BBC Cam Timing
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Teching In
Joined: Jul 2008
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BBC Cam Timing Sooo i took on a little project recently, the goal is to pick up this 468ci. BB in a 70' SS Nova...The car is a 3300-3400lbs(??), th400/3800 stall, 3.73 tubbed ladder bar car.
The old engine combo was...out of box MerlinIII oval port heads (269cc...2.30/1.88..119cc chamber), performer rpm air gap, .525" hyd cam, JE forged 11:1 pistons ran 7.30's. That combo ran very mild and sounded like a big block truck..lol
I sent the heads off to have have some port work done (to a very trusted circle track engine builder), and install some 280lbs @ seat 1.625 springs, then I orderd a Comp Cams {11-773-8} .660/.666 -- 254/260 @.050--110LSA.. roller cam, and a Vic JR. intake.
I'm thinking because it's a heavy car with a 3.73 gear it might be a bit of a turd in the 60', so should i run 2-4* advanced to give it a little bottom end, or will it not notice the difference because of the stall??
Any INTELLIGENT input is greatly appreciated!!
The old engine combo was...out of box MerlinIII oval port heads (269cc...2.30/1.88..119cc chamber), performer rpm air gap, .525" hyd cam, JE forged 11:1 pistons ran 7.30's. That combo ran very mild and sounded like a big block truck..lol
I sent the heads off to have have some port work done (to a very trusted circle track engine builder), and install some 280lbs @ seat 1.625 springs, then I orderd a Comp Cams {11-773-8} .660/.666 -- 254/260 @.050--110LSA.. roller cam, and a Vic JR. intake.
I'm thinking because it's a heavy car with a 3.73 gear it might be a bit of a turd in the 60', so should i run 2-4* advanced to give it a little bottom end, or will it not notice the difference because of the stall??
Any INTELLIGENT input is greatly appreciated!!
Thread Starter
Teching In
Joined: Jul 2008
Posts: 22
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Launching!
Joined: Oct 2006
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My personal experience is that you will notice nothing with only a 2-4* change. I retarded the cam 4* in my small block Nova and saw no measureable difference at the track (1975 Nova, 3700lbs, 3800RPM stall). I have read articles that say the same thing (more than 4* change needed to show any difference). I would install it straight up and mess with valve lash at the track to get an indication of what the motor and car like.
Since you dont give all the variables. First off you will need more gear. If you get that ridiculous cam you want to run. IF this is a track only car 4.56 4.88. according to comps website cam makes power from 3200 - 7000. Then you have oval port heads which defeats the purpose of high rpm. SO i took some of the info you gave me and plugged it into desktop dyno. The power drops with 4 degrees advance. now if you retard it 4 degrees it wakes up 644 horse 589 torque. Straight up 638 horse 598 torque. or 4 advance 626 horse 597 torque. IF you are going to run that cam that doesnt match the rest of the car I would run it straight up.
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Thread Starter
Teching In
Joined: Jul 2008
Posts: 22
Likes: 0
Since you dont give all the variables. First off you will need more gear. If you get that ridiculous cam you want to run. IF this is a track only car 4.56 4.88. according to comps website cam makes power from 3200 - 7000. Then you have oval port heads which defeats the purpose of high rpm. SO i took some of the info you gave me and plugged it into desktop dyno. The power drops with 4 degrees advance. now if you retard it 4 degrees it wakes up 644 horse 589 torque. Straight up 638 horse 598 torque. or 4 advance 626 horse 597 torque. IF you are going to run that cam that doesnt match the rest of the car I would run it straight up.
BTW when the head work is finished these oval port heads will out flow most out of the box rec. port heads, so your suggestion about the cam being too big is incorrect, not a big fan of the tractor gears you suggested either especially with that much torque and a 2.48 low gear, i do however think the converter may be a little tight for the cam which is why i was concerned with the low end torque, i tried talking the owner into a 4500+ stall but he insists that it's still 70% streetcar so i left him alone on that...in the end he'll be surprised when he gets it back either way.
i set it up straight up last night...i'll post a time slip hopefully next week or the week after..thanks again
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