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Old 06-13-2014, 08:13 AM
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454 cam selection

hey all, so ive done alot of reading on this forum and there seems to be a wealth of engine builders around. I recently picked up a 77 chevy c20 with a 454 and TH400 3.73 rear gears. Here is the wall ive hit now im trying to sart my cam selection since I have the rest of the mods figured out, ill give you the run down of what i have and what i want to do with it. thanks in advance for any help.

-original 24K miles on the engine
-454 Mark IV Number 331956 HI PERF
-stock 781 oval ports (stock valve size, some home port work/bowl blend/unshrouding/gasket matching, i want to use the stock springs as well)
-all stock bottom end with stock 8:1 CR
-stock HEI setup
-stock rods

upgrades planned
-edelbrock performer RPM (already purchased)
-Summit/flowtech brand LT Headers 3" collector (already purchased)
-comp cams roller tip cast rockers 1.71 ratio (already purchased)
-comp cams double roller timing set (already purchased)
-complete gasket kit through felpro stock head gasket size (already purchased)
-high volume oil pump
-holley 770 street avenger carb (already purchased)
-transgo shift kit
-stall (havent decided yet waiting on cam selection)
-accel 8mm wires

Here is the cam lifter kit I ordered but before install i want to make sure its the proper selection. i went small so i dont overdue the recommended lift on the stock springs.
http://www.summitracing.com/parts/sum-k1301

what i want with the motor, would be nice to be above 450HP and over 500TQ, will be a street cruiser that will melt the tires and occasionally see track time would be nice to be under 13 sec but thats probably stretching it.. also does any one know the stock stall in this trans??

again thanks for any help.


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Old 06-13-2014, 08:48 AM
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I'm gonna say something you probably don't want to hear...........the 8:1 is hurting this build and your goal in the worst way. I am not going to bad mouth your choice of parts but put 10:1 small domes and recurve the dist. to match combo you have chosen. You would come close to meeting your goal with the rest of your chosen components. The engine would be out of breath by 4500-5000rpm but would do fine till then. You would be lucky to crack into the 13 sec. time still. Not trying to be a jerk, just my 2cents on this.
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Old 06-13-2014, 08:52 AM
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Without knowing what you want to do with your truck; its hard to say. Too much cam for your compression, or not enough compression for your cam.

Id look at different heads to get closer to 9.5:1 or better, or swap pistons. OR less cam
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Old 06-13-2014, 10:15 AM
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I think the decision to base things around the stock valvespring was a mistake also. They were barely acceptable for stock cam use, and now 40 years old and you want them to deal with performance usage??!.

Springs are not terribly expensive if you know where to shop.

Competition Products - Performance Engine Parts, Racing Engine Parts and Accessories is one good source I regularly use for valvetrain.

I would definitely replace the valve locks also, BBC are famous for stock spring and/or lock failure causing a dropped valve.

Stock torque converter is about 1400 rpm stall.

Is this going back into the truck,or into some other vehicle??
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Old 06-13-2014, 10:16 AM
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you are going to have a 350 horse power engine with 8:1 CR.
to get 450 HP punch out the heads for 2.25 or at least 2.19 intake valves/1.88 exhaust valves. Clean up the casting flashes and or minor porting. measure the combustion chamber volume and change pistons(with proper deck height) to give you 9.5:1 compression. return the 770 Holley and buy an 850 Holley "HP" series.Use a small hydraulic roller cam around 224 intake/230 ex with .575 lift,,,108 icl and 112 lda.
This will make a 450 horse power tires shredder. You 8:1 ,,770 carbed ,, 200 duration cammed rat would probably spin the tires 15' and tow a trailer well,,,
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Old 06-13-2014, 10:39 AM
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also,return the roller tip rockers. Upgrade the H.E.I. to at least an external coil.
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Old 06-13-2014, 11:05 AM
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454 cam selection help!!

First of all I like your plan of 450 hp and 500# torque. But you are not going to get there with what you have planned. The easiest thing to do would be to purchase a 496 rotating assembly. Just tell them you need std. pistons. Check out this kit, I came up with 9.8 compression (0) decking the block and with a .041 thick head gasket. I guess with this kit and a good solid lift cam you would be at 550 hp and 600 lbs torque. http://www.cnc-motorsports.com/rotat...e-pistons.html. The comp cams roller tip cast rockers need to be sent back and get full roller rockers.The holley 770 street avenger carb also need to be sent back and get an Holley 850 or 950. Plan on a 3000 or better stall converter.

Last edited by cdminter59; 06-13-2014 at 11:12 AM.
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Old 06-13-2014, 11:20 AM
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You can make 440-450 FWHP & over 500 lb. tq quit easy with those 781 heads & a smaller FT Hyd. cam, But the compression needs to come up to at least a true 9.1, It can also be done with stock 781s, This is my combo & i'm at 450 hp.

.070" 454 445 block.
Probe 18cc dome pistons, 9.51 compression.
Stock 781s with Perf. VJ
Lunati FT Hyd. cam, 527/553, 224/234 @50, 112/107
Air-Gap intake, 950 carb
1.3/4" headers, HEI ignition.

If you do up the 781s with the larger valves with back cut, Bowl work & short turn, Drop in either a moderate FT Hyd. or milder Solid, 850dp, It will make over 500 hp easy.
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Old 06-13-2014, 12:03 PM
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wow, i knew i was new to engine building but didnt realize i was this far off with my build. so heres what i think i will do.

-upgrade springs, maybe comps 340lbs seat pressure with double spring, not sure which ones will get me the lift i want.
-open the valves to 1.88 / 2.19 with some minor porting and unshroud the valves since it will be tight.
-upgrade the pistons i guess i was really hoping to avoid getting in the bottom end since its so new looking the hone is still there, could i Mill the heads instead to bump CR?
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Old 06-13-2014, 12:09 PM
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You still haven't addressed the 2 most important questions...
Is this going back in the truck?
What the hell do you want to do with it?
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Old 06-13-2014, 12:14 PM
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shew 1600 for the rotating assembly, i know its probably a good deal but i forgot to mention im on a budget build... I KNOW the infamous BUDGET BUILD thing again lol. but i dont have the money to throw around for an all out build. so i guess i should have mentioned how do i squeeze as much power out of this thing for the ceap seats
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Old 06-13-2014, 12:19 PM
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You can certainly pull the heads off, check and make sure the deck is flat, and check the 4 corners to see if you need to have the deck cut; if you do, this may be a deal killer for you.
At this point you can also see how close to the top of the bore the piston comes up, and what kind of valve reliefs, domes or cups the pistons have...you may also get lucky and find a part number which would help immensely.
If the pistons aren't close to the deck; its going to be hard to get any efficiency out of this, no matter how much you mill the heads. You can play games with the head gasket, but if the deck isn't prepped properly you may have trouble with a shim gasket.
Once you know the state of your deck & pistons...now you can make an informed decision about milling the heads, larger valves to get the compression you like and the breathing you need for your performance goals. The camshaft should be the last piece of the puzzle.

BUT a towing rig, an off road truck, a street brawler or a daily cruiser...all have different requirements...start there
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Old 06-13-2014, 01:21 PM
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street brawler, will never see dirt and will never tow. just want to eat up that kid at the light or roll smoke when i feel like it.
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Old 06-13-2014, 01:29 PM
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This is kind of like apples and oranges but my 507" Cadillac build has 8.7:1 measured compression. It has lots of good stuff inside to make it reliable, mostly valve train components along with forged rods and ARP bolts everytwhere. It dyno'd 466 hp @ 5k and 535 trq. @ 4300. Now I was told by the dyno guys that if it was a true 10:1 engine it would probably be close to 500 hp and 600 trq.

It was built for the crappy gas we have to burn so thats why I kept the compression reasonable, it will still have PLENTY of power for what I want.
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Old 06-13-2014, 01:56 PM
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my bad autpogear, its going back in the truck lol. no dirt occasional track mostly street. im guessing the truck once i pull most the crap i dont want on it will weigh in around 5k
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