¡¡I've just found a aq171 for 600 bucks!! What pistons to use???

[Jan F]

Hello my name is Jan and I'm new to turbobriks, im from spain and i've recently aquired a 91 volvo 740 sedan for 600 bucks with a blown b230fb, then I bought a 96 b230fk squirter block, I was going to build it with the 531 that comes with the FB, but i broke one thread from the camshaft support, I was going to fix it for abt 500 bucks but then looking for some booat engines for a 2.5 stroker, to my surprise i found a aq171 wich is a 2.5 16v for 600 bucks with seased pistons to the block, no probloem since I am using the b230fk for the block, but i have read that the pistons for the 16v are diferent.
My question is, do i buy 16v pistons? do I modify the 8v pistons?
I have thinked to try and save the aq171 pistons but I have little hope.
Thanks!

 

[Radtap]

Do you plan on putting a turbo on the engine or leave it NA?

 

[Jan F]

Do you plan on putting a turbo on the engine or leave it NA?

Yes i was planing a yoshifab manifold adapter with a stock turbo or if i find something cheap maybe a whiteblock t5 td04, and planing on at least forged rods with reinforced bearings with an o ringed block and arp head studs and main studs for more power in the future, i've seen people machine the pistons to acomodate the valves, but my engine is a low compression and maybe i would nopt interfeer? idk

 

[ZVOLV]

It sounds like it would make a good boat anchor. The cylinder walls are going to be all rusty, the head is rusty, and the coolant passages are probably going to be clogged with rust.

 

[OVERDRIVE]

The 2.5 crank may or not fit your block because they changed the bearings sometime around 87/88. There are forged 16V 86mm stroke pistons you can buy right off the shelf. You will need pistons for 86mm stroke. Low compression/high compression doesn't matter with valve relief, the cc difference is not in deck height but the dish size. Penta heads are often really thrashed and need major repairs that could outweigh the cost of buying a B234F 16V head.

 

[Jan F]

The 2.5 crank may or not fit your block because they changed the bearings sometime around 87/88. There are forged 16V 86mm stroke pistons you can buy right off the shelf. You will need pistons for 86mm stroke. Low compression/high compression doesn't matter with valve relief, the cc difference is not in deck height but the dish size. Penta heads are often really thrashed and need major repairs that could outweigh the cost of buying a B234F 16V head.

I have thinked of that in theorie the dude selling it says that the head is fine and that it has low hours of use, i am of course going to check as much as I can for flaws, regarding the crank im going to try if not im going to list it to ebay or this forum

 

[Jan F]

It sounds like it would make a good boat anchor. The cylinder walls are going to be all rusty, the head is rusty, and the coolant passages are probably going to be clogged with rust.

You sound really fun at parties, ofc im not going to buy an engine whithout inspecting it but for 600 bucks is wotrh the 3h drive there, if I dont like what I see I won't buy it

 

[mikep]

I have thinked of that in theorie the dude selling it says that the head is fine and that it has low hours of use, i am of course going to check as much as I can for flaws, regarding the crank im going to try if not im going to list it to ebay or this forum

If it had a closed cooling system with water to water exchanger and a radiator cap, the head MIGHT be ok. Depends on how well it was maintained. If it was seawater cooled in salt or brackish, it is trash. The aluminum goes away before the iron it is bolted to.

 

[sbabbs]

The exhaust hole number 4 where the manifold bolts on is what gets eaten away the most on the head. I had one with some eating away so I had it welded up perfectly.. Easy to do as it's aluminum.. My machine shop motor builder did it. I'd check that hole. Also same thing if 8v boat head also, in those they put a steel ring. If motor is aq171C then it's rear thrust later style forges steel stroker crank.. If aq171a or b then center thrust..

 

[Jan F]

Update of the engine, the head is a quite rusty on just one cylinder, ended up getting the engine quite cheap for this, but the engine itself has very few hours literaly brand new in the places that water didnt get, the crank is mint, both are at the machine shop to see if the head is salvagable, looks like it is but rather expensive im going to fix it anyway bcs 16v

 

[Jan F]

The exhaust hole number 4 where the manifold bolts on is what gets eaten away the most on the head. I had one with some eating away so I had it welded up perfectly.. Easy to do as it's aluminum.. My machine shop motor builder did it. I'd check that hole. Also same thing if 8v boat head also, in those they put a steel ring. If motor is aq171C then it's rear thrust later style forges steel stroker crank.. If aq171a or b then center thrust..

i have recently disasembled both engines and both have rear thrust so it should be an aq171c i guess, so its an 89 this engine? idk luckily I can fix the head if not i do have a 531

 

[Harlard]

The 2.5 crank may or not fit your block because they changed the bearings sometime around 87/88. There are forged 16V 86mm stroke pistons you can buy right off the shelf. You will need pistons for 86mm stroke. Low compression/high compression doesn't matter with valve relief, the cc difference is not in deck height but the dish size. Penta heads are often really thrashed and need major repairs that could outweigh the cost of buying a B234F 16V head.

Late 88/Early 89 for the 1989 model year*

 

[bgpzfm142]

If your AQ171 2.5 litre crank has main bearings of 55mm diameter, it's one of the centre thrust bearing versions and won't fit into your B230FK block.

But if your 2.5 litre crank has 63mm diameter main bearings, it's a rear thrust bearing type and will fit okay.

Yoshifab (for one) sells suitable 16V pistons off of the shelf. KG Trimning and other places in the EU will also stock suitable pistons.

 

[Jan F]

Late 88/Early 89 for the 1989 model year*

I was llokin at ur photo and my engine ofc doesnt come with a car thermostate gousing but i have 2 from an 8v does it fit?

 

[Jan F]

If your AQ171 2.5 litre crank has main bearings of 55mm diameter, it's one of the centre thrust bearing versions and won't fit into your B230FK block.

But if your 2.5 litre crank has 63mm diameter main bearings, it's a rear thrust bearing type and will fit okay.

Yoshifab (for one) sells suitable 16V pistons off of the shelf. KG Trimning and other places in the EU will also stock suitable pistons

luckily its a rear thrust design i dissasembled it a coupple of days ago and it is already at the machine shop

 

[Jan F]

If it had a closed cooling system with water to water exchanger and a radiator cap, the head MIGHT be ok. Depends on how well it was maintained. If it was seawater cooled in salt or brackish, it is trash. The aluminum goes away before the iron it is bolted to.

it did it had the interchanger in front of the head gears, appart from beeing flooded in one cylinder the rest is literally mint

 

[ZVOLV]

Just put a new set of spark plugs in there and you're ready to go!

 

[fatcatbestcat]

Have you done a leak down test on that cylinder? Looks mint.

 

[spock345]

it did it had the interchanger in front of the head gears, appart from beeing flooded in one cylinder the rest is literally mint

Jan, I'm just gonna say it, that head is junk. The corrosion there looks bad enough that I doubt there is material left to hold the valve seats. It'll be cheaper just to go find another head.

 

[Harlard]

Jan, I'm just gonna say it, that head is junk. The corrosion there looks bad enough that I doubt there is material left to hold the valve seats. It'll be cheaper just to go find another head.

All of that is fixable with a lot of filler rod and many moneys’ worth of machine shop time.