Aluminum Head

[zblu]

yups, apparently the old holden cams were based on austin design work, go check the specks!
used to like the sound of a fiat 124 muffler! pipes are 2"

 

[Money_Pit]

Thanks Bundyrum

After looking at the previous post on cams with the graft charts I think it really help put things in percpective for a layman such as myself on choice of cams. How much do I really want to wind this motor out especially at the top end. I had the experiance of throwing a rod on an early MGB I owned many years ago and looking at the differences in the cams on the graft the biggest change occurs at the high end. How much can you wind these engines out without fear of damage?

My thoughts are to go with the DWR1 camshaft which is just a little hotter than the BJ8 grind and I like your idea on the ceramic coating of the header as well.

DT /ubbthreads/images/graemlins/canpatriot.GIF

 

[John Loftus]

[ QUOTE ]
I would have to say that the DWR head sounds the best proposition because as Dave says it takes a very experience person with a flow bench to get it right.

[/ QUOTE ]

Coincidently, I just received the latest email announcment from Moss and there is a "what sets us apart" section that mentions having a flow bench (see attachment). Of course, DWR has many many years of racing and production experience but it appears Moss is devoting more resources to performance parts over the last few years.

Regarding alum. vs. steel heads, isn't there a bigger market for aftermarket heads for the 100's just because the originals crack much more often? Seems like the 6 cylinder heads are pretty robust in comparison.

Cheers,
John

 

[Dave Russell]

Hi John,
It would appear that there are more four cylinder cracked heads around than six cylinder. My iron head is not cracked but as I said, it's way over ported. When faced with the problem of finding another "good" iron head & rebuilding it, the aluminum DW seemed far better. At the time, I was able to buy the DW head, including shipping, for nearly $1,000 less than the stateside offerings. I also decided that the "figure eight" valve seat inserts which Moss claims are an advantage, were inferior to the DW single inserts. Combined with DW years of experience & testing, compared to the unknown product It was an easy decision. Pic attached.
D

 

[Michael Oritt]

[ QUOTE ]
Regarding alum. vs. steel heads, isn't there a bigger market for aftermarket heads for the 100's just because the originals crack much more often? Seems like the 6 cylinder heads are pretty robust in comparison.

Cheers,
John

[/ QUOTE ]

It sure would seem that way--I think part of the problem is the head stud pattern. I had the usual coolant weepage from under the head on the right side between cylinders 2 and 3 for a while prior to the head's cracking between cylinders 1 and 2. I eventually replaced it with the stage 2 DW head and tubular exhaust system several years ago and have had no leaks or problems since.

 

[BUNDYRUM]

I'll try not to make this too long and technical as i can get carried away sometimes. I have to agree that the alloy head has to be a better bet than trying to do too much with an iron one these days. I think the problem lies not only with people grinding more and more out of the ports in an effort to get the port to flow some astrnomical numbers but also in machining more off the face to raise the compression. Sometimes people kind of forget what this engine was designed to do originally and having some high compression was not part of it. When this engine family first came out in the Austin A70 it only had a compression of 6.8:1 and the A90/Healey 100 was a staggering 7.5:1. Of course this was because of the low octane gas they had at the time in the UK. I know my own 100 has a compression of 9.3:1 because i don't think it's worth the effort to go much higher than this today (partly because of the gas again, funny how that is). The head face on the A70 is a lot thicker than on the Healey 100 but there again the combustion chamber is a lot smaller in size too (to match the smaller bore). the extra thickness and lower compression helping keep things together. For Healey 100 owners in this country things are a little more difficult as the A70/A90 and other BMC variants didn't come here in any numbers unlike say Australia so the problem with the availabilty of the heads didn't appear until later on. There are those that will try to tell you that the A70 head is not a good match for the Healey 100 but i personally know of one A70 head that was used on 3 different engines at one time or another but as we know there are always exceptions to any rule. The problem with valve seat inserts arose even when BMC were rallying the Healeys, they would drop the insert out even on new alloy heads. The first alloy heads they built were cast using the iron head patterns consequently the heads didn't last. When they made dedicated patterns just for the alloy head they improved but still had the valve seat problem but overcame this by casting the seats in the figure 8 pattern that was used for so many years. The other problem they had was that BMC were cheap so they didn't get to use some of the better quality alloy available not that there was much to chose from but had they had a better understanding they could have designed something better. I don't know that Jaguar had all that many problems with their alloy heads when they raced them. The first heads produced by SC fell into the same trap, they didn't investigate the alloys available at the time and just copied the original design. I know that in Australia the SC heads just didn't last as they were too soft, the washers under the nuts on the head studs would force themselves into the alloy. There is more on this subject but not right now. Regards, BUNDYRUM.

 

[Dave Russell]

While we are on the subject, milling (thinning) the head surface on any Big Healey engine is a good way to weaken the already somewhat marginal head rigidity & leave it vulnerable to distortion & gasket sealing problems. Especially on the four cylinder (A90 engine) the head deck thickness is only around .225" thick. Reducing this thickness by milling to increase compression ratio is a sure way to create head gasket sealing problems & or cracking. Folks claim to have milled .100" from the gasket surface to raise compression but never mention the almost certain gasket sealing problems. The remaining bottom deck thickness of .125" is just not rigid enough to give a reliable seal. Especially when combined with the less than optimum headbolt pattern on the Fours. The "good" aluminum heads have increased deck thickness which helps a great deal. They should not be milled for the same reasons.

Some engines with very thick bottom decks can tolerate this milling. Not these Healeys.

The only reliable way to increase compression ratio is to use pistons with a shallower dish, no dish, or a higher top crown. The Healey LeMans fours used a piston dish with four to 10 cc less volume than the 7.5 /1 pistons to raise the compression ratio in the range of from 8.1/1 to to 8.6/1.
D

 

[Skip & Lynne]

Just my 2 cents worth here but in my kart racing days I have seen some really beautiful porting work that actually produced less h/p on the dyno after porting. There are so many combinations that if you don`t know exactly what you are doing it could set you back. Port size, port shape, surface roughness (yes you need some roughness to mix the fuel/air charge),flow directions all come into the mix. I just enjoy my car for what it is. But you know a Cobra with a 302 now ya talking. Skip

 

[BUNDYRUM]

Hello Dave, thanks for the reply, i used dome top pistons to get the compression i wanted in my 100 after a lot of reworking of the combustion chambers and making them all equal. Hello Skip & Lynne, I agree with you about flow benches. They can produce some very good results provided the person using it knows how to interpret what the machine is telling him. Just getting the big numbers doesn't mean it will actually do any good and even flowing the exhaust port in the correct direction is something that a lot of people don't seem to be aware of, but oh well. Regards, BUNDYRUM.

 

[anthony7777]

dave russell,skip and lynne,it sounds unsual that youve experianced such a number of head gasket trauma,im wondering if the effected engines were new and or if the gaskets had ever been changed befor?ive seen several individuals replace head gaskets without resurfacing the block or the head,big mistake!i think it was mentioned here befor that an aluminum head is bolstered with additional material in specific areas to compensate for differances of expansion and contraction of the dissimlar metals.skip and lynne,as an aside,how are thinks in savn?in the late 70's i lived in an apt.complex called 'club riviera' next door to armstrong col.wonder if its still there? would spend much to much time shooting pool at 'the other end'rest.thats probably gone as well!all this while working on g2's and 3's at the "grum" service center,oh,even though my kid did spill a glass of milk in his lap and wrap the hand me down izuzu trooper around the telephone pole at the bottom of our driveway,i dont think ill ever complain about his driving skills again. /ubbthreads/images/graemlins/rolleyes.gif

 

[JamesWilson]

[ QUOTE ]
I don't doubt the benefits of an aluminum head but I wonder:
If half the $4,500 was spent on porting, polishing, valves etc. on a cast iron head, would it perform as well and be a better mate to a cast iron block because they're of the same material and heat and cool at the same rate?

[/ QUOTE ]

Here in the UK I can get an uprated iron head for roughly half the cost of the DWR head, without the weight savings or having the same confidence in the resulting performance. I already plan on going with a stronger cam, improved carburation and headers along with a number of suspension improvements...

I've driven one with exactly that kind of set up and really liked it, FWIW....

So what I expect I'll do is go with the alloy head too, even if I have to mount the unmodified iron head and use it for the year or so while I save my pennies.... /ubbthreads/images/graemlins/yesnod.gif

 

[BUNDYRUM]

anthony7777, the problem with the 4 cylinder cars of water seeping out from under the head between cyl's 2 & 3 is a common one. It doesn't matter whether the engine is new or old it goes back to what is called core shift in the cyl head casting either during the pouring of the molten metal into the core or in the cooling process. On some heads the core shift was a lot and on some it was not very much at all it's hard to tell what the factors were but we do know it happens. With regard to head gaskets just because a gasket "blows" doesn't mean to say there is something wrong with the head or block surface. It could be a timing or mixture problem. Just because you change the gasket doesn't mean you have to surface the head or block because if there is nothing wrong with the surfaces (i.e they are not warped) why go to trouble. (Now i know a lot of you out there are not going to believe what i'm going to say now but here it anyway). I cannot begin to tell you the number of times i removed the head from my BN1 for reasons like wanting to have a look in there, to replacing worn valve guides etc, grinding a bit more out of the ports/combustion chamber and i never even gave it a thought that i should change the gasket. I even removed the head and replaced it with an A70 one while mine was getting new guides/seats/valves fitted and even when putting the head back on again i still used the same gasket.I never experienced any problems of any kind with this old gasket but there again i never ran it out of water either. I put a new gasket when i rebuilt the whole motor and even then when i had the block and head faces skimmed i had the absolute bare minimum removed in an effort to not weaken the head that way. Now for a bit of trivia, i said in an earlier reply the material in the factory alloy heads was very soft, (yes we know aluminum is softer than iron) and it was the same with the 100/S heads but it was mainly the fact that the material couldn't be heat treated unlike todays materials. The 100/S heads cast in Australia in the early 80's were cast using a material that was heat treatable. These "new" heads were 2.5 times stronger than the original ones and that just came from the material alone even though they were cast with the original patterns. I never asked at the time about whether the "new" heads were any heavier than the old ones but i suspect they would be by just a small amount because the new material was denser than the old. Regards, BUNDYRUM.

 

[healeyneil]

Hi guys, new member here. My BT7 is running an original alloy head, with no problems. Its a heck of a lot easier if you ever have to take the head off. The head was fitted by a previous owner (around 1970) He paid £50 for it !

 

[Dave Russell]

Hi Neil,
Welcome to the forum.
That was the excuse that I used to my wife for getting the aluminum head. The iron one was just too hard to lift off & on without risk of damaging the shroud paint.
D /ubbthreads/images/graemlins/grin.gif

 

[JamesWilson]

[ QUOTE ]
Hi guys, new member here.

[/ QUOTE ]

Hi Neil... if you look you'll see your car made it here before you did....

 

[Money_Pit]

Just installed my ali head. See attachment

 

[Keoke]

Hi BUNDYRUM,That is interesting. Your experiences with the head gasket are the same as I have heard coming out of the UK with one small twist. They say that puttig Halomar thinned with thinners on the gasket and allowing it to dry is the secret. Even the V8 guys do this with shim type head gaskets on alloy heads-Fwiw---Keoke??

 

[Dave Russell]

[ QUOTE ]
Just installed my ali head. See attachment

[/ QUOTE ]
Hi MP,
When I try to view your attachment I get a "not found" error message. Would like to see it if you can tell me how to get it to display.
D

 

[Ed_K]

same here, someone removed or moved the JPG from the original location.

 

[Ed_K]

Whats going on on the forum ? I just tried to display an old picture of Dave's overflow tank and I received the same 404 error. Someone must be doing " file maintenance " which is removing old picture files ???