Head swap vs remanufacturing head on current car

yanga001 · Post by **yanga001** » 23 Dec 2022, 10:47

Hi Everyone,

So after two years of rough starts in the cold i think i may have a head gasket leak on the number 2 cylinder. I did a compression test about a year ago and all cylinders tested good so i thought nothing of it. Will do another one when the weather permits but wanted to plan for the worst.

I have a crashed v70 with an engine that burned a bit of oil (thinking piston rings) but was not overheated and has a good head for sure. I was wondering if it would make sense to take off that head, get it machined, redo the seals myself and then have my mechanic do the fitment and swap at the end as he is a good indy. Seems like it would save a good amount of time and labour.

The engines are the same years and i cannot think of a reason why the two heads would not fit. I would want to redo the seals on the donor head for my own knowledge and sanity. That car had about 340k km, the one i am driving has about 400k km.

The general consensus seems that reworking the head is more economical then an engine swap. The other advantage for me is that i could rebuild the donor head and continue to drive the current car.

Car needs a headliner which i have spare, a new flex pipe, and to swap the o2 sensor from a donor car into it. Outside of that i have a good amount of newer parts on it, and the used car market is insane. It would also be beneficial to tap into my parts to save money.

Post by **Clemens** » 23 Dec 2022, 15:15

That head swap with the one out of your other p80 sounds like a good idea. Down time is minimized, you save on parts and even if some valves were bad on your donor head you could use good ones out of your current head. sounds like a win win situation. Just make sure they are both VVT or non VVT (I think all 98s were non VVT, but I've never even been under the hood of a 98 p80).

Post by **wizechatmgr** » 23 Dec 2022, 15:48

If you have to swap valves, make sure to lap them in, don't just drop them in.

Post by **abscate** » 23 Dec 2022, 15:51

You need to match turbo to turbo heads, the valves are different.

No VVT on -1998 models

Post by **erikv11** » 23 Dec 2022, 15:52

Correct Clemens, all 98 were non-VVT (in the US market). Since those are both 98 NA engines (looking at OP's signature) I completely agree - rework the other head out of the car, then swap it in. Volvo brand only on the valve stem seals, e.g. https://parts.volvocarslisle.com/p/volv ... 72424.html.

Post by **scot850** » 24 Dec 2022, 10:28

I'll redo my note from yesterday as when I tried to post it the system here went down!

I would rebuild the current head as long as it is a suitable candidate. That way provided the bottom end has not had any damage, the engine will last many years more with re-ground valves and new stem seals and head gasket.

A used engine is a lottery as the effort to swap it over makes no sense unless your engine has grenade'd. Even unless you have seen the engine running before it was pulled you have no guarantee what you have.

The proviso here is if you get a really low mileage engine and re-gasket it then it makes more sense.

Neil.

Post by **kallekula** » 24 Dec 2022, 15:36

Let the machine shop do everything. It’ll save you time and head ache and it will look and function like a brand new head. That’s what I would do anyway. Good luck and merry xmas!

Post by **erikv11** » 24 Dec 2022, 19:37

That's what I've always done - give the machine shop the head, cam cover (to clean) and valve stem seals then come back when it's all shiny and ready to install. For me, it's plenty enough detail work to properly prep the block surface.

Post by **kallekula** » 25 Dec 2022, 09:26

Yeah block surface and pistons is all im willing to do. On some engines the pistons didn't even need cleaning. Difference between filling up with top tier gas and junk gas i guess.

yanga001 · Post by **yanga001** » 07 Jan 2023, 00:29

Wanted to update this thread:

So checking cylinder 2 and 3 after the engine was hot i noted that there was some liquid in cylinder 2 and a little less in cylinder 3. I do not seem to drain a coolant bottle over any small distances, and just completed a 600km trip with maybe 1/6 of the reservoir dropping, My only issue with the engine is on a cold start or hot start where it seems coolant leaks in.

I may go the route of pulling the head off my crashed car against my mechanics advice (he says an engine swap is the way to go as too many other things can go wrong), however in the meantime i have been eyeing some blue devil head gasket sealer.

I believe i have a very minor leak in this case which means it will either buy me the time or work for now. If i did change the head i would use the one i pulled from another vehicle as it would be faster and easier in my situation. Everything i have researched into the early hours comes to "this stuff really works" or "this is snake oil". The ones that seem to fail seem to be applications where vehicles drain a coolant reservior in one use. My car does not overheat, it doesnt lose coolant at a significant rate, and it runs great after it evacuates all the liquid from the cylinder.

I would do a full flush of my system with coolant flush however it is cold up here in Canada so i cannot leave the water in the system. I read soewhere that this stuff really only works with water so i would need to treat it for the 50 minutes, let it cool, and then swap in the normal prestone antifreeze i run and cross my fingers.