unruhjonny
07-22-2003, 02:07 PM
I have some questions pertaining to the interchangability and the performance of the 2.3 Quad four cylinder heads, as well as a piston queston.
Any guidance would be appreciated on either or both of these matters. If you would like, I can be emailed at unruhjon@hotmail.com - Thanks!
First, this is what I know;
If I have all of my facts straight, the first design (#22530955) was a 1987-89 casting which had 35.5mm intake and 30.0mm exhaust valves (which equates the exahst valve size being 84.5% of the intake). I also believe that the first design head has the biggest exhaust ports.
The second design (#25539086) should be a (late)1989-92 piece, which had 36.5mm intake valves, and 31.5mm exhaust valves (which equates the exahst valve size being 86.3% of the intake).
The third design (#24570753) should be a 1993 specific piece, and other than knowing that the exhaust ports were smaller, I only know that this head did have a service replacement number (#24573303).
The fourth design (#24575456), I am told has reduced exhaust port (once again), and some kind of modified water outlet hole...
This is all I know.
My first Quad 4 car (a #955 head 1989 Grand Am) responded significantly to a less restrictive exhaust system... (I sold this car).
I now am having to fix my second Quad four car - an 'A' code (#086) head car (1991 Grand Am)... but some backround info might help.
I bought this car with a bad engine - head gasket blown, and the original owner ran it for too long with water in the crankcase - the head was cracked in at least four places.
I had a complete Quad 4 from another car, which to the best of my knowledge ws an early 'D' code block (#955 head), with the 'A' code cams - this engine would fly (it would smoke completely smoke my first car, not to mention 2001 "Ram Air" V-6 Grand Am's).
Now I am having to fix an engine, as the bottom end needs to be machined on the replacement engine, so I have opted to rebuild the original engine. I am also wanting to leave the Quad 4 that is in my car complete, rather than part it out.
I am unable to find a 1989-92 head (#086) that is not cracked - the only ones I can find that are not cracked are the early (#955) casting.
Are there any improvements for the #753/ #303/ #456 heads over the #955/ #086 heads that I should seek one of the newer pieces?
Were the valve sizes changed on the 93-94 heads?
Does the 1994 head pose any problems when swapping onto an earlier block?
Do the larger exhaust ports on the early heads have any significant performance problems?? (especially the #955 head) - I would think that the reduced port size would pose a potential flow problem...
I have the understanding that for optmium performance in any regular comustion engine, the exhaust valve should be about 83% of the intake valve's size.. thoughts?
Also, the original pistons were differentiated by two or four valve reliefs, but it seems as though there might be an original application where the LGO engins would have had a flat top piston (according to some info I found).
I have ordered new pistons, but the machine shop recieved the four valve relief variant pistons, and were told that the two valve relive pistons are no longer available, and the compression should remain the same...
Any thoughts on this one? - Who are suppliers of pistons fr these cars? Does anyone know part numbers?
I want to keep the 10:1 compression, and I believe the two extra valve reliefs would have increased the combustion chamber to that of 9.5:1... Any opinion here would be appeciated.
(that's it)
Jon.
Any guidance would be appreciated on either or both of these matters. If you would like, I can be emailed at unruhjon@hotmail.com - Thanks!
First, this is what I know;
If I have all of my facts straight, the first design (#22530955) was a 1987-89 casting which had 35.5mm intake and 30.0mm exhaust valves (which equates the exahst valve size being 84.5% of the intake). I also believe that the first design head has the biggest exhaust ports.
The second design (#25539086) should be a (late)1989-92 piece, which had 36.5mm intake valves, and 31.5mm exhaust valves (which equates the exahst valve size being 86.3% of the intake).
The third design (#24570753) should be a 1993 specific piece, and other than knowing that the exhaust ports were smaller, I only know that this head did have a service replacement number (#24573303).
The fourth design (#24575456), I am told has reduced exhaust port (once again), and some kind of modified water outlet hole...
This is all I know.
My first Quad 4 car (a #955 head 1989 Grand Am) responded significantly to a less restrictive exhaust system... (I sold this car).
I now am having to fix my second Quad four car - an 'A' code (#086) head car (1991 Grand Am)... but some backround info might help.
I bought this car with a bad engine - head gasket blown, and the original owner ran it for too long with water in the crankcase - the head was cracked in at least four places.
I had a complete Quad 4 from another car, which to the best of my knowledge ws an early 'D' code block (#955 head), with the 'A' code cams - this engine would fly (it would smoke completely smoke my first car, not to mention 2001 "Ram Air" V-6 Grand Am's).
Now I am having to fix an engine, as the bottom end needs to be machined on the replacement engine, so I have opted to rebuild the original engine. I am also wanting to leave the Quad 4 that is in my car complete, rather than part it out.
I am unable to find a 1989-92 head (#086) that is not cracked - the only ones I can find that are not cracked are the early (#955) casting.
Are there any improvements for the #753/ #303/ #456 heads over the #955/ #086 heads that I should seek one of the newer pieces?
Were the valve sizes changed on the 93-94 heads?
Does the 1994 head pose any problems when swapping onto an earlier block?
Do the larger exhaust ports on the early heads have any significant performance problems?? (especially the #955 head) - I would think that the reduced port size would pose a potential flow problem...
I have the understanding that for optmium performance in any regular comustion engine, the exhaust valve should be about 83% of the intake valve's size.. thoughts?
Also, the original pistons were differentiated by two or four valve reliefs, but it seems as though there might be an original application where the LGO engins would have had a flat top piston (according to some info I found).
I have ordered new pistons, but the machine shop recieved the four valve relief variant pistons, and were told that the two valve relive pistons are no longer available, and the compression should remain the same...
Any thoughts on this one? - Who are suppliers of pistons fr these cars? Does anyone know part numbers?
I want to keep the 10:1 compression, and I believe the two extra valve reliefs would have increased the combustion chamber to that of 9.5:1... Any opinion here would be appeciated.
(that's it)
Jon.