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solid roller cam selection
I am in the process of building a 463 stroker. Main components are Scat forged crank with 4.25 stroke, Icon forged pistons 4.165 and Eagle 6.8 forged rods. Will be using a Northwind intake port matched to KRE 325 cfm heads. This engine will be going into my 79 Trans Am which is at 3600 race weight. Rear gear is 3.73 and I will stay with my 350 tranny and I run MT 275/60 x15 drag radials. The cam that Bullet recommends is 262/271 at .050 with lift at .680/.688 and LSA at 108 + 4. I want to keep the shift points at or below 6500 and this will be a street/strip car so I am willing to give up a little peak power to have slightly better idle quality. Thinking maybe a 110 or 112 LSA might give me a balance of what I am looking for. What do you guys think?
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112
Tom V. |
If idle is important, I'd agree with the 110 or 112 lsa. Who at Bullet did you speak with? I understand Tim is the one that speaks Pontiac fluently.
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Chuck is the only one I have talked to at Bullet, and yea I was thinking 112 would be my choice. Next week I will try to contact Tim if he is the guy most familiar with Pontiacs. The heads are on order so I don't have a flow sheet at this point.
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Agree, I have been dealing and talking with Tim about Pontiac Camshafts for many years.
He just did a special camshaft profile for a friend of mine. Tom V. |
Tom, thanks for the confirmation.
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Talk to Tim at Bullet
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Their cam pick is only as good as the info you share with them. If you think the cam might have a little to radical of an idle I would mention that. Moving the LSA 262/270 cam out to 110 or 112 with that much head is likely going to send the rpms more than what it sounds like you are hoping for.
I have always talked to Tim also. I would have thought if your not trying to rev the engine out with that much head for street and strip they would have used closer to a single pattern cam or at least a smaller split. Then they can keep the LSA in tighter, have adequate overlap and let the upper rpm nose over a little sooner with the smaller exhaust profile. I am not sure which profile was picked, but for street and strip Tim ground the .4176 profiles for us, but they have another similar profile with more with more lift that isn’t to bad on the street either if you are using 1.5s. Both seem to be a little gentler valve terrain parts and not require a bunch of spring pressure. |
Yea, as the old saying goes I am probably trying to have my cake and eat it too. Need to keep the rpms reasonable so the basic 2-bolt main block will live a long healthy life. But at the same time wanting to get the most I can out of the combo. As to the cam profile, the lift #s are based on 1.65 rockers which would indicate a .4121/.4170 lobe lift. Hopefully I can talk to Tim at Bullet next week and get his input.
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Here is a bit more that "Google" blessed me with. lol. Assuming 325 CFM intake / 230 CFM exhaust. The Bullet suggestion is pretty solid. Personally I'd go no wider than 110 LSA. https://i.imgur.com/nAoMtw2.png |
I think Greg Weigart is pretty happy with his solid roller i believe in the rpm range your looking for too
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Sounds close to the cam i have, you should be good with rpm range with that duration.
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Bill, thanks for your input. What are your shift points? And what race weight?
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I bought that for my 469 High Port combo, 3400 lbs and 6500 rpm. I never ran it, last year I had a 273/277 and went 6.40s
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My race cam is a little smaller at 262/266 at 0.050" with best shift points at 6500 going through the traps at 6700 and uses a 110 LSA with a 106 ICL. Intake is a street lobe and the other is a base design I think, works well.
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Greg, what is the lift for that cam? and what is your race weight? Thanks.
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AG, are the lift #s with 1.5 rockers?
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