2007 Mazdaspeed 3 Engine Block

Hello everyone,

I'm new here & this is my 1st time participating in a forum.

I joined HPA so my 17yr old son and I can get the help we need in trying to rebuild his 2007 Mazdaspeed 3 engine motor (2.3L DISI Turbo L3-VDT). We have never built a motor before but I do have some technical knowledge and going through the course on the program (HPA) have given me some knowledge & I gain some confidence.

He purchased the car 2 months ago but the engine has fail. We try getting a replacement motor but unfortunately the junk yard near us says they're no available motor nearby in Canada, closest is in the USA Texas.(we're living in a small town)

We took it upon ourselves to watch a couple YouTube videos & afterward we took the motor apart. The #1 & #3 piston had holes in them on the top and the block as well, had some scorch/burn mark in them, #3 cylinder was the worst. I have never worked on an engine before but I'm willing to learn and I believe doing this with my son will give us a better bond.

We're not looking to build a performance engine & this will be his daily driving. I would like to know the best step we can take in getting this motor alive again without spending a lot of money. The plan is that we would change the valve seals, clean up the valves as they would be reused with the springs as for the bottom end, the crank is in a great condition & we would just replace the 4 piston & connecting rods but see what the block looks like we would have to get a machine shop to bore the block & there's where I think the problems hence my questions comes in.

1. To have the block bore out so the scorching/burn marks comes out meaning we can't use OEM Pistons & Rings anymore?

2. Using aftermarket Pistons & Rings with bigger bore & different compression ratio, will the OEM ECU handle the modification without giving issues?

3. Would it be better finding a machine shop to re sleeve the block to OEM bore? (If that's an option)

Hope my questions are straightforward

Thanks

Unless there are factory over bore pistons available, if you have to overbore to clean the block up, then yes your options are getting another block or aftermarket pistons.

The stock ECU will not operate properly with aftermarket pistons in this application without a tune because they alter compression and piston dome design.

Damage to the block looks pretty severe, so in terms of cost effectiveness, I'd suggest getting a complete used engine in good condition.

Since this is a project, you could try to find a block in good condition and then perform the rebuild you planned.

You could also find a shortblock in good condition then go through it just for the sake of executing the process.

And ultimately the root cause of the failure has to be found otherwise it will repeat with the new engine. These engines don't melt through pistons without a major issue.

Thank you for your response Mike McGinnis, much appreciated. Suggestion noted.

You're welcome!

As mike said, you MUST identify the problem that caused the damage - four things come to mind

Too low an octane fuel used and ECU couldn't compensate for hard driving/abuse.

Injectors not supplying the required fuel - have them checked and serviced, which is a good precaution anyway.

Low fuel pressure - bit harder to check with the engine apart, but a basic precaution is to replace the fuel filter, as it's often overlooked.

It was driven hard when overheated and low/no coolant was in the block.

I'd partially disgree/agree with Mike about the pistons, as there is often a range of pistons available, from direct OEM spec' in a larger bore, to more specialised piston options. The first should be fit and go, but the latter could benefit from fine tuning, especially if higher compression.

That said, those bores look WAY to badly damaged for a simple re-bore - heck, looks like at least one hole through to the water-jacket - which means a new/used block or a full set of sleeves. I would be dis-inclined to buy a s/hand engine, sight unseen and that I hadn't tested, but it may be an option.

Other options may be to check Mazda specialists, and companies that offer exchange rebuilt engines/short blocks (minus cylinder head and other accessories). I don't know if Madza, themselves, sell re-manufactured/rebuilt engines or short blocks, but if so, they can be a good option.

I may stand to be corrected, but I think DARTON do a sleeving service where they will sleeve your block if you send it to them - they specialise in sleeves, so might be worth a call?

https://dartonsleeves.com/products/sleeves/mid-sleeves/hyundai-mazda-mitsubishi-mini-mopar/

Your engine doesn't seem to be one of those they will do the installation on but, if you go that route, I expect they will direct you to someone they trust - an approved shop - in your area if they're not prepared to do it for you..