2G 4g64 turbo and DOHC conversion

[ronny_4g64]

I know there’s many threads about this but all the information I find is too vague.
The question I have is for the components of the 4g64 block, if I were to just plop a DOHC head on the 4g64 would I need to do any swaps on block components as well? Or can I leave everything as is besides the oil drain plugging and timing belt situation?

Would I need to do anything to my ECU or will it perform alright as is? And as far as turboing the engine, what about compression ratio? I haven’t heard much on that.

I have little understanding of engines but I’m progressing, how much modification would be required besides ECU, engine harness, and the basics? I will be budgeting it since I’m young. Finally, will stock 4g64 internals (if I can use for this application) be safe with either or both mods? (1997 4g64 Spyder, 90k Miles)

 

[Sweetjp]

I just picked up a 4g64 myself and have been doing research. You'll need different pistons that have valve reliefs since it's going fome 2 valves per cylinder to 4. I'm planning to run a 9.0:1 higher than that might be a bit much for a street car. And also the rods, some guys claim that they hold up on 12lbs but I'm gonna buy som h beams. Regular 4g63 rods are the correct legth so that's easy. Wiesco seems to make the cheapest pistons that would work. You will definitely need ecu tuning. Adding boost is a big change to that motors parameters.

 

[randman2011]

@ronny_4g64 What are you trying to achieve? Answers change pretty drastically depending on how far you want to go. For the sake of providing some answers I'll assume you're going 16g and in general you're staying pretty mild.

The stock internals can be okay if they're in good shape. If you keep the boost low you can avoid dropping money on fancy rods and stuff, but as mentioned you will need to replace the pistons. Not because of valve relief issues (Spyder 4G64 is also 16 valve) but because this will result in a high compression ratio that would be difficult to tune around with a turbo. The best option would be some decent low end aftermarket 4G64 pistons and be done with it. Keeping the OE pistons would require going with a larger turbo to reduce backpressure and also running it at very low boost AND would be pretty difficult to tune. I don't know if there are OE pistons from other applications that could work on the cheap with a lower compression ratio, but honestly I would budget ~$600 for pistons and be done with it. Something like these. I don't know if the 4G64 rods are different from the 4G63 turbo ones but they are interchangeable.

My build is 9.0:1 compression and honestly I'd go a little higher. If I were to do it again I'd go 9.5:1 since I don't plan on running crazy high boost and would appreciate the extra torque, but 8.5 is stock and 9.0 is pretty standard these days.

When you're asking about the ECU, do you mean the stock Spyder ECU? You will have to spend money on other electronics to get the stock ECU to work for boost and you might as well spend a little more getting something that will work well. Any of the 4G63 tunable ECU options would work, but the stock 4G63 ECU would have trouble with the larger displacement and the stock 4G64 ECU wouldn't handle boost well. If you're trying to keep things on the cheap, a black box ECU would be the way to go here.

I know this post is a month old already, but hopefully this can get you started.

 

[Diamond Star Werks]

Just an FYI for the next person coming across this thread, with the exception of the timing belt and oil drain holes, these blocks can be run as is with a good tune. Stock 64 is good for the 350-400lb-ft range, YMMV. Stock rods and pistons hold up well. Contrary to popular belief 2G 2.4s do have oil squirters as well, they are just built into the rods instead of the mains.
I've also found that the size freeze plugs everyone seems to recommend (typically ppl who haven't attempted the swap) for the extra oil drains don't fit well and typical just fall through the holes. I suggest measuring the holes and using a freeze plug that matches the actual hole size or tapping the holes for a threaded plug.