Seeking input on my build
Le Mans Master
Joined: Apr 2011
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From: Hermosa
Race Director
Joined: Oct 2000
Posts: 15,056
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From: central FL, near the beach.
those dish 17cc pistons are so low, like 7.8:1, might want to kick around buying 50cc heads. that would give ~9.95:1 
or maybe 58cc heads.
those dart 64 are more like 67cc
kind of unexciting.
or maybe 58cc heads.
those dart 64 are more like 67cc
kind of unexciting.
Safety Car
Joined: Jan 2009
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From: anchorage ak
I thought it was aviator but couldn't remember. I've heard on more than one occasion that the l48 was over rated on the compression. I've not done any math but couldn't he run .15" steel head gaskets and get the compression in the 9 to 1 range with 64cc heads.
Last edited by bluedawg; Jan 14, 2013 at 09:31 PM.
Race Director
Joined: Oct 2000
Posts: 15,056
Likes: 79
From: central FL, near the beach.
they come stock with .022 shim.
works out to 7.5:1
maybe could get 8.9 with 15shim and 64.
but more like 8.5 with the actual 67cc as measured by REE...
9.95:1 sounds real good with 50cc(except less than ideal squish, but it is good enough with .039). 50cc could go 10.4 with .015 shim, if they scare your pants off, go 58cc.
works out to 7.5:1
maybe could get 8.9 with 15shim and 64.
but more like 8.5 with the actual 67cc as measured by REE...
9.95:1 sounds real good with 50cc(except less than ideal squish, but it is good enough with .039). 50cc could go 10.4 with .015 shim, if they scare your pants off, go 58cc.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
they come stock with .022 shim.
works out to 7.5:1
maybe could get 8.9 with 15shim and 64.
but more like 8.5 with the actual 67cc as measured by REE...
9.95:1 sounds real good with 50cc(except less than ideal squish, but it is good enough with .039). 50cc could go 10.4 with .015 shim, if they scare your pants off, go 58cc.
works out to 7.5:1
maybe could get 8.9 with 15shim and 64.
but more like 8.5 with the actual 67cc as measured by REE...
9.95:1 sounds real good with 50cc(except less than ideal squish, but it is good enough with .039). 50cc could go 10.4 with .015 shim, if they scare your pants off, go 58cc.
Also those stock 76cc heads measured out to be 80cc's so real compression was more like 7.7:1 all told.
Last edited by REELAV8R; Jan 15, 2013 at 10:57 AM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
REE
send those heads back "not as advertised, not 64cc"
and buy 50cc heads.
send those heads back "not as advertised, not 64cc"
and buy 50cc heads.
I guess 5% error is an acceptable spec for Dart. I understand that casting is not an exact method, but I would think tighter tolerances would be in order. You probably have to pay more $$ for better accuracy.
Race Director
Joined: Oct 2000
Posts: 15,056
Likes: 79
From: central FL, near the beach.
Live & Learn. That is why the op should look into smaller heads and call them and see the varience. i bet the 50cc are really 53cc 
58's prolly 61 cc
My OPINION is they don't want pinging complaints, so they make them bigger, just like some pistons are .020 down in the hole.
Last motor i built, i had to send HALF the parts back!
58's prolly 61 cc
My OPINION is they don't want pinging complaints, so they make them bigger, just like some pistons are .020 down in the hole.
Last motor i built, i had to send HALF the parts back!
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Safety Car
Joined: Jan 2009
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From: anchorage ak
The paperwork that came with the heads stated that the 64cc was a "nominal" measurement and to get true volume it would need to be measured. I called Dart and spoke to a rep who stated that the 67cc measurement I came up with was "within our specs for a cast head". And that if it had been a CNC'd head that it would be much closer to advertised volume. I have already shaved the heads so too late for me to return them in any case.
I guess 5% error is an acceptable spec for Dart. I understand that casting is not an exact method, but I would think tighter tolerances would be in order. You probably have to pay more $$ for better accuracy.
I guess 5% error is an acceptable spec for Dart. I understand that casting is not an exact method, but I would think tighter tolerances would be in order. You probably have to pay more $$ for better accuracy.
Last edited by bluedawg; Jan 15, 2013 at 03:18 PM.
Safety Car
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From: anchorage ak
Live & Learn. That is why the op should look into smaller heads and call them and see the varience. the 50cc are really 53cc
58's prolly 61 cc
My OPINION is they don't want pinging complaints, so they make them bigger, just like some pistons are .020 down in the hole.
Last motor i built, i had to send HALF the parts back!
58's prolly 61 cc
My OPINION is they don't want pinging complaints, so they make them bigger, just like some pistons are .020 down in the hole.
Last motor i built, i had to send HALF the parts back!
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Live & Learn. That is why the op should look into smaller heads and call them and see the varience. i bet the 50cc are really 53cc
58's prolly 61 cc
My OPINION is they don't want pinging complaints, so they make them bigger, just like some pistons are .020 down in the hole.
Last motor i built, i had to send HALF the parts back!
58's prolly 61 cc
My OPINION is they don't want pinging complaints, so they make them bigger, just like some pistons are .020 down in the hole.
Last motor i built, i had to send HALF the parts back!
I plan on measuring everything and ccing the new pistons as well after I receive them.
Thread Starter
Intermediate
Joined: Apr 2012
Posts: 42
Likes: 0
From: Wayne Pa
Neither my beloved Dart SHP heads nor the Edelbrock equivalent come in anything smaller than 64cc (67cc), and I really have to stay in budget...
I`ve learned an absolute TON because of this thread.
Keep up the good work!
I`ve learned an absolute TON because of this thread.
Keep up the good work!
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Neither my beloved Dart SHP heads nor the Edelbrock equivalent come in anything smaller than 64cc (67cc), and I really have to stay in budget...