B230ft bottom end with a 405 head?

Hey all

For those of you who don't know, I need a new engine, relatively soon. Head and block are in need of work. Rainbow auto service believe the piston rings failed on 1, 4 is following close behind (low compression). Anyway, I've got some stuff in the garage that I'm curious if it'll work.

I have a 94 b230ft complete engine and a few heads.

I believe there's a 398 head sitting in there too. *Just checked, its a 398, with a later style raised valve cover.

My goal is to keep kjet (for the time being), either use that 398 or a 405 kjet head. I've been informed that the 405 won't work without modifying the coolant jackets on the head. This got me thinking about what else could go wrong.

As of now my plans are to use the b230ft bottom end, and some kjet head on top. At this time I need to stay with kjet. Kinda need to throw something together sooner rather than later.

But we will see how long this 3 cyl redblock lasts.

To sum it up: I want to know if a 398 head or 405 head will bolt up to a 94+b230ft block, without major work. I need to keep kjet for now.

It’ll all bolt together.

culberro said:

It?ll all bolt together.

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a 405 kjet head will bolt up to a b230ft block without issues? i thought the coolant passages didnt line up?

ogamer777 said:

a 405 kjet head will bolt up to a b230ft block without issues? i thought the coolant passages didnt line up?

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Grab a head gasket and overlay it, but I'm 99.9999% sure there's not an issue. The original motor in the rally car was a b230f with a k-jet head.

The oil passage area through the head gasket is the one area you'll want to double check. There should be either a divot in the head, or a divot in the block to allow oil to flow easier to the head. Otherwise, the oil has to transfer from the block feed, to the head bolt hole via the small gap in the HG. That's not ideal.

It will go together fine. I've done it - 405 head on a 95 b230ft, not to mention a lot of other people. The main issue people have is the larger coolant passage head doesn't bode well with big boost apparently. Though you will also find people on here specifically have run ~14lbs and survived.

culberro said:

Grab a head gasket and overlay it, but I'm 99.9999% sure there's not an issue. The original motor in the rally car was a b230f with a k-jet head.

The oil passage area through the head gasket is the one area you'll want to double check. There should be either a divot in the head, or a divot in the block to allow oil to flow easier to the head. Otherwise, the oil has to transfer from the block feed, to the head bolt hole via the small gap in the HG. That's not ideal.

Click to expand...

Good to know. I'll order a gasket set and lay it on top once I get the head off the b230ft and see. Would that divot be absent in any case? Or would that mean that I need either a head with the divot or the block needs it? So not necessarily any head/block combo will work?

jlfenton95 said:

It will go together fine. I've done it - 405 head on a 95 b230ft, not to mention a lot of other people. The main issue people have is the larger coolant passage head doesn't bode well with big boost apparently. Though you will also find people on here specifically have run ~14lbs and survived.

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That's what I was concerned about. SCP vs BCP head. I believe 405 could come with either? Or I may be mixed up with the 531 head. I am not running any boost higher than 13ishPSI (stock turbo+intercooler overboost switch installed), but for futureproof purposes, I would like a SCP head.

*According to the internet* you will be good with that boost level. Before I did my motor I researched the hell out of this topic and concluded that things should be ok. Considering some of the sources were reputable long time users on here (can't remember who though) were saying they ran at ~14lbs I went with it. I'm still sorting out some things because I'm a noob etc, so I've only had it at 5-6lbs. Sidenote with a gtx28 the car is f'n fun! My first turbo car.

The SCP 405 head: I live in Australia so my research on what came when was regarding Australia, but it might also match to what you yanks got. The SCP 405 head only came on B23 turbos in I believe '84 in 740's, so they were EFI - no kjet injector holes. The rest are BCP.

jlfenton95 said:

*According to the internet* you will be good with that boost level. Before I did my motor I researched the hell out of this topic and concluded that things should be ok. Considering some of the sources were reputable long time users on here (can't remember who though) were saying they ran at ~14lbs I went with it. I'm still sorting out some things because I'm a noob etc, so I've only had it at 5-6lbs. Sidenote with a gtx28 the car is f'n fun! My first turbo car.

The SCP 405 head: I live in Australia so my research on what came when was regarding Australia, but it might also match to what you yanks got. The SCP 405 head only came on B23 turbos in I believe '84 in 740's, so they were EFI - no kjet injector holes. The rest are BCP.

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I am sure if Jaughlin comes across this post he will clear things up. Here in the states, I believe the only b23ft in a 240 you could get was a late 85, so options are somewhat scarce.

ogamer777 said:

Good to know. I'll order a gasket set and lay it on top once I get the head off the b230ft and see. Would that divot be absent in any case? Or would that mean that I need either a head with the divot or the block needs it? So not necessarily any head/block combo will work?

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There should be either a divot in the block, in the head, or both. If you end up with a combo where there?s no divot in either, you can add them easily enough.
The factory just drilled the block with a shallow ~6mm hole between the head bolt threads and the oil feed, connecting them. On the head side, the divot is cast in. You can easily trace it out (using a HG aaa a guide), and then add a relief that?s ~1mm deep with a dremel.

The north american 405 head is a big coolant passage.

They were available here only on the B23E, in Canada.

I've put them on B230's. I've never noticed the divot before, but I've never had any problems. I've run upwards of 18PSI for 50K Km with a Garret 60 trim T3 without issue.

Jordan

I put a BCP 405 from a conadian B23E on my B21FT over ten years ago and it's still running well. The engine is getting a little tired at 340k miles but the head is fine as that was rebuilt and installed at 275k miles.

In the Mike Aaro cylinder head aritcle. The word was not to run boost levels significantly above stock on a BCP head. Which in my experience it's been fine at 12-13psi for all this time. If you are going to run higher boost than that. He advised having the head welded so the passages are stronger before subjecting it to boost that high.

For reference, here are some pics of the oil passage divot and head gasket teardrop (click for full size):



The first 3 pics are a B21FT block (after machining) and a KJet 160 head (untouched), showing divots in both block and head. I ground down block divot a little more to make up for the machine shop decking. The 4th picture is of a B230 block where the divot is a comparatively deep blind drill hole between the passages.

I used the 530 head from the B230 on my B21FT, but the 530 head had been previously machined so I don't know if it had a divot from the factory, or if the deeper block divot was all it ever had.

OK based on your guys' input, I am leaning towards a 405. Anyone in PNW have one they wanna part with? I am gonna keep boost maxed at stock intercooler limit, 12.5ishPSI

Thanks bobxyz. Would it be beneficial to mill that divot a little more? Idea being more oil flow, better engine cooling?