Small base circle cam required ?
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 7,562
Likes: 9
From: B'Ville NY
Cruise-In III Veteran
St. Jude Donor '05
Small base circle cam required ?
For some reason I can't find Dart's website :confused:
I have a new Dart Little M block with 4.125 bore & 350 mains. The cam is in the stock location. I'll be installing a 3.625 stroke crank with 6.0" rods. I've heard that a production 400ci, 3.750 stroke & 6.0" rods requires a small base circle for rod clearance. Do I need to be concerned about this when I order my mech cam ?
If this helps, my intended cam specs are as follows: Dur @ .050 242 in/ 246 exh, lift .604 in/ .624 exh with 112 lobe C.
Thanks :cheers:
I have a new Dart Little M block with 4.125 bore & 350 mains. The cam is in the stock location. I'll be installing a 3.625 stroke crank with 6.0" rods. I've heard that a production 400ci, 3.750 stroke & 6.0" rods requires a small base circle for rod clearance. Do I need to be concerned about this when I order my mech cam ?
If this helps, my intended cam specs are as follows: Dur @ .050 242 in/ 246 exh, lift .604 in/ .624 exh with 112 lobe C.
Thanks :cheers:
Melting Slicks
Joined: Dec 2001
Posts: 2,025
Likes: 1
From: Billings MT
Re: Small base circle cam required ? (SmokedTires)
http://www.dartheads.com
I am running a standard GM 400 block with a 3.750 stroke crank, and profiled 6.0" rods from SCAT.
With my standard base circle Comp Cams XR-288 (.520/.540) There were no clearance problems at all with the rods.
With the taller lobes on your (presuming solid roller) you may run into an issue. Are those lift figures with a 1.5:1 rocker ratio?
It is not that much more to go with the small base circle, and considering the additional lobe height it may be a good idea.
:cheers:
I am running a standard GM 400 block with a 3.750 stroke crank, and profiled 6.0" rods from SCAT.
With my standard base circle Comp Cams XR-288 (.520/.540) There were no clearance problems at all with the rods.
With the taller lobes on your (presuming solid roller) you may run into an issue. Are those lift figures with a 1.5:1 rocker ratio?
It is not that much more to go with the small base circle, and considering the additional lobe height it may be a good idea.
:cheers:
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Small base circle cam required ? (VETDRMS)
3.750 and stroker 6 inch rods are clearanced for 1.050 base circle billet steel cams. In your case you should have to measure clearances.
I went from a Crane .930 small base circle to 1.050 comp cams. .120 difference doesn't sound like much in clearance. but when i was looking at the crank end of my rods I have very little day light. I can not advance or retard the cam very much without hitting. It's so on the edge that a smaller base circle is way more safe
[Modified by gkull, 4:21 PM 5/4/2003]
I went from a Crane .930 small base circle to 1.050 comp cams. .120 difference doesn't sound like much in clearance. but when i was looking at the crank end of my rods I have very little day light. I can not advance or retard the cam very much without hitting. It's so on the edge that a smaller base circle is way more safe
[Modified by gkull, 4:21 PM 5/4/2003]
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 7,562
Likes: 9
From: B'Ville NY
Cruise-In III Veteran
St. Jude Donor '05
Re: Small base circle cam required ? (VETDRMS)
Thanks guys. The cam lift is with 1.6 rockerrs, actually it's .567/ .585. I didn't think of that.
George I've been thinking about this since we talked about the ramps on a small base circle roller cam not being able to be as aggresive as a normal base circle ;) .
Travis congrats on getting your AFR heads
:hurray:
George I've been thinking about this since we talked about the ramps on a small base circle roller cam not being able to be as aggresive as a normal base circle ;) .
Travis congrats on getting your AFR heads
:hurray:
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Small base circle cam required ? (SmokedTires)
Dart only made the block. And to production (cam location) specs. They wouldn't be the final authority on your combination. Lobe height is definitely a factor, but the main determining factor is the con rod itself. A stroker profiled rod is likely to clear. I believe the minimum recommended clearence is .050. I would much perfer to use a full base circle cam, for strength if possible. Check with the manufacturer of your rods, on the part number you have. Then check it anyhow. Just about any rod can be ground for additional (minor) clearence. Good luck, and...
RACE ON!!!
RACE ON!!!
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Re: Small base circle cam required ? (CFI-EFI)
I had a custom grind " reduced" base circle cam made.
http://www.bulletcams.com
http://www.bulletcams.com
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Small base circle cam required ? (CFI-EFI)
(CFI-EFI) The shaft dia. on my billet steel .930 was the same as my 1.050 base circle. So strength is not an issue.
Crane sells pretty good stock small base circle cams and Bullet cams might be worth checking out.
Crane sells pretty good stock small base circle cams and Bullet cams might be worth checking out.
