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Old 02-01-2009, 11:15 AM
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Cam selection sbc

Hey I have a 82 z28 with a Goodwrench crate motor not sure how many miles on it.I now have 3.23 posi and a stock converter on a TH350. No emission,shorty headers 21/2 to a flow masster. Can,t see pushing the motor to 5000 rpm?Its going to be a week end street car with some track runs .I,m istalling Patriot cast Iron heads I found on ebay 64cc with 185 2.02 1.6 valves vortec style.I like the comp cam 268 extreme energy.But I,m wondering if there a better match for my porpose? I think I saw a comp cam extreme 262 Matbe better in the mid range ?If I do go to the track I my start changeing stuff like gears and torque converters ect.But I,d like to here some feed back and what kind of time could I exspect at the track?

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Old 02-01-2009, 03:05 PM
How fast is fast enough?
 
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I'd look at Isky. They have single patterns on a tight LSA which will produce great midrange. Of the two you mentioned I think the 262 would be much better for you considering you'll never see over 5,000 RPM. If you don't lan on driving over 5000 RPM there's no reason to put yor hp peak over that- even if you go with something more like an RV cam. I'd also watch the agressive cams, if you want a no-hassle cam you may want to go with something with a little less lift.
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Old 02-01-2009, 03:09 PM
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perhaps this one would be a good match.

264Mega

http://store.summitracing.com/partde...4&autoview=sku
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Old 02-01-2009, 04:09 PM
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Re cam selection

You mensioned a single pattern .Why? what would be the advantages?I know with the factory Vortec I read that the dual pattern helps on the exhaust side but with the patriot 1.6 exhaust maybe it hurts? and I know 185 flow it slightly high for my aplication so I need to be able increase velocity where ever I can.And with 64cc chambers compresion should be ok even w/ the dish pistons..I thinking your right just interested in the reasoning
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Old 02-01-2009, 08:08 PM
How fast is fast enough?
 
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moe exhaust duration is necessary for peak hp over 5500 RPM or so, however at lower engine speeds it just bleads off the power stroke too early. A single pattern (especially with headers and a free flowing eshaust) is better for low/mid range tq and power.

A great example is when people put dual 3" exhaust on a factory short block and loose power- its because the factory cams have excessive ex. duration to compensate for a shoked exhaust sytem with manifolds, cats, and mufflers.

You will make more hp with a dual pattern, BUT you will make more power under the curve with a single pattern with a free flowing exhaust. (In most cases).

I'm putting a engine together for my truck that is running a 274 H06 (well the Erson version of it) and it may be a good cam for you, thoguh somehting a hair smaller may be best if you'll never go over 5000 RPM. I got it from Competition Products for like $80 for a kit with lifters. Its a great budget cam for a hoped up engine running mostly stock parts. DD says I should be around 400 ftlbs at 4000 RPM, I'm sure its off a little, but anything close to that makes a fun cheap street car.
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Old 02-02-2009, 05:58 PM
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[QUOTE=ap72]moe exhaust duration is necessary for peak hp over 5500 RPM

Why is 5,500 rpm the magic number ?

A great example is when people put dual 3" exhaust on a factory short block and loose power- its because the factory cams have excessive ex. duration to compensate for a shoked exhaust sytem with manifolds, cats, and mufflers.


Have you ever seen a car run slower with a less restrictive exhaust system ? I have not.
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Old 02-02-2009, 06:01 PM
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Are you running a single exhaust with 1 Flowmaster muffler ? What is your compression ratio ? What is your intended purpose ?
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Old 02-02-2009, 07:18 PM
How fast is fast enough?
 
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[QUOTE=RustoRod]
Quote:
Originally Posted by ap72
moe exhaust duration is necessary for peak hp over 5500 RPM

Why is 5,500 rpm the magic number ?

A great example is when people put dual 3" exhaust on a factory short block and loose power- its because the factory cams have excessive ex. duration to compensate for a shoked exhaust sytem with manifolds, cats, and mufflers.


Have you ever seen a car run slower with a less restrictive exhaust system ? I have not.

5500 RPM is NOT a magic number, its a rough rule of thumb. If you want a more exact number 4462 RPM, but its still a rough rule of thumb.

And yes I have seen a car run worse with an open exhaust. And I've seen a LOT of bikes run worse.
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Old 02-02-2009, 07:27 PM
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2nd AP's comments on exhaust.
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Old 02-03-2009, 02:38 AM
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What cars ran slower and how much ? Was this quantified at the dragstrip or on the dyno ?
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Old 02-03-2009, 02:41 AM
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[QUOTE=ap72]
Quote:
Originally Posted by RustoRod


5500 RPM is NOT a magic number, its a rough rule of thumb. If you want a more exact number 4462 RPM, but its still a rough rule of thumb.

And yes I have seen a car run worse with an open exhaust. And I've seen a LOT of bikes run worse.

I apologize. Why is 4462 rpm the magic number ? And what car ran slower what was the build ? On bikes the exhaust is short you have to be careful with the lengths and sizes as you change them up. Please share some details.
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Old 02-03-2009, 09:41 AM
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[QUOTE=RustoRod]
Quote:
Originally Posted by ap72


I apologize. Why is 4462 rpm the magic number ? And what car ran slower what was the build ? On bikes the exhaust is short you have to be careful with the lengths and sizes as you change them up. Please share some details.

A rule of thumb means there is no magic number- you missed the point. Its a guideline. no magic what so ever. And I've seen it at the track a few times, but often on the dyno. Just about any late 70's through early 90's american car will have that problem with an open exhaust. If you don't want to take my word for it call up some cam manufacturers. I really don't want to get into cam design and application here- just as a rule of thumb free flowing exhausts lean more towards single pattern cams, the more restricted it gets the more you'll need a wider split pattern.

This is a simple thread that needs a simple answer. Something close to a single pattern (if not a single pattern). Installed a few degrees advanced, and NO MORE than 220 dur @ .050" and even that is a little high. I'd also run a tight LSA (around 107-109) but that is personal preferance.

Of the 262 or 268 the 262 would be much better for this application IMO.
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Old 02-03-2009, 12:53 PM
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sometimes smaller IS better.
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Old 02-03-2009, 01:27 PM
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Quote:
Originally Posted by david ahluwalia
Hey I have a 82 z28 with a Goodwrench crate motor not sure how many miles on it.I now have 3.23 posi and a stock converter on a TH350. No emission,shorty headers 21/2 to a flow masster. Can,t see pushing the motor to 5000 rpm?Its going to be a week end street car with some track runs .I,m istalling Patriot cast Iron heads I found on ebay 64cc with 185 2.02 1.6 valves vortec style.I like the comp cam 268 extreme energy.But I,m wondering if there a better match for my porpose? I think I saw a comp cam extreme 262 Matbe better in the mid range ?If I do go to the track I my start changeing stuff like gears and torque converters ect.But I,d like to here some feed back and what kind of time could I exspect at the track?
Both the 262 and the 268 are really nice potent street cams. The 262 surprisingly gives up very little top end power against the 268, but it fattens the torque curve and brings the max, (note I didn't say peak for the reason that this isn't a peaky cam), it brings the max torque compared to the 268 back down 5-600 RPM at the same number. This does a lot to put the engine's torque peak inside the cruise RPM range so when you hit it, it pulls hard from there up to redline.

This is a good way to have a solid performance street engine that also gets good mileage, has decent idle for the accessories, and allows you to avoid a stall converter purchase. Works well with street gears and OD transmissions. I think the Comp 262 is an overlooked cam that more guys running strong street machines would have been happier with for day to day use then the occasional blast at the track, than the choice of the meaner stick they're trying to live with.

Bogie
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