454 to 540 ?
04-17-2014, 09:30 PM
#21
Fast Singles Club
Gold Member
Matching the head to the cubic inch and rpm is paramount. We have build combinations that made over 700hp with a GM 781/049 oval port head. You have to be careful not to fall into the "bigger is better" trap, just because the price is the same.
A properly prepped 270cc intake runner head will outperform a 310cc Brodix on a 468 on HP and TQ. In addition, the BSFC will be lower, netting better economy. It's all about air speed, atomization and cylinder filling.
Camshaft is also very important. There are a few key considerations.
1. Intake events and valve lift, in relation to piston speed ATDC. At 70°-75° Of crankshaft rotation, this is when the piston is moving the fastest. You need to match this to events at the valve when the port is able to flow very strong. Remember, engines do not make vacuum, per-say, on the intake stroke, they just try to equalize the pressure differential between the cylinder and the atmosphere outside the engine.
2. Intake valve closing events. This is dependent on airspeed and will dictate cylinder filling ABDC. Close the valve too soon and you lose intake charge. Close it too late and you will back charge up the intake tract. Late closing is also responsible for low cylinder pressure.
3, Exhaust opening events. If you open the exhaust too soon BBDC, you will blow off some of the pressure meant to push the crank down on the power stroke. This in turn leads to pumping losses on the exhaust stroke.
4. Obviously, lift comes into play with the cylinder head data as well. Lobe centerlines and duration almost fall into place when calculating the timing events that are required for each engine.
Engine design is very fun to do. I've been fortunate enough to do this as a living for close to 30 years now, and over 25 with my own business. Each engine is a challenge as well as a job. I would not do it if I didn't enjoy it.
I suggest anyone getting an engine built to learn as much as they can and be involved as much as possible with the build. It's very rewarding.
A properly prepped 270cc intake runner head will outperform a 310cc Brodix on a 468 on HP and TQ. In addition, the BSFC will be lower, netting better economy. It's all about air speed, atomization and cylinder filling.
Camshaft is also very important. There are a few key considerations.
1. Intake events and valve lift, in relation to piston speed ATDC. At 70°-75° Of crankshaft rotation, this is when the piston is moving the fastest. You need to match this to events at the valve when the port is able to flow very strong. Remember, engines do not make vacuum, per-say, on the intake stroke, they just try to equalize the pressure differential between the cylinder and the atmosphere outside the engine.
2. Intake valve closing events. This is dependent on airspeed and will dictate cylinder filling ABDC. Close the valve too soon and you lose intake charge. Close it too late and you will back charge up the intake tract. Late closing is also responsible for low cylinder pressure.
3, Exhaust opening events. If you open the exhaust too soon BBDC, you will blow off some of the pressure meant to push the crank down on the power stroke. This in turn leads to pumping losses on the exhaust stroke.
4. Obviously, lift comes into play with the cylinder head data as well. Lobe centerlines and duration almost fall into place when calculating the timing events that are required for each engine.
Engine design is very fun to do. I've been fortunate enough to do this as a living for close to 30 years now, and over 25 with my own business. Each engine is a challenge as well as a job. I would not do it if I didn't enjoy it.
I suggest anyone getting an engine built to learn as much as they can and be involved as much as possible with the build. It's very rewarding.
04-17-2014, 09:58 PM
#22
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Unfortunately, that place has gone a little haywire lately with a guy getting a sex change and some real poor work by supporting vendors that they won't let go of.
I do a lot of work for marine shops up here and a few individuals as well. I'm thinking of getting into a larger boat again for river duty so I like the action over here. There is a lot of real world knowledge.
04-18-2014, 12:33 AM
#24
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This is a 498" oval port engine we dynoed a few weeks ago.
Hyd. Roller, pump gas.
The broad torque curve really makes for strong mid range and good fuel economy.
[ATTACH=CONFIG]522169[/ATTACH]
Just for fun, here is one we dynoed last weekend. It's a pump gas, 605" street Hemi. Again, big torque and exllent BSFC numbers. This is going in a car, of course, but a real driver...AC, overdrive, real pro touring.
You will notice the distinct difference in the BSFC numbers (Brake specific fuel consumption). The first engine was run on pump premium, which contains nearly 20% ethanol around here in the winter. The fuel curve reflects that. It's not only rather rich, but it likes a higher fuel mixture at peak torque than at peak horsepower. Straight alcohol engines are like this to a higher lever. They vary .around 2 on the BSFC from peak TQ to peak hp.
Now look at the second engine. Straight non-Oxy fuel, 92 octane. Nice straight fuel curve.
This is why dyno tuning is so important. Getting a good timing sweep, fuel curve and keeping EGTs in check are the goal.
Ok, sorry to totally hihjack the OP's thread!!
Hyd. Roller, pump gas.
The broad torque curve really makes for strong mid range and good fuel economy.
[ATTACH=CONFIG]522169[/ATTACH]
Just for fun, here is one we dynoed last weekend. It's a pump gas, 605" street Hemi. Again, big torque and exllent BSFC numbers. This is going in a car, of course, but a real driver...AC, overdrive, real pro touring.
You will notice the distinct difference in the BSFC numbers (Brake specific fuel consumption). The first engine was run on pump premium, which contains nearly 20% ethanol around here in the winter. The fuel curve reflects that. It's not only rather rich, but it likes a higher fuel mixture at peak torque than at peak horsepower. Straight alcohol engines are like this to a higher lever. They vary .around 2 on the BSFC from peak TQ to peak hp.
Now look at the second engine. Straight non-Oxy fuel, 92 octane. Nice straight fuel curve.
This is why dyno tuning is so important. Getting a good timing sweep, fuel curve and keeping EGTs in check are the goal.
Ok, sorry to totally hihjack the OP's thread!!
Last edited by rev.ronnie; 04-18-2014 at 01:04 AM. Reason: Add info
