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Daveyboy
12-26-2020, 12:49 AM
Hey guys!

Just wondering, i hear that on some engines if your head gasket blows and the engine seized up the way the engine is designed from the cylinder head up is saved I.e valves don?t get bent etc.. just the block components like bent rods etc.
Is the sr20det one of those engines?
Or if it blows and seizes both block and head comments are most likely bent and will all need replaced..

Thanks!!

NukeKS14
12-26-2020, 09:25 PM
The things you're asking aren't mutually inclusive;

I think you're getting confused between few separate things here;

An interference engine is a type of 4-stroke internal combustion piston engine in which one or more valves in the fully open position extends into any area through which the piston may travel.

So, if your timing belt/chain were to break/skip teeth, then you're going to have some valvetrain damage because some of the valves are going to be extended into the path of the piston at full travel (top dead center).

A non interference engine does not have the valves extend into the path of the pistons so a broken/skipped timing belt/chain doesn't necessarily mean a damaged valvetrain.

^None of that has to do with the headgasket blowing or being in-tact though.

Blown headgaskets can be in a number of different locations and for a number of different reasons. It also doesn't necessarily mean you're going to have a damaged rotating assembly. You could blow a headgasket between cylinders and all you'll have is low compression on those cylinders and a rough engine. You can blow a head gasket between an oil and coolant passage and wind up with milky oil that's overflowing. You can blow a headgasket between a cylinder and a coolant channel and wind up with overheating and boiling/aerated coolant. It really depends.

A siezed engine is a completely different thing altogether still. If the engine is siezed, you've most likely overheated main/journal bearings and or rod bearings and you're gonna have to tear the motor apart and have it inspected to determine the extent of the damage and what'd be required to get it in working order again.

I'd say if you blew a headgasket and continued driving the car until the engine siezed, it's PROBABLY toast and you'd do best to just find a replacement.

(I realize I didn't actually address bent rods and/or damaged rotating assy beyond the bearing side of things. Bent rods/damaged pistons don't result in a blown headgasket but may result in valvetrain damage if parts of the piston/rings are scattered into the combustion chamber.)

Daveyboy
12-26-2020, 10:53 PM
Hey!

Wow thanks for the great insight!
I wasn’t driving the car but I did get to it a couple of minutes after it supposedly seized..
There was coolant bubbling out the cam case and hoses etc.
There was also a small fire around the ac compressor under exhaust manifold area which was put out straight away.
A new engine has been ordered and the blown engine will be stripped and checked for damage and rebuilt giving the block is still okay!

first time stripping and rebuilding a sr20det and looking forward to it!

Phlip
12-27-2020, 05:44 AM
Blown headgaskets can be in a number of different locations and for a number of different reasons. It also doesn't necessarily mean you're going to have a damaged rotating assembly. You could blow a headgasket between cylinders and all you'll have is low compression on those cylinders and a rough engine. You can blow a head gasket between an oil and coolant passage and wind up with milky oil that's overflowing. You can blow a headgasket between a cylinder and a coolant channel and wind up with overheating and boiling/aerated coolant. It really depends.


I'd say if you blew a headgasket and continued driving the car until the engine siezed, it's PROBABLY toast and you'd do best to just find a replacement.
I did the bolded thing for months... Lived three miles from my job, car would puke coolant when I let it get to operating temp. Drove the car from NC to GA twice while it was happening like a dumbass.
My 20s were a wild time.
Did the head gasket, had the head fully checked out while it was off, resumed daily driving the car for four and a half more years and nary an issue.

NukeKS14
12-27-2020, 09:17 AM
Hey!

Wow thanks for the great insight!

first time stripping and rebuilding a sr20det and looking forward to it!

No problem. There are a lot of great resources out there for what you're doing. Good luck and my best advice is to find a reputable machine shop in your area and talk to them BEFORE you buy any parts. Most of those machinists can save you a lot of money and wasted parts in the long run if you just take the time to sit down and talk about your goals for the motor and listen to their advice. Getting hard to find great ones these days but IN GENERAL, if I walk in to a machinist and he's got engine parts and jobs all over the place it means they're busy and, to me, that's a good sign. If it's squeaky clean and you could eat off of the floor I tend to excuse myself. Always exceptions to that but it's been my experience anyhow. If you can't find one, Mazworx in Florida is awesome and from what I understand, he's the exception to the squeaky clean shop rule I have. I've done business with them and have testimony from people who've had him do machine work to their engine that I trust as well. He's got quite the catalog for high power SR stuff.

I did the bolded thing for months... Lived three miles from my job, car would puke coolant when I let it get to operating temp. Drove the car from NC to GA twice while it was happening like a dumbass.
My 20s were a wild time.
Did the head gasket, had the head fully checked out while it was off, resumed daily driving the car for four and a half more years and nary an issue.

Nice. Yeah it's hugely rewarding to knock out work on your own car. Not for the uninitiated/faint of heart for sure. I'd like to be telling your story in a few year after rebuilding my KA from cracked ringlands last winter (although I don't daily it; that'd end my carpooling days real quick.)

Daveyboy
12-27-2020, 06:29 PM
I did the bolded thing for months... Lived three miles from my job, car would puke coolant when I let it get to operating temp. Drove the car from NC to GA twice while it was happening like a dumbass.
My 20s were a wild time.
Did the head gasket, had the head fully checked out while it was off, resumed daily driving the car for four and a half more years and nary an issue.

Oh, lucky! I hope I can have the same luck as you mate!
I?ll post in to let you know how I get on!

[QUOTE=NukeKS14;6403958]No problem. There are a lot of great resources out there for what you're doing. Good luck and my best advice is to find a reputable machine shop in your area and talk to them BEFORE you buy any parts. Most of those machinists can save you a lot of money and wasted parts in the long run if you just take the time to sit down and talk about your goals for the motor and listen to their advice. Getting hard to find great ones these days but IN GENERAL, if I walk in to a machinist and he's got engine parts and jobs all over the place it means they're busy and, to me, that's a good sign. If it's squeaky clean and you could eat off of the floor I tend to excuse myself. Always exceptions to that but it's been my experience anyhow. If you can't find one, Mazworx in Florida is awesome and from what I understand, he's the exception to the squeaky clean shop rule I have. I've done business with them and have testimony from people who've had him do machine work to their engine that I trust as well. He's got quite the catalog for high power SR stuff.

Yes I see, thanks again for the great advice!!
I?m actually based in Okinawa! And I got a parts shop here that knows the Silvia well as I?ve been there too many times since I first layed eyes on it, (it didn?t run and wasn?t easy on the eyes). Since I got another engine coming from main land japan I can take my time and rebuild this engine and give it the clean up it deserves!

Thanks again for the advice!