Camshaft changes or not with stroke increased.

[Walter R. Malik]

These are engines that get run quite often. I love trying different combinations. We have a 4” stroke 3.625” bore 360 that we run on pavement. It’s very capable of winning but has a rookie driver. The big bore short stroke engines are proven winners and have been our main 360s on pavement and some dirt since 2008. They will go when you can keep the pipes lit. They don’t peddle good in the dry slick. They are like a high strung two stroke. The 3.915” engine is complete and ready to dyno. All engines have 23 degree heads. I’m going to dyno 5 engines when time permits.

It seems you have a different engine configuration for almost every different occasion and the need for one combination to be good at everything but, not great at all situations is not there.

The common 23 degree headed 360 Chevy sprint engine built around here has a 4.00" to 4.004" bore with a 3.562" stroke using a 6" rod length.

By rules, these are cast iron headed engines using production replacement blocks.

[David Redszus]

The common 23 degree headed 360 Chevy sprint engine built around here has a 4.00" to 4.004" bore with a 3.562" stroke using a 6" rod length.

If we know the torque peak rpm, we now have the piston air demand.

All we need now is valve size, max lift, and duration to determine valve curtain area. Followed by port CSA.

[n2xlr8n]

Great thread. Reminds me of 10-12 years ago.

Thanks, Fellas.

[ptuomov]

Here's a practical example.

Suppose that I'm running a 5.0L engine (100mm / 3.937" bore, 78.9mm / 3.106" stroke) that has well-breathing and arguably too big 4-valve heads. It's running really well with these flat-bucket hydraulic cams:
IN 0.414 lift 260 deg. @ .006 lash, 217 deg @ .050
EX 0.370 lift 246 deg @ .006 lash, 208 deg. @ .050
LSA 114, IN LCA 120.5, EX LCA 107.5
Peak power is there at the 6200-6400 rpm range. Nice street engine for a street car, passing smog, idling well, and making good power.

Now, suppose that I increase the displacement to 5.4L (keeping the same bore but increasing stroke to 85.9mn / 3.382") while keeping the intake, heads, valves, exhaust, etc. all the same.

How should I change the camshaft to make the engine "feel" the same as before, just more powerful?

[CamKing]

Here's a practical example.

Suppose that I'm running a 5.0L engine (100mm / 3.937" bore, 78.9mm / 3.106" stroke) that has well-breathing and arguably too big 4-valve heads. It's running really well with these flat-bucket hydraulic cams:
IN 0.414 lift 260 deg. @ .006 lash, 217 deg @ .050
EX 0.370 lift 246 deg @ .006 lash, 208 deg. @ .050
LSA 114, IN LCA 120.5, EX LCA 107.5
Peak power is there at the 6200-6400 rpm range. Nice street engine for a street car, passing smog, idling well, and making good power.

Now, suppose that I increase the displacement to 5.4L (keeping the same bore but increasing stroke to 85.9mn / 3.382") while keeping the intake, heads, valves, exhaust, etc. all the same.

How should I change the camshaft to make the engine "feel" the same as before, just more powerful?

You would need to go to 268/254 @.006"
Can't calculate lift or Lobe centerlines without more info.

[ptuomov]

Here's a practical example.

Suppose that I'm running a 5.0L engine (100mm / 3.937" bore, 78.9mm / 3.106" stroke) that has well-breathing and arguably too big 4-valve heads. It's running really well with these flat-bucket hydraulic cams:
IN 0.414 lift 260 deg. @ .006 lash, 217 deg @ .050
EX 0.370 lift 246 deg @ .006 lash, 208 deg. @ .050
LSA 114, IN LCA 120.5, EX LCA 107.5
Peak power is there at the 6200-6400 rpm range. Nice street engine for a street car, passing smog, idling well, and making good power.

Now, suppose that I increase the displacement to 5.4L (keeping the same bore but increasing stroke to 85.9mn / 3.382") while keeping the intake, heads, valves, exhaust, etc. all the same.

How should I change the camshaft to make the engine "feel" the same as before, just more powerful?

You would need to go to 268/254 @.006"
Can't calculate lift or Lobe centerlines without more info.

Interesting. Even a small increase in stroke and displacement seems to increase the recommended seat timing quite a bit.

Some additional info:

Dual 37mm intake valves.

The approximate cross-sectional areas for the stock 37mm valve intake port are:
- Intake port at the flange 1700 mm2
- Divided port where the divider wall starts [2*750, 2*850] = [1500, 1700] mm2
- Divided port where the valve guide is protruding, adjusted for the valve stems [2*(871 - 33) = 2* 838 = 1676 mm2
- At the valve seat ring 2*(750-33) = 1434 mm2

Something like a dual plane intake with 40cm and 30cm runners lengths from the trumpet opening to intake valve.

The bare head with a bellmouth flows about 300 CFM @28" at 12mm intake lift. From memory, the flow drops below 250 CFM in the worst cylinder (#5) when the intake is on.

Dual 33mm exhaust valves. Exhaust port circular 40mm CSA 1257mm2. Throat 28.4mm combined CSA 1267mm2.

[Walter R. Malik]

You would need to go to 268/254 @.006"
Can't calculate lift or Lobe centerlines without more info.

Interesting. Even a small increase in stroke and displacement seems to increase the recommended seat timing quite a bit.

Sometimes, 4.6L to 5.4L having the same bore is not just a SMALL increase in stroke ... almost 5/8" with Ford Mod Motors having their small bore.

[ptuomov]

You would need to go to 268/254 @.006"
Can't calculate lift or Lobe centerlines without more info.

Interesting. Even a small increase in stroke and displacement seems to increase the recommended seat timing quite a bit.

4.6L to 5.4L having the same bore is not just a SMALL increase in stroke ... almost 5/8" with Ford Mod Motors.

I'm adding 7mm or 0.2756" to go from 5.0L to 5.4L. That's less than 9% more stroke and displaecment.

[Walter R. Malik]

Interesting. Even a small increase in stroke and displacement seems to increase the recommended seat timing quite a bit.

4.6L to 5.4L having the same bore is not just a SMALL increase in stroke ... almost 5/8" with Ford Mod Motors.

I'm adding 7mm or 0.2756" to go from 5.0L to 5.4L. That's less than 9% more stroke and displaecment.

Regardless of percentage ... most people would call a .275" stroke increase more than small. I guess you consider it small.

[CamKing]

I'm adding 7mm or 0.2756" to go from 5.0L to 5.4L. That's less than 9% more stroke and displacment.

Yes, and only requires about a 3% increase in duration.

[ptuomov]

4.6L to 5.4L having the same bore is not just a SMALL increase in stroke ... almost 5/8" with Ford Mod Motors.

I'm adding 7mm or 0.2756" to go from 5.0L to 5.4L. That's less than 9% more stroke and displacement.

Regardless of percentage ... most people would call a .275" stroke increase more than small. I guess you consider it small.

It's probably just me anchoring to my context. The most common stroker crankshaft for the engine in question has 95.25mm / 3.75" stroke. If that's combined with 104mm overbore, it gets one to about 6.5L from the original 5.0L, which is 30% change.