What Determines MAX WOT Engine mechanical or Electronics?

[84EdH]

I have a 1998 5.7 vortec block with a high rise cast iron manifold and edelbrock carb. The ignition, engine peripherals, are from a 1995 Alpha 1 engine. The sticker on the 1995 flame arrestor cover has specs that includes "4200 to 4600 MAX WOT".

My question is does the newer vortec engine with roller cam change what the max wot numbers are, or is that determined by the ignition?

help appreciated!

 

[matt167]

Re: What Determines MAX WOT Engine mechanical or Electronics?

Camshaft makes a big difference in the actual engine max RPM. Roller cam's can use hotter profiles and rev higher without valve float using higher spring pressures. However, most SBC's are good to at least 5k, so your RPM limit is likely the recomendation/ max that Merc put fourth on the outdrive

 

[Don S]

Re: What Determines MAX WOT Engine mechanical or Electronics?

Flat lifters normally have the 4200 to 4600 rpm range, Roller lifters have 4400 to 4800. There are exceptions to both.
This holds true with Mercruiser, Volvo, OMC, Marine Power, PCM ect. Probably came from GM

 

[QC]

Re: What Determines MAX WOT Engine mechanical or Electronics?

Your question tells me that there may be something missing. Do you mean what determines, or actually governs max RPM? Or are you asking what determines the WOT range?

The range is determined by the mechanical combination and where the resulting horsepower is achieved from that combination. The MAX safe RPM is usually about the camshaft and valve train combo as noted. It is often limited by ignition if you are talking about a rev limiter.

 

[Don S]

Re: What Determines MAX WOT Engine mechanical or Electronics?

The rev limiter prevents you from going too far past the max WOT rpm,
The engine manufacture determines the max WOT range for a given engine.
The gear ratio in the drive and prop size and pitch is what is used to adjust the WOT rpm to keep it in the proper range.

 

[84EdH]

Re: What Determines MAX WOT Engine mechanical or Electronics?

I understand the prop selection and your intended use of the boat, (mixed cruising, water ski, tubing for myself), to keep RPM within OEM specs. This long block was purchased from an out of business OMC Dealer, so was built and intended for marine use. I think what Don suggests is the reasonable approach. 200 more rpm seems reasonable. I am not looking to break any records. I will be going through a prop selection process and was most interested in an RPM range to use as MAX for prop calculations.

thanks all for your help!

 

[Don S]

Re: What Determines MAX WOT Engine mechanical or Electronics?

If it's a roller lifters, go for 4800 max, if flat lifter go with 4600.

 

[84EdH]

Re: What Determines MAX WOT Engine mechanical or Electronics?

It is definetly roller lifters.

thanks again Don !