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7.4L, help with fuel injectors

carboncow

Contributing Member
So I bought a new long block and didn't put new injectors in it. I believe we have one bad injector and the rest are tired. Boat mechanic buddy did quick night run with me and things I'm onto something with the old injectors. Although we are going todo a compression test next week due to the intermittent behavior that cylinder has we believe the issue are the old injectors vs a bad valve or such. Spark is good.

Here is what I need...

Not going to buy OEM Volvo Penta injectors due to price. I've been told by my mechanic buddy that he believes OEM GM big block injectors for the 7.4L injector (L29) should be interchangeable but having trouble crossing referencing this.

I see some people stating 19lbs, 20lbs, 24lbs and even 30lbs which I assume is high performance...can anyone confirm the need and/or if the GM style for trucks will do?

1997 Vortex (Roller cam) 7.4L fuel injected. L29 engine

Long block was rates at approx,. 330-340HP.
 
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Bosch Ref # 0 280 156 081
Mercruiser Ref # 885176
Volvo Penta Ref # 12567905
Mallory Ref # 9-33102

When I punch these number in most suppliers never list the 7.4? Sees only 4.3 up thru small blocks. Assuming they all are the same and fit are these lower HP engines on lower lbs rating?

I'm still green here on understanding injectors so I understand I could be totally wrong but the last dozen listings I look up...and not once has mentioned 7.4L in their listing.

As shown here against the Volvo #: https://www.amazon.com/0280156081-12567905-Injector-Marine-Mercruiser/dp/B0875FRJ8M (I know the are most likely china brands).
 
you want to match the injector number to what you have now...injectors are rated to provide a given flow (product) with a given input pressure...and everybody does it a little bit differently.

You likely won't find a 7.4L application as they haven't made 'new' ones in years....

I would suggest you don't buy off brand injectors...many times, getting a set cleaned and checked is better in the long run...
 
you want to match the injector number to what you have now...injectors are rated to provide a given flow (product) with a given input pressure...and everybody does it a little bit differently.

You likely won't find a 7.4L application as they haven't made 'new' ones in years....

I would suggest you don't buy off brand injectors...many times, getting a set cleaned and checked is better in the long run...

Thanks...off brand is off my list. Bosch seems to come up a lot. The boat is not going to be pulled apart for a couple of weeks so I really cannot get to the part number off them. So you are saying there is no really sure way to know the need w/o that very unique number?

Interestingly I cannot even find injectors on V/P parts lists...not sure what they heck they got them under. Not that would help much as we never could figure out the exact code for that engine. Never found a V/P info plate on the 23 year old boat.
 
.... So you are saying there is no really sure way to know the need w/o that very unique number? ....
That's the best way...

the OEM takes the flow data from the injector's data sheet and sets up there fuel map accordingly...so matching what you have will give you the 'designed performance'....

Now, you can go and customize the tune in the computer and put what ever injectors you want....but that can get expensive (time & money) real fast....just my 2 ₵
 
That's the best way...

the OEM takes the flow data from the injector's data sheet and sets up there fuel map accordingly...so matching what you have will give you the 'designed performance'....

Now, you can go and customize the tune in the computer and put what ever injectors you want....but that can get expensive (time & money) real fast....just my 2 ₵

OK, had time to pull the intake in the parking lot at the canvas shop while I wait for them to get it in.

Not much for marketing on what I believe to be the OEM 23 year old injectors. They are definitely Rochester which I have been told were leaky junk and the other side had "W 52" on them and google'ing has little help in confirming the need.

Best I can tell from my way to much browsing is the 7.4L L29 engine was a 19lb injector 96-97 and may be a 24lb from 98-00 both at approx. 12 ohm's.

The real question is finding out which ones have the right physical shape...and if anyone can provide guidance. Photos attached. Note 6 hole pattern too.

Thanks for anyones input.

IMG_6206.jpeg IMG_6214.jpeg IMG_6213.jpeg
 
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