Ok.... I am starting my first thread... I would like to discuss cylinder head porting and what sort of gains can be expected from a good porting job.. Please find attached a flow bench data sheet on some standard TJ 02 heads... I hope other members out there have the same type of information so that I can compare results before and after, of course each flow bench will read slightly different but it should be an interesting read :D

never had my heads flow tested, i just got the guy to go nuts and thats what he did. I didnt get the power gains i was expecting but i didnt change the cam profile, i hope this time around once my new cams go in that i get bigger results

Yeah... I sort of went the same route but IMO the heads really need to matched to the cam profile that way I guess its not so hit miss.... I went the hit and miss route last time and I have ended up disappointed.... this time Im leaving no stones unturned if ya know what I mean ...:confused:

From what I gather, now days flow work doesn't increase HP like it used to. In the days of red block 202's when casting was crude and there was a lot to be gained out of head flowing.

A guy on performance forums "TK" states this a lot, and until you really get high rpm, big cam work the standard head is usually up to the task 98% of a flown head, which equates to about 2kw every 100kw. So for a Magna, thats about 3 to 4 kw gain.

Ok Thanks for your opinion :)

Oh don't get me wrong, there is nothing better than some R&D and time spent in specific areas!! I'll be following the thread closely for sure and can't wait to hear your results, and others.

Thanks Roy... its all good mate ! Im eagerly awaiting some information also

Cheers

A guy on performance forums "TK" states this a lot, and until you really get high rpm, big cam work the standard head is usually up to the task 98% of a flown head, which equates to about 2kw every 100kw. So for a Magna, thats about 3 to 4 kw gain.

Depends on the head. I've spoken to a few different guys who've built magna motors for racing, they found good gains out of the magna heads even with pretty mild cam profiles. One picked up 10-15wkw doing headwork while still using a standard ralliart cam profile.

Btw I've discussed the 6G74 motor with Tony Knight (TK on PF), he had some interesting things to say.


never had my heads flow tested, i just got the guy to go nuts and thats what he did. I didnt get the power gains i was expecting but i didnt change the cam profile, i hope this time around once my new cams go in that i get bigger results

I suspect you probably didn't get decent gains because they stuffed the work up. The idea of flowing heads without flowbench results just screams incompetence.

Unless the guy is very experienced with magna heads, he should have been flow-testing the heads while carrying out the work, multiple times during the process of necessary, to work out exactly what the head is doing. Carrying out head work "blind" without flow-testing along the way rings alarm bells (unless the dude knows that partiuclar head like the back of his hand).

Flowing modern multi-valve alloy heads is a very complicated process to get spot-on, it seems very few around really know what they are doing with them. Most "head guys" can get good numbers out of old school heads, but are lost when it comes to modern alloy heads - Most techniques that work on the former don't work on the latter.

I've spoken to Tony Knight about our motor and the Sprintex setup. He seems to be pretty much the undisputed "head guru" in Aus, and makes his living flowing heads (often huge $$$ builds). Here's what he had to say about the 6G74 motor + Sprintex combo:

"You could probably expect at least a 10% gain in power in the top end & probably more than that through the midrange."

Flowing modern alloy heads properly is a very time-consuming process...he quoted me around $2500 to do it properly. That includes full reco on the heads, porting & flow testing. No cams, standard valves. Oh yeah, he's known for being very reasonable with his prices.

The fact you payed $1600 (if I recall correctly) for your headwork which included oversize valves suggests the job may have been rushed and not done properly.

I hope you'll see some decent gains from the cams. But if your headwork wasn't done right, you may not see great gains.

Interesting little site : http://www.speedwaybids.com/calcs/powerfromcfm.html

As it happens, I have just dropped my new Ralliart heads off at Pro Engines to have them flowed, cleaned up and shaved. Their comment tallys with what others have said over the years on this Forum and have recently shared with me - the ports are already huge and do not need working in any way for an NA engine.

All your efforts should be focussed on deshrouding the valves (if you don't have Ralliart heads), removing all the casting and mould marks from inside the runners, shaving them to bump up CR, and (if you are going to run big cams, piggy back, big plenum) knife edging the runner dividers. My heads should be finished in two weeks, will post results to share.

MMmmm ..... interesting I am eagerly awaiting your before & After flow results .. BTW how much are you taking of the Heads in thou & how much have you taken off your deck height ? Im not so sure on your comments about the ports being huge as the exhaust outlet on the heads is only one inch ..... this is certainly not huge ! :confused: also the lower inlet manifold doesn't match against the heads..... again the ports in the heads are smaller than the lower manifold outlets. Agree with you comments on deshrouding and valve relief ..... as for massive flow difference between the ralliart heads and a standard heads I again eagerly await your results to compare.

Keep me updated


As it happens, I have just dropped my new Ralliart heads off at Pro Engines to have them flowed, cleaned up and shaved. Their comment tallys with what others have said over the years on this Forum and have recently shared with me - the ports are already huge and do not need working in any way for an NA engine.

All your efforts should be focussed on deshrouding the valves (if you don't have Ralliart heads), removing all the casting and mould marks from inside the runners, shaving them to bump up CR, and (if you are going to run big cams, piggy back, big plenum) knife edging the runner dividers. My heads should be finished in two weeks, will post results to share.

This thread looks to deliver some quality results :)

As it happens, I have just dropped my new Ralliart heads off at Pro Engines to have them flowed, cleaned up and shaved. Their comment tallys with what others have said over the years on this Forum and have recently shared with me - the ports are already huge and do not need working in any way for an NA engine.

All your efforts should be focussed on deshrouding the valves (if you don't have Ralliart heads), removing all the casting and mould marks from inside the runners, shaving them to bump up CR, and (if you are going to run big cams, piggy back, big plenum) knife edging the runner dividers. My heads should be finished in two weeks, will post results to share.

Agreed. I think alot of people assume flowing heads means enlarging the ports. But with modern alloy heads often the gains come from re-shaping specific areas of the head, as opposed to simply enlarging the port openings a great deal. I'm not a head expert, but my understanding is most of the gain in flow is picked from reshaping rather than enlarging the ports, and work on the chambers, seats, bowls & short turns.

Well if the ports are too large, you will loose intake velocity. This is basically what EZboys intake manifold was designed to address, keeping intake velocities high without causing excess restriction.

BTW how much are you taking of the Heads in thou & how much have you taken off your deck height ?
Keep me updated
Don't know yet - leaving that to the expert.

Will keep you all updated

Well if the ports are too large, you will loose intake velocity. This is basically what EZboys intake manifold was designed to address, keeping intake velocities high without causing excess restriction.

Yay! It's finally sinking in! :D Top marks to Phonic. In a perfect world I'd like to extend the dual runners into the lower inlet but the injector locations may upset atomisation, who really knows without spending a whole heap of time on the mill and then on the dyno? I'm open for sponsorship offers!

Schnell has hit the nail on the head with most of the work needing to be done with the heads. Graham Bell rattled off that exact list with the addition of upgraded valve-springs in his opinion. Most of the work (ex. deshrouding) can be done by the individual, practice on a junk head from the wreckers alloy bin first - get a feel for how much touch is needed with each cutter etc and what contours you can create and modify. That's all your hard-earned $ will be paying for. As I've always practiced: Why pay for something you can do yourself??

If you're going 'race-spec' get the heads finished and flowed tested by a reputable pro, if not get the dremel out or the die grinder and start throwing chips (of aluminium). With modern heads that are bolted to n/a street cars - LESS IS MORE! It's easy to gut the ports to bits, but that's not what you want to achieve. You should be aiming to minimise the disruptions to air flow into the combustion chamber and then out by port-matching heads and flanges, de-burring, radiiusing, and so on. Lots of info on Honda forums. Peak power isn't everything.

Yay! It's finally sinking in! :D Top marks to Phonic.

Yay me!!!lol .

Seriously it should be common sense, it's the same with exhausts. One of the reasons I fitted a single 3.5" catback to my clubsport in place of the factory twin 2.5". The 3.5" has a smaller overall diameter, but keeps the exhaust velocity higher and actually improved the midrange punch a little without compromising the top end.

As it happens, I have just dropped my new Ralliart heads off at Pro Engines to have them flowed, cleaned up and shaved. Their comment tallys with what others have said over the years on this Forum and have recently shared with me - the ports are already huge and do not need working in any way for an NA engine.

All your efforts should be focussed on deshrouding the valves (if you don't have Ralliart heads), removing all the casting and mould marks from inside the runners, shaving them to bump up CR, and (if you are going to run big cams, piggy back, big plenum) knife edging the runner dividers. My heads should be finished in two weeks, will post results to share.


I have to say i am very interested in what you are doing, as im looking at getting some Ralliart heads and was going to go down the path of shaving them to increase CR. Good luck with it, ill be keeping my eye on this thread, very interesting

Use standard Mitsubishi head gaskets take 2 thou of the deck height as more a resurface & 20 thou off the heads by doing this you will increase your CR & Im sure you will not have any piston to valve issues :confused: but you should be looking at replacing the pistons as well to increase CP not just shaving heads ! :D




I have to say i am very interested in what you are doing, as im looking at getting some Ralliart heads and was going to go down the path of shaving them to increase CR. Good luck with it, ill be keeping my eye on this thread, very interesting

I have to say i am very interested in what you are doing, as im looking at getting some Ralliart heads and was going to go down the path of shaving them to increase CR. Good luck with it, ill be keeping my eye on this thread, very interesting

Wanna be quick, last i heard only half a dozen sets or so left in stock at MMAL

Wanna be quick, last i heard only half a dozen sets or so left in stock at MMAL

oooooooooo might have to dig up some money, any one know how much i would be looking at for the heads and also the Ralliart cams?

oooooooooo might have to dig up some money, any one know how much i would be looking at for the heads and also the Ralliart cams?

cams are 270 a stick, heads are 160 PP and you also need valve springs and the rest of the assembly as well, as they are bare heads only.

hmmm might be cheaper trying to find a second hand ralliart engine and rebuilding it, ill make a few calls and see, thanks for all

hmmm might be cheaper trying to find a second hand ralliart engine and rebuilding it, ill make a few calls and see, thanks for allcome to sydney and buy my block and chisholm's heads and build that!

Might be easier than finding a ralliart engine lol


come to sydney and buy my block and chisholm's heads and build that!

haha, ooo its so hard to choose, i guess at the end of the day it comes down to how much money is in the bank lol

haha, ooo its so hard to choose, i guess at the end of the day it comes down to how much money is in the bank lol

Well as its been said in this thread, unless your planning on pushing big numbers then go the full hog on your heads, or just deshroud the valves, tidy the ports, knife edge, deck and enjoy.

Really depends on what you want out of the car as a whole, the fork in the road so to speak, to keep it daily driver give good topend while still having a decent bottom end for the grind, or going something very top end and not that crash hot to drive in traffic/day to day.

Assess what you want, then plan, then do it.

oooooooooo might have to dig up some money, any one know how much i would be looking at for the heads and also the Ralliart cams?

I'm selling a set of heads, PM me or post in my For Sale thread if you're interested.

cams are 270 a stick, heads are 160 PP and you also need valve springs and the rest of the assembly as well, as they are bare heads only.
Shaggy you can do this progressively and inexpensively. Whilst I have bought a brand new set of valves and a set of the Ralliart springs, I am reusing all my existing rocker arms, shafts, lash adjusters etc. You should be quite OK cleaning up your existing valves, and you could get away with running the std valve springs until you find money for Ralliarts or others (just don't regularly redline the car till you do). As for changing pistons, yes you can do that but that ramps expensiture into a whole new level...

Watch the space Flow figures and dyno results are just around the corner:badgrin:

Knew you were too quite. :drool:

Please see attached the updated Flow Figures ...... very happy with the results :D Thoughts anyone ?? Take note of the before @ the top of the page & after at the bottom. Chamber volume all matched at 45CC

Its been well over two weeks.... do you have any comparison figure's to share? I have placed mine up today.


As it happens, I have just dropped my new Ralliart heads off at Pro Engines to have them flowed, cleaned up and shaved. Their comment tallys with what others have said over the years on this Forum and have recently shared with me - the ports are already huge and do not need working in any way for an NA engine.

All your efforts should be focussed on deshrouding the valves (if you don't have Ralliart heads), removing all the casting and mould marks from inside the runners, shaving them to bump up CR, and (if you are going to run big cams, piggy back, big plenum) knife edging the runner dividers. My heads should be finished in two weeks, will post results to share.

Nope. Still waiting for Greg to finish mine. I told Him I was in no hurry and wanted attention to detail. So I get em when I get em

Nope. Still waiting for Greg to finish mine. I told Him I was in no hurry and wanted attention to detail. So I get em when I get em
don't hold your breath!!

he does good work, but you usually have to wait for it.

Cool Guess I was lucky.... :D As the place I had my heads done build and maintain all off Russell Ingall"s & super cheap auto super cars :D Guess I got in at the right time with the season all but over... Look forward to seeing your results as a comparison to make sure Im on the right track.... Dyno graph coming very soon