SBC cam help

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prairiehotrodder
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SBC cam help

Post by prairiehotrodder » Thu Feb 15, 2018 12:33 pm

Wanting to change cams in a 383 SBC for drag racing and have few questions.

The motor :
stock 350 block punched .040
Scat cast 9000 series ext balance crank with I-beam rods and Icon flat top forged pistons
11-1 CR with AFR 195 heads untouched.
AFR titan composite race intake
850 HP holley
comp gold rockers
Comp XE HYd roller 12-444-8 (248/254 @ .050 110 LSA, .562 / .580 lift)
Car is a 78 lemans with a 5500 stall and 4.56 gears, turbo 350 around 3000 pounds.

Car ran high 10.90's with 4.10 gears, we changed to 4.56 and have now gone low 10.80's but it feels like its not pulling in the lights and oil control is getting bad. We are using a stock pan and now have bought a high dollar moroso pan that will be going on this spring. We are willing to go to a solid roller now that the owner has his feet wet in drag racing. The main issue i want to ask is this , We had to do some rod clearancing to make the current cam fit, if we want to just change the cam / lifters / springs without taking the motor apart what is our best bet ? Will a small base circle cam work? Will a tighter LSA give more or less cam / rod clearance?
Currently going through the traps at 7050 RPM.
thanks
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Re: SBC cam help

Post by F-BIRD'88 » Thu Feb 15, 2018 5:21 pm

You will need to check both VTP clearance and cam to rod clearance with the new cam
reguardless. Its the joys of building a stroker motor. A small base circle cam will help.

When we did mine we checked it with the biggest roller cam we had on hand.
But guess what. When I do upgrade my cam, I will still need to physical check both
too. Just like you will.

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Re: SBC cam help

Post by Old School » Thu Feb 15, 2018 9:46 pm

I would try something around 260-264 @.050, 108 LS, .630 minimum lift up to .670 with the right springs. Should be worth some power over 5500 compared to what you have now. The lift will be the biggest plus, the hydraulic roller will act bigger than the solid at the same duration so your really aren't increasing the effective duration by what the number look like.

Valve control will be better with the solid above 6500 and the right valve springs. I have never had problems with rod/cam interference with a 350. What is the base circle size on the hydraulic roller? I would compare the base circle size, a call to the cam company should get that information.

Edit. Somehow I thought this was a 350. Now I have reread and seen it is a 383. A small base circle will usually fix the problem, especially after you have already clearanced the rods some. All that said, it is a try and see if it hits.
Last edited by Old School on Thu Feb 15, 2018 10:01 pm, edited 1 time in total.

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Re: SBC cam help

Post by prairiehotrodder » Thu Feb 15, 2018 9:49 pm

Hey thanks, old school. Its a 383 so there is less clearance.

This is the cam I've been thinking about all day:

comp 12-908-9

264 / 270
.630 / .630
106 LSA

just re-read my first post and see that i forgot to say it was a 383.
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Re: SBC cam help

Post by Old School » Thu Feb 15, 2018 10:04 pm

prairiehotrodder wrote:
Thu Feb 15, 2018 9:49 pm
Hey thanks, old school. Its a 383 so there is less clearance.

This is the cam I've been thinking about all day:

comp 12-908-9

264 / 270
.630 / .630
106 LSA

just re-read my first post and see that i forgot to say it was a 383.
I think you said it in the first line, I just overlooked it.

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Re: SBC cam help

Post by 6.50camaro » Thu Feb 15, 2018 10:23 pm

Which AFR 195cc heads are you using ? Street, race or competition Dan

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Re: SBC cam help

Post by prairiehotrodder » Thu Feb 15, 2018 10:40 pm

I think they are the LT1 heads with a 65cc chamber. Part number 1031
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Re: SBC cam help

Post by 6.50camaro » Thu Feb 15, 2018 11:54 pm

Those are the street cnc version. They have a minimum csa of 1.905 sq.in , with the bore and stroke listed the port goes mach .60 at 5900 to 6100 rpms depending on wether you use 1116 or 1150 fps as the speed of sound. I'm not an expert or pro head porter but I think you don't have enough csa in the port .Anyone can correct me if I'm wrong as I'm always will to learn more. Dan

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Re: SBC cam help

Post by CamKing » Fri Feb 16, 2018 10:13 am

Here's what I recommend.
Cam# SBCR, R79465-80465-110
262/266 @.050"
.465"/.465" Lobe Lift
110 LSA
.900" Base Circle
Mike Jones
Jones Cam Designs
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(704)489-2449

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Re: SBC cam help

Post by prairiehotrodder » Fri Feb 16, 2018 10:19 am

thanks camking, i'll mention that to my friend.

I'm also trying to convince him to step up to the AFR 210 Race ready heads. The heads he has will need the spring seats cut for solid roller springs and the 210's come with the bigger, better springs so now would be a good time to upgrade.
Brian

Also another question : Whats a tight lash cam all about?
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Re: SBC cam help

Post by CamKing » Fri Feb 16, 2018 11:57 am

prairiehotrodder wrote:
Fri Feb 16, 2018 10:19 am

Also another question : Whats a tight lash cam all about?
Increasing sales.
The height of the lash ramp has no effect on the stability of the valvetrain, or the aggressiveness of the cam.
The only thing that matters, is the velocity and acceleration at the lash point, and that's not effected by the lash ramp heught.
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Re: SBC cam help

Post by prairiehotrodder » Wed Apr 11, 2018 4:39 pm

Just an update to this build.

My friend bought a new set of the AFR 227 competition ported heads and a set of T & D shaft rockers to match.
The heads have a 65 cc chamber so compression should be close to the same at 11-1.
Then he bought a comp solid roller 12-863-9 with .900 base circle and the matching endure-X lifters. This should make this 383 really breathe and work great if he turns it into a 427 for next season. The cam is :
263 / 272 @ .050
.648 / .645 lift
108 LSA
Brian
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www.therocketshop.blogspot.com

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Re: SBC cam help

Post by F-BIRD'88 » Wed Apr 11, 2018 6:03 pm

Tell your friend his old XE 248-254 110 hyd roller cam is worth $100 (CAN) to me if he wants to sell it. (If it has no lobe tracking or damage)
I have a budget build that that cam suits. Going to use Solid Roller lifters on it.

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Re: SBC cam help

Post by RevTheory » Thu Apr 12, 2018 9:13 am

prairiehotrodder wrote:
Wed Apr 11, 2018 4:39 pm
Just an update to this build.

My friend bought a new set of the AFR 227 competition ported heads and a set of T & D shaft rockers to match.
The heads have a 65 cc chamber so compression should be close to the same at 11-1.
Then he bought a comp solid roller 12-863-9 with .900 base circle and the matching endure-X lifters. This should make this 383 really breathe and work great if he turns it into a 427 for next season. The cam is :
263 / 272 @ .050
.648 / .645 lift
108 LSA
Brian
Tell your friend he did well, Brian.

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Re: SBC cam help

Post by prairiehotrodder » Fri May 18, 2018 1:24 pm

This build took a turn for a lot of hassle. Putting it together and degreeing the cam last night. The card wants a 108 ICL. The chain set at dot to dot put the ICL at 117. We moved the chain to the +4 setting and now have a 112 ICL. We may leave it there. Had no P - V clearance on either valves. These AFR 227 heads have moved the valves a little. Gonna have to notch the pistons. Allready did a couple of the exhaust notches with a Lindy Tool (i'm getting lots of experience with these tools). Never built a motor yet where I had to notch for both valves. Will post pics for reference soon. If we moved the cam to the 108 ICL what would that do for PV clearance? I'm guessing it would make one valve worse and one better ? Which ones? Maybe then only have to notch one side of the piston ?
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