Head Games

I got my cylinder heads back from the machinist so time to go through them. First issue with them was deciding which heads to use. I had my engines original pair and the heads from the crap engine that I bough earlier.

The original heads seemed untouched and had never been restored. This probably meant a lot of work like valve guides, valve seats, valves, springs etc. Really expensive and in the end I would just have original heads with small valves and poor flow.

The second pair of heads had been worked on quite extensively. They had bronze valve guides, they had been machined for larger valves, the intake and exhaust runners and bowls were ported, they had screw in studs and they had been lowered a lot. Sounds really good but they were not without issues:

• Even the replaced valve guides were a bit loose. Not as bad as in my original heads but still.
• They had been lowered so much it would raise the compression ratio and might cause problems with the bolt hole alignment in the intake manifold.
• One of the studs was just a normal bolt that was even bent.
• The installed valves were too small! Standard size valves had been put in and they were really deep in the seats. I can't believe someone would have actually run the engine with them.
• Were they just cracked junk heads that had been put together to make the crap engine seem whole?

Comparison of original (top) and ported combustion chambers. Note the way too small exhaust valve.

I showed pictures of both heads in FMOC forum and one member agreed to go through them for fair price. He had tools to machine the valves and seats and experience to inspect the heads. So I delivered them to him and waited.

Some time later I got a call that the heads were done. I drove over and we checked the damage. He had inspected both pairs and suggested that I use the ported heads. They needed new valves and springs but that was small compared to the original heads which needed pretty much everything. He had also acquired used but almost like new valves for me. Their sizes were 1.9 inches for the intake and 1.62 inches for the exhaust. That just left the springs.

Stainless steel Ferrea valves

Comparison of original and new valves

The valves and seats had been machined and surfaces checked for straightness. He had also measured the combustion chamber volume which was about 47 cc. That's 7 cc smaller than original! The heads had really been lowered a lot. This would make my compression ratio pretty high so he ground the chambers back to 50 cc. Hopefully removing material from around the valves also improved flow.

Machined combustion chamber

Ported intake bowl

Chamber with the new valves installed.

Nice amount of room around the open valves

Even with the machining done, I still had a lot to do before dropping the heads on the block. I would need to find the correct springs, measure the valve-to-piston distance, lap the valves, paint the heads and finally assemble them. Oh, and hope that the heads would not be cracked and ruin my day when first starting the engine.