7.4 /454 Gen VI identification

[Maarten]

Hi all, this is Maarten from Amsterdam. I own a Cobalt 223 7.4 330 Bravo1 an a lot of bbl parts. Can someone help me identifying the pistons, heads and injection system on the attached photos? The engine block casting number says Gen VI Vortec but has been modified by a previous owner.

Thanks for your help, Maarten

 

[alldodge]

Welcome
The intake most likely came off a Merc 525. Look for the block casting number on the rear deck of the block just below the distributor

The motor has 502 heads, look around the rockers for a casting number and last 3 digits might be 088

 

[Scott Danforth]

The motor is a lot more HP than the 330 HP L29

Measure the bore. 4.250-4.313 is a 454. 4.470-4.500 is a 502

The pistons are not flat tops, however domed, so the compression ratio is most likely 10:1 or more

 

[Maarten]

Many thanks for your help guys, this is inline with what I thought. For the avoidance of doubt: This is not the "7.4 330" that is currently in my semi classic cobalt.

I want to build a new engine for it with forged internals. I think what I show in the pictures above could be a good starting point although it still needs quite some bits and pieces (and love & devotion) before it will be nicely realiable running engine. And then see if I can get it intune with that manifold and custom made EFI.

Will keep you posted if / once I start this project.

Any more thoughts are very welcome!

Here is the Cobalt:

 

[Scott Danforth]

The compression ratio needs to be seriously looked at for a marine build. Forged internals generally not needed unless running WOT for a really long time. A full neutral balance rotating assembly will do more to keep the motor together

 

[Maarten]

Thanks for that Scott, could you indicate why specifically in a marine application we have to be carefull with high compression ratios? We can get 98 fuel everywhere and 100 or 102 at places.
I understand what you say about forged/casted internals, I don't want to spend crazy money and looking for ~=425 HP. I want to use as much as possible what I have laying around.

 

[Bondo]

Ayuh,...... Welcome Aboard,....... Even with high octane gas detonation is a concern,......
Going to aluminum heads, you can go abit higher compression,....
Vortec heads are better that other older styles, if you stick with cast iron,....
Of course, aluminum fast-burn vortec style heads will give you the best bet, with higher compression levels,....

 

[Scott Danforth]

I don't want to spend crazy money and looking for ~=425 HP. I want to use as much as possible what I have laying around.

That motor in the pics is already build well over 425hp

Measure the bore to see what you have

Post the head casting numbers as AD asked in post #2

 

[Maarten]

Once I have the casting numbers, I will post them here.

M

 

[Maarten]

Once I have the casting numbers, I will post them here.

Head casting numbers are 14097088.
Bore diameter corresponds to the 454. Block casting is 10237297 (Gen VI 454)

 

[alldodge]

Thanks
Someone built a 454 mag (block, 502 heads, 525 intake), but may also have pushed power above 385HP.

Figure out what the cam specs are to determine if reversion is a possibility

 

[Maarten]

There may even be a stroker kit in it? Next time I am near the engine I will check stroke and camshaft.

 

[alldodge]

The number stamped on the piston might be enough info to determine what the specs are
The ECM did come with the motor, right?

 

[Scott Danforth]

the cylinder heads are standard 118cc open chambers. the pistons look to be 20 to 30 cc domes.

assuming a .030 overbore. the compression ratio is in the 9.6-10.5 range. which is pushing it with iron heads unless you run high octane.

 

[Maarten]

The number stamped on the piston might be enough info to determine what the specs are
The ECM did come with the motor, right?

I have the ECM, fuel rails, injectors, loom etc.
I will post the numbers on the piston after I have been near the engine.

 

[Maarten]

the cylinder heads are standard 118cc open chambers. the pistons look to be 20 to 30 cc domes.

assuming a .030 overbore. the compression ratio is in the 9.6-10.5 range. which is pushing it with iron heads unless you run high octane.

I run my engines always at 98 octane. Have access to 100 and 102 as well but don't think that would be necessary.
I might go for a milder cam (if there is a wild one mounted currently) to not generate to much heat for the cast iron heads (and I don't need any more then 425 max).

 

[alldodge]

High octane burns slower then low. Running a motor with high when built for low just reduces the amount of available HP

With marine motors reversion is key. Need to know the lobe separation and amount of overlap to determine how much protection is needeed

 

[Maarten]

High octane burns slower then low. Running a motor with high when built for low just reduces the amount of available HP

With marine motors reversion is key. Need to know the lobe separation and amount of overlap to determine how much protection is needeed

Reversion is indeed something to investigate since I do not know what exhaust system the engine has been running.

Thanks again (@all) for your responses, it is very helpful!

 

[Scott Danforth]

98 RON is basically similar to 93 R+M/2 here in the US

AD is correct on checking the cam.

 

[Maarten]

98 RON is basically similar to 93 R+M/2 here in the US

I learn from every message on this forum!