73 tall deck 302 problem
Thread Starter
|
New User
Joined: Mar 2008
Posts: 7
Likes: 0
73 tall deck 302 problem
I recently rebuilt a 73 302 with the tall deck and i put d80e cylinder heads on it and i have extremely low compression ratio is there tall deck pistons i can get or do i have to mill the deck on the block
Moderator
Joined: Jan 2001
Posts: 56,997
Likes: 2,744
From: Virginia
What pistons are you using? The 73-76 302's had the small chamber heads with the pistons that had the very deep dish. In 1977 when they went with the larger chamber heads, the piston didn't have as much dish to it. Simply changing the pistons to flat tops may solve the problem.
Postmaster
Joined: Feb 2008
Posts: 2,658
Likes: 5
From: Out of here
The pin height has a lot to do with compression ratio and yes there is a difference in tall deck pistons/rod assemblies.
Too short a rod or wrong pistons will keep your piston way down in the bore. Something that you should have noticed while assembling the motor.
And to answer your original question: no, you cannot mill enough material off the top of the deck to correct this. You risk the chance of weakening the deck and possibly hitting water jackets.
Too short a rod or wrong pistons will keep your piston way down in the bore. Something that you should have noticed while assembling the motor.
And to answer your original question: no, you cannot mill enough material off the top of the deck to correct this. You risk the chance of weakening the deck and possibly hitting water jackets.
Moderator
Joined: Jan 2001
Posts: 56,997
Likes: 2,744
From: Virginia
My book shows the taller block is .023 inches taller. It also shows the head usually used with this engine had a 58.2cc chamber while the D80E later head has a 69cc chamber.
It also has a chart that shows if you use the 69cc head on the stock 73-76 engine, the compression ratio will be 7.2 to 1.
If you use the original 58.2cc heads, the stock compression ratio was 8.0 to 1.
The book also shows the different pistons used and shows the 68-72 piston has a slight dish, and the 73-76 has more dish, making the compression ratio drop one point.
It also has a chart that shows if you use the 69cc head on the stock 73-76 engine, the compression ratio will be 7.2 to 1.
If you use the original 58.2cc heads, the stock compression ratio was 8.0 to 1.
The book also shows the different pistons used and shows the 68-72 piston has a slight dish, and the 73-76 has more dish, making the compression ratio drop one point.
Moderator
Joined: Jan 2001
Posts: 56,997
Likes: 2,744
From: Virginia
The book has most 302's at 8.206 inches, and the 73-76 302 at 8.229 inches.
Small block chevrolets are all the same I thought. 265 thru 400 all have the same deck height.
I don't know what Ford's problem was. They decide to turn the 302 into a 351w, and they have to recast the whole block and make a new intake manifold among other things? Of course we all know through the years they never could seem to make their mind up on what engine and motor mount bellhousing pattern they were going to use.
Small block chevrolets are all the same I thought. 265 thru 400 all have the same deck height.
I don't know what Ford's problem was. They decide to turn the 302 into a 351w, and they have to recast the whole block and make a new intake manifold among other things? Of course we all know through the years they never could seem to make their mind up on what engine and motor mount bellhousing pattern they were going to use.
Thread
Thread Starter
Forum
Replies
Last Post
