[IdahoDoug]

Figgie,
Super kind of you to express concern. So, the prior post probably explains that I'm going to leave it alone but your comment on water passages simply reminded me that in cleaning things up sometimes it can go awry. I watched a few videos and sometimes people will slip with the grinder bit and gouge a valve seat, etc. As I just got done lapping the valves, that would be a bummer and require a machine shop to put a new hardened seat in it, etc. So, just processing your wise comment there.

On the head, I'll go look more closely at it, but I haven't yet resurfaced it - just cleaned it and did a very minor lap to see if there are any issues, and knock down those little prong marks from the old gasket. It looked great. If I missed something, let me know what you were looking at and I'll look today.

The fuel injectors will go to Mr. Injector here in Coeur d'Alene who has done more than 12 sets for me over the years. He measures their output on receipt, cleans them, remeasures and then balances their output to the higher output units so they are as even as possible. Then he includes the before/after graphs. Great service and he has a lot of business from around the nation. So they will be checked. I can see from the spray pattern on the head that some were flowing more than others, which is remarkably common.

 

[figgie]

On the head, I'll go look more closely at it, but I haven't yet resurfaced it - just cleaned it and did a very minor lap to see if there are any issues, and knock down those little prong marks from the old gasket. It looked great. If I missed something, let me know what you were looking at and I'll look today.

Hi Doug,

this is what I am talking about. Compare the Red circled area vs the Orange Circled area.

 

[IdahoDoug]

Yes - absolutely correct in the difference - good eye! I had earlier put in my notes to clean up an edge there as well in that chamber. The head came off an engine in the U pull yard and there was a receipt in the car for head work for $1700 or so within the prior year (can't seem to find it, as I was looking for it a couple months ago). The gasket surface is in nice shape, it's flat as checked at a machine shop, etc. So a great candidate. But yes - that is a peppering texture that I'd assumed was some material that got into the cylinder at some point in its history. Sounds like you think it may be preignition and possibly an injector issue?

Well I think that's one of the most remarkable forum insights I've ever seen and I agree with you on that - thanks. I just went out and looked at the flow pattern from the injectors in each intact tract. Obviously it is all clean in there, but it's quite plain that cylinder's injector pattern was slightly different from the other 5. Good call - I'm impressed.

I think I have 12 total injectors to choose from, so after this conversation it seems wise to send over a few and tell him about the suspicion on the #3 injector so he is aware. Nice!!!!

 

[figgie]

I would definitely keep track of that injector that was on #3 if it was detonating/preigniting. i would venture a guess that it was running lean. My educated guess is detonation as it looks like something gets into that cylinder but the pistons usually don't exhibit the same pitting in the same area which makes sense since the pistons have a harder rockwell rating. The funny thing is that it looks like indentations and I have seen that on numerous heads (like a tiny something gets in there and just gets murdered) and usually on the exhaust side.

 

[IdahoDoug]

Further intel for you, I went back out and checked the valve seats thinking there may have been more tiny indentations than the others and that I'd needed to spend more time lapping those. Perhaps a witness mark or two next to the valve contact area from bits getting caught on their way out, etc. Nothing. So that indicates the bits were likely aluminum and thus not able to dent hardened valves or seats. So eliminates a ring fracturing, an intake nut falling in, etc.

Thanks - will keep track. The injectors are still on the rail as I'll be sending them out in a week or two. Will report on what he finds. Though I may have two full sets still on rails and I may have to look closely to see which was on this head. I quickly scavenged parts back when I towed this home and have forgotten what all I have - heh...

 

[figgie]

... and have forgotten what all I have - heh...

That has happened to me more times than I care to remember. lol

 

[IdahoDoug]

Heh. As you can see from my signature, the fleet here has gotten out of control and they're all runners except the Supra. So, I sometimes end up ordering a set of brake shoes, then going out to install when they arrive only to find I bought some a year or more ago when they were on sale. Argh. Say, what was that cleaning solvent you recommended for the head? I have it somewhere in a PM but if you're feeling generous with your time...

 

[figgie]

Chemtool B12 works wonders without attacking the Aluminum.

The purple industrial degreaser from Zep is probably the end all be all BUT no soaking, it has to be sprayed on, scrubed and rinse off as that does attack aluminum.

 

[Captain]

The purple industrial degreaser from Zep is probably the end all be all BUT no soaking, it has to be sprayed on, scrubed and rinse off as that does attack aluminum.

I've found Simple Green Pro HD to be a suitable alternative to the purple Zep, and it doesn't attack the aluminum. I used it on a very nasty head and all but the carbon on the exhaust valves came off.

 

[IdahoDoug]

OK, progress and of an unexpected sort. Above, i chickened out on porting and polishing the head. However, today I ran my fingers around a few of them and got out the dremel. First, based on research it appears that smooth intake port bowls are not worth pursuing as they'll cause fuel in curves to "stick' to the outside wall like a sheet. Rough surfaces like what Toyota appears to have deliberately made create surface turbulence that helps re-atomize the fuel and introduce it back into the air stream. So i opted not to go deep into the bowls on either exhaust or intake.

I found that there was a significant amount of aluminum I could remove to cause the last quarter inch or so of the ports to remove obstructions to greatly clean up airflow. Looking in them from the cylinder side, there were half moons of aluminum that did not line up with the hardened steel valve seat inserts. So I used a stone, then course sandpaper drums, and then a polishing wheel. Amazing difference to the feel as checked by a finger. Before:

The one on the right has a literal ledge of aluminum from about the 10:30 position if it were a clock face over to the 1:30 position,which was representative of the Before condition and I have not touched the ledge yet. The one on the right i knocked most of the ledge off with the stone (1st step). These are intake side.

Here's the After side below. It's representative of how they all line up now - both exhaust and intake. To knock the aluminum back enough to push the opening to line up with the valve seat required a LOT of material removal. I'm amazed to my finger how crappy the airflow was in that abrupt wall and on the opposite side there was essentially an abrupt transition to the opposite direction but a thick ring right at the seat causing another abrupt turn at the worst spot - right before the valves. It's all ground back and creates a smooth transition thats pushed out so the full circumference is friendly to high speed air movement. I'm glad you guys brought it up and I guess Idaho winters are long and this added something else to refine. From what I read there can also be significant HP gains as well. I'm planning to clean the intake and exhaust manifolds so I can do the same porting there as well. I'd expect to find quite a mismatch as these are production engines and that's pretty normal.

 

[IdahoDoug]

So after this, I placed reference marks on the exhaust manifold and the head, to check how these assemblies fit for airflow. Stock manifolds often have significant mismatches, which is why performance mods include this type of custom matching and machining so the ports line up.

The exhaust manifolds are attached with holes large enough they can be moved almost 1/4" up and down, which proved useful. After scoring lines with a pick of the two extremes, I found that up and forward matched very well. Toyota smartly made the manifold ports a few mm larger in diameter to account for this. However the rear manifold port was misaligned with its head port when all the others lined up. So, I relieved the manifold so the exhaust isn't hitting a half moon wall. Wow - take a lot more power to grind cast iron!

Then I cleaned the filthy intake runners with HD Oven Cleaner and it worked quite well. I don't know how a home hobbyist could achieve this as the thinner automotive type cleaners simply run off or dry up. The foaming action is perfect as the product stays on all the walls the entire length of the runner and I highly recommend it. I needed them clean so I could match them up to see if there are mismatches in the various sections.

Impressively, there is zero work to be done. Toyota did a superb job casting these and they matched perfectly. I was itching to dremel more material away with my favorable experience on the head, but there was nothing to do whatsoever. So, I'm down to a final cleaning of the head, as there's still a bit of carbon in the exhaust port bowls, and then I'll thoroughly rinse and clean the entire head to get rid of the valve lapping compound remnants, and any remaining pockets of carbon.

Making progress! Say if any of you know what the part is on the intake tube - I have a thread up asking what it is, so let me know. I'm asking because depending on what it is, some cleaning compound may be in there. It appears to be a part of the EGR system bringing crud into the intake but I'm not sure if it's worth opening to clean. Tx.

 

[figgie]

FYI,

the ports on the exhaust side are smaller than the manifold on purpose.

They are Reversion dams. Hopefully you did not port match them

 

[Piratetip]

This! @figgie

 

[IdahoDoug]

Thanks for the caution. Nope, just cleaned up airflow, knocked a clump of casting slag off here and there, and tried not to let the dremel slip and gouge my freshly lapped valve seats. Mission accomplished.

Well, I don't know why, but after the caution from the forum on opening that intake tube plate (see other thread), I got offline and thought "hmmm....." looks like my gasket kit DOES have this included. So yes I opened mine up and it's carboned up pretty badly. Indeed it looks like a chamber they needed to have access for the casting or the volume/airspeed to fulfill its function. I will be cleaning it out so this crud doesn't get loosened up and work its way into my sanitary engine. Here's a pic of what's in there:

I just got done cleaning it up and later today I'm going to clean the head a bit as well. Then, I'll go rent the valve compression tool and (Can't believe it) begin assembling the head. Wow..... There's always something slightly emotive about that moment. The first two clean assemblies you bolt together after months of taking stuff apart. Woohoo!!

 

[IdahoDoug]

Just a quick note on the reversion topic. My goal on the cleanup behind the valve seats (in the bowls) was to remove the ledge of mismatched circles that happens with mass produced bits. With regard to reversion, removing this exhaust lip helps with reversion in the following way. When the exhaust valve is almost closed in slow motion, air is only moving through a tiny gap that's dragging directly against the outer perimeter and collides with this ledge. In my case (and probably all 7M heads) this ledge was not all the way around but a half moon on 50% of the circumference. More on that later.

So removing the ledge allows faster airflow in the critical moment where reversion (dirty air goes past the intake valve) happens - allowing less restrictive exit past a nearly closed exhaust valve for better cylinder evacuation. And if you want to split hairs - less positive cylinder pressure as the intake valve is opening.

The uneven half moons create a potentially worse situation by creating more airflow on half the closing valve than the other half - creating turbulence in this relatively slow moving air when you want a steady movement of the column of air all going the same direction at the same speed.

Interestingly in the literature, the best reversion solution is to use an intake with individual runners and a common plenum to help absorb or deliberately shape the air pulses. Which is what the 7M uses.

Finally, on the reversion dam discussion on that linked thread, the exhaust ports on my head-to-exhaust manifold junction (both head and manifold) were untouched except for the half moon porting on the exhaust manifold where I discovered it partly blocked the head's port when the manifold is secured in the optimal position. Here's a photo below. I will lap the gasket mating surface before install to get rid of that flash rust, and probably touch up my porting work a bit more. I also lightly radiused the manifold opening edges as there was a slight lip/sharp edge but just a touch. As you can(n't) see the adjacent port edge looks untouched but they're all a tiny shiny edge now. The phone camera makes the adjacent port seem oval but they're circular:

 

[signalpuke]

Just skimmed the page and saw a lot of detonation damage on the head of that middle cylinder. Saw reversion mentioned, it's an old wives tale for better economy and faster heater (coolant temp) during cold start up. You don't want any reversion. Evacuate the exhuast, and find out if there was a faulty injector or a bad plug on that cylinder with the pitting on the quench pads. If you smooth them out, drip the cc across the head to make sure the CR is the same. If you don't fill it out or compensate for it in tuning it will cause issues later. Better to fix it now and not tune it out.

 

[IdahoDoug]

Signal - correct, reversion is not desired. I'm with you there. On the detonation, whatever it was won't be part of the operation of the engine now. This head was just a core for me, from another engine. I've stripped it completely had it measured at a machine shop and also again with a pricey borrowed straightedge, lapped the valves, cleaned up the cam and cam journals and done some mild porting. Now I am about to assemble. And run into the valve shim adjustment system - argh.

So tonight I snagged the valve compressor from the auto part store rental, so I won't begin the head assembly and find it's rented. The work area got cleaned, tools put away and re-racked to switch gears for assembly with clean conditions. I made a huge parts washer with a giant plastic storage bin, super hot water and Simple Green, and a duplicate tub next to it with super hot rinse water. It was already clean to the eye, but there's always a nook and cranny somewhere with crud that this loosened up. The head is now covered by a towel against any grit and I'm pretty stoked.

I was also told by a machinist to hand scrub the valve seats, and the spot on the valves the grinding paste was on to be absolutely sure there are not a bunch of grains partly embedded that will come loose. So I put the valves in the simple green tub and gave them a scrubbing with a scotchbrite pad to dislodge any remaining bits. Same on the valve seats with a brass brush as well.

On the valve adjustment, I am going to fully assemble the cams/springs/followers versus just holding the valve tight and measuring. It's going to take more time, but given the camshaft when fully assembled gets jammed up against the journal caps in operation, I thought it more accurate to have the cam like this. For those who haven't seen it, you can also install the cam without the springs temporarily and measure by hand pushing each valve against its seat to measure cam clearance. If you have perfect/new cam journals and a perfect/new cam that might work better, but this is a used engine and these tolerances are not perfect due to typical 7M cam/journal wear.

Because I'm doing it this way, I bought the clever little special tool that makes it easy to take the adjustment shims out. I may need some advice on this process with the shims, but we'll get to that in a bit.

I'm oddly nervous - like I'm forgetting something as this sea change happens. Hmm, think I'll read the factory service manual steps again...