Reversion (again)
 

Can someone give me the magical cut off point at which the duration of the valves and their overlap (in degrees) at which reversion can be eliminated?

My engine builder and I are butting heads over this. His contention is that their is NO magical figure (ie 110 degrees of overlap vs. 114) and all cams have reversion, it is just a matter of how much. I do respect his years of experience but need others input here.

My stellings exhaust exits under a swim platform and I am sucking water back in when idling around the docks. No reversion running on hose on the trailer.

Re: Reversion (again)
 

one other item that can help is idle speed, the faster the idle the less water you will ingest, also a cam with a wide lobe seperation angle will work better[114degree's] now a cam ground on a 108 lobe seperation might make a little more power it will have more overlap, causing more water ingestion, duration of about 255degrees at .050 lift is starting to push a wet exhaust system a bit, good luck i'm sure someone else with more info than I have will help out soon
Mark R

Re: Reversion (again)
 

Interestingly enough with my stock 350 Magnums which have a 'moderate cam" in the oil samples I sent in a couple times after 25 hours the samples always came back negative on water content.

Sending in an oil sample is a pretty good idea. There are several places that do this; mine were done at Blackstone Labs.

Reversion has kept me from hot-rodding my engines. I don't think all engines have reversioin problems continually; though if the circumstances are right anything is possible.

Re: Reversion (again)
 

2112 give me some info on your package . so i can help you CMS Racing engines P4-5

Re: Reversion (again)
 

Thanks, I am resigned to making new tailpipes at this point.


Bore= 4.625"
Stroke= 4.5"
Compression 9.0:1
Flow intake 480 cfm at 28 inches
Flow exhaust 366 cfm at 28 inches
Intake valve 2.45"
exhaust Valve 2.02"

Cam specs
INTAKE EXHAUST
Duration @ .050 270 280
lobe separation 110 degrees
Seat duration @ .020 304 324
Gross lift .722 .722

Rocker ratio 1.73

Exhaust exitsunder the swim platform, there is a recess underneath near the transom, Pipes used to come out 6 inches but I had them shortened to only 1.5 inches past the transom. The boat sits very low in the water. the platform is right at water level. two pics to show how the exhaust is routed.

The pipes are not in the water but they stir things up when idling.

Re: Reversion (again)
 

Something compressed my outline

Cam specs
INTAKE Duration @ .050 270
Exhaust duration @ .050 280
Lobe separation 110 degrees
Gross Valve lift for both .722"
Seat duration @ .020 304 degrees for Intake 314 degrees exhaust

Re: Reversion (again)
 

Be careful in thinking you have reversion until you check a couple of things such as the amount of drop you have in the system because ive seen instances were the boats were rigged from the factory with the exits real close to the water line and the water will actually come up the pipes during launching and you may get moisture in the engine that way Reguardless i believe the cams are big and the lobe sep. would benefit being slightly wider but check several things before you go to new pipes. The engines look great and Im sure your engine builder did a good job.Good luck Laz Mesa PS do you have water in the oil by any chance

Re: Reversion (again)
 

Yes, water in the oil is the problem.

I utilized the factory exhaust hole when having the custom exhaust made. I have flappers on them now.

I have also pressure tested the engine's cooling systems and oil cooler. the Engines will hold 25 lbs for about 20 minutes and then loose about 1 pound per hour for the next 12 hours.

Re: Reversion (again)
 

If you loosen the connection between the tailpipes and the header pipes water will pour out while the engines are running. With those cam specs, unless you run dry exhaust, I would guess reversion. I had mine welded closed except for two small holes to cool the tips and mufflers and dumped the rest overboard.

Re: Reversion (again)
 

pressure test the exhaust itself.
Good luck.

Re: Reversion (again)
 

Did that too. No leaks

Guess what I am looking for is the magical lobe separation (mistakenly referred to as overlap in post #1) that may make a monumental change in the reversion. Maybe one of you has solved this same problem by doing this since I know many have utilized the same factory exhaust location that I did.

As I said, The engine builder said I could not get enough separation to solve this dilemma and need to get the tailpipes up and out of the water.

Re: Reversion (again)
 

PatriYacht has the right idea. I did roughly the same thing to my boat and have no problems.

Re: Reversion (again)
 

2112 you should covert to dry exhaust and the cam is a little to big if you want valve spring life and help stop reverision . i would use something around 254 to 258 intkand 260 to 266 at .050 and 112.lsa. I have a race boat with 515ci. engine dry exhaust that exit about 14* above water and the cam is only 242. intk and 248 exh 110 lsa. and you can watch the water trying to revert. the water exits out side the pipe.
food for thought

Re: Reversion (again)
 

Yup, I did the same.

Re: Reversion (again)
 

I am jacketed all the way to the end. 99% of the water dumps out the transom, each pipe has a 1/8th inch hole at the very end to keep the muffler/flapper wet.

Re: Reversion (again)
 

Yikes. I thought all of your water was going out the tailpipe.

Re: Reversion (again)
 

2112
Given that you boat in fairly cool water, your problem may be condensation. Do you run oil temp guage or oil thermostat?

Re: Reversion (again)
 

2112:
Your motors are obviously big block Fords and with those big flow numbers, big valve sizes and and your cam numbers your overlap number is big, which all equates to very slow mixture speeds at idle. Even with low water flow on the system, your exhaust outlet height coupled with the above will be a high reversion canidate even if you widen the LSA 4 or so degrees. The bigport Ford heads are not known for great velocity under these conditions so your motors must be set up for a high 6000rpm + range to need duration numbers like those. You are probably going to have to re-route you exhaust outlets higher, maybe to the corners to stay away from reversion unless you do a moderate size cam change. Those are some nice lookin Fords, What kind of power did they dyno and where is the rev limiter?
Raylar

Re: Reversion (again)
 

Yes I have an oil thermostat That routes the oil through huge teague coolers.

Raylar; The engines were set up for high rpm the make 820 pounds of torque at 5200 and 870 horses at 6600, Runs a single 1250 dominator Rev limiter is set at 7000.

I think with all else, the cam change might not be enough.

Re: Reversion (again)
 

The exhaust is as high as I can go underneath the platform. Anything higher has to go over the platform.

Re: Reversion (again)
 

Unless you could have a fiberglass man do some creative rework above the step it would probably be messy and dangerous. Patriyachts idea seems like a simpler -lower cost option and might take care of the reversion. Your boat has an awesome setup and those rpms and torque numbers are fantastic for a carbuerated motors. I just wonder how long those bravos can take those kind of torque and rpm numbers?
Raylar

Re: Reversion (again)
 

Bravo's were are very heavily modified with every trick possible.

I am not afraid to mod the fiberglass, I have already had to redo vast amounts of poor glasswork from the factory (I special ordered the boat new).

Patriyacht's suggestion was predicated on all that water being dumped into the tailpipes which it is not. They are dry to the end with 1/8th inch holes at the very end to moisten the flappers.

Re: Reversion (again)
 

The reason I asked, I have a 509 with a big cam and jacketed exhaust down to the point they exit under the swim step, exhaust under water at idle. leak tested the engine and exhaust manifolds. still had scum under the valve covers. I installed flappers in exhaust with no change. During rebuild i installed 2 panavac crankcase vent system, one off each valve cover. Still had scum under valve cover even with 230-240 oil temps. We blocked off 1 panavac and connected hose into air cleaner from one valve cover. Left the other operational, my oil and valve covers cleaned up in 1, 1 hour run. (panavac uses exhaust gas velocity to create suction on crankcase)

Mark

Re: Reversion (again)
 

I'm not familiar with the Ford cam situation, but those numbers on a big Chevy would suck the water bottles off the shelf of the nearest 7-11.

Re: Reversion (again)
 

Motors are of course all air pumps. I have always run big Fords with huge cams but this is the first time I have had exhaust run under the platform.

These are 605 inch motors, Essentially the same as a tall deck chev with Pontiac Big Chief heads, with that in mind, is there a cam profile that won't suck the water off the 7-11 shelves?

Re: Reversion (again)
 

With a dry-all-the-way-to-the-end header and your port separation angle, I'd say about 255 exhaust.

Re: Reversion (again)
 

Call Laz at

www.mesabalancing.com

Trust me this guy will help you to the tee.

Re: Reversion (again)
 

Fords... :D:D

Re: Reversion (again)
 

There are beautiful air pumps and not so beautiful air pumps.

I chose the former, not the latter. :D:D: