I.E ratio for heavy nitrous 565

[63 Nitrous Ratt Vette]

I have a set of Brodix CNC -3 BB extra's I am having some work done on. This motor will be set up for semi heavy nitrous use (300-550 hp). Is it worth it to have the exhaust side ported to really flow killer #'s, or is it better to tune that with rocker arm ratios and cam specs.....any general guidlines??

Thanks,

John

[airflowdevelop]

The difference between a 300 shot and a 550 shot...is like comparing a orange to a clove of garlic....

How about some info on the combo?

Dennis

[hsutton]

The difference between a 300 shot and a 550 shot...is like comparing a orange to a clove of garlic....

How about some info on the combo?

Dennis

Dennis, Look above and see what the 2200 lb., '63 Corvette went in the eighth mile with an "oval port 454" and a 350 H.P. nitrous hit.

[63 Nitrous Ratt Vette]

I am still tossing around ideas. I want the car to be able to run in the 7.5 range and occasionally a little faster. I already have a short deck CNC GM block, the BB-3 heads and a Sniper intake. I will run a Fogger or two also. I would like the motor to be reasonably reliable and am thinking I need to make 1350-1400 hp to meet my goals. I plan on it being a dedicated nitrous motor.

I am not opposed to aluminum rods, but would rather run steel. I am aware of the possible issues with steel rods and that much nitrous. I might back the compression down to 12.5 to 1 or so because of that. I ran a 36 jet in my 454 succesfully with steel rods, oval port heads, 10.7 to 1, steel rods and Sunonco 110.

In my mind I have gone from a 555 to a 588 and back....4.25 in. stroke, 4.375 in maybe ?? With the 4.25 crank it would be easy to run a very friendly ring pack with or without aluminum rods. Might be tough with a 4.375 in and steel rods.

[BTR Bill]

To answer your original question:
Don't worry about making the exhaust side better. You will be fine the way it is. You don't need to worry about the exhaust port flow on a nitrous motor on any of these good flowing cylinder heads. It is controlled by the camshaft. Furthermore, I don't worry about the I/E ratio's either.

[63 Nitrous Ratt Vette]

To answer your original question:
Don't worry about making the exhaust side better. You will be fine the way it is. You don't need to worry about the exhaust port flow on a nitrous motor on any of these good flowing cylinder heads. It is controlled by the camshaft. Furthermore, I don't worry about the I/E ratio's either.

Thanks Bill; I have always read otherwise but when my last motor picked up .15 in the 1/8 going from a 32 to a 36 jet I started to think maybe exhaust flow was over rated on a nitrous motor; particularly when you consider that was with a pump gas 454 and mildly ported Edelbrock oval port heads.

[BTR Bill]

I am sure most people would disagree with my findings, but many follow everyone else like sheep and don't think for themselves or really think about what is really going on during each cycle. As far as the amount picked up from a 32 to 36 jet, there are so many variables determining the ET increase i.e. chassis, timing, N-F ratio, solenoid oriface size, etc. the performance increase could be a little or quite a bit .

[63 Nitrous Ratt Vette]

I am sure most people would disagree with my findings, but many follow everyone else like sheep and don't think for themselves or really think about what is really going on during each cycle. As far as the amount picked up from a 32 to 36 jet, there are so many variables determining the ET increase i.e. chassis, timing, N-F ratio, solenoid oriface size, etc. the performance increase could be a little or quite a bit .

I agree there could be more to it than just the jet change....my point was at least in theory the exhaust side of the little oval port heads flowed enough to allow the extra nitrous (32 to 36 jet) to make more power. I was agreeing that maybe the BB-3's (that flow much more than the ovals) should allow my 555 to make 1350+ hp.

[EngineTech1]

I'm not sure where you're information is coming from saying that you don't need to worry about how good your exhaust port is on a nitrous engine but I've yet to see a nitrous engine that didn't pick up when a mediocre to good exhaust side was picked up to being a great exhaust side. There is usually a lot of power lost on the exhaust side of most nitrous engines that aren't built by an engine builder that knows nitrous engines.

[Ed-vancedEngines]

If it is not too late already becuase of parts you may have already bought. You need to make up your mind about how you want to accomplish your goals.

I, or other good builders could get you where you want to be with an all motor engine after you get some good head work done with a good sheet metal tunnel ram. That would be a dead serious engine that you better not think about trying nitrous with.

You can get a decent all motor engine built that will accept nitrous with good tuning up to a point.

Or you can get a serious nitrous engine built that will be down on alll motor power but will knock your socks off with nitrous.

All three of those possibilities can be done with the block you already have and probably many of what parts you have.

Like I suggested on another thread. Spend the money to get a great Professional head porting done for the exact application you plan on doing. You don't just tell them to do the best they can with your heads. Specify the use and if nitrous how much and all other aspects of your engine to the guy working the heads to give him some direction of what your needs are.

I could build you an engine that would make you happy, So can Darin's company, and Larry and many others here. If you want a 632 then it can be done. If you want anything it can be done. BUT. You will spend less money to use what you already own and make it work.

With your weight it should not be real difficult.

Hope we are helping you some between all of us here.

Ed

Ed

[Windsor377]

This is a pretty interesting thread. I think the underlyinig theme is that the numbers that the customer (63 Vette...cool car by the way) is very easily attained. I agree. I also think when someone is going somewhere they've never been before things can be daunting.

Ed just hit the nail on the head.

[63 Nitrous Ratt Vette]

Ed, and others. I greatly appreciate the time all of you take to respond to my posts. I am just hear trying to learn. I am one of those guys that asks a lot of questions to help me figure stuff out. In all honesty I prefer to build my own stuff......when business gets a little better, or I can not get where I want, I can see me hiring a pro. I do not want to be one of those guys who has someone else do all the work on their cars.

The goal with this engine is to put my vette into the sub 7.5 range as reliably as possible. With my pump gas, oval port, steel rod, 454 and a 36 jet I was able to go a 5.09 in the 1/8, works out to a 7.99 or so in the 1/4. If, and that is a big if, the car continues to respond to more power like it has (so far more power, more better:D) it should not be very difficult to put the car below a 7.5 (max cert) I guestimate it will take approx 1300-1350 hp to put the car below a 7.5. The car is a full tube frame, chassis, struit, 4 link car.

My plans as of now:

I just sent the heads back to Brodix for a touch up. They did not quite do what they were supposed to do on the bench and the chambers were pretty ugly for a full CNC head. I plan on running them as is when I get them back from Brodix.

Probably bore the block out to 4.6 for a 565-582 if I run a 4.375 in. crank. I will probably stick to a 565. Hell I might leave it a 555.

I already have a Sniper intake.

I will run a Nitrous Supply Fogger and may have Jeff Prock help me with the nitrous tune. I would like to make 900-950 on the motor and spray another 400-500. I would like to run steel rods, 12.5 to 13.5 to 1 compression, and keep the motor at 7500-7800 rpms of so.

Because of the weight of the car and how well it seems to react to power, I do not need to get real killer on the motor combination. The car is only certified to 7.5 anyway. Yes, I would like to break past that once or twice, but I do not need a motor that will run 20's in this car........maybe the next one

Ed, I understand the all motor, sorta best of both, and all out nitrous combos. I think what I have spec'd ought to put the car into the sub 7.5 range. If I fall short it may be time to call in an expert. A lot of the fun of this sport for me is doing the research and trying things out.

Again, I appreciate all your help and comment.

John

[63 Nitrous Ratt Vette]

Here is a pic of the car

[Ed-vancedEngines]

Ed, and others. I greatly appreciate the time all of you take to respond to my posts. I am just hear trying to learn. I am one of those guys that asks a lot of questions to help me figure stuff out. In all honesty I prefer to build my own stuff......when business gets a little better, or I can not get where I want, I can see me hiring a pro. I do not want to be one of those guys who has someone else do all the work on their cars.

That is great. I begain my first engine building for myself becuase of some of those same reasons, and I quickly learned that I could do my own engines and get more life from them than I was getting at a couple of race car shops. Now to be honest most of my early life I was a precision machinist and worked to very tight tolerances, so I am sure that carried through into even my first race engine.

I would like to make 900-950 on the motor and spray another 400-500. I would like to run steel rods, 12.5 to 13.5 to 1 compression, and keep the motor at 7500-7800 rpms of so.

I don't want to pat myself on the back too hard in this but I am trying to give you some encouragements. I got a little over 900 hp with an all motor 461 cu in engine way back in the early 1980's, with some old Ancient Pro Stock heads from Warren that he had played with forever, and I also was using 16.85 - 1 compression. 4 speed car 2980 lbs @ 156 mph.

So with your bigger engine, newer heads, and better later tech parts it should be possible for you too. BUT I would suggest more compression ratio if you are thinking of all motor power and more rpm too. If you are considering motor power with nitrous added and you can tune it, I see nothing at all wrong with you going to 15.00 -1 or maybe a little more even. For major nitrous, I would go with compression like you are thinking though. For something like that with strong nitrous I would say maybe 13.00 to 14.50 -1 . with a large quench clearance. Of all motor I would go much tighter.

I would like to make 900-950 on the motor and spray another 400-500. I would like to run steel rods, 12.5 to 13.5 to 1 compression, and keep the motor at 7500-7800 rpms of so.

No reason you can't use steel rods at that power level. Go for them.

I know a guy that is doing over 1500 hp with Eagle crank and Eagle rods with better bolts and it lives. He is right on top of his tuneup all the time though.

Wish you the best and if I can help wit info feel free to call.

Ed

[63 Nitrous Ratt Vette]

Ed, I am a pretty decent nitrous tuner and feel comfortable creeping up on big hits. I know I need to go to a better fuel than the Sunoco 110 I was using in the 454. I had some detonation issues with that tune (the one time I ran it)...although they were probably due to oil in the combustion chamber. That being said I will probably run VP NOS in the 555 when I run big hits.

So you figure I can run 14.5, with steel rods and a 500 hit ??.......if my tune up is good? Any direction on where you would set the quench??

Thanks again.

John