correct...

The stock 3L exhaust port has the exit at >1.0... Not good... I would guess everybody hear would benifit from shrinking the exhaust port exit to .8-.9. You want that exhaust gas to be moving FAST...

The fact I have seen flow bench gains by reducing the port exit makes me believe I have not reduced it enough yet... The best hp gains will come with reducing the exit even further...

Quote:

Anyways I didnt touch at least 1" from the flange area beyond removing casting flash. I do wonder if deshrouding the exhaust valve hurt or helped. Apparently at least on some motors partial shrouding can help HP (I dont know about flowbench #'s though). I did a pretty massive deshrouding simply because there was plenty of room and the bigger valves sort of screwed up whatever was the stock shrouding. I figure it helped the low lift Intake numbers on the bigger valve but apparently not the exhaust.

In your case you had to do some deshrouding because of larger valves... Most cylinder heads do well with shrouding simply because you don't want to dump the air directly into a vacuum (speaking about the intake side...) You need to "transition" it by having a "pressure recovery" area.

Deshrouding is one of the areas that a flow bench can lie to you on. Flow gains from deshrouding are not always engine hp gains. That said, with stock size valve, I don't believe there is much benifit to deshrouding...

Quote:

The goofy "pockets" that the valves are seated in just complicate things when you go to a bigger valve because you need to remove lots of material just to get back to stock shrouding.

[RoadWarrior222]

Quote:

Originally Posted by Ondonti I find that weird as mr G. bell seems to think exhaust port diameter should be .9-1.0 the diameter of the exhaust valve. The stock throat is about .55-.6 of the stock exhaust valve diameter from what I had measured on Franks cut up heads.

Yeah I did my own figuring for ideal exhaust port diameter, for fat midrange N/A torque and HP peak @ 6000 and came up with 1.25 which is 0.905 of the 1.38 valve diameter, (And I'll take a set of SS headers with 44" primaries in that diameter too please, I've got a crisp new $50 bill waiting )

[Ondonti]

Quote:

Originally Posted by c2xejk You are measuring the wrong areas... The throat is the narrowest area under the seat. On a stock 3L head it is about .87 valve head. Doesn't leave much room for improvement. As a general rule of thumb, you want to keep it in the .85-.90 range. Smaller for street applications. Push it much beyond that and you will think you have made a gain since high end numbers will go up. Unfortunately, you likely will have killed hp... As for the port diameter. The rule of thumb is .8-1.0. For street cars, you will be much happier at .8. Going to 1.0 may yield top end gains, but hurt low rpm power... To realise the top-end gains, you will need to really be on your game and have other parameters correct... The stock 3L exhaust port has the exit at >1.0... Not good... I would guess everybody hear would benifit from shrinking the exhaust port exit to .8-.9. You want that exhaust gas to be moving FAST... The fact I have seen flow bench gains by reducing the port exit makes me believe I have not reduced it enough yet... The best hp gains will come with reducing the exit even further... In your case you had to do some deshrouding because of larger valves... Most cylinder heads do well with shrouding simply because you don't want to dump the air directly into a vacuum (speaking about the intake side...) You need to "transition" it by having a "pressure recovery" area. Deshrouding is one of the areas that a flow bench can lie to you on. Flow gains from deshrouding are not always engine hp gains. That said, with stock size valve, I don't believe there is much benifit to deshrouding...

I was measuring from the shortside @ a 45 deg angle to the roof, pretending the porrt was round, and getting .6 or so of the exhaust valve....I think. That was a LONG time ago. . I realize that the port opens up horizontally at this point but I dont know how much difference that makes.

Edit: I just looked at the crossection pictures and I definitly made a mistake years ago as I was comparing the exit diameter not the exhaust valve diameter. I think i did that cause when i stuck an exhaust valve backwards into the exhaust port, it sinks in about a centimeter so I figured they are similar sizes. dont really remember now what i was actually comparing to.

[kreel]

I'm looking to eventually do a bunch of head work when I get the chance. Are there any real good books or resources that you guys can recommend? After reading through this post I have an idea what is going on...but I'd like to learn a lot more of the general details. Thanks.

[irocelectric93]

Doesn't lonewolf do 12v heads?

[RoadWarrior222]

Quote:

Originally Posted by kreel I'm looking to eventually do a bunch of head work when I get the chance. Are there any real good books or resources that you guys can recommend? After reading through this post I have an idea what is going on...but I'd like to learn a lot more of the general details. Thanks.

Found an amazingly good article the other day...
Cylinder Head Porting Basics - Popular Hot Rodding Magazine

RW222

Edit: BTW there's some head section pics for the 3.0 that might help people figure it out...
Here