Should I build/buy a built head?

OK, so most of you will know about my twin turbo install.

The good news is that it's nearlly time to start putting parts back onto the car!

I was going to start cleaning the block and the head in the next few days, but I've been thinking about removing the head and bolting on a built job, including cams, valves, retainers, springs and a port job.

Thing is, if I do this, I'm going to have to take out a loan. Without doing the head the install will owe me about £6K when all done and dusted, and I'd probably have to budget close to £2.5K for a built head if it was to be done properly.

So what do you guys recon?

I think bang per buck I'd just swap the cams and re shim them... you won't IMO gain enough to warrent the expense if you spend 2.5k.

I'd go for 264i/264e or 272i/264e (with timing adjustments to limit overlap) Jun Cams and Jun Cam Gears.

I guess it depends what your ultimate goal is and if you think it makes financial and labour time sense to do it now (if you need to do it all) or do it later.

Alexs comment makes sense to me.

OK so I think I'm going to go with Alex's advice.

Next question, which cams?

I want to try and drive the torque curve as far down the rev range as possible. So I'm thinking about maybe going for something like a 264 inlet 272 exhaust.

What do you guys recon?

Prob speak to Terry S or maybe CW re cam choice

OK so I think I'm going to go with Alex's advice.

 

Next question, which cams?

I want to try and drive the torque curve as far down the rev range as possible. So I'm thinking about maybe going for something like a 264 inlet 272 exhaust.

 

What do you guys recon?

I believe you have to minimise the overlap for torque...Basically the longer the valves stay shut the better, as this puts more energy into pushing the piston down, but then you've got to get the air out and have a clean burn too...

As I said I'd go for JUN cams. This is not because of willy waving but because they have more lift than the equivelent HKS cams. The extra lift means you can run a shorter duration.

It all depends on what you want from the engine, prower levels, boost levels etc. If you want torque then I think you should go 264in and 256ex (JUN 9.3mm lift Cams) if you will be using high rpms a lot then go up a stage to 272in/264ex....

That's my understanding but I'd prefer you to confirm that with someone that's down it. FWIW though the VALCON system for the VVTi switches the intake from a 256 to a 272 through the rev range...the 256 at low rpm's for torque and the 272 a high rpms for power...so going by that I think I'm right in what I've said.

JUN cams, for sure, a copy of a Cosworth profile i believe, more lift, as Alex says, and very accurately ground. I'd go for 272's both sides or thereabouts. I went much wilder with my Skyline, but it's a track car, and will rev safely a lot higher than the JZA80

Nice one chaps.

The turbo's I'm using are supposedly rated up to 900bhp, which is stupid power and the rest of the car isn't built for it. Most specifically the clutch I've got won't stand much more than 650lb ft. So with the top end effectively "capped", I'm thinking of trying to exploit more down the bottom end, so may well go with the 264/256.

Good info on the Juns though.

Cheers,

Tony

Has anyone tried the 272/264 combo yet, mine are sitting in my house waiting to go on, but i wanna dyno before and after to see the affects.

Has anyone tried the 272/264 combo yet, mine are sitting in my house waiting to go on, but i wanna dyno before and after to see the affects.

Ian's will be tested soon...just not yet.

I'd love to know who has voted for building a head...

I'd love to know who has voted for building a head...

Not me

I voted for it.

1. More power at lower boost (VERY important on pump fuel)

2. Larger powerband from incresed revs (nice on any car, VERY nice on one with such big turbos)

I would be sticking in 272I and 264E cams with some slightly stiffer springs (maybe 60lb off the seat). If you can afford to have some headwork done (by someone who really does know what they are doing) then I would at least give the head some attention in the throat area, some polishing of the combustion chambers, a decent valve seat job, check the chamber volumes.

Then if you could stretch to it (and no doubt against what some people will say) I would get the ports opened a little and I would probably raise the CR a little nearer to 9:1 and fit oversize valves on both the intake and exhaust. With the ports modified to suit and the larger valve sizes you will see more torque for less boost and the raised CR will help with the spool and low speed torque. If you're not planning on running stupid boost figures (which you shouldn't anyway with the stock pistons and liners) then this will net you some good gains. If I remember you have an AEM, no doubt you're running on Optimax 100% of the time and have excellent intercooling, cooling system and you should budget for an oil cooler at some point - it might not be needed but be prepared to fork out for a kit if your oil temps go much over 110degrees.

The big unknown is your turbo system, I do not know anything about it. It may be that those turbos need over 1.5bar of boost to even get anywhere near their peak efficiency. My suggestions really hinge around a correctly matched turbo kit. If the kit is good for 900bhp you might be a little disappointed with the trade off in spool time copared to torque figures running daily boost of a max of say 1.25-1.3bar. At least with a decent valvetrain you'll be able to venture a little higher rpm wise, increasing the powerband for those big blowers! I hope it all works out well though, looking forward to the results.

By the way, I know a great head guy in the US and am back and forth a fair bit with parts etc. If you want some contact details or at least someone to discuss things with pm me and I'll give you his details. Although, you're probably not a million miles from people who can do the work you want though are you! Anyway, just let me know.

I voted for it.

 

1. More power at lower boost (VERY important on pump fuel)

 

2. Larger powerband from incresed revs (nice on any car, VERY nice on one with such big turbos)

agreed with this do it then at a later date add what i believe to be the best combo without the need for new valves etc 264/264 combo

BTW: I voted for the headwork but personally I would not take out a loan and put myself in debt to do it. Depends how short term the loan/debt is planned to be I suppose.