1990 Ford Mustang Head Swap - Back In Business

Here are the heads as they came out of the box. Unfortunately, due to time constraints, we were unable to test them on a flow-bench. They picked up plenty of horsepower over the GT-40Y heads that were on our test subject's engine during baseline evaluation.

The short-block is from D.S.S., and the owner added a set of GT-40Y heads, a TFS Stage 1 camshaft, and a TFS Track Heat intake manifold. The exhaust system was a bit small for our liking-BBK shorty headers, 2.5-inch H-pipe with high-flow catalytic converters, and 2.5-inch Flowmaster after-cat exhaust setup. Long tubes would have been righteous for this engine combo. The exhaust pipes were also kinked, thus killing even more power.

The first order of business was to start pulling apart stuff. First to go was the inlet pipe and MAF sensor. Then the upper intake manifold was removed as well as The valve covers are removed, and the 1.6 roller arms are pedestal-mount style. These will not work on the RHS heads. We upgraded to Comp Cams Pro Magnum rocker arms.

The valve covers are removed, and the 1.6 roller arms are pedestal-mount style. These will not work on the RHS heads. We upgraded to Comp Cams Pro Magnum rocker arms.

Rather than disconnect all of the injectors and fuel rails, we chose to remove the lower intake manifold, injectors, wiring harness, and fuel rails as one piece. The injector harness and fuel rails disconnect easily from the main wiring harness and fuel supply and return lines. Pulling it off as one piece makes it easier to put back together.

The serpentine belt is removed along with the alternator, tensioner, and other engine accessories.

The larger 3/8-inch studs are torqued down to 60 ft-lb. We also used Loctite on the threads. It should be noted that you should use assembly lube on the studs before bolting them down. Also, we chose to use washers under the studs so they would not gall the aluminum surface they were mounted to.

Unbolt the rocker arms, remove the pushrods, and take out the distributor (we closed the distributor hole with a billet cover). Once those are removed, unbolt the head bolts and remove the cylinder heads, which pull out easily.

The bare RGR/JPC short-block is just sitting and waiting for the new RHS heads to be bolted to its deck surface. Before that happened, we removed the old head gaskets and cleaned the surfaces, especially the silicone sealer left over from the intake manifold.

A threaded insert was installed in the front of the driver-side head. This is for mounting the accessories on the front of the engine. Once again, use Loctite on the threads.

Do something that is often skipped-clean the heads. Packing material and leftover debris from the warehouse can and will get stuck in the small crevasses. We used brake cleaner to wipe down the deck surface and the air hose to blow out the ports.

With a clean deck surface and the ARP studs removed, the Fel-Pro head gaskets are placed on the block.

RHS heads are laid on the block and held in place by dowel pins.

The ARP studs are ready to be installed in the block. The top studs' threads are covered in moly-lube while the lower threads are wrapped in Teflon tape-the reason being is the lower studs protrude into the water passage. An Allen key groove has been machined into the top of the studs, making the screw-in process easy.

The ARP studs are ready to be installed in the block. The top studs' threads are covered in moly-lube while the lower threads are wrapped in Teflon tape-the reason being is the lower studs protrude into the water passage. An Allen key groove has been machined into the top of the studs, making the screw-in process easy.