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Shaved Heads

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kurts100

kurts100

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Will be rebuilding a '60 BT7 engine and will be upgrading to BJ8 cam and carbs, and adding headers and possibly a slightly lightened flywheel /ubbthreads/images/graemlins/thirsty.gif. Friends of mine are into Triumphs and always talk about shaving their heads (engine) for increased horsepower. I haven't seen that discussed too much with Healeys. Is that something to consider with a Healey or not?

Thanks,

Kurt /ubbthreads/images/graemlins/thirsty.gif
 
I'm not sure. The Triumph deck thickness seems to be quite a bit more than some other engines. The Healey Four only has about .220" deck thickness. Don't know about the Sixes. I think that a deck thickness of less than .200" would be asking for gasket sealing problems. Someone will likely be able to give you a deck thickness on the sixes. I think folks usually go with higher compression pistons rather than severe head milling.
D
Edit: The deck I'm refering to is the bottom surface of the head. The same would apply to the top surface of the block.
D
 
Dave,

Thanks for the response to my question. When you talk about deck thickness are you talking about the top of the block or the bottom of the head? Sounds like the Healey engine may not lend itself to that. The other thing my Triumph friends talk about is porting and polishing the head (TR-6). I just read the recent post on that and it doesn't sound like it is something that's done much with the Healeys.

Thanks again!

Kurt
 
Kurt,
I think the key thing to remember with any head work is that it should be done by a qualified machinist with a flow bench. If you just go in and start polishing ports you could do more harm than good.
 
You might talk to some of your local speed shops. It is possible, and maybe a good thing, to just have the head leveled. Where it's placed on a huge like grinding wheel that is perfectly flat. I've even heard of some engine blocks done similarly. Without grinding too much off you end up with a perfectly level mating surface that should seal perfectly. Again, that may be possible with a four cylinder but a six may be too long to fit on the wheel. I believe DMH has probably done all that there could be done to a production engine to increase engine horsepower. Of course, time changes. Good luck with your project.
/ubbthreads/images/graemlins/cheers.gif
 
Kurt,
You should be aware of the fact that shaving the head will increase the compression ratio, which will in turn require an increase in the octane of the fuel used.
 
You got that right Ray. No more regular gas and it might even knock on premium. All I did with mine was to have the decks leveled; it might have taken .003 to .005 but I had good gasket surfaces to work with when I put it back togther.
 
Thanks for everyone's input! Looks like I'll just have the top of the block and head milled slightly to make sure they are level. Also, it doesn't sound like porting and polishing the head is the thing to do with Healeys. Curious about the high compression pistons that Dave mentioned. Would those require a higher octane gas and if not would they knock? I usually run premium unleaded anyway. Also, what makes a piston high compression?

Thanks,

Kurt
 
A piston has higher compresion by allowing less air space above it. They can be flat, convexed (smaller concave then OE) or have a longer spacing between the wrist pin and the top.
 
Another thing to consider when skimming the head is valve clearance. With a BJ8 cam and stock rockers, it shouldn’t be an issue. Add higher rocker ratios and/or wilder cam, to the mix, and you can get the exhaust valve to hit the block. So the block has to be machined before that becomes an expensive noise. (I know, I'm late to the party)
 
Is a high compression piston something I should consider when rebuilding this engine for fast street? I spoke with Gary at Rocker Arm Specialists who was very helpful and he said a rebuilt set of rockerarms would be a true 1.5 ratio which i think is what the factory ratio was.

Thanks again,

Kurt
 
I believe your engine already has 9 to 1 compression ratio. You could go to 9.5 to 1 if really good fuel is used & you pay strict attention to engine tune. Hardly worth the expense & extra trouble for a street engine IMO.

The late BJ7 - BJ8 cam, or equivalent, & HD8 carbs would make a worthwhile addition, as would headers.

The rocker arms are very nice & might give a little extra power. As Greg says, you need to check exhaust valve to block clearances any time you increase valve lift.

Leveling the block & head mating surfaces if needed, paying strict attention to bore condition, piston clearances & fit, Valve & valve seat fitting, crankshaft & bearing fit & condition, --- In short, all of the stuff that is done for a good "blue printed" engine, will go a long ways to assure a reliable engine that puts out it's maximum power.

The differences with an engine that is fully blueprinted & assembled "just right" can make 20% difference in power output & engine longevity.
D
 
Very interesting review Dar. Definately worth reading. Says many of the same things Dave said. Thanks guys! Glad I asked the question. I learned alot.

Kurt
 
Is there an answer to this post
IE can the 3000 head be milled and if so by how much to raise compression say to 10:1

Presume stock BJ8 cam, pistons, and rocker ratio
 
Greg, did you mean hit the piston? Also this must be a really old thread, the post by Dave Russell struck me, never met the man, but a fine contributor to the forum, and still missed.
 
glemon said:
Greg, did you mean hit the piston? Also this must be a really old thread, the post by Dave Russell struck me, never met the man, but a fine contributor to the forum, and still missed.
Click to expand...

Block is correct. The valve is actually outside the cylinder diameter and witha high-lift cam or high-ratio rocker arms it will hit the top of the block. I had to make pockets in the block when I went to my DWR cam.
 
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