Discussion on the potential of the 7MGE

[gofastgeorge]

There are higher compression pistons than the 11.5:1s

http://www.supramania.com/forums/showthread.php?t=61597

And Wiseco will make any compression ratio you want.
(for a price)

 

[Velocityfreak]

Im not building a NA, however when it comes to turbos the head modifications are similar, have a study at my photos if you like. I believe i have reached the potential with the 12 hours of port work I have done to the head. This is head #4 for me, ive done a 5mge, a 4age and a 5sfe. I stole some port work Ideas from the 4age n2 racing specs from TRD back in the day of formula atlantic, and applied it to the 7mgte head (same head diff cams). the intake runners/port, combustion chamber and exhaust runners/port and valves are all going to get finished with a ceramic coating to increase the efficiency of the cooling system, the volumetric efficiency has been increased, so should minimize pumping loss. The valves are going to recieve a safe mild lightening and gram match.

practice on a scrap head first, and wear safety gear/goggles and mask, cause those aluminum powders can be dangerous.

http://img8.imageshack.us/gal.php?g=snc00332.jpg

 

[AJ'S 88NA]

Im not building a NA, however when it comes to turbos the head modifications are similar, have a study at my photos if you like. I believe i have reached the potential with the 12 hours of port work I have done to the head. This is head #4 for me, ive done a 5mge, a 4age and a 5sfe. I stole some port work Ideas from the 4age n2 racing specs from TRD back in the day of formula atlantic, and applied it to the 7mgte head (same head diff cams). the intake runners/port, combustion chamber and exhaust runners/port and valves are all going to get finished with a ceramic coating to increase the efficiency of the cooling system, the volumetric efficiency has been increased, so should minimize pumping loss. The valves are going to recieve a safe mild lightening and gram match.

practice on a scrap head first, and wear safety gear/goggles and mask, cause those aluminum powders can be dangerous.

http://img8.imageshack.us/gal.php?g=snc00332.jpg

Nice work. Only took you 12 hours to do that. I worked several hours on a head and didn't look as good as that. What did you use as far as tools?

The Kamikaze Supra that was referenced, was a turbo 7M. I remember the article way back, not hard to get 300 from a turbo

 

[Velocityfreak]

What i use is a rotozip - it looks like a drill bit, but has flared ends to cut metal to remove the casting flash, I use this bit to hit the entire head first as it knocks most of the big stuff right off, but i dont use it to cut anything. I usually go thru 1 bit per head they are $15 for a pack of 5. I will then use the small cutting carbide bits to knock down the protrusions after that i use flap wheels, the 60 grit ones, cause they cut really nice and u can see any high spots, and actually polish/cut the cylinder when they wear down. that takes the majority of it,

I use grinding stones on the inside of the valve seats to match them up to the ports, and then i use the end of a grinding stone to cut the excess valve seat/ the part that sticks into the cylinder head. Of course my job is an artist painter (profession) and i have excellent hand eye coordination so i rarely ever hit a seat. If i do, i pull back quick enough not to damage it. I didnt hit any of the seat seals on this head, so it came out perfect to my specs. Even if i did, i would have them recut the seats. I didnt fully polish the ports either because they need a 180-220 grit for the ceramic coating to grip to. My 4age i went crazy polishing it, and went a little overboard on that head.

But notice on the head, there is still some flash around albeit, it has been smoothed out and polished. I didnt want to enlarge the port to much, so i took off about a 1/32 in the majority of the port, and a 1/16 right around the valve ports, this will keep the velocity up in the port, and still flow extremely well. The exhaust side recieved most of the attention around the seat area as its undersize from my perspective. A little math calculations puts its about 10-12 percent to small, so try and get this number to match when finished use PieRsquared to find the area of both intake and exhaust. Multiply intake area x .8 for turbo, or .75 for NA. Then you divide this by 3.14, and take the square root and that will give you the diameter the exhaust seat width should be.

Doing the calculations will net you the best performance, and it is common for my heads to gain 15 % on average. I think this 7mgte head will give me around 15-20 percent more flow with the turbo. The 4age i gained 25 percent with the addition of ITBs.

I might offer my service for $300 a head, but u gotta pay shipping both ways. Turn around time would be a week if anyone is interested. Im not really trying to make a buisness venture cause breathing the dust and getting it in the eyes sucks balls, but i have the right equipment for it. PM me if ur interested.

My first head took me something liek 20 hours, and from there i am getting faster and faster, but still producing better results each time, now that I have done this head, i could probably get it done in 10 hours with the same results.

 

[IJ.]

Get some before and after flow figures before offering this "service" please..

 

[amichie]

I might offer my service for $300 a head, but u gotta pay shipping both ways. Turn around time would be a week if anyone is interested. Im not really trying to make a buisness venture cause breathing the dust and getting it in the eyes sucks balls, but i have the right equipment for it. PM me if ur interested.

My first head took me something liek 20 hours, and from there i am getting faster and faster, but still producing better results each time, now that I have done this head, i could probably get it done in 10 hours with the same results.

I think you are getting ahead of yourself a little here.

Flow bench, dyno or even road test results such as 0-100km/h times are usually required before even convincing yourself of the benefits of the mods you have performed..

 

[AJ'S 88NA]

Before and after dyno sheets would be nice to see. I would think you would need some way of grinding all the ports and such the same so the flow numbers would be somewhat uniform.

The first head I did I spend about 40 hours on, taking a little at a time and trying to do the same amount to each port. Can't say if it helped as the rod let loose shortly after. Maybe it did, just too much extra power for the stock rod

 

[wiseco7mgt]

The divider on the intake side is very square ,id round that off a bit more if it was me and also round off the tops of the exposed valve guides to to get rid of any sharp edges. Is the intake side matched to the gasket?

 

[Velocityfreak]

Im leaving the divider alone, it doesnt need to be pointed, its counter productive and if done wrong could cause negative turbulence. If TRD doesnt want the divider touched, im not touching it.

I dont touch the valve guides, im following spec from the TRD bible, the same applies here. the ports between the 7m and 4a are near identical, except for the floor is slightly different. Ive heard horror stories of people playing with the guide size. You think toyota and yamaha didnt have this in mind when they designed the head? Personally when I see someone play with the guide I immediately suspect a bad job. Sure the hondah guys can get away with it, cause they sound like rice anyways, and they rev way too high anyways.

i match my porting time per cylinder, if I do 6 minutes of one style, I match all the same ports with equal time. and my final flap wheel is one size whichever size im working with, if one port is to small the tool rpm will let me know, it will stop if the port is too small, and the tool will max out if the port is too large. (im looking for a consistent RPM based on the tool across all the ports) You want before and after, you got it im going to dyno it stock im pickin up the turbo tomorrow, i gotta do some basic maintainance before i make a first pull, as soon as i pull off the stock head, and slap this one on we will find the exact percentage of increase. I gotta get a baseline first, and then redo the headgasket anyways. This isnt going to happen right away because i still need to ceramic coat everything.

Boost will stay the same, and I will try and dyno it at the same temp. Im excited to see the results of this head. It should be interesting!

If you guys would like to see the TRD bible let me know. Theres some good strategy in there.

Yes I agree a bench flow would be the best setup. Ill see what I can rig up.

ideally each port job will be different depending on your goals, if you are looking for all out high strung RPM then sure you may want to touch the valves and divider, but I wouldnt, im going by tried and true methods as per TRD.

the TRD bible is around online, I think i found it on club4ag, i downloaded it to PDF, you want to look at N2 specs, TRD bible part 6 page 3,4,5, they go over the basics of head prep

 

[Velocityfreak]

Before and after dyno sheets would be nice to see. I would think you would need some way of grinding all the ports and such the same so the flow numbers would be somewhat uniform.

The first head I did I spend about 40 hours on, taking a little at a time and trying to do the same amount to each port. Can't say if it helped as the rod let loose shortly after. Maybe it did, just too much extra power for the stock rod

First of all you are not "grinding" anything as its aluminum, you will burn through it fast, you dont want to change the design of the port. The only thing you touch with a grinding stone is the steel seat, and at that the most you are opening this up is a couple mm. you are only getting rid of the scruff the original casting flash. I am not altering the port in anyway except concentric repeatable patterns on each port.

You dont want to go at it on the head, or enlarge anything. Only address the areas that need attention, and dont mess with the rest. Just remove the flash which is the first step. 40 hours is too long with a grinding wheel. thats why you use a practice head to get use to the tool, and holding it, and control. there has to be precision when dealing with this tool.

thirdly, wear the safety gear, getting sharp aluminum shavings in the eye can render all your hard work useless if you cant get to enjoy the fruits of your labor.

 

[IJ.]

Some of us have a clue......

 

[AJ'S 88NA]

First of all you are not "grinding" anything as its aluminum, you will burn through it fast, you dont want to change the design of the port. The only thing you touch with a grinding stone is the steel seat, and at that the most you are opening this up is a couple mm. you are only getting rid of the scruff the original casting flash. I am not altering the port in anyway except concentric repeatable patterns on each port.

You dont want to go at it on the head, or enlarge anything. Only address the areas that need attention, and dont mess with the rest. Just remove the flash which is the first step. 40 hours is too long with a grinding wheel. thats why you use a practice head to get use to the tool, and holding it, and control. there has to be precision when dealing with this tool.

thirdly, wear the safety gear, getting sharp aluminum shavings in the eye can render all your hard work useless if you cant get to enjoy the fruits of your labor.

I had a so called "professional" port job done on a head. It looked like they took a die grinder and about 15 min. to do it. Got my money back when I showed them pics of the one I did.

If all you are doing is taking the flash off then anybody can do that with a little time and a dremel, zip tool or something similiar. Might add a few HP. I believe if you are "porting" a head you have to know were and how much to take out, not just smooth it. The cross section of IJ's shows a lot. There's a lot of info here that owners have done as far as porting, what tools, pics, etc. If I were to have another done I'd take it to a shop that has done 7M's, have flow charts and maybe proof of the gains.

Let us know how your's turns out, but to be honest, I don't think too many people would spend $300 for a couple of HP.

And of course it's just my opinion, others will probably have their's.

 

[gofastgeorge]

Im leaving the divider alone, it doesnt need to be pointed,

100% correct, a sharp leading edge is only benificial when flow goes supersonic,
which sould never happen in an intake port,

But rounded may be benificial, only a flow bench would know for sure.

the ports between the 7m and 4a are near identical, except for the floor is slightly different.

Almost, but the 4AG (400cc cyl volume) port is 65mm wide,
and the 7M (500cc cyl volume) port is only 52mm wide.
And on race only 4AGs (formula Atlantic),
they cut the port even wider & taller yet.

Ive heard horror stories of people playing with the guide size.

One should never modify port based on people's stories.

You think toyota and yamaha didnt have this in mind when they designed the head?

As with all production parts,
the finished product is seldom as good as the original concept.
Production ease, and cost,
field serviceability by hammer headed shop technitians,
and 100,000 mile life expectancy,
all figure into the final product.
Short or very small diameter valve guides will always vanish from a good design,
when it reaches the production floor.
As will smooth contour port bends.
They all end up with a huge lump where they have to bore the hole for the guide,
just to speed up the machining process.

Boost will stay the same,

Hmm, thought this was the N/A section.........
Any problems in a stock port,
or any created by a bad attempt at porting,
can easily be delt with by just upping the boost pressure a few pounds.
(as long as your not at max boost already, and the porting isn't too bad)

And if you don't do as AJ did, and cut cross sections out of an old head,
then you better forget about major port work.
(unless you want to attempt welding up water jackets)

I have a head set asside just for chopping up at some later date.
Until then, I will stick to removing casting flaws, and the seat/port junction.
Which by the way, seems to mostly go away
when doing a 70 degree cut under the seat after going to oversize valves.

Just wish I could find some 2mm os ones like SIGMA (parrent co. of HKS) made for the 7M.

 

[amichie]

Just wish I could find some 2mm os ones like SIGMA (parrent co. of HKS) made for the 7M.

The intake valve seats in my head are only about 33.5mm in diameter. It seems they are too small even for stock 2jz valves. I guess if you can source oversize valve seats then oversize 2jz valves could be fitted.

 

[gofastgeorge]

Yeah, the one set I had seen, had all new bronze seats with them.
Damn, just thinking about the work involved changing the seats makes me tired.

 

[hvyman]

anyone think its possible to run 14-15:1 compression with the right amount of fuel and tuning?

 

[gofastgeorge]

Typically, that high of ratio is only run with very long duration cams.
Like 272 & up.
I have seen 4AGs with that type of compression ratio (typically 14.5:1).
But they rev way beyond (14,000) the physical limitations of a 7M due to the rod/stroke ratio.

I have a line on an 87mm stroke crank for the 7M, that I found in Europe.
Ex-ralley car crank.
But it will take custom pistons, and/or rods to make it work.
With 85mm pistons, the displacement is back to 2950cc.
The shorter stroke will help the rod/stroke ratio, and the max RPM that it can run.
The guy only wants $100 for the crank, but I am waiting for shipping costs.
(probably more than the crank)
And I hope it isn't junk...........

 

[hvyman]

if you could de-stroke it run more compression with fuel and tuning + plus other extensive work i thik that the ge could make power. sorry for this(i hate hondas)... but built hondas can get good amounts of hp when properly built i think the same can be applied for the ge.

 

[amichie]

Does anybody know the actual dimensions of the intake valves seats and what is the practical limit for oversize valves using the factory valve seats??

 

[IJ.]

+1mm can be done if you throat the stock seat the same amount, anymore is pushing it and you risk having a seat fall out.