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Old 05-20-2007, 10:11 PM
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Comp Cams Xtream Energy 268 camshaft


Engine specs.

350 4bolt main bored .030 to 355cid
steal crank (3.48" stroke)
Holley 650cfm 4150 double pumper on a edelbrock performer RPM
Sealed power flat top -5cc flat top
Speed pro piston rings
Stock rods with Milodon chromoly Rod bolts
all felpro gaskets
heads are chevy heads with a stage 2 port job
Manley Stainless steel valves 2.02int. 1.50 ex.
Comp cams roller tip rocker arms 1.6 ratio int. 1.5 ratio ex.
z-28 valve springs
Comp cams XE268 camshaft
Moroso Chrome oil pan
Moroso Chrome valve covers
comp cams 84000 series lifters, which are very strong and expencive





here is all the information on my camshaft that i know.

Brand: COMP Cams
Product Line: COMP Cams Xtreme Energy Camshafts
Part Type: Camshafts
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,600-5,800
Intake Duration at 050 inch Lift: 224
Exhaust Duration at 050 inch Lift: 230
Duration at 050 inch Lift: 224 int./230 exh.
Advertised Intake Duration: 268
Advertised Exhaust Duration: 280
Advertised Duration: 268 int./280 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.477 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
Valve Lift with Factory Rocker Arm Ratio: 0.477 int./0.480 exh. lift
Lobe Separation (degrees): 110
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: No
Grind Number: CS XE268H-10


i have build my 350 sbc engine around this camshaft and put 1.6 roller rockers on the intake and 1.5 on the exhaust and the heads were originaly 1.94/1.50 and i made them into 2.02/1.50 (not 1.60) i had it dynoed and it read 380 HP @5400 & 410 Lt. lbs. of tourque@ 4300

what is my intake lift with the 1.6 roller rockers compared to the 1.5's stock?

what will my idle sound like?

would i see more horse power if i switched to 1.6 on the exhaust also?

do you see any problems in my set up that would free up HP and/or tourque?

was it a good idea to do this with the rockers?

see any problems?

any suggestions???

just to let you know this is going to be my daily driver Nova!

thankyou in advance

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Old 05-21-2007, 04:16 AM
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268 Cam

Hi I think you have built a mighty fine engine those Hp and toruque figers are fairly stout for a daily driver 350. Your heads are working fairly well to get those figers with a fairly modest cam. The engine will work good with your standard drive line as well. To get your valve lift with 1.6 rockers you need the cam lift first wich is 0.32in inlet,0.323 ex. simply multiply your cam lift by rocker ratio 0.32* 1.6=0.51 inlet lift, 0.323*1.6 =0.52 ex lift. Your idle should sound real nice and be fairly zippy off idle and will have a noticable lope at idle. You may see more hp with 1.6 rockers but keep an eye on tourque as it may cost a bit, if it does stay with the 1.5s as this is your strong point giving up tourque for more hp will make a heavy car with high gearing in a daily driver slower anyday. One thing to watch with standard rockers is that the ratios are seldom 1.5 ,due to manufactering tolerances they can be as litle as 1.4 (that gives up a fair bit of lift and duration of your cam). Also if you go to 1.6 rockers make sure you have at least 30 thou clearance at full lift from the rocker stud to rocker slot. A paper clip is a good checking tool if you can fit it between the stud and rocker slot at full lift your sweat ( youl have to bottom out lifter though as it will bleed down and not give full lift at valve)It will wipe cam lobes and break studs in no time if not enough clearance.Also check for pushrod to head clearance ect. Just get that motor in to the nova you wont be disapointed cheers.

Last edited by Detroit Muscle in NZ; 05-21-2007 at 04:22 AM.
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Old 05-21-2007, 12:15 PM
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LOBE lift X rocker ratio = lift at the valve(gross)

eg:.316 x 1.5:1 = .474 INTAKE
eg:.340 X 1.5:1 =.510 EXHAUST

now with a 1.6:1 rocker ratio:

eg: .316 X 1.6:1 = .5056 INTAKE
eg: .340 X 1.6:1 =.544 EXHAUST

A quick way to convert the lift at 1.5 to lift at 1.6 is;
Multiply lift by 1.066666

eg .510 X 1.066666 = .544

Last edited by 383silverado; 05-21-2007 at 12:32 PM.
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Old 05-21-2007, 12:47 PM
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Quote:
Originally Posted by Detroit Muscle in NZ
Hi I think you have built a mighty fine engine those Hp and toruque figers are fairly stout for a daily driver 350. Your heads are working fairly well to get those figers with a fairly modest cam. Also check for pushrod to head clearance ect. Just get that motor in to the nova you wont be disapointed cheers.
ya the heads are flowing very well! they have better flow specs. then Edelbrock 180 heads with 1.94 valves. and that is esspesally impresive because the heads are original 333882 heads which are known to have the worst flow of all GM heads ! but i got them Stage 2 race perparing ported and polished with Manley S/S race flow valves. this is my first engine build and i did 90% of the assembly by myself and im only 17! 5% help from my dad and 5% i consider the heads being assembled by the engine shop! they said i did an exelent job assembling the engine. im hoping to get a very noticible choppy idle because my exhaust is hooker headers to a 3"-2.5" reducer and then a 26" section of chambered pipe then turn downs. and this is going to be my daily driver to school and work and every where i dont have enough money to buy a car that has good gas milage because i put all of my money into this '71 Nova!
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Old 05-21-2007, 03:27 PM
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Hey there! I'm 18 and sitting on a 400 with 333882 heads...

I've been thinking about getting them cleaned up, ported and polished plus new valve guide inserts installed. If you don't mind sharing, about how did the port and polish cost you? I might be able to get some help from a friend who teaches auto at a community college, but mostly i'm on my own. My school doesnt have a very good auto depart.

thanks!


p.s. good luck with gas mileage ... gas prices sure are crazy these days!!!

p.p.s. '71 Nova Very cool. I'm runnin' around in a '77 1/2 ton At least it was cheap though!

Last edited by Fasttrack137; 05-21-2007 at 03:42 PM.
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Old 05-21-2007, 03:41 PM
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Quote:
Originally Posted by Fasttrack137
Hey there! I'm 18 and sitting on a 400 with 333882 heads...

I've been thinking about getting them cleaned up, ported and polished plus new valve guide inserts installed. If you don't mind sharing, about how did the port and polish cost you? I might be able to get some help from a friend who teaches auto at a community college, but mostly i'm on my own. My school doesnt have a very good auto depart.

thanks!


p.s. good luck with gas mileage ... gas prices sure are crazy these days!!!
ya i know gas prices are getting crazy!!! but anyway the total cost of the head rebuild was $650 give or take. and i think it was about $350 to get the race stage 2 porting done to them. but a let agressive port and polish would be cheaper! i accualy had some nice heads befor i had these and i tried to port them out by myself and totaly effed them over! but i wouldent try doing it yourself. but if you can get some help maybe because all i had was a book and my tools! but i would be carful porting 333882's if your not skilled because they are very thin castings and crack easly and you can barly bore out the exhaust port because they are so thin but a new set of valves like the ones i got would REALLY improve flow!!! and defenatly test them for cracks befor you get any work done because thos heads are prone to crack!

P.S. what a 333882's doing on a 400. i thought they were only a 350 head but i dont think they will flow any more then i got mine to to keep up with your 400 flow needs! but i dont know anything about your engine sooooo yaaa
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Old 05-21-2007, 03:48 PM
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Hey thanks for the heads up! Yeah they are stock heads; from MorTec.com
Number.....Year.....Engine........Notes
333882.....74-80...350/400......76cc chambers


i found a few other sources that said the same thing - those heads were stock on the 400 as well - just had steam holes. I checked pretty thoroughly because the previous owner really cobbled stuff together. Like using scotch tape to tape up wiring connections It barely ran. I was expecting 350 heads on there or something, but these have the steam holes so thats good i guess...



What are your feelings about buying new heads? Summit sells cast iron heads that have the bigger valves and supposedly outflows stock (plus has 64cc chamber vs 76 for slightly better compression ratio) and they cost about 650 for a pair.


fyi - i've got a 400 small block ... i reckon 333882's would cause some confusion if you thought i was talking about a modified 396 BB
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Old 05-21-2007, 03:55 PM
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no no no i knew you were talking about a 400 small block! i know more then most when it comes to engines. and i know everything that your talking about even tho im 17. but your probly older soo. i think you said but im not sure how old? but anyway i think you would be better off buying World product S/R tourquer heads from summit. they are good flowing heads. i wouldent buy the summit heads for one reason and one reason only they have a BIG SUMMIT RACING logo on the ends of the heads which in my mind is just not classy and would not look good at all! what is this engine going into???
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Old 05-21-2007, 04:50 PM
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Yeah i'm older ... by a year ...

Hadn't noticed the logo - your right though ... that would look a little goofy.
I'm cobbling something together from scratch for the engine to sit in. I've been building go-karts since i was 15 from scratch. I've got a lathe and milling machine (small - i've only got a garage and a very limited budget ) which i've used to make everything from steering spindles (easy) to 6 speed transmissions (hard )for the gokarts. I feel like its time to move on to something a little more challenging.
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Old 05-21-2007, 05:55 PM
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6 speed tranny, eh? I think you should elaborate on that a bit! lol. Im younger than all of you and Im building a 350 right now. It should be pretty close to the hp and torque listed above, it will prolly be a bit lower though. I dont trust dynos, especially ones on the computer.

Steve
PS: I wouldnt worry about the summit logo its only a set of heads, its all about power.
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Old 05-21-2007, 06:28 PM
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I don't want to steal the thread but i'll give the basics

I started with a 6 speed transaxle from an old craftsman lawnmower. In order to bring it up to "go-karting speed" i ran a 4 inch pulley on the crank and a 2" pulley on the input so it was spinning twice the speed of the engine. Its max input was 2000 rpm - needless to say it didn't last long when the engine was running 4500 rpm...

I broke the shift key and locked up the differential. When i tore it apart i found the differential gears were all hashed up and three of the six output gears that the sliding key contacted were damaged. The debris from the shift key had gotten thrown around inside the tranny and didnt some damage.

One gear was cracked in two and had come off the shaft. It was the gear i was attempting to shift into and i dont think it could handle all the torque thrown at it so suddenly and in only across its diameter. The other one was shredded beyond repair and the third just had some chewed up teeth.

I bought some 99% nickel welding rods for the cast iron... $1.33 each!? I welded the cracked one back together and took a quick pass at the teeth with a file to clean them up. The next two were more difficult. I had to find a spur gear hob that was pretty close to fit and then grind it to fit the teeth profile. I then brazed a bunch of material onto the gear with damaged teeth and hobbed it. The next one was made from a round of 1018 steel. The blank was made on the lathe and mounted on a shaft which was then held in the rotary table to be hobbed.

After repairing/making gears i then set about designing a tranny that could handle high speed shifts. I settle on a dog clutch design because of its reliability and simplicity to make. I made my own case out of 1/8" plate with 1/4" thick strap to tie all of the shafts together. I've got needle bearings (they were lying around from a weedwacker engine) on the output and input and bushings on the inside. Driving the whole setup is a centrifugal clutch. Not ideal - it takes some time to disengage before shifting, although this can be somewhat regulated with a brake on the crank, but it was a spare part with a bad drum... so the price was right. I made a new drum for it which incorporated a shaft that couple to my transmission so no belts to slip.

The shift pattern is somewhat goofy... 1-2 is quick, but then you have to pull sidewise to disengage the shifter from the dog ring, then travel upwards about two inches to pick up the 3-4 dog ring. Then another upwards travel to find 5-6. Each time you are locking the driven gear to the output shaft via the dog clutch. No countershaft - just an input and output parallel. Its not a fast performance shift by any means - not at all like a shifter cart, but it was loads of fun to build and even more fun to drive. Its neat to drive something you built completely yourself. Its fun to be able to bring life to and idea in your head, imo.

<edit>
If you have any questions feel free to pm me - don't want to hijack the thread.
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Old 05-21-2007, 06:31 PM
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Quote:
Originally Posted by steveyb4342
Steve
PS: I wouldnt worry about the summit logo its only a set of heads, its all about power.
well there not the best flowing heads anyway so with thos heads its not all about the performance!
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Old 05-21-2007, 06:33 PM
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Well Chevymastermind - i think you sold me on the world products if not the torquer heads. They have some specifically designed for large displacement small blocks with 220 cc intake runners and 2.06 intake valves! They are a little more pricey - but it gives me something to save up for, right?
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Old 05-21-2007, 06:39 PM
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Quote:
Originally Posted by Fasttrack137
Well Chevymastermind - i think you sold me on the world products if not the torquer heads. They have some specifically designed for large displacement small blocks with 220 cc intake runners and 2.06 intake valves! They are a little more pricey - but it gives me something to save up for, right?
BE CAREFUL !!! with such HUGE intake runners and HUGE valves you WILL lose tons of Low end tourque ! i would just go with the tourquers if its going to be a street engine! thos wont work good on a basicly stock engine! unless you build it ALOT! im talking about atleast 550 horse power out of you 400sbc. wouldent do it if i were you! i would go for tourque!
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Old 05-21-2007, 07:44 PM
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Originally Posted by chevymastermind
BE CAREFUL !!! with such HUGE intake runners and HUGE valves you WILL lose tons of Low end tourque ! i would just go with the tourquers if its going to be a street engine! thos wont work good on a basicly stock engine! unless you build it ALOT! im talking about atleast 550 horse power out of you 400sbc. wouldent do it if i were you! i would go for tourque!

Not a streeter - i always wanted to build a monster engine and now that i'm scrapping my project truck, i figured i can offset the pain of seeing that stylish old polyester ( ) chevy body hit the junkyard by building up a radical engine for a homebrew ratrod. Or mouse-rod in this case I've already got a 750cfm holley (which i reckon will be undersize?) and a rpm intake manifold. Its a dual plane, so yeah that may not be the best match with such a big intake runner. I'm still in the something-to-think-about-while-sitting-in-classes stage! i'll post my final thoughts here and see what you guys think.
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