One thing I remember about chamber sizing and power, with valve jobs and combustion volumes being equal, the engine with the smaller cylinder head chamber volume would make power more efficiently than an engine with a large cylinder head chamber. Something to do with reducing the amount of dome on the piston, while having the same compression ratio, would help increase combustion speed, and would also reduce the ignition timing advance needed to make peak power. It apparently also reduces the octane requirements, between having a faster combustion speed, and having less surface area in the combustion chamber, which both helps reduces the chances for knock.
Great video Eric! I may have missed it, but is there a difference in flow between the stock heads without milling (comparing a 76 cc chamber to 66 cc chamber?) Thanks!
So to make the same compression with both heads the 70cc head will need an 15cc dome on the piston. So in reality when the engine is assembled which cylinder will have better flow, the one with the dome or the one with a flat top piston?
Having angle milled fuelies in the distant past 0-80 theynworked well and I had 12-1 with flat tops. Would I do it agauin?? No. A decking the block achieves more for less. B if nesecary use a small dome piston.
Do you have any advice for switching to an aluminum head? I have a warmed over '69 412 block 427 with 840 heads. Compression is around 11:1 and it's around 500hp. 840 heads are a closed chamber 107cc Rec port. I need to cut some weight without losing any Tq/Hp in my Nova (3650lbs with me in the car)
That's a very substantial flow difference, enough to make a power difference. I flat milled my AFR 220's .030 and ran into that top cut pretty good, about like the heads you have there.
Greatly appreciate this video sir, I’ve been trying to learn about this a lot as I’ve recently had a set of old rhs pro action factory 50cc heads redone for my small black build and I haven’t been able to find much good info on chamber size
Does airflow velocity change when valves are opening ,as in piston starting to move when pulling air in past the valve (piston speed) compared to flowing a head on a bench with air at a constant speed or am I overthinking it
One thing I remember about chamber sizing and power, with valve jobs and combustion volumes being equal, the engine with the smaller cylinder head chamber volume would make power more efficiently than an engine with a large cylinder head chamber. Something to do with reducing the amount of dome on the piston, while having the same compression ratio, would help increase combustion speed, and would also reduce the ignition timing advance needed to make peak power. It apparently also reduces the octane requirements, between having a faster combustion speed, and having less surface area in the combustion chamber, which both helps reduces the chances for knock.
Be very interesting to see how the dyno #'s would look between those two heads as CFM is not everything. But great info!
I respect you don't want any drama, so deleted comment , Thanks for the content 👌
Very good information
Great info Eric, it is amazing the order of operation to make the head come out correctly.
Great video,thanks Eric
Great video
Great video Eric! I may have missed it, but is there a difference in flow between the stock heads without milling (comparing a 76 cc chamber to 66 cc chamber?) Thanks!
So to make the same compression with both heads the 70cc head will need an 15cc dome on the piston. So in reality when the engine is assembled which cylinder will have better flow, the one with the dome or the one with a flat top piston?
Having angle milled fuelies in the distant past 0-80 theynworked well and I had 12-1 with flat tops. Would I do it agauin?? No. A decking the block achieves more for less. B if nesecary use a small dome piston.
Get holes perpendicular to the deck, not parallel. I’m picking nits but I still love the content.
Wouldn't doing a radius skim cut on that valve seat to help flow on the angle milled heads? I'd think bumping it on the Serdi would help 🤷
Do you have any advice for switching to an aluminum head? I have a warmed over '69 412 block 427 with 840 heads. Compression is around 11:1 and it's around 500hp. 840 heads are a closed chamber 107cc Rec port. I need to cut some weight without losing any Tq/Hp in my Nova (3650lbs with me in the car)
So what is the benifit of angle finish ? thanks for sharing, all the best to you and your loved ones
That's a very substantial flow difference, enough to make a power difference. I flat milled my AFR 220's .030 and ran into that top cut pretty good, about like the heads you have there.
Greatly appreciate this video sir, I’ve been trying to learn about this a lot as I’ve recently had a set of old rhs pro action factory 50cc heads redone for my small black build and I haven’t been able to find much good info on chamber size
Wouldnt a larger chamber require less material removal to drop the cc volume compared to a smaller one?
Lets say a head will be angle milled to get at a 21 degree setup. How to correct dowel pin holes?
Does airflow velocity change when valves are opening ,as in piston starting to move when pulling air in past the valve (piston speed) compared to flowing a head on a bench with air at a constant speed or am I overthinking it
Wouldn't it be easier to get a dome piston