OST-125: Building a big valve 5AGTTE (yes, twin turbocharged)

[oldeskewltoy]

So, it has been a very long time since I did one of my engine build logs. This one is rather unique. My client wants to build a big valve 5AGTTE.



Discussions began in October 2025, settling on a big valve stroker turbo build using an HKS stroker crankshaft, Molnar rods, Traum custom made pistons, and a Yaz twin turbo manifold!

The original plan was to build a smallport.....

arrival on pallet


now on a stand



BUT things change.... #5 intake cam journal destroyed.



more to come......

[oldeskewltoy]

That's some interesting manifold: not a sequential twin turbo, but one feeds the outer cylinders and the other one feeds the inner cylinders! Huh

Remember the firing order 1-3-4-2. The manifold feeds the turbos with alternating exhaust pulses. This, in theory should spool the twins simultaneously.... upto a reported 22 PSI


The Yaz kit was available over 20 years ago, and for a bit more info here is a write up from someone else who built their engine around that kit: https://www.driftworks.com/forum/thread ... -go.32177/

So, the 1st photo of the manifold with a gasket affixed



Top panel shows how much porting the manifold required to fit to the "new" exhaust ports on the big valve head.

After porting, all the flanges were machined for perfect flat fitment. Last, the manifold was sent to Jet-Hot to get their most durable heat coating.




more to come.....