GM's new 4.2L DOHC twin turbo V-8 !!

[Newold1]

Please start another thread on Vintage bike racing and their riding techniques, Please!

[mk e]

Just filling time until you have more details on the new dohc 4.2

[Bazman]

This was the OHC engine I was hoping for from GM....



The Mercury Racing SB4 7.0, basically an LS7 with quad cams and 32 valves. Rated at 750 horsepower at 7,500 rpm on pump fuel (closer to 775). Maximum recommended engine speed is 8,000 rpm.

https://www.enginelabs.com/news/sema-20 ... te-engine/

Now THAT motor with an OEM warranty would be tits

[Newold1]

This is Mercury Marines DOHC LS7 base engine conversion. Cool looking power plant BUT:

Been available for about 4 years now. Has not been accepted well in the marine trades or aftermarket performance markets.

Way to expensive! Can't remember exactly but I think they are priced at about $75,000. Won't come close to meeting current emissions standards. Does not have great horsepower per cubic inch production versus just some stock GM LSX and LSA engines

Mercury was trying to work off some of the racing success of their big QV$4 1350-1650HP offshore racing engines which use the same DOHC cylinder head technology . They sell for about $225,000 a pop!

I think it's pretty much an abject failure for Mercury Marine and it will probably disappear shortly if it has already not.

[hoffman900]

I never understood that price point, especially considering a NASCAR lease engine is probably around $50k.

Economies of scale I guess.

[GARY C]

I'm a little skeptical of OEM's reliability testing before introduction of new technology
When I was a Ford Service Manager we introduced the 2.0 Koln built OHC engine and
Stated that the engine had millions of miles of durability testing in Europe
Well of course the rocker arm otc cam lobes started failing promptly some before 20,000 miles.
Proper Types of oil not specified
The Reynolds metal Vega Bores similarly failing likely because of susceptibility to coolant leaks
And having a tiny cooling capacity.Corrected with "Durabilt" engine blocks
NorthStar and other aluminum block engines head bolt thread failures repaired with Threadsert s
Now the new multiple lawsuits and recalls in re CP-4 Bosch pump failures in diesels because of incompatibility
With US Grade diesel fuel.
Mercedes AMG head bolt and gasket failures.
And hundreds of more examples
So it's just my opinion but I wouldn't own the new engine without a full coverage extended warrantee !!
Dave B.

Historically in the auto industry the first year or two of a new model release is basically consumer funded R&D.

[GARY C]

I think sometimes WEon this engine forum should spend a little more time studying and educating ourselves in new engine development offerings and understand in particular in a case such as this before we start making so many OPINIONS not necessarily based on real facts and information.

Some more real information on this new GM RPO LTA twin turbo engine:

1. Development on this engine began over 4 years ago at GM.
2. The engine has undergone over two years of actual on road in testing durability cells at GM.
3.This engine is currently being set up for assembly as we speak at the new GM high performance engine assembly facility at Bowling Green Kentucky
4. 20 psi boost on this new engine design is mild, it can easily sustain 30-40psi of boost for extended horsepower and torque.
5. Having 5500 psi fuel pressure in engine fuel lines is not a problem at GM look at fuel pressure levels in LT5 and Duramax diesels.

Just saying I think a few on here should take a more complementary view point with new engine technology, especially when it comes from a company like GM with incredible engine platform success it has had in the last 20 years or so!

I agree with Hoffan900 here:

WE SHOULD DO MORE HAILING AND LESS BAILING!

JMHO

Wasn't it you that just said these company's are all about propaganda and money?

[Bazman]

This is Mercury Marines DOHC LS7 base engine conversion. Cool looking power plant BUT:

Been available for about 4 years now. Has not been accepted well in the marine trades or aftermarket performance markets.

Way to expensive! Can't remember exactly but I think they are priced at about $75,000. Won't come close to meeting current emissions standards. Does not have great horsepower per cubic inch production versus just some stock GM LSX and LSA engines

Mercury was trying to work off some of the racing success of their big QV$4 1350-1650HP offshore racing engines which use the same DOHC cylinder head technology . They sell for about $225,000 a pop!

I think it's pretty much an abject failure for Mercury Marine and it will probably disappear shortly if it has already not.

At $75k I'd agree with you... however they only sell for $33k turn key with a tuned ECU and accessories! They were under $30k for the engine alone. They've sold quite a few, and it'd be an real shame if it were not a profitable success!

Yes, you could likely build an NA LS7 OHV that made 750hp for under $30k (including buying the LS7) BUT it won't be anything like this, and it won't come with a manufacturer's 1 year warranty, and frankly, there'd be very few engine builders that could build an engine as good as this for under 30k that would run to 8000rpm and be used daily. No doubt there's a handful in here that could sell and make a profit at $30k something that would compete - but I bet it needs more maintenance being OHV at 8000rpm. My 2 cents, and glad to be proven wrong

A blueprinted/massaged one of these would easily make 800hp. I think they're very cool and reasonably priced for the exotic piece they are. I'd buy one myself if I had a spare 30k laying under the mattress

[Bazman]

Back on topic: the new 4.2 DOHC TT has a flat plane crank.... listen to it here

https://www.lsxmag.com/news/corvette-c8 ... -at-night/

Sounds good, but not as good as the ZR1 imo, perhaps the final version will have more bass

[mk e]

Back on topic: the new 4.2 DOHC TT has a flat plane crank.... listen to it here

https://www.lsxmag.com/news/corvette-c8 ... -at-night/

Sounds good, but not as good as the ZR1 imo, perhaps the final version will have more bass

I think that tells us for sure that there are 2 versions of the engine, Caddy and vette.

That thing seems to be revving well past the 5500rpm caddy spec and a flat crank makes sense in a vette designed to compete with Ferrari, not sure the caddy version would have that and the vibration it brings.....Ferrari builds a 90 degree crank version for the Maserati line.

[Newold1]

Bazman

Thanks for the update on that Mercury Marine DOHC LS7 engine pricing. When they were first released a few years back they were being quoted as $75K in some articles. $33K is not cheap but I wonder if Mercury Marine is just possibly getting rid of previously built inventory. Yes, I am sure it could exceed 800HP with some tweaking and for sure turbo upgrades but that would seriously push the pricing into the stratosphere,

Thank you also for the 4.2L TT flat plain crankshaft info. See, I had not idea the engine was so designed or equipped. We all learn dailey here on Speedtalk.

[Truckedup]

Mercury Marine designed and or built the DOHC V8 in the earlier ZR1 Vettes? Do you think they have a hand on the new engine?

[Bazman]

Bazman

Thanks for the update on that Mercury Marine DOHC LS7 engine pricing. When they were first released a few years back they were being quoted as $75K in some articles. $33K is not cheap but I wonder if Mercury Marine is just possibly getting rid of previously built inventory. Yes, I am sure it could exceed 800HP with some tweaking and for sure turbo upgrades but that would seriously push the pricing into the stratosphere,

Thank you also for the 4.2L TT flat plain crankshaft info. See, I had not idea the engine was so designed or equipped. We all learn dailey here on Speedtalk.

All good, I've enjoyed many of your posts and learned a lot.

Yes $33k is a lot, but it's actually good value imo. I can recall back in the 90's a really good race engine was $50k back then, but nobody I knew in the 90's was making 750hp NA that could drive daily on pump gas, last ...and do it on a cheap budget.

Even today, at 750hp NA stuff gets serious if we want durability. Cheapest way would be to buy a used NASACR and refresh it - but it'd hardly be maintenance free or daily driver friendly lol

e.g. CNC Motorsport do a 700hp pump gas LS441 for around $20k (but unlike the SB4 that excludes accessories). To handle the abuse the SB4 7.0 can and get the added 50hp while retaining street manners - that price could double without a blink.

What do you guys think? How much to build a 750hp 8000rpm daily driver.... and yeah, it has to be NA and go a year between resetting tappets and checking the springs... and what platform would you use? I'd be thinking something like a 4.5" bore short stroke Hemi just because they're strong

[Bazman]

Mercury Marine designed and or built the DOHC V8 in the earlier ZR1 Vettes? Do you think they have a hand on the new engine?

Lotus (UK) designed the 32V ZR1, and Mercury built them. I'd say Mercury learned a lot from that partnership. Lotus was at that time one of the more famous Formula One brands.

Another reason why I feel that the Mercury Marine quad cam engines will be well designed. Also, if you want to see if your engine will blow up - put it in a boat.

[Newold1]

I have spent many years building and upgrading marine offshore endurance engines and also spent a lot of time and frustration trying to keep them running more than one race or outting. The biggest thing I learned right along with manufacturers and builders like Mercury and some others was that if you want to find out what you are doing WRONG with an engine and its build and components, put in in a boat in a racing and endurance application. When it comes back broken or in a basket you quickly see and analyse what went wrong. You usually do this many multiple times before you get a real endurance piece that stays together for at least one race and can be replicated for subsequent builds! Once you get to this point you can actually start adding more power and performance until you get to that very quick result of breakage and you end up starting all over again!

If Mercury and other good marine endurance engine builders do this well it's because they went thru the "walking on hot coals" adventure I described above!