7M cylinder head porting

[jdub]

^^^Why wouldnt you want to port the exhaust side? or the exhaust manifold to match the head ports?

-Sam

Three words: exhaust reversion dam (Google is your friend)
You want the exhaust ports smaller diameter than the manifold ports. Doesn't mean you can't smooth and remove restriction inside the port.

Thanks for the info, I'm just curious about the effects it would have on a lower HP motor, i.e. stock.

I'm acquiring an engine to rebuild and just want to find out as some extra info before I map out a plan. I'm aiming at 400+ but slowly modded over a 2 year range or so.

I plan to put internals that will handle that better than the stock internals so I don't have to worry and not tear back into the engine when it's in the car. Porting the head was something I was looking into and this thread came along

I asked my above question because I was wondering if it just wouldn't make a difference on lower horsepower motors or would the extra flow hinder performance.

I visualize the engine being more free-flowing and not making much difference as lower horsepower levels but I don't know much, which is an understatement so far about engine dynamics or physics. I'm in the learning process right now. Thanks

You will only see a big benefit on a high HP motor...400 is the beginning of that range. You will also need oversize valves and perhaps a cam to gain full potential...get ready to shell out some $$$ if you go that far. Otherwise, any motor will benefit from smoothing out and reducing restriction inside the ports...increased VE is always a good thing. As said earlier, don't go nuts....a mild port/polish is fine for your goal.

 

[McGyvr]

Here are a few pics of mine. I ported the exhaust quite a bit, but it's still smaller than the manafold. 3 angle grind on seats. Should have sold the aluminum I removed to pay for beer for the prodject! lol

 

[enjoi.this]

Continuing on with the cylinder head porting, I finished off the exhaust ports (did some more cleaning and radiused some sharp corners) Also did some combustion chamber work. Radiused the sharp squish area on the port sides of the chambers and removed the factory valve shrouding.

With doing this modification more of the valve will be used during intake and exhaust. Take note of how much more the vavles are exposed. I believe about 1 third more of each vavle is now being used.

I am lowering the compression ratio, but will be running an HKS 1.2mm MHG (which is thinner then stock) so hopefully I will retain close to stock c.r.

In the first 2 pictures I very carefully handled the MHG and placed it on the cylinder head to mark out where the new gasket will sit around the cylinder. Gives me a basic guide line to where my limits are to cut out material.

This time around I used more basic tools, just air powered angle drive with 3 different carbid cutting heads. a medium and small rose bud and 1 medium straight cut. You could get away with just using the small rose bud (just takes more time to remove material)

Picture of the stock combustion chamber

Starting to remove material on the first cylinder.

These last three pictures are fairly self explanitory.

This is the finished product after about 2.5 hours of work. Takes much less time to do this mod comparing to port work. All the valves where put into the head and I took a emery roll and texturize and smooth the chambers. Id give this mod a 4 out of 10 on the difficulty level. But GREAT CARE must be taken with enlarging the chamber, you do not want to go past the gasket area! Otherwise you will have a very large paper weight. I gave myself plenty of space not to cut too close to the gasket. (want to be safe here) If knock occurs the gasket wont be exposed as much, could prevent a BHG.

 

[jdub]

Nice...now for the valve job

There's a product called Cratex Rubberized Abrasives that is very useful for smoothing out your work. Here's a link:
http://www.nolansupply.com/superabrasives.asp?supercategory=Rubberized+and+MX+Abrasives

 

[IJ.]

Going to CC the chambers?

 

[blupastu408w]

looks OK, but I wouldnt have touched the combustion chambers if you dont know what you're doing. By unshrouding the valves that much, you removed the tumble/swirl that was engineered into the chambers by Toyota. Tumble and swirl is extremely important... it totally dictates flame front speed and direction. It also keeps the fuel from washing out the cylinders and collecting in the ring lands (bad).

I'm not an expert in this field, but I do know enough about cylinder head porting and c.chamber shaping to know that a dome shaped c.c. is not a good ideal. I hope you take my criticism positively as it certainly is not offered in a negative manner. I also know how much time you must've spent doing it.. so you're not going to be happy with my posting... If you use this head still, please at least CC the chambers so that each cylinder has close to the same static compression ratio.

 

[enjoi.this]

Nice...now for the valve job

There's a product called Cratex Rubberized Abrasives that is very useful for smoothing out your work. Here's a link:
http://www.nolansupply.com/superabrasives.asp?supercategory=Rubberized+and+MX+Abrasives

Thank yah sir
Ill look into those rubberized abrasives, could be useful on the next head job.

 

[enjoi.this]

Going to CC the chambers?

I wasnt planning on cc'ing them, Id need to make a plate and a plug for the sprakplug hole but it would be good info to know how much larger the chamber is overstock. Even having the information up on here could help someone else out. Any input ian?

 

[IJ.]

looks OK, but I wouldnt have touched the combustion chambers if you dont know what you're doing. By unshrouding the valves that much, you removed the tumble/swirl that was engineered into the chambers by Toyota. Tumble and swirl is extremely important... it totally dictates flame front speed and direction. It also keeps the fuel from washing out the cylinders and collecting in the ring lands (bad).

I'm not an expert in this field, but I do know enough about cylinder head porting and c.chamber shaping to know that a dome shaped c.c. is not a good ideal. I hope you take my criticism positively as it certainly is not offered in a negative manner. I also know how much time you must've spent doing it.. so you're not going to be happy with my posting... If you use this head still, please at least CC the chambers so that each cylinder has close to the same static compression ratio.

Toyota did it with the race 7M's.

I wasnt planning on cc'ing them, Id need to make a plate and a plug for the sprakplug hole but it would be good info to know how much larger the chamber is overstock. Even having the information up on here could help someone else out. Any input ian?

A spark plug will work fine, "even" is more important than volume Chris.

 

[enjoi.this]

looks OK, but I wouldnt have touched the combustion chambers if you dont know what you're doing. By unshrouding the valves that much, you removed the tumble/swirl that was engineered into the chambers by Toyota. Tumble and swirl is extremely important... it totally dictates flame front speed and direction. It also keeps the fuel from washing out the cylinders and collecting in the ring lands (bad).

I'm not an expert in this field, but I do know enough about cylinder head porting and c.chamber shaping to know that a dome shaped c.c. is not a good ideal. I hope you take my criticism positively as it certainly is not offered in a negative manner. I also know how much time you must've spent doing it.. so you're not going to be happy with my posting... If you use this head still, please at least CC the chambers so that each cylinder has close to the same static compression ratio.

Its always good to get the negative side on things. now how would you get any better at what you do? Of course I will be using this cylinder head, just because you think it wont work doesnt mean its going to stop me. We will see the benefits it provides for me.

If it doesnt work out, which ever I tried something new and ill start again to make something even better. Although how you say hemi shaped combustion chabers are not ideal, just think back abouts 30 years to the muscle days with hemi heads. They made very big power for what they were.

Jdub pointed me in this direction, and I will take his opinion over yours on this . I will cc the head once I get it back from machining also. This head isnt just going on a stock engine and will be seeing almost 20psi of boost.

 

[blupastu408w]

Toyota did it with the race 7M's.

I'd like to know the true source of that photo. That chamber does not look like something done by Toyota. It looks like a backyard mechanics (like me) attempt at using a flat top piston.

I've been wrong before though... like I said, I'm no expert.. I dont port heads for a Winston Cup team or anything. I've just done a LOT of reading and a LOT of seat time with a die grinder over the last 15 years.

 

[enjoi.this]

Toyota did it with the race 7M's.

A spark plug will work fine, "even" is more important than volume Chris.

Alrighty thank you Ian, Next step on the head is cc'ing once I get it back. Gerry my machinist is also going to inspect my current valves and seats. If they are not excellent to work with I will be purchasing .5 oversize valves from suprarich.

I will be breaking in my engine in stock form, once I get up to around 12K on the engine Im going to hit up the dyno in town to see what kind of numbers this head work could produce in stock form. then once again when larger turbo + supporting mods are installed at 15psi then eventually 19psi.

 

[IJ.]

I'd like to know the true source of that photo. That chamber does not look like something done by Toyota. It looks like a backyard mechanics (like me) attempt at using a flat top piston.

I've been wrong before though... like I said, I'm no expert.. I dont port heads for a Winston Cup team or anything. I've just done a LOT of reading and a LOT of seat time with a die grinder over the last 15 years.

Group A race engines ran this configuration, at a guess I'd say they were based on production castings.

I'm not saying it's right or wrong just that it exists and my point was it's been done and worked, my other point is it's important that the chambers be equal volume.

 

[blupastu408w]

Alrighty thank you Ian.

Just remember that what works efficiently at 9500rpm with a 0.600" lift cam doesn't necessarily work well on your average 20psi/7000rpm daily driver.

I'm new to this board but not to wrenching on things. I have a hard time believing that no one on this board is familiar with tumble/swirl benefits and the flame front/direction/speed thats been engineered into our (7m's) combustion chambers and piston shape combination. :aigo:

 

[IJ.]

No I don't have any understanding of propagation.....

 

[GC89]

That head design was infact used by toyota but only in their group a race engines

Ninja Edit: beat me to it Ian

A hemipherical head really shines in race conditions as if flows very smoothly. The draw back is that it flows too smoothly and lower flow conditions suffer due to a lack of turbulance. I think you have a good compromise here chris should gain you quite a bit up top while still handle the low an mid range well.

 

[blupastu408w]

Its always good to get the negative side on things. now how would you get any better at what you do? Of course I will be using this cylinder head, just because you think it wont work doesnt mean its going to stop me. We will see the benefits it provides for me.

I didnt think or even hope that you would. I would have been surprised had you spent so much time on the head and not at least CC the chambers.

Although how you say hemi shaped combustion chabers are not ideal, just think back abouts 30 years to the muscle days with hemi heads. They made very big power for what they were.

You haven't seen the hemi head have you? It looks like a typical inline V8 chamber, rotated 90 degrees to place the intake valve closer to (and at a better angle to) the intake port. The shape is somewhat hemi-spherical but they didn't know anything about tumble/swirl back then either. They didnt learn (or care) much about that until the 70's when miles per gallon became important and emission controls were mandated...

Like I said, it was just constructive criticism and I'm glad you didnt take too much offense to it. I dont know this sites rules on posting links, but I'll try to post a great article I just found that has some great tips and good reading.

http://racingsecrets.com/article_racing-10.html

 

[enjoi.this]

That head design was infact used by toyota but only in their group a race engines

Ninja Edit: beat me to it Ian

A hemipherical head really shines in race conditions as if flows very smoothly. The draw back is that it flows too smoothly and lower flow conditions suffer due to a lack of turbulance. I think you have a good compromise here chris should gain you quite a bit up top while still handle the low an mid range well.

Thanks GC, I didnt feel the need to go "all out" on this one and went with something I felt was somewhat conservative. I am VERY curious to see what sort of numbers I can make comparing to someone with a stock head and equal supporting mods. To maybe even prove this is a good mod for others to use on theyre street cars would be great.

 

[blupastu408w]

Hope your build goes well and meets or exceeds your goals. I'll just add that you should polish your piston tops and combustion chambers - this is proven to help keep heat in the chambers and away from the piston. Give it a search on your search engine, i believe if nothing else I've said on this post is useful then at least that is.


Ok, well I've been a member here since 2006 and was getting nagged about making a post or having my account deleted so I guess I'll just go back into lurking mode and shut up.

 

[IJ.]

Personally I wouldn't have done it as the 7M needs all the help it can get to ward off knock, don't know if you saw the pics but I sliced up a head before I had mine ported to check wall thicknesses.

No need to go back to lurking you have knowledge that can help the guys why not share?