WOT running time?

[Christopher Gentile]

Okay here is a question in debate!
On a stock 4.3 V6 , what is the recommended running time @ wot 4800rpms on this engine.
Should you run it a burst of 10-12 seconds before bringing it back from the edge, or what.
I have heard that you should not run a 6 cylinder very long at this rpm or you could be asking for trouble in the long haul.

Inquiry minds want to know. Thanks

[Gearhead99]

Most stock motors aren't going to run WOT for long extended runs. They just aren't built for it. How long is tough to say. I don't see where 15-20 seconds is to much.

Never heard about not running a 6 cyl. WOT long. Shouldn't make any difference 4,6,V-8. They are all stock engines.

[MAXCAT]

I work for GM Powertrain in engine development and validation. The specific engine I work on is the 496ci./8.1L engine (a great marine engine you should buy one). We validate our marine engines on what is called the "Dock Test". This test was developed with Mecury Marine to durability test marine engines. The test consists of running the engine at it's WOT rated speed for 55 minutes and idling for five minutes. The test bogey is 300 hours and often times they make it. To sum up, as long as you are not over revving the engine it will last for extended WOT runs.

[RedDog]

This is a GREAT QUESTION topic and I want to follow it more!

All I can add is that I'm sure Genuine Trouble will last at WOT longer than I will :eek: :eek: :eek:

[TORYSMINX]

I had the same setup and I used to run her no problem WOT for 20 or more seconds. I ran it like this for like 100 hrs and changed the oil every 15 hrs. Ran like a champ and no oil burn. Rock on...

[Blewbyu]

I had a 3.5 Litre BMW 220 in my old Glassply/Donzi (long story).Ran it all the time @6000 RPM.It was an inline 6.Smooth as silk.Still strong @3000 hrs.
The other beast tho- the V-6,has a natural harmonic IMBALANCE.I ain't an engineer, but would wind a 4.3 to WOT a whole lot less than a V-8 or inline 6 just because of that imbalance.Some manufacturers are better able to manage the "balancing act" than others,but if for no other reason-save your valvetrain life by holding off on WOT.The marine 4.3 is far superior to the automotive 2.8/4.3 version-a well known "Grenade" motor.

[Tomahawk]

Maxcat - great information and good to know - thanks! BTW - welcome. :)

[HP 600SC]

MAXCAT,
good information! Have the pushrod issues
been resolved on the 496"s

[MAXCAT]

It is funny how word gets around. The issue with the pushrods was one of supplier quality. Strange things happen when you move from experimental parts to production. Yes the issue has been resolved. The parts did not match print specs where the tube necked into the ball. Don't get me wrong an engine running 10 second bursts of WOT will be very reliable, but I think it is a little on the conservative side conpared to our testing. It is a DONZI run it hard and enjoy it.

[Rootsy]

if my memory serves me correctly i believe earlier 4.3's had an issue of breaking crankshafts due to that harmonic imbalance... I believe GM rectified this on later engines, but the imbalance is still more than the V8's

[boxy]

I have over 400 hours (a lot of them at or near WOT) on my 1990 4.3 LX ( Regal Valanti 190) It pulls just as strong now as the day I got it. From my own experience with this motor, I would say that you are good to go at WOT for longer than 10 seconds at a burst. :D

[Gearhead99]

The balance concern with a V-6 vs a V-8, both 90 degree "V". Is that in a 4 cycle engine it takes two complete revolutions to have all the cylinders fire. So on a V-8 you have 8 impulses on two revolutions. This divides evenly with inpulses at the top and bottom of the revolution. On a V-6 the impulses are 6 on two revolutions or 3 for each one. This puts the firing impulses at 120 degree intervels. Makes for shaker engine. A 60 degree V-6 helps some with the vibs. That why V-6's are hard on cranks, etc.

[Sam]

Maxcat, do you work in Warren at the Tech Center ? I am a supplier and am over that way often.

Sam

[MAXCAT]

Hey Sam. Yes, I work at the Powertrain building at the Tech Center. If you are ever in the building look me up. This web site cracks my girfriend up. Everytime there is a new DONZI on our lake (12 DONZIS 270 ACRES - 21 in the heyday) there is a made rush to check it out. She says this website is the same thing on a much larger scale. The imbalance inherent in 90 degree v6 engines is the reason that it has a balance shaft.

Ravi Mathura

[blackhawk]

10-12 seconds? It was my understanding that marine engines were built to withstand extended high rpm runs(as compared to auto engines). Granted, I'm not saying you can run them WOT all the time, but 10-12 seconds seems like a VERY short burst. The 6 vs. 8 cylinder makes sense but I would still think you could run a 4.3 for a lot longer than 1-12 seconds. I have run my 502 WFO for A LOT longer than a few seconds. My friend has a 1996 Four Winns U-19 with a 5.8L EFI and I have been on Lake Michigan with him and we have ran WFO for over 20 miles at 65 mph on several occasions! :eek: Do the math on that one!!!