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Old 01-06-2013, 04:51 PM
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Cam question

Can someone explain to me why roller cam with same specs as hyd. Flat tappet have lower rpm operating range. I look at a flat tappet cam and it was .488/.510 and the rpm range was from 3000 to 6500. I look at a retrofit roller .488/.495 and the rpm range is 1000 to 5000. That means if what I read was correct I need to set my heads up for a lot more lift to do retrofit

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Old 01-06-2013, 05:02 PM
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Well cam advertising guys kinda make **** up sometimes. So you got to look at the dur at .050 and the way the lobes are on the cam lsa or Centerline.

I would need to see the actual spec on each cam.

Post a link if you can?
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Old 01-06-2013, 05:56 PM
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Here's what I was looking at
Summit Racing® Camshafts SUM-1107 - Mobile SummitRacing.com
Howards Cams Retrofit Hydraulic Roller Camshafts 110235-12 - Mobile SummitRacing.com
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Old 01-06-2013, 06:56 PM
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Lobe seperation is 112 and 114 this is only minor actually their duration is very different. One is almost 10 degrees longer on the one cam and lift is different as well.

I would suggest either asking on this forum for help finding the correct cam or call howards or isky or comp cams and get some good advice for your engine. They will be able to go over all the details and find thecorrect cam for your build.

Now if you got to pick one your self i would suggest getting one from edelbrock they only sell a few good grinds that work pretty goodnin most cases.

You still need to make sure you heads can take the lift the am has. Most stock heads an support 5000 rpm and .450 lift.

Hope this helps. I am not good at explaining the complexities of camshafts.

I will get yeld at for saying this but alot of times the biggest one that wil fit without going to the machine shop is usally the best one to get. But that is a bold and sloppy statement. Cause every build is different.

But duration is the programming the dictates how the engine will try to respond. Basicly its the engines "computer" and it times all the events and longer duration usally means high rpms. Shorter duration usally means lower rpm and more tq down low.

Power usally only comes from raising the engine peak higher up in the rpm band. Which will be more power pulses at peak tq and will equal more power overall. Higher the rpm the higher the tq peak the further the hp wil go up. If the heads can support what the cam is asking for.

Hope this helps.
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Old 01-06-2013, 07:00 PM
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20 degrees difference in duration
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Old 01-06-2013, 07:19 PM
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Quote:
Originally Posted by vinniekq2 View Post
20 degrees difference in duration
Vinnie you and your accurate math. LOL
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Old 01-06-2013, 07:29 PM
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I guess what I would be asking is what cam to use . The car is an 85 Monte Carlo, has 3.73 rear end and th350 I will run stall converter. The motor is 350 .030 flat top 4 v relief . I was going to use vortec heads that hav been cut and new springs good to .520 lift summit recommended that 1107 cam that I posted the link to that seem like alot of cam for a street car any suggestions.
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Old 01-06-2013, 07:37 PM
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cam choice is tough to pull a number out of the air.what RPM do you want to run? will you consider a roller cam? are you using none modified vortecs? what is the car used for,DD or ss? or both? what else do you have on the engine? what type of exhaust are you using? and so on,,,,
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Old 01-06-2013, 07:54 PM
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The car is goin to be street strip I don't hav any other parts other than what I told you so open to anything . Going to use long tube headers and 2.5 in exhaust. Open to intake and carb suggestions also. The heads are
Summit Racing® Vortec Cylinder Heads SUM-151124 - Mobile SummitRacing.com and the intake I was thinking about is Summit Racing Street & Strip® Stage 3 Intake Manifolds SUM-226019 - Mobile SummitRacing.com
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Old 01-06-2013, 07:58 PM
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I guess I should also say I'm trying to build on a budget that why I was lookin at so many summit brand parts plus there right up the road so parts are readily available and I don't have to pay any shipping
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Old 01-06-2013, 07:58 PM
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Quote:
Originally Posted by Jmszip610 View Post
I guess what I would be asking is what cam to use . The car is an 85 Monte Carlo, has 3.73 rear end and th350 I will run stall converter. The motor is 350 .030 flat top 4 v relief . I was going to use vortec heads that hav been cut and new springs good to .520 lift summit recommended that 1107 cam that I posted the link to that seem like alot of cam for a street car any suggestions.
Does it still have the computer controlled carb? Cam may not work well if its much bigger than stock.

This may be the only one you can run andi have no clue if it will realy work well. I would call comp cams and see fi they can help pick one.

http://www.compcams.com/Company/CC/c...?csid=124&sb=2
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Old 01-06-2013, 08:01 PM
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Quote:
Originally Posted by Jmszip610 View Post
I guess what I would be asking is what cam to use . The car is an 85 Monte Carlo, has 3.73 rear end and th350 I will run stall converter. The motor is 350 .030 flat top 4 v relief . I was going to use vortec heads that hav been cut and new springs good to .520 lift summit recommended that 1107 cam that I posted the link to that seem like alot of cam for a street car any suggestions.
On the 1107 cam, did you see the part where they recommend a static compression ratio of 10.0:1 to 11.0:1? If you know, specifically, that your static compression ratio is between 10 and 11, great, use that cam. If you have no idea what your static compression ratio is, then you have no business changing out the cam.
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Old 01-06-2013, 08:14 PM
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what Hcompton and tech both said. and I would not use a hydraulic flat tappet cam that big.thats just a personal opinion.
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Old 01-06-2013, 08:24 PM
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Not com controlled using Holley 750 vacuum secondaries . Don't know what static comp is . I also thought that cam was to big.
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Old 01-07-2013, 04:42 AM
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I would use a cam with 110 LSA, not 114. LSA of 114 is more of a n02/blower/efi cam and would reduce throttle response and would lower dynamic compression.

I would recommend a cam one size smaller. 224 to 230 degrees on the intake and 234 to 240 on the exhaust. 10" converter with a 3000 stall.

A holley 3310 750 vacuum secondary is a good carb. I would use a regular rpm intake (not rpm air gap).

Ignition timing is more important when you start messing with the cam. Get a distributor that is adjustable. Use 24 degrees at idle and 34 total. And another 10 degree from the vacuum advance canister.

A 350 with 64cc heads and 4 reliefs should be close 10:1 cr (9.7 or so). You would need to know the piston part number and take a few other measurements to get a more accurate compression calculation.
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