Carobu Engineering… any experience?

No experience but if faced with a similar situation, I wouldn't hesitate. Been looking into these builds since I first got my 308 in 2013. Stock appearance but in some cases, close to an extra 100 hp? Sign me up.

 

I lean towards "stock" as much as possible, but with my 208 GT4 I would be VERY tempted! On the other hand, not too many original 208's out there. This would be a tough decision, but no doubt would transform the car.

 

The driving experience of a 308 is simply transformed with 100 more hp. Getting that power with 20% more displacement basically means 20% low end torque, again transformative in how it feels. Just better in every way.

Where is the 280hp number coming from? I don't see numbers or dyno graphs on there web page for the package?

 

I found a 308 QV motor dyno'd at 348 hp on their "Ferrari" tab at top, then "Dyno Tested Engines."

http://www.carobu.com/308-qv-358rr-stage-2

Of course there are other shops that have had similar results. Nick's, Newman...

 

Yeah, I've seen those and just though 280hp seemed lowish if it's a crank number so I was curious to see the dyno curve.

Lots of options for cams and porting though, so for sure there could be a big range in output. For sure a bigger engine will have more low end torque and probably more everywhere which is nice on the street.

 

That one has a different engine management system. With electronic they were free to put in aggressive cams that CIS will not tolerate. Does not really keep a stock look. The GT4 is carbed. Too many put too much cam in them and they end up not very pleasant to drive. Making it a 3.5 and put a bunch of compression in it will make a big difference and still have good driveability.

I would never however keep the factory rods like their picture has.

 

So what happened with the GT4 after it broke down?

 

I haven’t used them but I have been looking at their site for some time as well. It seems like if you are in need of a rebuild, why not go that route. Especially if it can still have a stock appearance. How does their pricing compare to what you have been quoted for your stock rebuild?


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I have been studying these for a long time and engaging in threads with the developers and more advanced DIY'ers for over a decade and was about to pull the trigger on building one, less doing the machining. very cool and very expensive. 360 crank, new rods, other bespoke parts, likely new oversize carbs or EFI is really a benefit to get the most out of the tweaking. Think about the 30-40K you would normally pay for a rebuild and add 20K on top for new parts. Carobu is one of the few trusted companies that does this upgrade (Nick's, Bradan). They even manufacture their own parts, including their own long stroke main crank, vs. the stock 360. That part alone is like $4-5K. Used 360 cranks values have fluctuated and you can find them from 2-4K - it just depends on what the seller feels like asking. They know why we are buying these and inflated the price. It is up to you if you wanted to go high compression large bore piston. The other aspect to get the most out of your build is a more aggressive profile cam. At that point you might want to look at new stainless valves and possibly a more performance oriented valve spring. It is best to approach this all at once because you need to approach tuning you engine as a holistic system.

The 2V engine has a power cap due to the cylinder head's intake design at around 300hp. QV's can go over 400 because they breathe better. The heads are not lego'ish interchangeable.

You wind up with an engine that is a bespoke piece of art. You can see how this is a slippery slope and a rabbit hole.

 

Of the three shops you mentioned, which do you think produces the best final product?

 

I’ve never used any of them. They both seem to have engineered solutions. Nick and Scott were the first to really be doing this and have tested a lot of the limits to what’s possible with 400 - 450 hp naturally aspirated engines.

 

The first 3.4L conversion I did was done is 2011 and I've built a number of them since. The 2V engines make 335HP with minimal head work and the 4 valve with EFI makes 375HP. I've done 2V CIS stock looking builds but not dynoed them, only driven back to back with a 328 and verified the 2Vi was quicker than the 328. Im currently working on three 3.6L builds. As mentioned earlier, they transform the car into what it should've been IMO with no sacrifice in drivability or longevity. Adding a quick ratio steering rack is the cherry on top.

 

Ahhh....numbers.

A 79mm 360 crank and 3.4 liter.....83mm bore? And 328 head gaskets work maybe? Or do I have my numbers wrong?

Was the 375 hp QV a factory intake?....I've heard the intake is the flow limit and ITBs will let them run past 400hp?

 

It was the stock intake you ported for me, quite some time ago on that one.

 

That's what I was guessing. The 4v heads come right up nicely when you start porting but I thought that intake would be the death of me..... the runners just aren't big enough to match what the heads can do. but you wrung 375 out of it anyway so well done!

 

Yeah 325-335hp is the crank hp number I came up with as well. Cat Cams sport grind, 10.5:1 compression, slightly larger intake valve seats and valves, 83mm bore with 360 crank, and they do like mad. 274hp at the wheels was where I landed, just a fantastic engine when it's done. Huffaker built 3L race engines running huge compression and make great power with just 3L (somewhere above 350hp), but that's an entirely different animal.


The stroked carburetor road engines are capable of likely a good bit more but it would be a pain. Along with slightly larger intake valves, the 34mm stock intake ports could be opened a bit to say 37-38mm (porting at the roof as much as possible), match the intake manifold runners to same and open at the carburetor side to 44mm to accept 44DCNF carbs or 44mm throttle bodies..... that's a lot of work for another 20-30hp.

In the end it's just air/numbers. I dig what the Auzzies are doing with the old Torana inline 6 engines with just 3.2L, what screamers.

 

With throttle bodies you aren't restrict like with carb trying to make them work well down low so 44 is probably on the small side. On my 4V heads even 54mmTBs are a measurable restriction or the flow bench and normally if you see it on the flow bench you see it on the dyno. About 48mm is where I'd start on a well ported 2V I think.

Flow is hp and bigger ports flow more....but the torque peak is very much linked to port velocity so opening up ports to get flow means raising the engines rpm, or increasing its displacement so it needs that air at a lower rpm. That is the beauty of these 3.4-2.6l 30-8 builds, you do what would be a race port on the head, but it becomes a nice street head when mated to the higher displacement bottom end. Really nice setup imo.

 

Hello Paul...Was my yellow car the first 3.4 you did? It has very nicely passed the test of time!

 

On my 2V carb car with 40DCNF's, we saw 350 bhp on the engine dyno, with open stacks, at sea level. The factory air filter assembly (but with K&N) dropped power 40 bhp. What are people doing to overcome this flow restriction that starts to become noticable over 5k rpm?

 

Thank you, I did two at the same time but yours was first on the road.

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Cut a hole in the lid

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I'm on Paul's list for a 2V engine, and very excited to get started. I'm committed & already have the 360 crank & rods and hope to get the car to him this fall. Let's hope it's a good winter project!

 

I don't think I've ever done a build where the air cleaner wasn't an issue. There is always so much going on and some much that just is what it is that the air cleaner ends up an afterthought. I've jumped through all kinds of hoops on my 308 building something I'm pretty sure will have exactly the issue you are descrtibine but I'm trying to get past 800hp and I figure the setup is probably solid to 600 so it might help you.

I modified the original V8 plenum to fit the V12, you could use your air filter box without the filter on a caerb'd build and added an air intake to both sides
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Then routed the tubes to K&N filters mounted at the side vents
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I think most of the 308 solutions I've seen are a version of this...hoses to the side vents. Or as Paul said cut a hole to get a bigger filter at the engines, you can stack filters so 2 or 3 of the K&N filter you have would probably do it....then feed the box with hoses to the side vents.

You could use the trunk too, that is basically what the newer longitudinal engine cars do. If just comes down to how bad you want that 50hp.

 

Several years ago a GT4 with a Carobu motor was sold at the RM auction in Ft. Lauderdale. I’ve long since lost the details and I doubt the old RM auctions are archived on the web, but it’s a place to start. As I recall the seller was a doctor from Virginia, be I could be mistaken. The car was featured in FORZA, so that might be a better starting point to get some information.