Upgraded engine lost speed any help?
09-11-2006, 06:44 AM
#31
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Re: Upgraded engine lost speed any help?
Originally Posted by jeffswav
I tried the prop yesterday. The Hydrodive prop did not work well at all. I could not get enough bow lift, porpoised all over the place. If I aired out the prop I could get the RPM to 4800 but lost speed. I put my mirage 25 back on today. I am pretty sure at this point it is the cam that made the difference. Thats what I get for listening to the Tech Line for advice. I should have bucked up and went with a bigger roller cam.
This may not have been a good prop for you to evaluate since it sounds like your boat likes bow lifters ?
I have a Mirage Plus 23" sitting on the shelf you can test if you pay shipping. It's not for sale so I need it back - before the snow flies would be fine.
09-11-2006, 08:18 AM
#32
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Thread Starter
Re: Upgraded engine lost speed any help?
Originally Posted by SB
jeffswav -
I checked my Holley catalog and did not see an MPI intake for the peanut port heads. Do you have one or is it for the large oval port heads ?
Where your large oval ports modified correctly for the larger valve installed ? Meaning - chamber, bowl, and throat porting ? Not modifying the chamber and bowls when installing larger valves can actually decrease airflow. Although I have not dealt with closed or semi-opne chambers, however I would think that larger valves would come closer to the as cast chamber walls and cut some airflow. Some relieving would be necessary. Again, check with head person since I have no experience with these heads.
I checked my Holley catalog and did not see an MPI intake for the peanut port heads. Do you have one or is it for the large oval port heads ?
Where your large oval ports modified correctly for the larger valve installed ? Meaning - chamber, bowl, and throat porting ? Not modifying the chamber and bowls when installing larger valves can actually decrease airflow. Although I have not dealt with closed or semi-opne chambers, however I would think that larger valves would come closer to the as cast chamber walls and cut some airflow. Some relieving would be necessary. Again, check with head person since I have no experience with these heads.
Thanks,
Jeff
09-11-2006, 08:34 AM
#33
Registered
Thread Starter
Re: Upgraded engine lost speed any help?
Originally Posted by SB
jeffswav -
I checked my Holley catalog and did not see an MPI intake for the peanut port heads. Do you have one or is it for the large oval port heads ?
Where your large oval ports modified correctly for the larger valve installed ? Meaning - chamber, bowl, and throat porting ? Not modifying the chamber and bowls when installing larger valves can actually decrease airflow. Although I have not dealt with closed or semi-opne chambers, however I would think that larger valves would come closer to the as cast chamber walls and cut some airflow. Some relieving would be necessary. Again, check with head person since I have no experience with these heads.
I checked my Holley catalog and did not see an MPI intake for the peanut port heads. Do you have one or is it for the large oval port heads ?
Where your large oval ports modified correctly for the larger valve installed ? Meaning - chamber, bowl, and throat porting ? Not modifying the chamber and bowls when installing larger valves can actually decrease airflow. Although I have not dealt with closed or semi-opne chambers, however I would think that larger valves would come closer to the as cast chamber walls and cut some airflow. Some relieving would be necessary. Again, check with head person since I have no experience with these heads.
I have pictures of the heads on speedwake under Cam & Head question.
Thanks
09-11-2006, 09:43 AM
#34
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Re: Upgraded engine lost speed any help?
I just looked at them.
http://www.speedwake.com/upload/show...threadid=41376
The chambers look very odd.
But what I just said means schit because, again, I have no experience at all with these heads and 'looks' mean squat, especially with lack of knowledge.
Your best to talk to someone who may have intimate dealings with these castings such as Jim V or etc. Until you do I would never assume 'ported and reworked' heads mean good performance.
http://www.speedwake.com/upload/show...threadid=41376
The chambers look very odd.
But what I just said means schit because, again, I have no experience at all with these heads and 'looks' mean squat, especially with lack of knowledge.
Your best to talk to someone who may have intimate dealings with these castings such as Jim V or etc. Until you do I would never assume 'ported and reworked' heads mean good performance.
09-11-2006, 10:15 AM
#35
Registered
Re: Upgraded engine lost speed any help?
Crane134241..............Lunati 30219
Seat .004" 286°, 296° .....N/A
Seat .006"...N/A..........279°, 284°
.050":..... 226°, 236°......230°, 235°
Lift 1.7: ...534", .553".....540", .550"
Installed ICL.107°...............112°
Installed ECL.117°...............116°
LSA..............112°...............114°
Installed events at seat: can't really compare. Crane published at .004" and this Lunati at .006". Let's move to .050"
Installed events at .050 :
IVO...........6° BTDC...........3° BTDC
IVC..........40° ABDC..........47° ABDC
EVO.........55° BBDC..........53.5° BBDC
EVC.........1° ATDC...........1.5° ATDC
overlap ....7°....................4.5°
Seat .004" 286°, 296° .....N/A
Seat .006"...N/A..........279°, 284°
.050":..... 226°, 236°......230°, 235°
Lift 1.7: ...534", .553".....540", .550"
Installed ICL.107°...............112°
Installed ECL.117°...............116°
LSA..............112°...............114°
Installed events at seat: can't really compare. Crane published at .004" and this Lunati at .006". Let's move to .050"
Installed events at .050 :
IVO...........6° BTDC...........3° BTDC
IVC..........40° ABDC..........47° ABDC
EVO.........55° BBDC..........53.5° BBDC
EVC.........1° ATDC...........1.5° ATDC
overlap ....7°....................4.5°
09-11-2006, 05:44 PM
#36
Registered
Thread Starter
Re: Upgraded engine lost speed any help?
Originally Posted by SB
Crane134241..............Lunati 30219
Seat .004" 286°, 296° .....N/A
Seat .006"...N/A..........279°, 284°
.050":..... 226°, 236°......230°, 235°
Lift 1.7: ...534", .553".....540", .550"
Installed ICL.107°...............112°
Installed ECL.117°...............116°
LSA..............112°...............114°
Installed events at seat: can't really compare. Crane published at .004" and this Lunati at .006". Let's move to .050"
Installed events at .050 :
IVO...........6° BTDC...........3° BTDC
IVC..........40° ABDC..........47° ABDC
EVO.........55° BBDC..........53.5° BBDC
EVC.........1° ATDC...........1.5° ATDC
overlap ....7°....................4.5°
Seat .004" 286°, 296° .....N/A
Seat .006"...N/A..........279°, 284°
.050":..... 226°, 236°......230°, 235°
Lift 1.7: ...534", .553".....540", .550"
Installed ICL.107°...............112°
Installed ECL.117°...............116°
LSA..............112°...............114°
Installed events at seat: can't really compare. Crane published at .004" and this Lunati at .006". Let's move to .050"
Installed events at .050 :
IVO...........6° BTDC...........3° BTDC
IVC..........40° ABDC..........47° ABDC
EVO.........55° BBDC..........53.5° BBDC
EVC.........1° ATDC...........1.5° ATDC
overlap ....7°....................4.5°
Thanks,
Jeff
09-11-2006, 08:21 PM
#37
Registered
Thread Starter
Re: Upgraded engine lost speed any help?
I found some more information on the 820 heads. There is not a lot of detail, but if they put them on the Vette they must be pretty good. They were put on LS-5 & LS-3
The heads 3993820 are 1971 454 OC 365Hp and are Corvette in my book and may have other applications.
Heads were used on '71 454 Vette and '71-'72 400/402/454 applications on both trucks and all car lines.
The first cast iron open chamber head was the GM casting #3993820. This head was used for all 1971 big block applications except Corvette LS-6. It is a 2.06/1.72 valve size head with the large oval ports
The heads 3993820 are 1971 454 OC 365Hp and are Corvette in my book and may have other applications.
Heads were used on '71 454 Vette and '71-'72 400/402/454 applications on both trucks and all car lines.
The first cast iron open chamber head was the GM casting #3993820. This head was used for all 1971 big block applications except Corvette LS-6. It is a 2.06/1.72 valve size head with the large oval ports
