Let’s talk 3.8 mivec

[DCIV]

So say you get a 3.8 from a junk yard and want to build it to run in a 3/s. What’s the cost and modifications needed.

So you need a 3.5 pan or modified 3.8 pan.

I’m guessing even chromed ecu can control a 3.8? Mivec window switch?

Rods and pistons have to be upgraded, does ray make stroker rods and pistons? What’s the L then?

Something with the head ports on the headers are different?

Fill me in, what am I missing? What’s the cost at the end of the day?


Coop

[ChargerX3]

Do you really want to go down this road? 3s I presume?

[DCIV]

[quote=""ChargerX3""]Do you really want to go down this road? 3s I presume?[/quote]

End game type stuff yes. I have been looking for a 3.8 for a long time. If one could ever come to my pull a part I would grab it and before I put it in I would build it.

My motor mount plate would make it simple to instal minus oil pan.


Coop

[ChargerX3]

If you were putting this motor in a truck or monti it would be loads easier. I was about to put this block in my 3s but it’s more work than I wanted to tackle. First major obstacle is that it’s a crossover oil pump block. This changes what oil pans you can use, throws off accessories, and the biggest issue is the oil filter is right where your driver side shaft connects.

What’s the solution? Build a 3.5 SR block and put the heads on it. That’s a lot less fab work and the pistons are already figured out with pampena. Ray also can source your rods. Carry over the 3.8 crank and you will be 3.7L.

Chrome can handle everything just fine.

Heads have different exhaust flange and configuration. Will need to build your own manifold. With the taller and slightly wider deck space will be tighter all the way around. You will also need to reuse the MIVEC intake or a similar wide block 6g74/75 intake.

There is more but those are the big things atm.

[DCIV]

[quote=""ChargerX3""]If you were putting this motor in a truck or monti it would be loads easier. I was about to put this block in my 3s but it’s more work than I wanted to tackle. First major obstacle is that it’s a crossover oil pump block. This changes what oil pans you can use, throws off accessories, and the biggest issue is the oil filter is right where your driver side shaft connects.

What’s the solution? Build a 3.5 SR block and put the heads on it. That’s a lot less fab work and the pistons are already figured out with pampena. Ray also can source your rods. Carry over the 3.8 crank and you will be 3.7L.

Chrome can handle everything just fine.

Heads have different exhaust flange and configuration. Will need to build your own manifold. With the taller and slightly wider deck space will be tighter all the way around. You will also need to reuse the MIVEC intake or a similar wide block 6g74/75 intake.

There is more but those are the big things atm.[/quote]

Just curious, could you not use a remote oil filter block and put the oil filter whereever? Think Matt m’s race car. He did it. Just an adapter with AN fittings instead of an oil filter housing?


Coop

[ChargerX3]

It’s possible and I looked into the same but it’s going to be a tight and quick turn and will sit right on top of that shaft. More I looked into it the more I disliked the idea.

That’s just the start though. Timing belt and front of block components are all in different places. Accessories will be an additional challenge. You also can’t use a 72 TT pan. That means you have to fab an existing 74/5 aluminum one. you will also have to find a way to feed your turbos because your filter is on the other side and TT oil bits won’t adapt.

Then there is your engine mounts. There are few. The SR block is much better equipped.

I was in a similar boat several years ago. Thought I could make the whole swap work. But by the time you have to tear the block down to do pistons and rods anyways, the SR block starts to make much more sense. You really only lose .1 L going that route and it’s honestly worth it because of all the TT parts you can reuse.

So go buy a 94-96 sr block and 75 MIVEC heads and intake manifold and call it a day. That’s the best possible way to build it.

[Jeff V.]

Does variable cam stuff even make that big a difference on a boosted engine? I'm wondering if it's worth dealing with the MIVEC stuff at all?

Just go with the old John Monin setup. 3.5 block, DOHC heads and a few adapter bits to fix the issues with the deck height.

[ChargerX3]

Yes it makes that much more of a difference with the added MIVEC. Especially high rpms as I was once told.

[DCIV]

Okay. You talked me out of the 3.8 mivec.

But I can put mivec heads in a 3.5, to get 3.7 do I need the 3.8 crank and special rods and pistons? Or just the 3.5 crank? That may determine how I go about buying stuff. If I just need a bare block from one car and a crank from another.

Way back in the day before ray did strokers he made a post. A post that was later deleted, being a mod I could see it. Steve if your still a mod you can find it. He talked on how to make a 4.1L and he gave math on it. I was thinking a stroked 3.8 might be that 4.1 since you can make a 3.0 a 3.5. Maybe it needed a custom crank and thus not feasible but maybe it was just a combination of parts like the 3.5.


Coop

[ChargerX3]

Yes. Use the 75 heads and crank. The 3.8 has a longer throw than the 3.5. That puts you at 3.7 by the time you bore it out a little. 4.0 would likely be a stroker build and almost entirely up to making a new crankshaft.

Just remember that as you start to chase bigger cubes several things start to happen. In our case with longer stroke to piston ratio you start to build more piston speed per stroke. This puts added strain on internal components and will decrease your overall safe redline speed. A positive is that you generally start to build higher torque #s. In our case though rpms are more favorable.

I remember a conversation with Nelson a while back when I was chasing the 3.8. He kept telling me to build a 3.5 like him because it was the perfect combo and that any 3.8 or bigger would not be able to survive long term. He gave some decent reasoning but then again he didn’t like others building something nicer than him so it could have been bs. The fact is that there have only been few successful 3.7/8 MIVEC builds so there is little info. When I was last looking into it the only 2-3 guys who posted about it loved it but blew up their motors shortly after. One kept the stock rods iirc and the other 2 sucked valves. There are now fixes for both of those.

If you can find rays post I wouldn’t mind seeing what he said. I’m just swamped with a sick family and starting a new business at the moment.

[stealthee]

My buddy Chase made 415 awhp with a 3.5 with 14bs on only 12 psi.

[DCIV]

I can’t find it. I’m not a mod anymore. But it was before ray was famous and no one had done a 3.5 yet.


Coop

[DCIV]

[quote=""ChargerX3""]Yes. Use the 75 heads and crank. The 3.8 has a longer throw than the 3.5. That puts you at 3.7 by the time you bore it out a little. 4.0 would likely be a stroker build and almost entirely up to making a new crankshaft.

Just remember that as you start to chase bigger cubes several things start to happen. In our case with longer stroke to piston ratio you start to build more piston speed per stroke. This puts added strain on internal components and will decrease your overall safe redline speed. A positive is that you generally start to build higher torque #s. In our case though rpms are more favorable.

I remember a conversation with Nelson a while back when I was chasing the 3.8. He kept telling me to build a 3.5 like him because it was the perfect combo and that any 3.8 or bigger would not be able to survive long term. He gave some decent reasoning but then again he didn’t like others building something nicer than him so it could have been bs. The fact is that there have only been few successful 3.7/8 MIVEC builds so there is little info. When I was last looking into it the only 2-3 guys who posted about it loved it but blew up their motors shortly after. One kept the stock rods iirc and the other 2 sucked valves. There are now fixes for both of those.

If you can find rays post I wouldn’t mind seeing what he said. I’m just swamped with a sick family and starting a new business at the moment.[/quote]

And I get all the stroke talk but these people are trying to make 1200-1500hp all the time. That isn’t me. So while yes they are 100% right. If a 3.8 can be had for same price as 3.5 then I would want to do 3.8. Or if a 4.0 can be bad with the right parts combo then why not. I want to take my time and get the right parts once.


Coop

[ChargerX3]

Yea the largest you can go is 3.8 with stock parts. If you do a crazy bore then you might squeeze a 3.9 or 4.0 but that would make for very thin cylinder walls. Iirc the 3.5 has thicker cylinder wall castings to start with so plenty of room to grow and add boost.

The 74/75 will cost about the same for internal parts as most items are identical. Where the 75 get more expensive and custom is mounting exterior items mentioned above. Best price is to pick up a more common SR block and then scalp the heads and crank off a MIVEC 75. It’s not that much more and you gain .2-.3 liters in the same block. Depending on timing I may have an extra crank and set of heads.

[DCIV]

Don’t tease me! Set a price for those head and crank.


Coop

[ChargerX3]

Lol you’re not that far enough along anyways. Lol.

[Chris GTO TT]

opcorn2:

[DCIV]

[quote=""ChargerX3""]Lol you’re not that far enough along anyways. Lol.[/quote]

All I need at that point is a block, rods and pistons.

How much (ball park) do I need to set aside for your parts?


Coop

[mjannusch]

The Pampena 6G72 stroker setup is a lot easier than trying to hunt down all the parts you need for the 6G74 setup. Everything fits, don't have to worry about hood clearance, etc.

What is your power target?

As far as I can tell, the 3.8L stuff is pretty much unproven at this point. I'd assume you want to be actually driving your car, instead of wrenching on it constantly. Low-end torque isn't exactly awesome on our driveline components, either.

[DCIV]

[quote=""mjannusch""]The Pampena 6G72 stroker setup is a lot easier than trying to hunt down all the parts you need for the 6G74 setup. Everything fits, don't have to worry about hood clearance, etc.

What is your power target?

As far as I can tell, the 3.8L stuff is pretty much unproven at this point. I'd assume you want to be actually driving your car, instead of wrenching on it constantly. Low-end torque isn't exactly awesome on our driveline components, either.[/quote]

So your right, the 62/3.5 stroker is what I would go with if I had a 4 bolt block. I do not. I have a 2 bolt block. I have a spare 4 bolt block but if I have to go out and buy stuff anyways why not get a little more L? Honestly...why not?

Power goals? That’s a loaded question I believe because there are tons of ways to make even 1k from a 3.0. I want enough power to hang with anything I might pull up next to. I want a power band that lends itself to cruising.

Is the 3.8 stuff unproven or just untested. That’s a very good question. From everything I read the mivec heads flow way more and since I don’t have built heads (rays head lift fix only) why not change to a better head if I spend the money?

And I would build everything before I dropped it in over a winter, don’t care if it’s 2 winters from now, I want to collect what I need.


Coop