doug2507

iTrader: (6)

Hi,

I'm going to be strapping a pair of V6 heads onto my 257. I've been on the phone to someone regarding working the heads (chambers matched to 2.5/port/polish) and have been advised that V5/6 heads are not the best suited for the job. They recommended getting a set of V3/4 heads due to the later ones cracking between the sparkplug and exh. valves.

Has anyone had any experience with failures on these heads? I'm on a fairly tight budget and dont want to have to go source another set of heads/manifold etc.

Engine will be a built 2.5 with a 20g for competition.

Doug.

Playsatan

iTrader: (2)

I heard the same when fitting my v5's to my 2.33. Absolute rubbish.

Look at all the big power cars (Andy F, Lateral etc), they all run v5's. I'm not saying they are better or worse, just that they won't be a problem.

doug2507

iTrader: (6)

Cheers...

Anyone else like to comment before i commit...

Peanuts

iTrader: (15)

I would have agreed entirely, were it not for the fact that I was witness to 2 seperate sets of v5 heads being stripped from engines and both had little cracks that warrented them being binned.

doug2507

iTrader: (6)

Do you think this is mileage/output related or just in general?

Peanuts

iTrader: (15)

hhhmmm, both cars were on the happy side of 350, 1 at 40k miles and 1 at about 50k miles.
Both had seen track time and more than a few shots up the strip.

But if you had a tuned motor you would be using it in this fashion anyway? so a normal useage etc applys.

Interestingly, I stripped back some v1-2 heads that had seen hard 158,000 kms and the heads were tip top ready to re-use

doug2507

iTrader: (6)

Seems like it will be a bit of a gamble using them then. Its just one ballache after another...

Whats the worst that could happen if the heads cracked..??

ZEN Performance

My heads are cracked, they were cracked a long time ago, and haven't been a problem. I would be nice to not have cracks, but hey ho, I can't afford new heads every 6 months.

V3/4 heads would require a new inlet manifold and opens up a generally sizeable can of worms. What ECU are you going to run?

Peanuts

iTrader: (15)

o/t- Paul is the v2 dccd ecu on the left side of the steering wheel?

jaytc2003

iTrader: (1)

slightly off topic but are the v1 heads any good?

Peanuts

iTrader: (15)

I heard that v1 sti heads arent that great, allegedly the v1-2 RA heads are better but 3/4 onwards is where the fun starts to kick in.
my own v5 heads on my last car were fantastic!

jaytc2003

iTrader: (1)

sorry Doug2507 for jumping in, but I dont suppose anyone has a link where I can find out about the differences between the heads used etc?

doug2507

iTrader: (6)

Andy, on the left on mine but think Paul mentioned the earlier ones are on the right?? Can get you a pic of mine later on if you want...(dash out so everything exposed...ish)

Sticking with the Apexi. A motec would be nice but its not an option. Gearbox 1st.

My main aim for concern is reliability. The bottom end should be fine. LP rods, mahle pistons, race bearings, cometic etc. Even the bores at the moment are perfect. Still showing previous honing marks and +.002 clearance for pistons. (.001-.003 required). Putting it together myself (1st time doing a rebuild myslef ) providing there are no issues fitting the bearings/crank.

The only reason i'm getting the heads done/chambers matched for the 2.5 is to keep it together, and hopefully produce a better/smother/responsive engine. Was contemplating doing the ports myself (matched to gasket/polish/knife edge) and the inlet manifold/t.b etc.

I dont want to spend £500+ getting the chambers done if the heads are going to be thrown in the bin after a couple of seasons.....On the other hand i dont want the expense of new heads/manifold and the rest that goes with it.....

RCM advised changing to ver3/4 when i spoke to them about getting the heads done. £550+vat for opening up the the chambers and £600+vat for port/polish which is a bit more than i'm intending on spending on heads for a 20g 2.5.

Also looking into the possibility getting the block/heads ringed (like wills rings in an imp engine) but RCM dont do them for an open deck (semi) and dont know anyone that does....

Email sent to SMG for advice/headwork/rings.

Peanuts

iTrader: (15)

SMG do porting for much less money than you quote above!

looking into compatibility of your ecu and my loom etc as well, as per other thread
unless you can pull out your loom into the bargain?

doug2507

iTrader: (6)

Had a look at that the other day for Graham but its a BIG job. The loom for the dccd ecu goes into the main loom so separating the wires would be too much of a headache. After studying my pdf making a new loom doesnt look that hard tbh. Its all fairly simple stuff, even for a numpty like myself...

Peanuts

iTrader: (15)

I suppose the million dollar question is.......

Are the controllers compatible....?

doug2507

iTrader: (6)

In what respect.?

I'd be willing to send it down to you to try out if there are any suspected issues.

Would think it would be generic throughout the classics but thats just a guess....

Peanuts

iTrader: (15)

okily dokily
pm winging its way to you now

doug2507

iTrader: (6)

Paul, i've just had a look through J.B's 2.5 thread (for the hundredth time!) for a guide as to what works and what doesnt.

The rings idea is right out the window as i'm using a cometic gasket. (1.6). Whats the best way for ensuring that the block and heads are flat as can be? For measuring, do i just take measurements off as many points of the block face/heads as i can?

Quite happy to have my V6 heads done now after a bit of research. Theyve done 65k now with no sign of any problem. If they crack, they crack.

I'm on a steep learning curve at the moment so any usefull advice would be appreciated.

Btw, i noticed what i can only describe as what looks like a birth mark about 1/3-1/2 way down one of the bores. Scored my nail over it and couldnt even feel it. If you know what i mean, whats caused it?

Kevin Groat

Doug,

Only just caught up on this thread, can't help regards the choice of heads but if you're needing any physical help give me a shout. I live just around the corner from you and I'm giving serious thought to 2.5'ing my STI V3. Wouldn't mind having a look at your car/engine while it's in bits. My plans had been to use the new 2.5 short block and my V3 engine as a donor. Having run my car on the rolling road in Ellon at the SIDC day I think the V3 heads/cams may be somewhat wild for the 2.5 lump. I managed 326 bhp @ 7,500 rpm and that's the standard engine with a decat and k&n - I suspect running max bhp @ 7,500 rpm wouldn't suit the 2.5 lump, anything you've read that might shed some light on this?

R19KET

Don't worry about the V3 heads/cams being too big for the 2.5lt. The 2.5lt will eat them well before you get to 7500rpm................

Don't forget the 2.5lt is 25% bigger.


Mark.

Type-R

Running V3 heads on my 2.5 Type R 330/340
No Probs ! so far anyway !

doug2507

iTrader: (6)

Kevin, where abouts are you? Feel free to come round if you want, the kettles always on. Away abroad on Sat afternoon till ~Oct sometime though. Splitting the block tonight which should be interesting....

Back on the subject of heads....there doesnt seem to be much metal between the valves. How are o/s valves fitted? Offset?

What sort of C.R should i be looking to achieve with this engine? (new v-max a consideration?)

Kevin Groat

Doug, I'm in Logierieve - the old Smiddy. The STi v3 is a white wagon and we've a blue Legacy GTB as well. Is your car in the garage at the house? I know roughly whereabouts, which number is it?
Don't know if I'll manage tonight as I've a golf electric window to sort

doug2507

iTrader: (6)

Ah...drove by the other day and saw you tinkering on it with the bonet up. Lovely looking wagon! Number 6 mate. Think there's a bloomin big caravan sitting outside the neighbours for reference. Just give us a shout if you're gonna pop your head in. Should be in all week.

Cars round the back of the house. Had to shuffle some stuff around the garage just to fit the engine/myself in!

harvey

iTrader: (48)

Many V5 V6 STi heads I have seen have a crack from the plug hole to the valve seat. About 50%. First time I saw this and the head was replaced. A short time after the head came off again and although it was a new casting there was a crack in one of the combustion chambers again. I then found this was a common problem, probably an inherrent / manufacturing fault and as long as the crack is not too bad affecting the valve seat the engine seems to perform OK.