Engine and Transmission Tech

Engine overview:

I finished a total remake of the Ford 302 in my MGB. I bought it 11 years ago as a crate engine from Ford with a standard bottom end and Ford GT40X aluminum heads. In its new form the only major part I kept was the bare block. It is basically a long rod, standard stroke engine (3 inch stroke) with upgraded heads (AFR 165). The rod - stroke ratio with the 5.4 inch long rods is 1.8 (the same as a 289), versus 1.7 with the standard 5.09 inch rods. While many may disagree that the theoretical benefits of long rods such as better high rpm breathing, lower piston side thrust, and gentler piston acceleration and deceleration at the top and bottom of the stroke have any practical benefit, the one obvious benefit is less weight. For a given length, rods are lighter than pistons, and the new short piston/long rod assemblies weigh 159 grams less (each) than the standard items, even with the added strength of forged rods and pistons and high strength ARP rod bolts. The crankshaft is forged and internally balanced. It is much more rigid than the original and the harmonic vibration at around 2000 rpm is now gone. I am also using a lightweight aluminum flywheel and a lighter than stock McLeod twin plate clutch. So the moving masses in the engine are about as light as is practical. Throttle response is noticeably better, both on and off the throttle. For instance, the fast slowing of the engine off throttle allows quicker shifts without shocking the drivetrain.

I set the rev limiter to 7000 RPM and the engine easily reaches that; I especially need to watch the tachometer in first and second gears. The power peak is probably around 6000 rpm based on the cam, intake manifold, and carburetor size. However, the drop in power above the peak seems to be gradual so 7000 rpm is still useable. And it appears that the hydraulic lifters (Comp Cam) cope fine with this.

Although the cam is somewhat more aggressive than before, it does not behave any differently on the lower end. The engine still pulls well from 1400 rpm in fifth gear, actually seemingly better than it did before; probably because the compression has been raised from about 9 to 1 to about 9.8 to 1.

So, I have basically accomplished what I set out to do; increase the top end capability with minimal loss in the low end, and obtain smoother operation all around. The absolute power is probably also up, but that is not as important to me. Disclaimer: the engine only has 500 miles on it so far and I am being somewhat gentle with it, so my opinion may change when I really start to push it, but I doubt it.

I also wanted forged pistons for safety reasons. If a valve drops on hypereutectic pistons they explode and the block or pan is usually breached. Oil under the car at high speed could be fatal. Forged pistons remain intact under such conditions and the engine has a better chance of staying together. The SFI rated flywheel is another safety benefit.

Intake manifold:

First of all, I am still using a carburetor (Quick Fuel Slayer series 600 CFM vacuum secondary which might be slightly undersized). I switched from an Edlebrock performer manifold (not a performer RPM) to a Weiand/Summit stage 1 manifold. The new manifold is the same height as the Edlebrock but the design seems much better. The Performer manifold is just an aluminum version of the stock Ford manifold while the Weiand/Summit manifold is very similar to the Performer RPM manifold (undoubtedly the best all-around manifold available), only with less height. Tuning with the Edlebrock Performer was a nightmare. It required an extremely rich accelerator pump setting and overly rich primary jets to avoid hesitation, though hesitation was always present unless the engine was fully up to operating temperature. And blocking off the manifold heat made it impossible to avoid severe hesitation even with the biggest accelerator pump cam available. The new manifold, with a very mild accelerator pump cam and standard primary jets, never exhibits a sign of hesitation, even when the engine is completely cold. I suspect I could block off the manifold heat with no adverse consequences. For these reasons I advise against using the Edelbrock Ford Performer manifold.

Heads:

The Ford GT40X heads are very good, but the AFR heads have somewhat better flow numbers with smaller ports. This means a higher port flow velocity which works well with the longer rods (in theory). Long rods give the pistons a longer dwell time at the top and bottom of the stroke. This means that the times available to fill and empty the combustion chambers in a long rod engine are the same as in a short rod engine at a lower rpm, which is why long rods are supposed to give better high speed breathing. High gas flow velocities mean more gas inertia which also has the effect of filling/emptying the chambers better as piston dwell time decreases with rpm. So, the AFR heads work along with the long rods to give better high speed breathing without resorting to excessive valve overlap, which preserves low end performance and gives the widest possible power band.

Oiling system:

I installed a Canton screen type windage tray, a Canton drag race oil pan which has some baffling and a crank scraper, and a high volume, standard pressure oil pump. This is not as good as a full race system but gives better oil control than an open sump with no screens or baffles, still allows easy access to the starter, and does not decrease ground clearance.

Clutch:
I tried a McLeod twin plate clutch to see if it was really a major advance over a conventional clutch. It is. The pedal effort is comparable to a 4 cyl MGB and the action is very smooth and progressive. The only problem is cost… Note: I am using the Nissan ¾ inch slave cylinder everyone seems to recommend but I found that I had to use a larger Tilton 13/16 master cylinder; the ¾ inch MGB master cylinder did not give enough throw.

Larry, waiting on a Dyno pull, should make over 300+ RWHP and 350+ Ft. #'s Tq. The AFR heads do a great job. What cam part # did you choose?

All Hail the Mighty B Cam!

I am not using a B cam (maybe I should have).

The cam specs are:

Comp Cams XE270HR, intake 118 degrees at 0.050 lift, exhaust 224 degrees at 0.050 lift; 112 lobe separation, total lift .544 I and .544 E (with 1.7 rockers). This is the largest cam Comp cams listed that did not begin to significantly affect idle vacuum. Its power band is rated from 1800 to 5800 rpm.

Larry,
Sounds like a great upgrade! Did you have fun doing it? I really like the way you continue to upgrade your car over the years. What's next on the list?

Scott

Looks like pretty much perfect selection of components. Should give maximum "area under the curve". Too bad more people don't use this intelligent approach to their engines. One question, why high volume oil pump?

There is general advice that a high volume oil pump is good insurance for high RPM engines. In fact, Melling (maker of oil pumps) also advises this. In addition to standard and high volume pumps, Melling makes a high pressure pump, but does not recommend this except for certain full race engines. Melling claims that there is no downside to their high volume pump since extra oil is dumped through the pressure relief valve so there is no significant increase in the power that needs to be transmitted through the distributor drive gear and oil pump shaft in normal driving. (But I have an ARP oil pump shaft just in case because the standard shaft can fail even with a standard pump.) With high pressure pumps, wear on the drive gear can be significantly increased. My motivation for trying the high volume pump is that I have problems on track days in that after only 3 or 4 laps there is a big drop in oil pressure and I have to stop and let the oil cool/settle. Maybe the pump, in conjunction with the other oiling modifications, will allow a few more laps. But there is certainly no need for the high volume pump for just street use.

> I have problems on track days in that after only 3 or 4 laps there is a big drop in oil pressure and I have to stop and let the
> oil cool/settle.

One problem we've seen is much of the oil getting pumped to the top of the engine with what's left in the pan sloshing away from the pick-up under hard cornering and/or braking. No pump will help if you are sucking air. Some use an Accusump but on our Pantera engines, we use a "10 quart" (more like 8.5 quarts plus one quart in the filter), flat bottom gated and baffled road race pan. If you find you are still having problems with the drag race oil pan, this is the type of oil pan we run on street and road race Panteras:



I'm pretty sure Aviad and Armondo (used to work for Aviad) make a similar SBF pan designed for road race Cobras. What sort of rod and main bearing clearances are you running? High volume pumps can make a difference where the clearances are large and pressure drops off as the oil thins out. When the clearances are tighter, we run standard volume/pressure oil pumps. Here's a short video of a street/road race 384 cubic inch Ford Cleveland V8 after a dyno flogging:

[youtu.be]

Engine is a pump gas (91 octane) street/road race build for a Pantera that runs in the open road races like Silver State and Pony Express where they shut down 90 or so miles of public road and let you run in various speed classes. The owner runs in a class where he tries to average 150 MPH without exceeding 165 MPH so the RPM stays elevated. Displacement is 384 cubic inches via a 3.75" stroke crank in the stock cast iron block. Lifter bushings were installed in the right side lifter bores and a restrictor in the passage feeding the left. 0.0025" main and 0.0022" rod bearing clearances and a stock out-of-the-box Melling M84A oil pump in an Aviad/Armondo style gated and baflled Pantera road race oil pan filled with 20W-50 Valvoline VR1 oil. The engine had been run for an hour of warm up/break in time and about 15 pulls worth of tuning work. Best pull was 623 HP at 6800 RPM and 521 ft-lbs at 5100 RPM through my Pantera 4-into-1 shorty headers and 2 1/2" diameter mufflers. The video was taken immediately after all of the tuning runs were done and it shows how much difference reducing the leaks in the engine can make oiling system can make when it comes to oil pressure.

Dan Jones

You have pretty much covered it all, Dan. My thoughts were that the high volume pump would cause problems instead of solving them. Generally, high volume oil pumps are for worn out engines.

Any good oil drain-back tricks for SBF?

I absolutely realize the advantages of a proper sump. There are very nice road race pans made for the Ford 302 but the “T” shaped one is a very difficult to fit; it appears that it can only be installed while the engine is hanging in the engine compartment off the hoist such that the pan is behind the chassis engine mounting brackets. Alternatively, the front cross member can be removed then installed under the engine (while hanging off the hoist) which is also a huge pain. And the starter can only be removed after the header is removed. There are also deep, non “T’ pans that are easy to install, but ground clearance is already minimal and I would worry about a punctured or badly dented sump. For a pure race car I would absolutely use the “T” sump but not for a street car. I even asked Canton if they could make a custom standard sump with the oil inlet trap from the “T” sump but they said there was no room. Also, I do not think my problem is the pump sucking air but rather the oil being splashed all over the engine during cornering and getting hot and maybe foamy. This is because pressure is fine at the start and only drops after a few laps. Once it drops, it remains low even at idle until the engine cools off. An oil cooler might help, but I think it is better to keep the oil more in the sump instead.

In theory a high volume pump does not deliver more oil to the upper part of the engine than a standard volume pump because flow is limited by pressure and pressure is not any higher. A high pressure pump is a problem, however.

I do agree that 302 drain back is not good, filling he engine with oil after an oil change is a slow process because the oil fills the valve cover and drains very slowly into the engine. Any suggestions in this area would be welcomed.