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Discussion Starter · #161 ·
Yes, that's the one I have.

I'm having a hell of a time finding oversized 5MGE pistons. Does anyone know of any manufacturers? I'm finding plenty of oversized 7MGE pistons but not sure where that would put my compression. I think my current concoction has CR somewhere in the mid 10's. If a complete 7MGE rotating assembly in a 5MGE had compression in the high 8's, then I suppose that would be ideal for a project I've been considering.

Any experts still around here that would know?
 

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I have a set of 20 over 5m pistons brand new in the box. I found a set of the 8.8 5m pistons with rings. They would make 9.2:1 compression on your setup, which is better for boost than the domed pistons would be. PM'ing you the link. They are 20 over.
 

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I've seen several 7MGTE rebuilds using only ARP studs on the stock HG. They say it holds "low boost", but I suppose that's subjective. Not saying its a good idea. Just that it's been done. At any rate, I ordered a new HKS gasket because I dont trust my judgement either.
Yeah I have a bottom end from a guy who went that route. He managed to blow the gasket out of 5 of 6 cylinders and flooded the entire block with coolant. It's a time bomb. I know people who have gotten some years out of that combo, but it always goes eventually, spectacularly sometimes.
 

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Discussion Starter · #165 ·
Methinks they get brave and turn the boost up once they retorque with those pretty new bolts. I guess there's a reason almost every 7M swap needs a rebuild before installing.
 

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Discussion Starter · #166 ·
Had a couple hours to break the head down today.

I had the head rebuilt at a local shop that's since gone out of business. I wanted to ask the tech what this ring is on the number 1 intake valve spring seat. It wasn't there when I disassembled it years ago. Is it a shim? If so, I've never seen a valve spring shimmed and would have to wonder why he'd put one there.
16258


All other valve spring seats were normal.
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I think some lapping may be in order.

16261

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Hey, now, I dont remember breaking this one :unsure:
16263
 

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Looks like they used a random piece of metal as a replacement for the factory spring seat. There is supposed to be a stamped washer under each valve spring.
 

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Discussion Starter · #168 ·
Looks like they used a random piece of metal as a replacement for the factory spring seat. There is supposed to be a stamped washer under each valve spring.

I dont recall anything being between the springs and reliefs(?) when I broke the head down for the first time. It only had about 150k miles on it at the time so I'm pretty sure it was the first time the valve train had been disassembled.

Then again, there's all kinds of stuff I'm coming across that I dont remember doing. Knowing myself back then, I wouldn't be surprised to find out I discarded them because i didn't understand their purpose (which, of course, would have meant they had no purpose).

Sounds like I'll have to find some. When I built the 2ZZ in my corolla last year, that was the first time I'd come across such a part. Any other head I've ever tinkered with had valve springs that make direct contact with the cutouts/reliefs. I figured Yamaha put them in the 2ZZ head to help alleviate the stress on both surfaces caused by rotation of the springs at high engine speeds. But now that I'm enlightened, who knows how many vital engine components I've tossed 🤷‍♂️

Oh, well. I sure hope this build goes better now that I dont know everything.
 

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I think pretty much every aluminum head has a variation of them to protect the head itself..
 
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Discussion Starter · #170 ·
Copy that. Is it called valve spring seat? Locator? Either I suck at searching or they dont make them anymore. Maybe both.

I can't help but think that any washer with the same thickness that fits in the relief would suffice.
 

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Discussion Starter · #172 ·
Nice!
Everything is sold out or discontinued. No surprise there. But at least I have the dimensions so I can get some regular steel washers now. I'm glad some OGs are still around to help the rookies 👍
 

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Discussion Starter · #173 · (Edited)
Went to Bad Iron Machining in Bradenton for the bore and hone. They tried .020 over to clean the pitting in cylinder one. No dice. So, now I'm the proud new owner of a .040 over 5M block.
20210318_173846.jpg


Also lapped the valves, found a set of valve spring seats, cleaned the head a little bit (mostly just the valve seating areas and gasket mating surfaces for now) and got the cylinder one intake valve assembly..assembled to test the clevite 212-1351 valve springs. Fitment is perfect and they are stiff. I could compress the stock valve springs about 1/4" by hand with the valve train assembled but I can't push these suckers down at all.

OEM valve spring on left, Clevite spring on the right.
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Cylinder one intake valve spring compressed
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Keepers set and valve assembled
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Did your machine shop do what looks like gasket matching on the ports, or is that how they all look? I've never examined a 5M head up close, so I don't know what they look like.

- Jim
 

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Discussion Starter · #175 ·
Unfortunately, the ports are all untouched. I considered removing some material, especially on the intake side, but I dont trust myself that much with this particular project and the cost of such work by a shop tends to exceed it's worth in my opinion.
 

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Understood. I generally just clean up the ports on the head and manifold to blend them all together, and also clean up the valve pocket under the seat if it has casting chunks in it.

Does it help? I dunno. It's one of those things you might be able to measure on a dyno, but would never feel in the seat-of-the-pants dyno. I just do it because it looks nicer.....
 

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Discussion Starter · #177 · (Edited)
Quick post with some more random ponderings and questions:

As I discover more about this engine every week and see just how scarce the aftermarket is, I believe I'm narrowing my options down to two.
Either way I go, I think it could only be beneficial to have the rotating assembly balanced; something I've never really considered and possibly one of many reasons my builds have never lasted.

I've been researching the balancing process and it seems like, with some care and accuracy, the pistons and rods can be done at home. I've also read into some home equipment builds for crankshaft balancing, but trying to justify the cost of building such a machine and the room for error, it seems the better decision would be to take the crankshaft, flywheel, clutch, balancer, timing gear and snout bolt to my machinist for a proper balance.

Question: Does anyone have experience balancing pistons and rods with home equipment?
The pistons seem simple enough. Weigh all components separately 3-5 times, calculate the average for each one, find the lightest piston, and slowly remove material from the thickest areas possible on the 3 heaviest pistons until they all weigh within 5 hundredths of a gram of the lightest piston. It looks like the pistons and wrist pins are the biggest deviants, while the rings and clips tend to fall within the target threshold from the factory.

Here's where I get hazy: How, exactly, does one ensure they are fully supporting the small end of the rod while weighing the big end and the bearing?
I can see that the jig is pretty easy to build, but is there a certain angle the small end needs to be supported at? If I'm interpreting correctly (big 'if'), the balance will be close to optimal if the top side of the beam is perfectly level with the small end being supported by a freely rotating/rolling device that fits plumb inside the bushing. After that, the process is pretty much the same as the pistons balancing.

Is it really that simple, though? I hope it is but it seems awfully easy and, if so, makes me wonder why everyone isn't doing this.

The intent here is more for learning than saving money. Negative responses welcome.
 

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Discussion Starter · #178 · (Edited)
(Continued from post #177)

Another question, and one that might get me banned:

With the head needing milled again, it seems this motor will be of inherently high(er) compression. High enough that boost may be detrimental at any level, even with the early 5m pistons.
Should I decide to stay NA, I've been thinking about ways to increase piston volume rather than having the head milled again beyond resurfacing.

Flamesuit on :
There are several success stories floating around on the internet about using various metal items such as coins and washers to add volume to the piston's dome. Two documented miata builds show the builder using quarters for their near identical weight. They both drilled holes through the centers of the coins and one spot on either side of the dome and then used screws to mount the coins to the pistons. One used high temp epoxy as a filler between the surface of the piston and the quarter. The other used JB weld. I'm assuming this is to prevent excessive heat from building between the coin and piston but no mention of the fillers purpose is found in either thread.
They also both balanced the pistons.

Purely exploratory, I'm going out on a limb to see if anyone has ever heard of/accomplished such a modification.

My immediate thought? It could be done. With screws holding the coins down and adhesion from the filler, I cant imagine they would ever come loose. Balancing the pistons afterward would prevent vibration caused by the minimal weight deviation of the coins and filler.
Seems to me there are two issues; the potential for misshaping the dome and the potential for combustion temps to exceed the limits of the filler used.

Any thoughts?

I know this is probably a knee slapper, but figured I'd throw it out there to see what kind of responses it might generate, if any.

This would also be geared more toward learning, fwiw. My expectations for this car have become more earthly. Rebuilding again down the road may not hurt my feelings at this point.
 

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Quick post with some more random ponderings and questions:

As I discover more about this engine every week and see just how scarce the aftermarket is, I believe I'm narrowing my options down to two.
Either way I go, I think it could only be beneficial to have the rotating assembly balanced; something I've never really considered and possibly one of many reasons my builds have never lasted.

I've been researching the balancing process and it seems like, with some care and accuracy, the pistons and rods can be done at home. I've also read into some home equipment builds for crankshaft balancing, but trying to justify the cost of building such a machine and the room for error, it seems the better decision would be to take the crankshaft, flywheel, clutch, balancer, timing gear and snout bolt to my machinist for a proper balance.

Question: Does anyone have experience balancing pistons and rods with home equipment?
The pistons seem simple enough. Weigh all components separately 3-5 times, calculate the average for each one, find the lightest piston, and slowly remove material from the thickest areas possible on the 3 heaviest pistons until they all weigh within 5 hundredths of a gram of the lightest piston. It looks like the pistons and wrist pins are the biggest deviants, while the rings and clips tend to fall within the target threshold from the factory.

Here's where I get hazy: How, exactly, does one ensure they are fully supporting the small end of the rod while weighing the big end and the bearing?
I can see that the jig is pretty easy to build, but is there a certain angle the small end needs to be supported at? If I'm interpreting correctly (big 'if'), the balance will be close to optimal if the top side of the beam is perfectly level with the small end being supported by a freely rotating/rolling device that fits plumb inside the bushing. After that, the process is pretty much the same as the pistons balancing.

Is it really that simple, though? I hope it is but it seems awfully easy and, if so, makes me wonder why everyone isn't doing this.

The intent here is more for learning than saving money. Negative responses welcome.
No opinion on running boost, as I'm an "NA" guy.

As far as balancing goes, yes, it's always nice to balance an engine when you rebuild it, if you want to spend the money. I "assisted" my engine build back in "Ye Dayse of Olde", and you're pretty much correct on balancing the pistons and rods. He had a fixture that held the rod on either the big-end or small-end, and he weighed them individually. For the pistons/pins/rings/etc, he used a scale. To lighten the pistols he'd mill off a bit of the bottom of the pin boss. For doing the crank/flywheel/balance/dampener, he had a Stewart-Warner rig that was made to do engine balancing. I think the rod fixtures and scale were also part of the setup he bought.

As far as the =/- of the weights, he balanced things to +/- 1 gram.

For further reading, try this search result, and pay attention to the Hot Rod articles.

- Jim
 

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Discussion Starter · #180 ·
No opinion on running boost, as I'm an "NA" guy.

As far as balancing goes, yes, it's always nice to balance an engine when you rebuild it, if you want to spend the money. I "assisted" my engine build back in "Ye Dayse of Olde", and you're pretty much correct on balancing the pistons and rods. He had a fixture that held the rod on either the big-end or small-end, and he weighed them individually. For the pistons/pins/rings/etc, he used a scale. To lighten the pistols he'd mill off a bit of the bottom of the pin boss. For doing the crank/flywheel/balance/dampener, he had a Stewart-Warner rig that was made to do engine balancing. I think the rod fixtures and scale were also part of the setup he bought.

As far as the =/- of the weights, he balanced things to +/- 1 gram.

For further reading, try this search result, and pay attention to the Hot Rod articles.

- Jim
Some good reads in there. A few that I've seen before but that Hot Rod page in particular was a new one. Pretty much reinforces my thought that the crank and lower rotating parts need to see a machinist. No way in hell could I afford a balancing machine. I could probably build a gravity balancer out of some old flexplates and bearings with a steel frame, but that seems a little excessive for the moment when a machinist will typically do the job much more accurately with a digital balancer for $50 or better. Maybe an interesting endeavor for the future, though 🤷‍♂️

An entire gram still seems like a large deviation for the effort, imho. There are manufacturers that sell sets within that threshold. It shouldn't take much longer to get down into at least the tenth range.

I was looking at one of my old pistons today and did notice how much material there is around the wrist pin holes that could likely be removed safely. I've also read that the bottom of the skirts is a good area to take from if you make sure to smooth it out well while grinding.
 
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