Small Base Circle Cam w/383
Small Base Circle Cam w/383 My builder says we had to go with a small base circle cam on my 383 to clear the rods. I'm just wondering if this is standard practice with building 383's?
I have 6" eagle h beams in my 383 with a standard xfi280 cam. No clearance problems at all with the cam. I did have a good amount to grind off the block though. My 421 in my Nova has 6" scat h beams and that did need a small base circle cam. That's a 3.875" stroke where the 383 is 3.75" stroke.
FWIW I've built quite a few 383 SBC with all sorts of different rods and I've never had to do that for a 383. That said, still maybe possible you need the small base but its unlikely ...
FWIW I've built quite a few 383 SBC with all sorts of different rods and I've never had to do that for a 383. That said, still maybe possible you need the small base but its unlikely ...
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I-beam. I believe this is them, if not they're real similar.
http://www.summitracing.com/parts/LUN-LAA1/
Fazz: What kind of numbers (track times/dyno) are you getting with that cam and you're current set up?
I am taking a hard look at that 280xfi grind for an upgrade. It's a lot of lift for stock ported heads, but it gives me room to upgrade my heads in the future.
http://www.summitracing.com/parts/LUN-LAA1/
Fazz: What kind of numbers (track times/dyno) are you getting with that cam and you're current set up?
I am taking a hard look at that 280xfi grind for an upgrade. It's a lot of lift for stock ported heads, but it gives me room to upgrade my heads in the future.
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Verdad Gallardo My best run to date is a 13.2 @ 109 on street tires and lots of knock retard. My headers where hitting the k member when it warmed up. I got like a Max of 32° with it like that. I've since fixed that but still needs help with the tune. I'm considering finding an lt1 dyno tunner here in socal very soon.
When are you looking to get a cam by? I have a bottom end vibration in mine that I will be pulling the motor out to get it rebalanced. Being I'm in there I was thinking of giving LE a call for a custom cam to match my heads better. If I do my xfi280 will be for sale.
that said its still is an awesome cam. It really come to life in the mid range. Check out my youtube videos under the same screen name.
When are you looking to get a cam by? I have a bottom end vibration in mine that I will be pulling the motor out to get it rebalanced. Being I'm in there I was thinking of giving LE a call for a custom cam to match my heads better. If I do my xfi280 will be for sale.
that said its still is an awesome cam. It really come to life in the mid range. Check out my youtube videos under the same screen name. That's kind of why I was asking about the Small Base Circle because I wanted to order a shelf cam and the xfi280 looks like the best fit for me, but I'll have to play it safe and go small base circle again. Last time it was 4 weeks for Comp to do the "custom grind" (same specs as cc305, but Small Base).
We're in the same boat with the knock. I did everything I could imagine to get rid of it, and finally just parked the car for a few weeks and just got around to pulling the motor to find 3 broken push rods. Luckily I have SA rockers and only the pushrods were damaged. I'm rethinking everything now. My headers were also vibrating my whole car, but I don't think that's what was causing the knock for me. I'm just hoping once we get the motor "repaired" and back in the car that the knock goes away.
Solomon tuned mine for $70, but I have all the tuning cables and hardware and my motor was knocking before he tuned it, so my best track time of 13.08 should be easy to beat if I can get rid of this knock.
We're in the same boat with the knock. I did everything I could imagine to get rid of it, and finally just parked the car for a few weeks and just got around to pulling the motor to find 3 broken push rods. Luckily I have SA rockers and only the pushrods were damaged. I'm rethinking everything now. My headers were also vibrating my whole car, but I don't think that's what was causing the knock for me. I'm just hoping once we get the motor "repaired" and back in the car that the knock goes away.
Solomon tuned mine for $70, but I have all the tuning cables and hardware and my motor was knocking before he tuned it, so my best track time of 13.08 should be easy to beat if I can get rid of this knock.
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Joined: May 2009
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From: NW AR
Before I say anything, I'll start off your parts could be different. However I have built bigger stroke LT1 engines, with H beam rods and we still didn't need a small base circle camshaft. You might need to clearance a little on the shoulder of the connecting rods. You can even get to 4" stroke on a LT1 with a regular base circle camshaft if you have the right parts, it has been done. I personally haven't gone above 3.875" Stroke with 6" H-beams.
Really ask to see what they are telling you before you drop money on a custom camshaft.
Really ask to see what they are telling you before you drop money on a custom camshaft.
well first you have to define small base circle... anything other than a stock camshaft will have compromises on the base circle. You shouldn't have to cut the base circle down more than will already be ground in by default of lobe choice with a 3.75" stroke unless you're using some funky rods with huge bolts. Cam specs and lobe design will change your cam/rod clearance as well...
There ARE trade-offs to making compromises on the base circle, big ones.
There ARE trade-offs to making compromises on the base circle, big ones.
The small base cam is what I have in my motor now from last year's build, but I just dropped the motor and was thinking of upgrading and just wanted some opinions on why my builder HAD to get a small base circle cam. I think it was recommended by the engine parts warehouse for clearance issues.
"There ARE trade-offs to making compromises on the base circle, big ones." - Not sure what this means; care to elaborate?
"There ARE trade-offs to making compromises on the base circle, big ones." - Not sure what this means; care to elaborate?
The bigger the base circle, the better off your valvetrain is. Like I said... define small base circle. If you know how much clearance you have now... you/your builder can get a ballpark of where it would be with a different lobe and base circle. If you're trying to run a .460 lobe you're stuck with a ~.940 base circle at best with a standard sbc journal cam. Depends on the core you're trying to run as well, some lobes can't be put on certain cores.
Call a big name cam manufacturer and ask them the pros and cons on small base circle stick. More than likely they'll tell you that it's for clearancing stroker crank/rods. And have nothing to do on which is best, small base vs. normal base circle cams. Just my 2 cents.
I'd counter with...
call a small name cam manufacturer who will tell it like it is, rather than just trying to sell you something There's no question the bigger the base circle is the happier your valvetrain will be.
call a small name cam manufacturer who will tell it like it is, rather than just trying to sell you something
There's no question the bigger the base circle is the happier your valvetrain will be. [QUOTE=Wicked94Z;14784645]Like I said... define small base circle. QUOTE]
Just got the cam pulled out. The base circle is 1.050. If I was to buy a Comp Cam shelf grind, what would the base circle be? I'm looking at the 280xfi.
Just got the cam pulled out. The base circle is 1.050. If I was to buy a Comp Cam shelf grind, what would the base circle be? I'm looking at the 280xfi.
Small base circle has no effect in performance of a particular duration cam. And that includes valvetrain longevity. Call Comp Cams, Ultradyne Cams, Lunati Cams, etc. It's just for clearancing stroker/rods.
The size of the base circle has a HUGE effect on valvetrain dynamics, longevity and stability. I don't know where you're getting your misinformation.