Re: 5.0L w heads
A New Angle In Cylinder Head Development For 302/351-W!
By: Jon Kaase
I have been working on this cylinder head project for 30 years, dating back to the days when I worked for “Dyno” Don Nicholson. The first 28 years was in theory only, one year in design and one year in dyno testing. Why another small block Ford cylinder head, you may ask? There are so many to chose from today, why jump into such a crowded arena? It’s fairly simple. Build a cylinder head with the advantages of the Cleveland and the Yates legal for NASCAR heads and incorporate them into a user friendly Windsor package. We needed a cylinder head that would fit all existing intake manifolds and exhaust headers. A head that won’t require a rocker arm system that brings its own payment book. A head that functions well at all performance levels regardless of engine size. How about a head that makes 586 HP on a Ford 392 crate engine? How about a head that makes 511 HP from a junkyard 302? Read on!
There is one concept that all Pro Stock and NASCAR cylinder heads share; the intake valve is moved back toward the intake manifold and has maximum clearance to the bore. The exhaust valve is as close to the bore as practical and the intake valve is very close to the exhaust. Valve placements are shifted to enhance the quality and quantity of the intake charge. Current thinking is that an air and fuel mix doesn’t particularly like to be crashed into the chamber wall and cylinder on its way down into the bore. When the small block Ford head was designed in the sixties (or the fifties) it wasn’t clearly understood what was needed. Then the Boss 351 style heads came into vogue ten years later and with its success, some of us started to realize the real importance of intake valve location.
There are many quality Ford cylinder heads available in the marketplace today; most have some degree of compromise. If you try to move the intake valve away from the cylinder wall, the rocker arm has to be twisted to line up with the new valve stem location. If you try to make the intake port wider at the pushrod bump, the pushrod has to be leaned away from the port wall resulting in more valve train problems. Typical fixes for these misalignments are offset seat rocker arms or complete offset rocker systems. The offset pushrod seat, stud mounted rockers work for race cars but will eventually wear the valve guides and guide plates. The shaft rocker systems work much better but can sometimes exceed the cost of the cylinder heads.
Our new Ford small block cylinder heads have canted valves for three reasons. The pushrod meets the rocker at 90 degrees resulting in no side load to the guide plate or the valve guide. Any 1.6 or 1.7 ratio, 7/16” stud, roller rocker will work (even cheap ones). Not that we recommend using a low quality rocker on any engine, we just want to illustrate that this cylinder head does not use any special or trick rocker arm set. Since the valves are canted, they gain bore clearance as they open. This has an obvious positive effect on airflow. This is not a new concept as 429/460 Fords and big block Chevrolets have always used canted valve systems.
Advantages of the JEG’S/KAASE cylinder head:
1. Will fit all existing intake and exhaust manifolds
2. Uses any 7/16” stud rocker arm for the small block Ford
3. Intake valve has more cylinder wall clearance than any small ford head ever built
4. Valve will clear pistons (flat top, without notches) with up to 255 degree roller cam
5. Will out perform and out flow any head which uses original port locations and stud mounted rockers
Conventional wisdom would have been to build two prototype heads, do all the testing and if satisfied, build patterns and tooling. We skipped all this and built production heads before any testing was conducted. As you guess the first day of dyno testing was a little tense with cost of these two heads cresting $75,000.00.
We chose to use the Ford Motorsport 392 crate engine for the first round of tests. It’s a great buy considering all the new first class performance parts included with the purchase. We also rounded up a junkyard 302 from a 1989 Mustang with over 100,000 miles. We bought a set of AFR 185 CNC ported heads as well as a Ford Motorsport 351-N sportsman oval track heads. The 392 came with SVO GT-40 aluminum heads.
We started our testing with the Ford 392 out of the crate, installing a Holley 750. The engine already has a Comp Cams 232-240 hydraulic roller cam installed from Ford Motorsport. This configurations best test results were 446 HP, 450 FT/LBS of torque. The next configuration we changed to the AFR cylinder heads, the best test was 485 HP, 480 FT/LBS of torque. Then came the moment of truth, we changed to the JEG’S/KAASE designed heads with the canted valve layout and our results are 506 HP, 493 FT/LBS of torque. As you can imagine, performance parts work in systems or combinations and you may have to change more than one component to gain the full benefit. You can’t take full advantage of a good set of cylinder heads if the cam timing is limiting their air intake. We decided to add more cam and changed to a Comp Cams’ 256 degree mechanical roller. With everything else remaining the same the JEG’S/KAASE headed 392 picked up 80 HP, bringing our total to 586 with 487 FT/LBS of torque. Stop and think about this for a minute, this is a street type compression, bone stock crate engine with nothing more than cam and head change and it’s nearing 600 HP. Then we changed back to the AFR heads, losing 53 HP down to 533. The AFR 185 heads are well respected in the industry and we knew it was one of the heads that we needed to surpass if we were going to be a contender in the cylinder head marketplace. Mission accomplished!
Ford’s 351-N sportsman head is an excellent oval track race only unit with 10 degree valve angles and relocated for bore clearance. This head has never failed to deliver great horsepower numbers for us and I believe it to be the best Windsor cylinder head Ford has to offer. We ran these heads with the same Comp Cams 256. We obtained a best of 524 HP, 477 FT/LBS of torque with this combination.
By now we were starting to feel we had a really good product, but one doubt remained; testing was done on a large engine (392), how will they react on a 302? We borrowed a 5.0L, 1989 Mustang engine from Mustang Parts Specialties. This was a high mileage (100,000) EFI engine and my first introduction onto electronic fuel and ignition management. I feared we would need a whole front clip and dashboard brought into the dyno room. The MV Performance people were very helpful in bringing everything together I needed to get up and running. How would this wimpy little engine react to a good set of cylinder heads and would it stay together long enough to do all of our testing?
Our stock little 302 made 251 HP and 317 FT/LBS of torque, a good start! We already knew that installing our good heads and leaving the stock cam installed would be like putting a dress on a barnyard pig, so first change was to install a 218-228 hydraulic roller (about a 20 degree increase over the hydraulic roller). The power was now up to 268 HP, 330 FT/LBS of torque. Next we installed a Holley Systemax intake gaining 30 HP to 298. When we changed to the JEG’S/KAASE cylinder heads our little 302 picked up 83 HP! Now the dyno was reading 381 HP, 373 FT/LBS of torque. Installing our 256 degree mechanical roller increased the power yet again to 425 HP, 389 FT/LBS of torque.
At this point we had reached our goals and should have stopped punishing the stock bottom end of our junkyard 302. Like any good racer, I decided to install an Edelbrock Victor intake with a Holley 750 and go for the record. Until this stage we kept the RPM’s below 6800, but the shorter intake runners would like to peak power a little higher.
Sensing there was danger in the air we had pulled the pins in the fire extinguishers and rehearsed who had what duties when the explosion would erupt. We were astonished when the little junkyard engine cranked out 511 HP @ 7800 rpm!
It will be interesting to see how much power a real race engine can achieve when we are actually trying, that is with high compression, porting, big cam etc…
These new cylinder heads require their own valve cover and pushrod length. I tried really hard to make stock covers fit but there was no way without compromising the rocker arm placement. When you think about it, valve covers are a better investment when compared to the cost of a set(s) of valve springs and the damage that such failures can cause.
We have not tried these heads on turbo or supercharged applications. They should work really good considering their rugged .625 deck thickness
Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic!
Tuned & maintained by "Peppertree Perfmormance". Dart block, Scat 4340 steel crank, Custom C.P pistons.Oliver rods.. Mal Wood twin plate clutch.. Twin SC61/2's,482 rwkw/ 645 rwhp..
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