cam/exhaust.reversion
 

I am helping my brother get his engine installed and running. He has a Regal Velocity with side exit exhaust that are at the waterline and only in water as waves pass over when idling around. I have been reading these and other forums and am now worried about reversion with the cam/exhaust combo he has. I realize that we are backing into this but hope a riser or exhuast change,if needed, will help us avoid disaster.

Crower cam hydraulic roller
int 583 duration @.050 237* opens 10.5 BTDC
exh 609 duration @.050 245* closes 6.5 ATDC
lobe seraration112*
installed intake centerline 108*

Engine is a 491 cu/in 4.285 bore/4.250 stroke
rods 6.385
Brodix race rite oval ports w/cnc chambers
9.75:1 compression
performer rpm with 1" spacer (I have a merlin single plane if that would be better)
nickerson 850 carb
crane Hi-6 ignition box w/merc dist 14*initial 34* total

Currently using Revolution Marine manifolds and risers.

Is he going to have a reversion problem?

Does anyone know if there are any off the shelf risers available for these manifolds should he need them? (EMI look pretty close) I have included pics ot the exhaust as he does not have a lot of length to work with unless he loses his mufflers or can get risers with built in ones.

Lastly. If he needs to purchase new manifolds/headers what would be the best to use if one did not have unlimited funds.

I doubt you will find any better exhaust that will work with the side exits. Run it and check for reversion at idle.

If it reverts, you could have some custom spacer blocks made to increase the height and angle of the risers.
Other than that, the only other real option is a smaller cam on a 114 lob sep.

I would sell the cam to somone else and call Bob "RMbuilder" and get a custom roller designed for your need. Then you will not have to worry about it.

Griff thanks. That is our current plan. I had a friend make up some 2" spacers so O2 sensors could be installed. Unfortunatley they don't have any wedge in them.

jeffswav thanks. I have read that advice on here and several other posts. My brother is running out of funds as well as the desire to complete (has been appart over 2 years now). I think another engine pull and dissasembly would put him over the edge.

bump

do you have room to raise the riser up ?

So blowing the engine because of reversion would probably put him in a intitution. LOL I think spending the money on the correct cam would be a better choice. I have been thought this before, it will cost a lot more later if you blow it up.

ezstripper
I believe he has enough room for 3" additional riser height. We were thinking a spacer with some wedge and/or longer/taller risers.

jeffswav
I guess the question I should be asking is "will the cam cause so much reversion that a longer riser will not cure it." Don't want to just throw more money at it, but don't want to blow it up either. If nothing short of a cam change will help then that is what will happen. He was thinking of stainless risers anyway, however if the cam has to go that is where the time and money will have to go. Just trying to get some opinions from those that know.
Thanks

If he desides to run it as is, check the oil very often. It will turn it to chocolate milk real quick if you are getting reversion. The berrings usually fry first then it goes down hill from there. I spun a bunch of berrings and broke my crank in 2 peices. I had moisture throughout the engine, mainley under the valve covers.