Hey guys,

Last night I picked up a nitrous plate kit really cheap and want to run it on my car. My motor is a small block 400 .30 over. With stock internals, dish pistons, stock heads, Muthathumpr cam, Flowtech Headers, Elderbrock performer intake, holley 670 carb and flowmaster exhaust. Could anybody give me a rough hp estimate on my motor? I know there is no true way of knowing without a dyno. Also what would be a safe size to run on the nitrous? I was thinking about a 125 shot. I'm going to shift around 5K just to be on the safe side. I'm running the kit on a microswitch also to be safe. This is my first time running nitrous so i'm needing a little help with this. The motor in my car is fresh and was done 5,000 miles ago. Thanks, Josh

 

I'm not sure of your stock mechanical fuel pump is up to the job

you'll need to retard the timing when you plan on spraying and also never have anything less than all Premium fuel in the tank. Colder plugs and perhaps upgrading to an MSD ignition might also be in order for keeping you engine around.

Or, you could just bolt it on, do nothing and wait until one of your rods goes buh bye

I view a 50 shot as a toy for occasional use. Anything over 100 shot and I would build the engine for nitrous.

But, i don't like walking and looking at my car on a flat bed.

 

I was going to upgrade to a Holley blue electric fuel pump and retard the timing by 6 degrees and run NGK colder plugs. I'll rarely spray the car. maybe 4-5 times a year.

 

The following numbers are a close approximation, but your compressed head gasket thickness and bore diameter specs are an unknown.
296 hp @ 4500 rpm, 365 ft lb torque @ 3500 rpm.
Having the stock 8.5:1 c.r. isn't doing your setup any huge favors. Do some shaving and bump it up to 10:1, and your numbers jump to the 321 hp @ 5000, 390 tq. @ 3500 range.

 

Thanks 69 camaro. I'm trying to get to the 400hp mark before nitrous. I was thinking about taking the motor apart and putting a set of forged flat top pistons in, new air gap intake and a set of pro comp heads 2.02 1.60 valves. 210cc runner size and 64cc combustion chamber. then stepping up to a Holley 750 carb.

 

I was able to get the numbers off the back of the block it was 3951511 sbc 400 with 255 torque and 265 hp from the factory 70-73 from a B or G body. Heads are 3973493 sbc 400 heads with 1.94 intake 1.5 exhaust. Would this mean my hp would be over 300hp with all the mods I have done to it?

 

It'll change a little for the better. Not knowing what you had, I based your engine on a 255 hp model with 8.5:1 c.r. The 265 hp has 9.0:1 c.r. Unless I missed something else, the mods you have done to increase hp are the cam, and the 4 barrel intake/carb. Contrary to popular belief, headers and big exhaust DOES NOT add hp to the engine. Flywheel hp, as yours was/is rated, is already based on a free flowing exhaust. Headers "frees up" some of the hp the engine already has, but was being held back by the stock restrictive exhaust. If you really want to make it go, save up some money for a pair of AFR aluminum heads, and you're going to be adding an easy 50 additional hp right there. Let me play with some more numbers.

 

That makes me feel a little better. Thanks for all the help. I was looking at the pro comp head with 64cc combustion chamber with 210cc runners and 2.02 1.60 valves. Would these be a good set of heads to go with? They are pretty cheap at $600 a pair. I would just have to drill the steam passages in them. I was going to change to a air gap intake with a single plane. Also thought about adding a set of 1.6 roller rockers to help out. I'm trying to do all I can without messing with the bottom end since it was just done.

 

Pro Comp heads. Are you shopping for good performance heads, or looking to get some fancy door stops?
Do some research. There are claims of them using inflated flow numbers, and many cases by users of poor quality control.
Ever hear the saying "you get what you pay for"? You really do get your money's worth, they are "Chinese quality" heads.

 

wow I had somebody tell me they were good heads for the money. Thanks for the heads up. I guess I will save up for some good heads then.