[Advice needed please] BHG: Repair top only or top+bottom end?

[Rollus]

Hello Supramania!

As the title says, I have a dilemna for reparation of my BHG.
I have a quotation for a good local shop, that I'm told it is trusty, and I have a good feeling with them.
This quotation is for top end + bottom end repair (machining, etc..), with OEM gaskets and Cometic MLS head gasket. This repair is a very big amount, that I couldn't easily afford (but with some effort, I could).
I know that machining only the top end with OEM only parts would cost half this big amount.

Here is the background and the foreground for this 7MGTE engine:
Background:
When I bought it it was 88000km, it was reworked and a dirty cheap shop helps me to swap it in place of my old weared 7MGTE. (I know by pulling appart crankcase and cam covers that he has been reworked).
I had a first BHG at 89500km, next to an unplugged hose..
Now this engine is 100000km, and has a second BHG next to the same unplugged hose..

Foreground:
Internals are stock but reworked, I don't plan to change turbo at the moment, just a piggyback + bigger injectors to run ethanol (E85).
I may want some more horses soon, but no more than 300 until I rework my automatic transmission.

Conlusion: What should I do?
- repair both top end and bottom end with OEM gaskets but a Cometic MLS headgasket for a big amount of money I can't easilly afford
- repair top end with OEM gaskets with half a big amount of money I can afford

I attach a poll to this topic, please vote I will be very happy if you may explain your advice in answear to this post

Update: I think I will get both top end and bottom end machined. Got new question in post 7 about Gasket Set

Regards,

Reynald

 

[Jayhall]

the oil has had coolant mixed in with it, if you dont replace the bearings you will know the exact cause when the motor develops rod knock. Just my opinion

 

[Rollus]

Thanks for your opinion

The oil is clean (but will double check it).
Got mixture in water (and radiator cap pressure valve opening) or steam in exhaust..

 

[Jayhall]

oh ok. I could see not doing the bottom end if you caught the BHG right away and oil contamination is minimal. A gamble, but with way better odds.

 

[Rollus]

OK thanks

I drove about 520 km with this BHG.
First 400 on national roads (cruising), and 120km in heavy traffic (5 home/work trip + 1 home/garage trip).
It's during the first 400km that I have light overheating and coolant consuption.
After 2 home/work trip, I've seen big coolant consuption and a cracket radiator cap.
I've replaced it, the 3rd trip was OK but little coolant consuption (I think about air flush), and last 2 trips light overheating and coolant consuption and at the end coolant in exhaust.
At the end I uses water instead of coolant (it's bad I know but when stopped in the traffic, you do as you can when coolant tank is empty). I never put more than 2 liters of coolant at once.

 

[IndigoMKII]

With the light over heating, remember it's only an aluminum head. Make sure the head is still flat and don't forget to test the hardness of the head. As for changing the top and bottom end, ask yourself this. Do you really want to cheap out and have the worst case scenario by having to rebuild the top and bottom end due to rod knock JUST after you re-did the top end?

I would do both and find out why this engine has had BHG's so close together.

 

[Rollus]

Thanks for your answear.

I will definitely send top and bottom ends to machining and put a Cometic MLS headgasket (think stopper type may be overkill at the moment, isn't it?).
My early goal is to achieve 300+ and later what I can safely achieve with stock internals.
The BHG happened close together because of the crappy work of the first garage (no block surfacing, doubt on head surfacing, bad quality clamp on hoses, etc..)

For rod knock, both top and bottom ends have been rebuild 12K kilometers ago. I haven't oil problems so I can't imagine that.
By the way, I see that Mizumo 7MGTE Full Gasket Set include Piston Rings and Main Rod Bearings. The garage who rebuild my engine quotes me an OEM Toyota Gasket set.
What does the OEM set come with ? Because OEM set is something like 400USD and 220USD for Mizumo full set...

 

[Grandavi]

rebuilding an engine isn't a "simple" thing. I wouldn't do it at just "any" shop either. If they dont understand the 7M.. they wont know what to look for.
Generally... if your head is good, it needs to be lapped for a metal headgasket. At that point your going to want ARP headstuds (imo). If you lap the block correctly you should never have a bad headgasket again providing you dont do silly things to the engine.
A properly built 7M is pretty well bullet proof. However.. the "proper" part is not a simple task. Tons of little tidbits to throw at you in regards to doing it, but if you have a shop doing it, they should know what they are doing.. I would ask if they are familiar with the 7M.. if not.. find one that is.

That's my opinion... I had my shortblock built and my original head rebuilt for my current build (about a week before its done). For your power goals I would stay OEM pistons (they are perfectly fine), and I also used the OEM seals and gaskets (for intake/exhaust), but hand made the paper ones. (very simple really... ). Not familiar with Mizumo.. and I'm one of those "not-too-bright" OEM guys... I trust most of what Toyota puts out there...

 

[Rollus]

The shop is serious and well known around there. They have already rebuild some 7M (stock and forged), swap a 2JZ in a 240Z, got hands on a Ferrari, etc.. (but all this has a price, and the bill will hurt me )
I've got a passionate talk at the end of a day with the guy who will work on my engine, and I feel I can trust him.

The engine has already been rebuild, and the repair is now about blown headgasket. It will have new ARP studs.

Thanks for your opinion about OEM stuff

 

[7M4EVR]

Hey guy, I was in the same situation about 6 months ago. I pondered the same question your asking day in and day out. I wanted my car done now and I didn't have the funds at that exact moment to do it right....well...I'm STILL finishing up my build and it WILL be done right.

It has taken me about 6 months to get everything but I don't regret the decision at all. For one, I am now way more excited to get it back on the road because it is now one bad ass machine "to me anyway". And for two, I will not constantly be worrying about it overheating or blowing coolant all over on a 15 min drive lol. You will just be way more happy with the car if you do it right the first time man i promise.That and you will most likely be saving money money in the long run. Look at it like this...spend more now to spend none later OR spend less now to spend a lot later....:biglaugh:

 

[7M4EVR]

Sorry didn't see the edit...I'm not gonna lie Im going with an eBay gasket set (except for the head gasket) although I will probably be buying seperate, higher quality gaskets for the ones that are going to be a PITA to change if they go bad.

 

[Rollus]

Ok thanks, I will doing the right way.
I will challenge the shop on cost indeed, but I won't go cheap.

Thanks to all for answer, you clear my mind and Ho I forgot: I wish you all an happy new year full of happiness, good drives, but not much trouble..