A little more on P7 engines. First, please understand what these engines were designed for. They were designed for NASCAR racing only, not drag racing.

In NASCAR, there are three touring series; Cup, Busch and Truck.

The rules are different for each class. The Cup engines are FLAT TAPPET ONLY. That is where the extreme rocker ratios come from(to to 2.1 to 1). On a flat tappet cam, you can use a high ratio rocker and get better area under the lift curve. Also, with flat tappet cams, you use lower pressure springs----the high ratio rockers will last, at least for one race and that is all an engine builder cares about. After the race is over, the rockers go in the trash.

The truck and Busch engines both use roller cams with high spring pressures. You don't see rocker ratios higher than 1.80 to 1. But, the heads and cams are different for the two classes. Busch uses a 390 CFM Holley type carb, thus the cams are smaller and oftentimes the heads are too. The truck engines use 830CFM Holley type carbs and oftentimes the heads are bigger too.

I mention the Holley TYPE carbs because many are not Holley carbs but Titanium billet "lookalikes". They weigh less than two pounds and cost bigs $$$. That is the reason you never see any on the used market and the few you see are dyno carbs. That may change since NASCAR is converting to injection but none of the big $$$ carbs are on the market yet.

Now, lets talk about general cylinder head rules----NASCAR specs valve size(not stem size), valve angles, intake port centerline specs and intake port square inch areas. Most NASCAR engine builders machine away any excess aluminum(weight) around the intake runners---since the size of the runner is spec'd. Therefore for drag racing, there may not be a lot of excess "meat" available around the intake runners. You see a lot of heads with smaller MM size valve stems----these are generally one race valves. Guess what happens to the valves after the race-----trash can! Same with springs, sometimes retainers, titanium shoulder locks, etc. One note----the springs take a specific retainer and titanium shoulder lock. You get into trouble if you don't match the spring to the retainer and the lock.

Now about the cast iron blocks, They are 9.00" deck blocks, same a SB GMs. And, the blocks are big bore(up to 4.185") but short stroke, around 3.25". The main bearing saddles are for a 2.25" Ford type bearing. Only the Elliot aluminum blocks are for a larger 2.50" main bearing. You can easily get a longer stroke crank---all you do is buy a custom billet crank---up to about 3.625" for a 9" deck iron block. And you can bore the blocks larger---but where do you find the deck plates? And the blocks are very hard and last for many, many laps. Our block has thousands of laps on it---still standard size and we have changed pistons four times. We think the iron block can go to about 400" with a reasonable rod length and still run good RPMs.

Since these are purpose built engies, they have no provision for wet sump oiling-----DRY SUMP ONLY!

About out of breath----need coffee!