getting my head ported right now

Hi Guys;
First off special thanks to Dr Dyno aka Dinno, following his article i have been thinking of doing mine for a long time. Finally today got the machine shop to order the 2.02" intake/1.60" exhaust valves, and they will do a full professional porting, will let you guys know how it feels.

Ravi

Glad you liked my article Ravi.

http://www.jeep4.0performance.4mg.com/head.html

I kept the stock valve sizes on my DIY ported head and just had 0.010" milled off the surface. Since I also used a Mopar Performance gasket (0.043 thick vs 0.051" OEM gasket), I bumped up the compression ratio from 8.8 to 9.1:1.
Little or no gain in torque below 2500rpm but really starts to do the business from 3000rpm upwards. Pulls hard to stock 5250rpm rev limiter and wants more.

thanks for your reply, would you think this(ported head with big valves) warrant new Injectors?, right now, i have your home brew FIPK, bored throttle body. I will however be sending my TB to Accurate power to get it bored even more, Also been thinking about borla header. wanted to know your response on what woud be the best injectors to go for.

Thanks;
ravi

I have Ford Racing 24lb injectors in my 4.0, so you could take the same route especially if you're going to install a header.
My engine runs slightly rich even with the ported head but it doesn't ping in 120* weather despite the higher CR so I'm happy. Gas mileage is about 18mpg city and 20mpg on the highway at an 80mph cruise, so it's about the same as when my 4.0 was bone stock..

Thanks again for your prompt reply, there is some bad news, the machine shop says that they cant get the valves, so i told them to port it as per your write up, hopefully i will get some HP

rav said:

Thanks again for your prompt reply, there is some bad news, the machine shop says that they cant get the valves, so i told them to port it as per your write up, hopefully i will get some HP

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AP has the valves your looking for, and im pretty sure that clifforad and hesco have em too...


how much $ they charging you

PS, your XJ is really coming along!

Hi guys;
After 3 days of testing and clocking 200 miles, i would really like to thank Dino for his Ported head article. There is no loss in the low end torque as many pundits claim.There is no gain in HP on the low end(less than 3000 rpm), but the moment you cross the 3000 rpm mark there is tons of power now, i used to climb the mountains of logan at 50-55, but now its 65-70 mph.
If you look at the non HO head and try and match the intake & the exhaust ports, the holes in the gasket are way too big as compared to the opening's in the head, i just kept the gasket on the head, sprayed it blue ink, took of the gaskets and just took of chunks of metal(i left a liittle bit from the mark that i inscribed, did not want to have the ports bigger then the gasket), coupled with the relocated IAT sensor, there is much better throttle response, now all i need is bigger injectors(like the HO) and send my TB to AP to bore it to 62mm(mine is 60 right now).

Would higly recommend this to any NON-HO head or a HO.

Ravi

rav said:

Hi guys;
After 3 days of testing and clocking 200 miles, i would really like to thank Dino for his Ported head article. There is no loss in the low end torque as many pundits claim.There is no gain in HP on the low end(less than 3000 rpm), but the moment you cross the 3000 rpm mark there is tons of power now, i used to climb the mountains of logan at 50-55, but now its 65-70 mph.
Ravi

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I'm glad you found my article useful Ravi. You've had a very similar result as me from your ported head. I estimate that I gained about 14hp @ 5000rpm from my ported/milled head.
A common mistake that many people make when porting their heads is to enlarge the ports too much. Port airflow velocity is reduced at low rpm and that accounts for the loss of low rpm torque. The key to maintaining low rpm torque while gaining HP is to remove humps, bumps, and any other restrictions that reduce airflow velocity and cause turbulence while matching port cross-sectional area to the valve size. It looks like we've both succeeded there. Job well done!

For those with the larger valves, have you taken into account valve shrouding? I was looking at my spare head the othe rday and remembered some guys put in larger valves , but the valves already seem pretty close to the edge of the combustion chamber and it seems to me that any larger valves might end up actually hurting flow becaus ethey would be that much closer to the cc wall , restricting flow. just curious if anybody has found anything on that. I am working on porting that head right now and i was surprised to see how much can be done weith the ports, they have that huge casting line running right through the middle of them, and i took a lot off of the short turn and right around the valve. Also has anybody experimented with backcut or radiused valves yet? i know that my valves had a factort backcut on them but im wondering how much gain ther eis in machinig the edge off of the cc side of the valve margin,. thanks for the advice, Chief

Chief93XJ said:

For those with the larger valves, have you taken into account valve shrouding? I was looking at my spare head the othe rday and remembered some guys put in larger valves , but the valves already seem pretty close to the edge of the combustion chamber and it seems to me that any larger valves might end up actually hurting flow becaus ethey would be that much closer to the cc wall , restricting flow. just curious if anybody has found anything on that.

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You're absolutely right and that's why I elected to keep the stock size valves. The exhaust valves ARE shrouded as they are in stock form (only 2mm between valve and CC wall) so you can imagine that oversize exhaust valves will be shrouded even more. You can remedy that to an extent by grinding away part of the CC wall closest to the valve, but I could only take away 1mm from the wall before reaching the margin of the head gasket bore.
The stock intake valves have about 5mm of clearance from the CC wall but once you fit oversize intake valves, they also become shrouded. Again, you can only grind away 1mm from the CC wall before reaching the margin of the head gasket bore.
Since ported 4.0 heads with oversize valves have valve shrouding problems, the low lift flow numbers are actually less than with stock size valves and it's only at higher lifts that the flow numbers are greater.

Dr. Dyno said:

Since ported 4.0 heads with oversize valves have valve shrouding problems, the low lift flow numbers are actually less than with stock size valves and it's only at higher lifts that the flow numbers are greater.

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excuse me for my stupidity, but when youre talking lift, what are you referring to? (cam?)

Yeah lift can be described 2 ways 1: as cam lift or how much lift the cam lobes hace or 2: as valve lift as how much the valve actually lifts after factoring in the rocker arm ratio . most rocker arms have a ratio around 1.5: or 1.6:1 . Not to confuse , but as a note, stock rocker arms can be very inaccurate from one another , its not uncommon to see a set of rocker arms that should be 1.5:1, for example, that are actually anywhere from 1.45 to 1.55 or even worse maybe.

hjeepxj said:

excuse me for my stupidity, but when youre talking lift, what are you referring to? (cam?)

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Valve lift, or the distance that the valve is lifted off its seat. Maximum valve lift with the stock 4.0 cam is 0.424" and since the rocker arm ratio is 1.6:1, maximum cam lobe lift is 0.265".

If you DIY be very careful working the floor of the ports as they turn towards the underneath of the seats...the basic shape must be retained or you will get turbulence. The easiest flow gains are mainly in the bowl areas... especially the valveguide bosses. And as with any engine, a good 3 angle valve job should always be done...this helps the air get moving at low lifts. Don't polish the intake ports...you need a course finish to help create a boundry layer...polishing is ok on the exhaust..but does little good.