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Discussion Starter #1
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 :D
-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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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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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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More for Less Racer
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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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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 224º intake/230º ex with .575 lift,,,108º icl and 112º lda.
This will make a 450 horse power tires shredder. You 8:1 ,,770 carbed ,, 200º duration cammed rat would probably spin the tires 15' and tow a trailer well,,,
 

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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/rotating-assemblies-new/bb-chevy-496-kits/scat-1-91610bi-bb-chevy-496-street-and-strip-performance-balanced-rotating-assembly-10-2-1-srp-dome-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.
 

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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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Discussion Starter #9
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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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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Discussion Starter #11
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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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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Discussion Starter #13
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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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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Discussion Starter #15
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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8:1 cr...I'd get a blower and have some fun. If it blows up, get another 454 and do it again. Yeah its redneck; but its a 3-ton truck
 

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naz4kez....I wrote this post then deleted it a few times but here goes, I need to ask anyways......lets get back to some fundamentals/basics....Do you understand the difference between a SCR, a DCR, how it pertains to engines and the engines overall characteristics? Do you also understand why a proper quench /squish area is important to the overall? Do you understand the filling and emptying cycle of an cyl and why a camshaft is so important to the overall? Do you understand the importance of a strong valve train with proper geometry to the overall? (especially with a BBC?) Do you understand the need for a proper fuel curve and a proper ignition curve to the overall engine operation? The constraints of an application to the overall with a given octane requirement?
I think we all can get you there but we need to know where you are at in understanding engine operation and the why's.
Then you will understand why we are saying the things we are saying.
Not being condescending, just want to help.
 

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> 454 cam selection help!!

You got a good deal on a 454 engine. Now have you taken the engine apart yet? There is a lot of information you can get while the heads are off. You can use a straight edge and feeler gauges to measure the distance each piston is down in the bore. Write all this information down in a tablet. I had my 454 block milled to zero so I could use the most common head gaskets and to have my quench set at .040. You can measure the valves in the 781 heads you have. Look thru the springs and see what type valve seals are used. You will need to decide on your camshaft. You can look online at the cam and get the recommended springs. Its best to buy in a kit for a better price. I would call Howard's Cam or Isky cams for a recommendation for a cam kit. I have been reading these forums and Comp Cams has too many lobes on their hyd. lifter cams wiping. I would not use their cams unless it's a mech. roller. Check your pistons out do they have a dome or are they flattops. If they are flattops it would be cheaper to find a set of closed chamber heads 802,290,820,280 are some casting numbers. A 100 cc head with your deck milled to 0 will give you 9.2 compression ratio.
 

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Cheap version, Bigger valves,850 HP Holley,deck the block and skim the heads,deal with w/e CR you get.Use true roller rockers on a BBC,good quality headers close to 2" primaries,long tube,,,a short duration hydraulic roller with .550 lift,,,, duration will depend on final CR,think around 210º or less if under 9:1 CR with 108º icl and 112-114º lda
 

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Just a few thoughts.....

"-edelbrock performer RPM"
Good choice for a street motor, will make more power under curve than any other manifold idle to 6000. Sidetrack the Air Gap, use the standard Performer RPM #7161 for oval port heads. That Air Gap BS is just a way to snooker more money out of the unsuspecting hot rodder. Only way you might possibly need an Air Gap is if you only drove in the summer in Phoenix.

"Summit/flowtech brand LT Headers 3" collector"
Make sure the flanges are at least 3/8" thick. Thinner flanges will warp from the heat and will leak and spit out the gaskets.

"comp cams roller tip cast rockers 1.71 ratio"
Steaming piles of dog poo. Worthless in my view. The trunnions on these have been observed turning blue from the heat generated by the ball and socket arrangement, particularly with strong valve springs. The roller tip is next to worthless, it does not roll on the valve tip, it skids across it because the roller is too small in diameter to effect a mechanical couple with the valve tip. If Comp really wanted to build a good rocker arm, they would have built one with a roller trunnion and a conventional "walking shoe" tip.

"high volume oil pump"
Street motor does not need a high volume pump. All it will do is to add stress to the pump drive and the drive gear on the cam and the driven gear on the distributor. Use a standard pump.

"holley 770 street avenger carb"
Needs more carb.

"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"
You don't know the exact static compression ratio, so there is no way you can intelligently choose a camshaft. For the love of God, stop and ask questions first. If this motor is indeed stock SCR, then it needs a stock cam, one that will close the intake valve at the proper time to make reasonable cylinder pressure and still ward off detonation.

"upgrade springs, maybe comps 340lbs seat pressure with double spring, not sure which ones will get me the lift i want."
A Top Fuel motor might need 340 lbs on the seat, but anything else will need less pressure than that. I know you have mistaken seat pressure with open pressure. If you are planning a flat tappet cam (BIG MISTAKE IN A BBC, then the over-the-nose at 340 lbs would no doubt result in a few roached lobes pretty quickly. Big block Chevies just have a natural tendency to eat flat tappet cams. Use a hydraulic roller cam. Use a hydraulic roller cam. Use a hydraulic roller cam. Use a hydraulic roller cam. Howards sells cam and lifters for about 600 bucks. You'll spend more than that cleaning up the messes from fragged flat tappet casualties. Every time you frag a flat tappet cam, the entire motor needs to be disassembled and cleaned of the shrapnel from the cam and lifters that went south. A roller tappet cam does not need any special break-in procedures or special jumping through hoops during assembly. Just bolt it in, fill the pan with any off-the-shelf detergent oil and run it.

"could i mill the heads instead to bump CR?"
No. You need another point and a half (9.5) and you'd never get there cutting the heads.

Measure the stack of parts that you have or will have. For instance, compression height for a standard 454 piston is 1.640", connecting rod length center to center is 6.135" and the radius of the stroke is 2.000". Add these values together and find a stack dimension of 9.775". This will be the "stack' of parts that you will fit into the block. Now, since the blueprint "block deck height" dimension of a BBC is 9.800", this means that a standard stack of parts will leave a "piston deck height" of 0.025" (piston down in the bore with the piston at top dead center) of 0.025". (Any of the pistons will be down in the bore by a figure of twenty five thousandths of an inch with any piston at top dead center).

The factory used shim gaskets that would make a nice, tight squish which would deter detonation and effect good fuel mileage. Now, if the piston deck height is still 0.025" and you add a composition gasket, which is much thicker than a shim gasket, then you have destroyed the detonation resistance of the motor due to a much wider squish. Check the block decks and the heads for being flat within a couple of thousandths. If they are not, have your machine shop take a light cut to clean them up so the shim gaskets will work and the motor won't spit them out.

A far better plan: Check the main bearing bores for being round and parallel and correcting them with an align hone if they are not. Once the mains are round and parallel, chuck the block up on the mains and cut the block decks to the same dimension as your stack of parts, or if you want to keep a little more meat in the block, the stack dimension plus 0.010". That is called "zero-decking" the block and you'll be able to use a conventional composition gasket to set the squish. (0.040" gasket plus 0.010" piston deck height equals 0.050" squish, which is, in my opinion, just about right for a big block motor. Now that the block decks are equidistant from the centerline of the crank, the heads will bolt on squarely and the intake manifold will bolt onto the heads squarely and seal up properly.

Forget trying to do any gasket matching on a street motor. A study of fluid dynamics will tell you that the majority of flow is right down the middle of the port, so grinding on the sides or edges will only accomplish sore arms and wearing out of grinders. If you port match, the ports will end up looking like an Anaconda that swallowed a pig in side view. Where the ports are larger in the area where you port matched, the mixture slug will slow down because of the increased volume there and may drop fuel out of suspension because of the slowdown. Then on the next intake stroke, the cylinder gets a gulp of raw fuel. Leave the ports alone unless you have a PhD in Fluid Dynamics or have 30 years of experience as a professional head porter.

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