MKIV TT Head rebuild pics

Ages and ages ago I asked if people were interested in tech pics of jobs I do here, then forgot all about it...

Anyway, if anyone is interested here, with owners permission, are some pics of a rebuild and very mild gas flow job on a used MKIV TT head. I cleaned up the exhust ports under the seats, did a 3 angle valve seat job, and radiused the backs of the inlet valves. The exhaust valves were cut with a wide seat to dissipate heat better, a narrow seat flows better, but this is a road car engine to be used in a hot country, so longevity was paramount. Unseen in the pics, the exhaust valve guides were sleeved with phosphor bronze inserts, and the valve buckets (tappets) which had become water damaged (rust...), were blasted with coconut shell to reclaim them, the damage was minor, thankfully and they cleaned up fine. As hopefully can be seen, cleanliness is essential, prior to the re assembly the head was hot tanked, then steam cleaned, paying attention to all oil feeds. The cams fitted were HKS, as were the adjustable vernier timing wheels. The original shims were ground on my surface grinder to suit the new clearances. If people find this stuff interesting I'll try and take my camera out to the workshop more often, currently it is being used to follow the hatching of a bantam, from shell to fully mature (hopefully...) then the same with some peafowl. Anyone wanting pics of this need only ask, the wife will be VERY happy to share the magic moments :-)

Head pics, in thumbnail format, click to enlarge, are at:

http://www.formula3.demon.co.uk/mkiv_head/mkiv_head.html

very interesting Chris.

what do you estimate are the power / torque benefits of this head work ?

My (limited & probably wrong) knowledge of the benefits of head-work / gas flowing etc. suggest that it's a highly time-intensive (and therefore £££ intensive) process which although does offer benefits, might be out-weighed on a turbo-motor by other methods. (on a bhp per buck basis).

On an atmo-engine, where there's fewer options for big bhp/torque improvement I guess head-work is higher up the list though ?

interested in your experiences etc.

Originally posted by Doughie

very interesting Chris.

what do you estimate are the power / torque benefits of this head work ?

My (limited & probably wrong) knowledge of the benefits of head-work / gas flowing etc. suggest that it's a highly time-intensive (and therefore £££ intensive) process which although does offer benefits, might be out-weighed on a turbo-motor by other methods. (on a bhp per buck basis).

 

On an atmo-engine, where there's fewer options for big bhp/torque improvement I guess head-work is higher up the list though ?

 

interested in your experiences etc.

Correct, better places to spend money on most turbo engines, but as the head needing stripping anyway, and the port work was very basic, and only around the exhaust ports, it seemed a good time to just tidy it up a tad. Valve seats needed doing anyway, so radiusing the valve backs was no big deal, and i use a 3 angle stone for the seats as a matter of course on "nice" heads.

On an N/A engine, particularly a race head, I would have gone a LOT LOT further. Actually, caveat here, most race heads, from pukka race engines, are extermely good to start with, but YKWIM :-)

it must be very interesting as a performance tuner / to take a close-up look at the state of the head-work that Toyota themselves settled on during design of the mkiv. I guess that you can read a lot into that with regards their opinion of where they, as a manufcaturer of a performance car, should "pitch" the cylinder heads of the mkiv in the performance curve.

in the end, I think that Toyota has such a reputation with regds. to reliability / longevity that even on a mkiv, their fastest road car, they would always err on the side of caution. I guess ultimately that's the philosophy of their company, and it's served them pretty well.

Or is it just a matter of pure economics that manufacturers "skimp" on stuff like head work cos it simply takes along time to do ?

It is good to see that head again, it looks so much better than the last time I saw it.

I am pleased the minor rust was not too big a problem.

Thanks for posting the pictures, it is good to see the work of true a crafts man.

When I took the head off the donor car it looked like the MKIV set up may be none interference.

Originally posted by Doughie

it must be very interesting as a performance tuner / to take a close-up look at the state of the head-work that Toyota themselves settled on during design of the mkiv. I guess that you can read a lot into that with regards their opinion of where they, as a manufcaturer of a performance car, should "pitch" the cylinder heads of the mkiv in the performance curve.

 

in the end, I think that Toyota has such a reputation with regds. to reliability / longevity that even on a mkiv, their fastest road car, they would always err on the side of caution. I guess ultimately that's the philosophy of their company, and it's served them pretty well.

 

Or is it just a matter of pure economics that manufacturers "skimp" on stuff like head work cos it simply takes along time to do ?

Modern heads are virtually invariably very good. They have to be to meet emissions and give good economy. The MKIV head is excellent, good chamber shape, good port shape, good port velocity ( a pal measured a head a while ago on his decent flow bench, the figures were very good for a production head).

Modern casting techniques can produce good shapes with good finishes. Cosworth still produce some of the best castings, and it is amazing just who they do stuff for. I would be very surprised if Cosworth hadn't had some input into the MKIV head, the ports and chambers smell "Cosworthy" to me.

The cam followers are very light for a shim under lobe set up, and are a fair diameter, although a really wild pair of cams could run the risk of needing a bigger follwer, and there isn't much room to accomodate those. The cams themselves are excellent and hollow, saving weight and running cooler.

Originally posted by Terminator

It is good to see that head again, it looks so much better than the last time I saw it.

 

I am pleased the minor rust was not too big a problem.

 

Thanks for posting the pictures, it is good to see the work of true a crafts man.

 

When I took the head off the donor car it looked like the MKIV set up may be none interference.

Thanks! The head / valve interface with STOCK cams is none interference, not sure with the HKS ones, always assume NOT when in doubt!

Just resurrecting this thread. The head that Chris did the work on was mine and is still going strong, now mated to my rebuilt engine.

Chris do you still have the pics of the head? The link no longer works, could you relink the pics if possible, as it may be useful reference for others.

cheers

Sorry, I think they are long gone.

I don't know if any of you have seen this website, some nice articles. I found this one a while ago, and after reading this thread I though it might be of interest, especially to you Chris.

http://www.t04r.com/techarticle.php?id=5

Cheers,

Mark