Head Games, Big Ball Bearing Boost & Laughing Gas
In the last 4G63 Power Options series article, we started looking beyond the bolt-ons. For this installment Doug's Dynopower wasted no time in focusing on the cylinder head which had escaped unscathed so far. A ported unit, complete with stainless-steel valves and stout internals, is an excellent way to maximize the efficiency of the turbo's boost.
Once Doug's Dynopower removed the stock head, the crew was amazed with the virtually perfect stock ports; no severe mismatches between the valve seats and pockets as most production heads have.
At any rate, another head was ported and fitted with heavy-duty stainless valves from Supertech Performance, Inc. The Supertech valves are black nitrided for increased durability and less friction. The valve's seat surface is hardened as well-a much-welcomed attribute with today's fuels.
From a performance standpoint, the valve's undercut stems let more air pass the valve even at low-lift or low engine speeds, which means more potential down low in the powerband. A fresh set of Crower valve springs and retainers round out the valvetrain combination.
Upon installation, Doug's Dynopower used a metal head gasket and ARP head studs. Sometimes engine builders get carried away with hogging out large ports and fitting oversized valves in a cylinder head. The result is a race head that may produce big numbers on the flow bench, but won't perform on the street in the real world. The head, turbo and cam are a team and need to deliver the goods at a usable engine speed. A turbo engine's head doesn't necessarily need the same mods as a N/A cylinder head.
For a street-use 4G63 engine, new stock-size valves, a set of fresh springs, mild port work and a set of cams like the 414 Crowers produce a head package capable of supporting upwards of 500 hp. (A side note, the Venom sheetmetal intake helps tremendously from 4000 rpm on up.)
While the use of an aftermarket intake on a 4G63 is always in dispute; on this application the Venom unit is very effective. A loss of low-end torque is miniscule when compared with the mid- and top-end gains made with the straight-runner intake. This reiterates the importance of supporting mods and we should add the intake manifold to the aforementioned list of turbo, head and cam.
Topping the 4G63 with a built head netted roughly 20 whp when ran at the same boost level. Boost built faster and much more smoothly. The engine revved to 7500-8000 rpm very quickly in any gear.
Distinctly different was how the engine seemed to make the same power as before with 1-2 psi less boost. The gains from the head and valves would be even more noticeable at higher boost levels. Driving the Galant on the street and dropping the hammer at mid-range in the powerband causes the car to spin all four tires at 18-19 psi-quite a sight to behold. With the Garrett T3/T4 ball-bearing turbo starting to spool at 2000 rpm, turbo lag is not a concern.
The T3/T4 turbo Doug's Dynopower had used on the Galant flows roughly 49 lbs of air. Doug's Dynopower says it worked great, probably the best sized unit for a street vehicle that can also handle up to 25 psi for the track on race fuel. Wanting more flow for the engine, Doug's Dynopower elected to jump to a Garrett GT Series full ball bearing unit from Tial Sport. The Garrett GT3040 model flows 55 lbs of air.
To complement the new turbo, Doug's Dynopower also used a Tial 46mm external wastegate. The Tial unit is beautiful, perhaps the last external wastegate an enthusiast will ever need to purchase. It can handle up to 800 hp in flow.