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BN1 head
- Thread starter zblu
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I have a cracked one also.
"They" say that there are two kinds of cast-iron 100 heads: Those that have cracked and those that are about to.
"They" say that there are two kinds of cast-iron 100 heads: Those that have cracked and those that are about to.
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ZBLU,
I have a stock head that is not cracked. NOT for sale though. I replaced it with a DW aluminum head to get the benefits of better ports, better valves, better headgasket sealing, & to reduce weight. See attached pic.
On these iron heads the deck thickness is about .230". Milling off .125" only leaves a deck thickness of .105". Combining this very thin deck with the less than optimum headbolt pattern leads to headgasket problems & likely contributes to the cracking problem due to head flex.
The only way to raise compression ratio without weakening something is to use pistons with a shallower top dish.
Rather than get a spare iron head, save up your money & get a good aluminum head. The DW head has been optimized for port & valve flow, is very sturdy, & adds noticeably to horsepower. I think that Michael O. will verify this.
D
I have a stock head that is not cracked. NOT for sale though. I replaced it with a DW aluminum head to get the benefits of better ports, better valves, better headgasket sealing, & to reduce weight. See attached pic.
On these iron heads the deck thickness is about .230". Milling off .125" only leaves a deck thickness of .105". Combining this very thin deck with the less than optimum headbolt pattern leads to headgasket problems & likely contributes to the cracking problem due to head flex.
The only way to raise compression ratio without weakening something is to use pistons with a shallower top dish.
Rather than get a spare iron head, save up your money & get a good aluminum head. The DW head has been optimized for port & valve flow, is very sturdy, & adds noticeably to horsepower. I think that Michael O. will verify this.
D
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[ QUOTE ]
save up your money & get a good aluminum head. The DW head has been optimized for port & valve flow, is very sturdy, & adds noticeably to horsepower. I think that Michael O. will verify this.
[/ QUOTE ]
Yes it does, esp. when matched to the DW tubular exhaust to take full advantage of the porting, etc. When I bought mine the head came in three "stages"--I think they were called "street", "fast rallye" and "race". I opted for the fast rallye and got the matched 4-2-1 exhaust system. I also got the hardened head studs and nuts, etc--as Dave says the stud pattern is part of the problem.
Of course there are the roller rockers and cam and damper and timing chain, etc. etc., and afer that you'll want to start on the bottom end of the engine...but start with the head, exhaust, studs and head gasket.
save up your money & get a good aluminum head. The DW head has been optimized for port & valve flow, is very sturdy, & adds noticeably to horsepower. I think that Michael O. will verify this.
[/ QUOTE ]
Yes it does, esp. when matched to the DW tubular exhaust to take full advantage of the porting, etc. When I bought mine the head came in three "stages"--I think they were called "street", "fast rallye" and "race". I opted for the fast rallye and got the matched 4-2-1 exhaust system. I also got the hardened head studs and nuts, etc--as Dave says the stud pattern is part of the problem.
Of course there are the roller rockers and cam and damper and timing chain, etc. etc., and afer that you'll want to start on the bottom end of the engine...but start with the head, exhaust, studs and head gasket.
Thanks Dave Russell and Michael Oritt,
Dave the head I have on is on visual of your pic even more modified than yours with bigger valves and more work done to the chamber than appears to be the case in your pic, and even more work in the inlet areas!, have actually added the 125 back onto the head by a means that so far is working, Am hoping to get an original so as to keep the car stock
Michael, have tuned extractors etc, car has been LM set up for decades!, if I feel the need for speed its cheaper to buy a Subaru WRX!
Dave the head I have on is on visual of your pic even more modified than yours with bigger valves and more work done to the chamber than appears to be the case in your pic, and even more work in the inlet areas!, have actually added the 125 back onto the head by a means that so far is working, Am hoping to get an original so as to keep the car stock
Michael, have tuned extractors etc, car has been LM set up for decades!, if I feel the need for speed its cheaper to buy a Subaru WRX!
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I have an iron head that has the valves & ports modified much the same as yours. Intake ports are two inch plus. The more conservative "appearing" aluminum head has far more power & efficiency. It was designed by actual flow & dyno testing. The over ported Intake manifolds were filled to match the smaller aluminum head ports. There is such a thing as over porting, which looks impressive but reduces torque. Too large valves also weaken the already marginal chamber strength. These engines have a crankshaft harmonic problem which limits safe rpm to a bit over 5,000. Very large ports & valves will be of no benefit & actually a detriment at the lower rpm.
D
D
pan
Jedi Warrior
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Hi, I am a new user and this is my first contribution. I have had my 100 since 1968 so have experienced most of the problems. My suggestion regarding the head problem is to seek out a head from an Austin A90 Atlantic. This may prove difficult as the Atlantic owners are now wary of us Healey folk. A few perfectly good Atlantics were cannabilised to keep 100s in the road! Did the A70 sell in the States? The 2.2 litre is basically the same as the 2.6 except for the bore and the heads are interchangeable. There are several differences but will work. They look differnt externally but I have seen one modified to look like a Healey head.