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Estimated HP gains?

  
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Estimated HP gains?

 
StevieRayHubcap StevieRayHubcap
New User | Posts: 2 | Joined: 01/14
Posted: 01/11/14
12:40 PM

Hey, y'all! This '70s dinosaur has a question about calculating horsepower gains with nothing but a cam change, a 30 over bore (+6ci over stock-negligible), and a stock Q-jet recalibrated for the new cam? I'm using the stock intake and Q-jet so I can run the shaker hood unmodified, stock 6X-4 heads with a fresh 3-angle, hardened-seat valve job, and the new beehive springs that come with the cam kit--I'm using the Comp Cams K51-222-4 cam/lifter/valve spring/timing set kit, and I'll be adding the roller-tip rockers, but in stock 1.5:1 ratio. Compression ratio is about 9.0:1 (stock small-chamber heads). Am not stroking, juicing, or boosting it. Just a plain ol' cam swap. I can't find the math to figure the gain; I know it'll be minimal, but I don't want a drag car, just a seat-smasher. They did that pretty well with the factory set-up even with just 220bhp and a posi rear. The block is the original XX481988 WC (4-spd). Here are the cam numbers:
Stock (GM # 100003402): 274/298; .395/.401; LSA 113.5 deg. Made 220bhp @ 4000RPM & 320lb/ft torque @ 2800RPM (advertised)
Comp grind # P XE262H-10: 262/270; .462/.470; LSA 110 deg. Carb professionally tuned to new cam specs. I don't know how much it would gain, but I'm guessing about 25-40 hp at most. Probably make a lot more torque and feel stronger, too.
Also, new oversized but otherwise stock cast pistons and the factory cast rods should handle this minimal increase, right? I know Pontiac used 2-bolt blocks for 400's up to 350 bhp...  

ddemello ddemello
New User | Posts: 15 | Joined: 01/14
Posted: 01/11/14
04:50 PM

you could try the camquest6 program, if they have a cam similar to the stock one. or maybe a dyno simulator?  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 475 | Joined: 11/13
Posted: 01/11/14
10:56 PM

hello

i see you are new, welcome.

what is your elevation?

400 ci at .030 over with unmilled 6x-4 heads [94 cc] = 8.23 static compression.

this is extremely low, imo you would get more benefit from increasing your compression to around 9.5 instead of installing that cam.

that cam has an earlier intake valve closing time than the stocker which may boost cylinder cranking compression which is good.

basically that cam will likely give you a bit more bottom end perf.

if your gears are around 2.80 - 3.00, changing to lower ones like 3,31 will give you quicker acceleration than the 262 cam.  

thinman56 thinman56
User | Posts: 112 | Joined: 04/13
Posted: 01/12/14
07:16 AM

Have to agree with Shy on this one, until you get compression up that cam does not give you much.  For what the simulators are worth, the cam change only adds a couple horsepower, but adding 1 point of compression, even with the stock cam, should get you 20 to 30 hp.  

StevieRayHubcap StevieRayHubcap
New User | Posts: 2 | Joined: 01/14
Posted: 01/12/14
12:00 PM

So, then my option are reduce deck height to what, 0, run a thinner head gasket, or just shave the heads. Also run a 170-180 thermostat. This would be cheaper than changing all the cam stuff anyway. Then I wonder--do I get into a situation requiring new, shorter pushrods?  

ddemello ddemello
New User | Posts: 15 | Joined: 01/14
Posted: 01/12/14
01:42 PM

wouldnt advacning the cam close the intake valve even sooner? this would help too then? would bigger ratio rockers help too?  

shyrgfuh3 shyrgfuh3
Enthusiast | Posts: 475 | Joined: 11/13
Posted: 01/12/14
11:04 PM

hello;


you have not answered my question regarding your elevation yet.


So, then my option are reduce deck height to what, 0,


I never go 0, i go .005". This gives ne 1 more cut on the block for when I warp it from running 18 lbs of boost on my 12:1 compression engine. Once it's 0, you can still cut it again but some pistins will then stick above the block by the amount you mill the block. this is not ideal.



xxxxx



run a 170-180 thermostat.


Why?



xxxxx



I wonder--do I get into a situation requiring new, shorter pushrods?


if you shave things it is possible, yours might not be ideal now anyway therefore you shpuld check them. push rods are only around 60.00 anyway.