Drag Racing Online: The Magazine

Volume VIII, Issue 6, Page

Reher-Morrison Racing Engines' David Reher and Darin Morgan answer your questions about cylinder heads or anything else concerning your racing engine building problems. Remember who you're are dealing with so no soft-ball questions.


I'm installing a set of Dart PRO 1 310cc cylinder heads. heads on my 468 BBC.

After much discussion I decided on these "small" runner heads to keep velocity high and build torque. Reading you're tech columns on you're web site convinced me smaller is usually better when it comes to cylinder heads.

I polished the chambers, cleaned up the bowls, radiused the exhaust seats, gasket matched the port entries, removed all the casting flash and polished the exhaust ports.2.25/1.90 valves. My question is how much power do you think these heads will support and if I decide in future to go to a 496 will the heads be too small. Thank you for your opinion. Congratulations on you’re successful career.


Sal Ferlito


Well, first off I would like to congratulate you on the good choice you made in regards to cylinder head size. You will find that not only will you make more torque you will also make more top end power. There is somewhat of a fallacy that has hung around for decades but never seems go away. That fallacy is that large ports will make more top end power than ones that are properly sized. I think this is one of the reasons people still choose heads that are far to large for there engine and its intended rpm range. The final thing you asked was how bad would it hurt you to put that head on a 496. Well let’s look at the data and see.

The mean inlet velocity for the 310cc port on a 468 at 7500rpm is 363ft/sec and the engine is well suited to 7700rpm for max power.

With the 496cid engine however, the mean velocity at 7500rpm is 387ft/sec, which is a little fast for that RPM so that makes this engine well suited for max power at 7325rpm. So what does all this mean? Well, the 310 heads on the 468cid want to make peak power at 7700rpm and the 496cid will want to make peak power at 7325rpm. Of course this is all based on the premise the engine is cammed and has an intake manifold and bottom end capable of supporting that RPM range.

The 310cc heads will be ever so slightly small for a 496 but I wouldn’t panic because there is no change in port size that will make either situation perfect although both situations are livable and both engines will accelerate well. Neither engine is “ out of tune” from a cylinder head perspective so don’t worry. Use the 310s on the 496. As far as consistency goes, the 496 for all intensive purposes will probably be a bit more consistent than the 468.

I would like to give you a projected power output for the engines but without knowing the specific Camshaft, manifold, header and carburetion specifications, I can’t be accurate. I can tell you that the 496 will probably make about 50 more Horsepower and than the 468.

David Reher asked Darin Morgan to answer this question because it is his area of expertise.

Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
Visit our web site at http://www.rehermorrison.com

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David Reher Can Fix Your Cylinder Head and Engine Problems.

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