rebuilding and nervous!!

[7M4EVR]

Okay so got my 87 supra last Feb and after sorting out minor problems drove great for a couple months then finally started pouring coolant out of overflow and making waterfall sounds and started making a tapping noise that came from top end or at least thats what we concluded and that got louder and faster with rpms. I was planning on rebuilding anyway so put car in shop pulled off top-end and took head apart and checked everythin. the head was a little warped but valves all looked ok.Wasn't gonna waste time checking clearances on a head I'm getting rid of.

The cylinder walls all look awesome and timing was spot on. I had no signs of milky oil and oil level and pressure was fine. So I bought all new complete head new turbo new radiator ARP hardware new hoses gaskets and seals newRC 550s/Lexus wahlbro pump basically all new top end..what I am scared of is if I put this all back together and don't at least do all I can to at least check bottom end I won't forgive myself.

That being said what are some ways I can check the bottom end as much as possible without pulling completely? Or at least start ruling things out. Trust me I would love to pull it apart piece by piece and replace everything but gotta pick and choose on a budget you know how it is...I know the 7m is strong internally stock and in a perfect world I'd throw new top end on and go zoom but I want to feel mildly confident the knock was for sure in top end. Sorry for long post but I figure more info the better. Many thanks in advance!

87 7mgte
102000 miles
When problem occurred I had 3inch custom exhaust with downpipe.3inch piping kit .ssqv bov
.manual boost controller. K&N intake.

 

[hvyman]

Could have rod knock. Wouldn't doubt it either. Te knocking could have echo'd through the motor making it sound like top end.
If nothingooks to be wrong with head it's most likely top end.


Did you drain the oil out?

Apart from pulling block and checking clearances it's pretty much a gamble.

 

[Dan_Gyoba]

My rod knock sounded like top end.

If you are rebuilding for BHG, then you should replace bearings anyway. I had a really slight BHG and the bearings all seemed fine. 2 years later, rod knock.

This time, it's all getting done.

 

[T3rril79]

My rod knock sounded like top end.

If you are rebuilding for BHG, then you should replace bearings anyway. I had a really slight BHG and the bearings all seemed fine. 2 years later, rod knock.

This time, it's all getting done.

Agreed, bearings are really inexpensive compared to headache generated from not replacing them at all. I know when I did mine, my oil was not milky at all but the coolant was always merky. I wasn't sure if the headgasket was one or not but I didn't want to take chances on a random breakdown so I replaced everything.

 

[SaltyMKIII]

these guys are right. i had the same issue with my engine i thought it was in the head. so i ripped the engine out to give her a rebuilt and thats what i found. good luck with her

 

[7M4EVR]

Correct me if I am wrong but if I already had rod knock replacing the rod main bearnigs isn't going to fix anything what it will do is prevent future problems and i agree its worth it to do it now while I'm tore into it. But taking the top-end off and replacing everything is one thing and digging into the bottom end is a whole new can of worms. Do you guys know of any tricks of the trade to peek around down there for signs of bad bottom end parts without pulling motor, dropping pan or unbolting tranny?

 

[Dan_Gyoba]

If you have rod knock, then the only way to fix it is to replace bearings.

If you don't have rod knock, but have blown your head gasket, chances are that you will have rod knock very soon. Again, the way to fix it is to replace bearings.

Either way, it should be done.

In any case, with a knocking sound coming from your engine, it needs a tear down.

 

[Numba1Stuna]

Well, first I agree with them all 100%. And if it is rod knock, like it sounds like, yes you do need to repave your bearings. If you don't want to and just throw it back together, one way you can test is by removing spark plugs one at a time until the "knock" stops. If it stops, you have a knock in that cylinder the plug was pulled from.

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[Numba1Stuna]

*Replace, not repave.

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[7M4EVR]

I see what your saying i guess i was thinking "inside of the box". I guess there is more than one way "rod knock" occurs. I was thinking that since the cylinder walls and top of pistons look perfect then I might be lucky and it was just in top end. But your all saying bearings. So chances are the bearings are worn causing a gap between rods and crank making a knocking sound? In which i would have to get my crank machined as well? Thanks guys this is my first knocking engine...so bear with me.

 

[Numba1Stuna]

If it was parked and not messed with as soon as the knocking occurred there is a better chance of no or slight Crankshaft damage. However if you've still been driving it, or starting it, or revving it up to diagnose it, more then likely it needs turned and you will need custom sized bearings, which are available online. Hope the best for ya. I just sold a crank to a guy in Italy too lol. $200+$300 to ship...

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[7M4EVR]

^Thanks man i did start it a few times and barely gave it throttle to show it went with the RPMs but i guess there is only one way to find out...I'll be starting this weekend and ill let you guys know what everything looks like. Just an FYI i work in International Shipping and know how to get pretty good rate cuts on shipments overseas!!

 

[7M4EVR]

Could have rod knock. Wouldn't doubt it either. Te knocking could have echo'd through the motor making it sound like top end.
If nothingooks to be wrong with head it's most likely top end.


Did you drain the oil out?

Apart from pulling block and checking clearances it's pretty much a gamble.

Sorry hvyman I just went back and noticed your question. I did drain the oil looked like normal used oil i didn't have it chemical tested or anything and i did stick a magnet through it to see if there were any little metal shavings and didn't see any. I havent cut into the filter yet though.

 

[supraguy@aol]

Check your crank pulley. If it loosens up, it will sound exactly like rod knock.
And i disagree with just about everybody on the bearing replacement. It will NOT be a gauranteed fix for rodknock.
If you pull the old bearings and find a few that are damaged, you still dont know the condition of the rod. If it's out of round, you'll get rodknock again in short order. The only gauranteed fix for rodknock is to have the crank checked, and the rods resized if necessary. Yes, it takes time, money and effort, but like you said- what if you put it all together, and you end up where you are now? Just my thoughts.

 

[Numba1Stuna]

^ That was implied, but not directly mentioned, and I completely agree. That's what I did on rebuild. I went all out completely disassembling the block and head. I've got pics and videos of my rebuild if you feel in over your head. Check it out, the link is in my signature. Feel free to ask any questions bro.

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[pogoism9]

Check your crank pulley. If it loosens up, it will sound exactly like rod knock.
And i disagree with just about everybody on the bearing replacement. It will NOT be a gauranteed fix for rodknock.
If you pull the old bearings and find a few that are damaged, you still dont know the condition of the rod. If it's out of round, you'll get rodknock again in short order. The only gauranteed fix for rodknock is to have the crank checked, and the rods resized if necessary. Yes, it takes time, money and effort, but like you said- what if you put it all together, and you end up where you are now? Just my thoughts.

This. Make sure you spec the rods using the TSRM else you will be doing it all over again in short order.