Conflicting Information About Head Work

[Kane 34]

So, I have recently made a few phone calls to garages about prices for engine work that I will be looking to get on my mi16 prior to rebuilding. From what I have read here on the forum it is suggested to go for 3 angle cut seats and back cut valves although one machine shop has said to me that there would be relatively no benefit to me doing this.

 

Now I am a complete beginner when it comes to rebuilding engines and was looking to see if someone could clarify for me the advantages to getting this work done? My plan at the moment is to build a standard, reliable engine (as it will be my day to day runabout) but I do have the intention of adding bits and pieces like cams, possible throttle bodies etc at a later stage.

 

Sorry if this has been covered before, tried having a search and seems a lot of people just say to get it done not specifically what it will offer to the engine.

 

Cheers

 

Kane

[dcc 855]

a general search on google and a few hours reading on 3 angle valve seats is all what can help you here.

 

my own experiences are when I rebuilt my landrover head I didn't bother with getting seats cut, i just lapped the valves in, but with a higher performance engine, I got the seats cut (as per my own 2.2 engine build).

[Kane 34]

I think that I have a rough understanding that cutting valves and seats to suit will improve flow around the valves during operation thus increasing performance. Although the thing is that when I spoke to the machinist earlier he mentioned that there would be very low increases in flow (1-2 cubic feet I think is what he said) from doing this. Would this small increase in flow make a notable improvement on the overall performance?

 

I was all set on having the work done after seeing the amount of recommendations from people here on the forum but now that I have had someone tell me otherwise it has thrown me off a little.

[welshpug 1,657]

Its not about flow, its about how the air behaves.

[brumster 135 1 Cars]

I never bothered with 3 angle valves on my XU9J4 - just a complete refurb to original spec, mild skim, ARP rod bolts, dropped some lairy cams in, stuck it on bodies - job done lovely motor!

[Anthony 1,003]

XU9J4 and XU9J4Z had 3 angle valve seats as standard (or rather, they should do, but not always done very well)

[Kane 34]

Sorry I was just going on what I have read here:

 

http://www.carcraft.com/techarticles/116_0612_valve_angle/

 

From this article it seems that there can be vast improvements made on specific valves but obviously depending on the quality of valve/seat finish from the factory.

 

Yeah Anthony I have read the same on Taylor-eng.com that it is fairly rare to find correctly cut seats straight out the factory and unless your building a race engine then these heads flow relatively well enough at standard.

 

Seems like it will be fine to just get them cleaned up and lapped in, good for me as I'm trying to keep costs down.

 

Thanks for the advice

[welshpug 1,657]

Get them cut properly, and you wont need to lap them in, the trick is to put it together properly, good quality gaskets etc, most bits are available from a dealer at reasonable prices still, checl the bearing clearances with plastigauge, make sure you have an accurate torque wrench.

[Kane 34]

I think from what I have been reading I now have a little better understanding. I am going to get the valves and head cleaned up and see if the condition is up to scratch then from there I'll decide what option to go for.

 

I will be checking and double checking everything when I am putting it back together and will also be using quality parts so that should be fine.

 

Thanks again for the help

[GLPoomobile 958]

No expert speaking here, but if absorbing s*ite loads of info from the VERY well educated people of this forum, like sponge, for too many years counts, then here's my 2 cents.....

 

Build the head totally standard. An Mi16 head already flows very well. And if you were swayed towards a few modifications to take advantage of future upgrades, then for god's sake entrust the work to somebody who knows these engines and is recommended on here, not just some random engine builder you've found locally. For example, Mark Shillaber seems to be highly regraded for this sort of work, I believe.

[Kane 34]

I agree with what your saying and I would send the stuff away to someone recommended on here like Paul Gardias but that would stretch the budget even further which I doubt could do at the moment. Do you know where Mark is located or could you recommend anyone up this way that would be worth giving a call?

[welshpug 1,657]

carriage costs very little in the grand scheme of things when building an engine properly.

 

Seems a common theme, that many of the people to know in pug world are down in Cornwall!

 

Very little up in Scotland that is known of down here, or at least with a good rep...

[GLPoomobile 958]

There is one company up in this neck of the woods whose name would imply that they specialise in head work, but don't think you'll find many (any) recommendations to go anywhere near their front door

[Kane 34]

Oh yes I have heard of them.. ​ haha will not be using them I don't think

[petert 586]

A good 3 angle job can make a huge difference ie on an 8V XU. However, on an XU9J4, whilst it is on in the drawing, there is usually insufficient material in the seat insert to get the bottom cut it. ie the diameter of the seat insert is usually too large. Upgrading to a larger diameter valve is the only way to get a true 3 angle seat. I'm certainly not suggesting you attempt this, but here's a good yarn.

http://forum.205gtidrivers.com/index.php?showtopic=31290

Any decent head place will attempt to cut 3 angle seats by default, either with a carbide profile cutter or a full CNC seat cutter.

Your priority should be to make sure the guides are within spec first, then do your best with a three angle cut.

After cutting new seats there will be insufficient valve seat pressure, so you'll need to put an additional shim under each spring. A decent head place will also test your springs for you.

 

Other than postage, I don't see why sending a head to Paul Gardias or Mark Shallibar would be any different in price to a local shop. You'd know the quality of workmanship would be superb.

 

Even though you're building a standard engine, definitely upgrade the inlet cam, you'll never regret it. Something like the 16H426B is ideal.

Edited May 30, 2013 by petert

[Kane 34]

Thanks for your input Peter. I am planning on having the guides checked and replaced if necessary (or the use of k-lines).

 

After a couple more hours trolling through the forum it seems best just to bite the bullet and send the stuff off down the road as most of you have suggested.

 

The inlet cam is the next plan for the engine once fitted so will probably be in touch.

 

Thanks

[petert 586]

Further, steer clear of any place that offers 3 angle seats as an "optional extra"!

[rallyeash 155]

GMC are up north?!

[welshpug 1,657]

Couple of combe racers went gmc to sb, now faster...

[rallyeash 155]

Yeah will di claudio being one. But for a road build I don't think its not going to be an issue and prob not worth driving the other side of the country for.

[welshpug 1,657]

theres this great thing called a courier service....

[rallyeash 155]

Haha. Also gettin sb to find the time will be your next issue.

[welshpug 1,657]

indeed, but there's also shillaber as mentioned, and jre, all worth asking.

[rallyeash 155]

Certainly is!

[Kane 34]

Ok a little help with the abbreviations? Haha

Who are Sb and Jre?