7MGE Engine rebuild

[oregonjoe]

So it finally happened, after almost 20 years my 1990 Supra blew its head – just as forecasted. My wife has been driving the car lately and tells me it has been using water at a gallon a week for the past few months. Past few months?? I reply, it should never need water I inform her. So I go out to look under the hood and old coolant is everywhere. Start the engine and water explodes out the radiator like a volcano. Turn the car off and sounds of steam from within the block.

Yup – just like most Supra owners, signs of a blown head gasket. Pull the spark plug on the No. 6 cylinder and it’s the same color as the coolant confirming my suspicion.

Now, I’ve been reading the Toyota forums because I’ve just replaced the timing components on my 94 4Runner and they were a great help. I even started a rebuild on another 4Runner when this happens. After discovering the Supra forum I figure I could lend my experiences here and perhaps get some guidance.

I have rebuilt several engines, mostly Chevy blocks. Since this car is 20 years old, I’ve decided to do a full rebuild from the ground (oil pan) up. I am going to pull the engine and try to document my adventure here with as many pics as possible as I have found them very useful an all the other forums. I have garage to work in and some fiends with lifters and tools so I can take my time.

Of course always willing to take advise as well as give some. Stay tuned.

[Kevin]

go turbo

[oregonjoe]

Fast forward on progress to where I am at now.

From my experiences with the 4Runners, I started by removing the radiator and fans. This gives me better access from the start.

Then removed the air ducts and water hoses to the timing cover.

Next the throttle body and top part of the air intake. My wife is helping by labeling plastic bags as we go for all the bolts and small parts. She started with a PINK marker because she thought it would look nice but had to switch to dark green when we could not see it on the bag.

The top part of the timing cover comes off and the belt looks a little worn but not bad for 20 years. It will get replaced along with the idler

When I did the first 4Runner, I had a heck of a time getting the cam sprockets off. I actually broke one trying to wedge a socket in the sprocket. Had to get a replacement pair from the junk yard for $70 (lesson learned). Why did Toyota not put some holes behind the sprockets to insert some stopping bolts I will never know. Finally had a friend weld up this special tool to hold the sprockets still so I could turn the bolt. Took me 4 days on the 4Runner to get them off with out the tool. Also work great for holding the crank while I go the damper off.

Anyway on to the Supra. The same tool worked great again on the sprockets but could not be used on the damper like the 4Runner. Just no spines to grab on. Luckily I had read through the forums a used the pry bar in the flywheel technique. Only problem was removing the starter which is a real pain. So I had to finish removing the air intake manifolds to get to the top of the starter. Problem here is that Toyota runs the fuel lines through the intake runners making it impossible to remove without having dismantle everything on the drivers side.

So in summary – to take off the damper you need to stick a pry bar in the flywheel

To get to the flywheel you need to pull the starter.

To pull the starter you need to pull the intake manifolds.

To pull the intake manifolds you need to remove everything else.

A day latter I can stick a pry bar in the teeth and pray not to break one. Damper finally comes off and I can finish with timing belt removal.

As a side note. I have since learned that there is a way to actually use the starter to turn the engine to get the damper bolt loose. Will have to try this next time. But remember to remove the fuel pump fuse first. I had to reconnect the battery to raise the windows and forgot to remove the fuse only to see a mini spout of fuel as the windows went up.

[oregonjoe]

Now I can finally get to the valve covers and head bolts. Sent wife down to parts store to get the special HEX socket to remove head bolts. Yes – it does need to be 3/8” to fit into the recess and past the CAM shafts. I decided to leave the cams in place and not remove them from the head so the machine shop can have the whole assembly to look it. No bearings on the CAMS so wanted them to check tolerances when doing the valves.

Head came off easy after following the correct loosing sequence. Put all the bolts in postal flat rate box with holes punched so I would not mix them up. But have since realized that was unnecessary since I was going to need new bolts anyway.

On that topic, as I was removing the bolts most were tight but number 5 came undone almost without any torque. Mighty suspicious ! The number 2 bolt came out hard and when I looked at it - was not clean and dry like all the rest but showed signs of corrosion.

After removing head noticed coolant in the number 2 head bolt hole – not good. After cleaning the hole further looks like a crack in the threads of the hole to the water jacket. Going to have to remove engine and take block to machine shop to have it checked. I am thinking of going to studs and sealant in the bolt hole may work.

The Number 6 cylinder defiantly had a leak between the water ports and cylinder. The valves were reddish brown while all the other cylinders were whitish tan. The other cylinders were clean an shiny while number 6 has been burning water for a while. The head gasket has a significant oval shape extending to the water jacket – YUP BLOWN GASKET.

I was surprised to see how clean the other cylinders looked after 20 years. I will have the shop check out the block but looks like all it need is some cleaning an a hone to be good as new.

[oregonjoe]

Well, since the block has to come out – in comes the hoist. I put a jack under the oil pan and transmission and unbolted the bell housing and engine mounts. I bolted the chains to the engine mount holes since I did not want to use the head bolt holes if one of them was already cracked. Balanced just fine and lifted right out by my self. This engine lift is a rally great tool you only get to use a few time in your life but it really works.



Now I get to look at the clutch and flywheel. Going to need some resurfacing and the clutch disk was worn to the bone – time to replace along with the throw out bearing and pilot bearing



Got the engine on the stand and upside down to remove the oil pump. After unbolting one bolt it would not budge so I removed the pump drive shaft still not budge. Figured was a pressure fit so used a screw driver on the block to pry it off.



Next it was time to pop the pistons. The cylinders had no ridges so they came out really easy. Bagged each one in numbered bags. The rod bearings looked a little worn but were very even with no hat spots. The crank looked very good too so hopefully it can be reused. I am going to take it to the shop in the block to have them check tolerances and we will see what the verdict is on the head bolt hole crack and crank. Cross my fingers.



A week of nights and two cases later

[oregonjoe]

I’ve taken the head and block to the shop to have them cleaned up and inspected. The head and valves looked good for 20 years of use.

The good news on the block is no cracks after the magnetic test – so its just a hone on the cylinders and good to go. The bad news is the shop wants $500 to do a valve job on the head – even without replacing any valves. Claim the 24 valves takes a lot of labor and that OHC need to be ground to adjust!



So – I took the head back to do a little porting and polish. The head had some casting marks and ridges from 20 years ago. Since I bought the car I have learned a thing or two about engines. One of which is that they are massed produced from casting molds. These molds are not all created equal and there can many flaws that are left as is in production. Some flaws include sharp ridges from casting seams and defects in the individual molds. Other are sharp angles from the machining process after the castings are poured. In production - they are all ignored.



The cylinder chambers in the head have some sharp edges that can collect heat and cause preignition so I ground them off to smooth the transitions out the valve ports. Careful to not touch the valve seats.



I focused on the exhaust ports and smoothed out the walls and take out any burrs and casting ridges. Just a little touch up on the intake side to remove any large defects as I understand its better to leave the “sandpaper” effect on the walls.

[cvbikeguy]

Originally Posted by oregonjoe

I’ve taken the head and block to the shop to have them cleaned up and inspected. The head and valves looked good for 20 years of use.

The good news on the block is no cracks after the magnetic test – so its just a hone on the cylinders and good to go. The bad news is the shop wants $500 to do a valve job on the head – even without replacing any valves. Claim the 24 valves takes a lot of labor and that OHC need to be ground to adjust!

Attachment 2254

So – I took the head back to do a little porting and polish. The head had some casting marks and ridges from 20 years ago. Since I bought the car I have learned a thing or two about engines. One of which is that they are massed produced from casting molds. These molds are not all created equal and there can many flaws that are left as is in production. Some flaws include sharp ridges from casting seams and defects in the individual molds. Other are sharp angles from the machining process after the castings are poured. In production - they are all ignored.

Attachment 2255

The cylinder chambers in the head have some sharp edges that can collect heat and cause preignition so I ground them off to smooth the transitions out the valve ports. Careful to not touch the valve seats.

Attachment 2256

I focused on the exhaust ports and smoothed out the walls and take out any burrs and casting ridges. Just a little touch up on the intake side to remove any large defects as I understand its better to leave the “sandpaper” effect on the walls.

Attachment 2257

so you didnt have to take the head to the machine shop? will the replacement gasket be fine with just taking the block to the machine shop itself? sorry if im jacking your thread but this has been extremely helpful for me. thanks so much

[oregonjoe]

No - head was in shop for cleaning and resurface then I took it back once all the valves were removed to do the porting. Then - back to the shop to have the valve seats done, valves installed, and then adjusted with shims. Total machine cost for the head was $450.

You want tot do the porting before the valve seats are done so you don't mess up the seats. Critical since they determine adjustment and timing.

If you really want to do it right and can afford the time - take both head and block to machine shop so both surfaces can be done clean.

Then new head gasket will be fine - remember I used studs and tourqued down to 90 ft-lbs.

[cvbikeguy]

Originally Posted by oregonjoe

No - head was in shop for cleaning and resurface then I took it back once all the valves were removed to do the porting. Then - back to the shop to have the valve seats done, valves installed, and then adjusted with shims. Total machine cost for the head was $450.

You want tot do the porting before the valve seats are done so you don't mess up the seats. Critical since they determine adjustment and timing.

If you really want to do it right and can afford the time - take both head and block to machine shop so both surfaces can be done clean.

Then new head gasket will be fine - remember I used studs and tourqued down to 90 ft-lbs.

and you said the block was 400?

thanks so much for your help

[cre]

With the vGauge don't plan on using the stock oil pressure sender... the sender itself is internally dampened not the stock gauge.