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311 Engine Upgrades

Old 08-14-2020, 09:41 AM
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Default 311 Engine Upgrades

The year 2020 has sucked. Period. The end. I’ve only been out on the 311 once earlier this summer because of a exhaust valve problem... long story short... heads decked one too many times causing the valves to hang open just enough to cause reversion. The #7 exhaust valve on the port engine ended up being toast. I don’t like working on the engines in the boat so they’re coming out, And since I have these nice AFR heads and Crane cams etc sitting around collecting dust, I figure it’s time to start making some changes.

Heads are being taken down to 114cc to bring compressing up to approximately 9.25. I’ll be using 621 cams that at first may seem rather conservative but with the flow of the heads should act a lot bigger. I’ll be using Merlin intakes with Mighty Demon 850s.

I’m trying to get the fuel system figured out. My 502s have no provisions for mechanical pumps so everything will be electric. I thought about using a water pump with the mechanical pump provision but there isn’t any room unless I change the pulley configuration (something I really don’t want to do). My question... where to mount the pumps? I’m thinking the only spot available is on the inside of the stringers opposite the sea strainers. I had also thought that maybe I could modify the MPI fuel systems to work but I don’t have a pump curve for the factory pumps and it seems like it would be easier to just run some Mallory Comp 140s. Does anyone know what the fuel pickups in the tank will support or will I need new pickups? I was thinking -8 AN for the entire system.

The goal is 600 hp... should be pretty easy to get there and be reliable at only 1.2 HP per CID. The engines should come out next week barring any weather issues.

Last edited by TomZ; 08-14-2020 at 09:43 AM.
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Old 08-14-2020, 10:42 AM
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Good luck with the upgrades Tom. That old girl will run really well. Very similar setup that we had in the Monkey...sort of
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Old 08-14-2020, 10:50 AM
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Thanks Chris! Iím looking forward to next season. Hope youíre well!
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Old 08-14-2020, 12:10 PM
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Good Luck and keep us posted on the technicals and progress.
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Old 08-14-2020, 12:44 PM
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Thanks Tom!

Howís your 311 making out? Enjoying the Gulf?
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Old 08-14-2020, 12:48 PM
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Sounds like some pretty decent upgrades Tom. I think itís safe to say this year has sucked in many ways. But when your motors are done atleast youíll be fresh
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Old 08-14-2020, 01:46 PM
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Originally Posted by TomZ View Post
Thanks Tom!

Howís your 311 making out? Enjoying the Gulf?
Faster than I expected...78 mph gps (2 people 3/4 fuel light chop) with the "economy" 4 blade props. I have not even tried the top speed 3 blader's.
Starboard Bravo seems to shift hard in reverse (when warmed up) but I think its the linkage/cable...as lubricant looks clean and no water.
Dock space is available!
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Old 08-15-2020, 08:59 AM
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Tom, I always hate to hear about engine trouble. But it seems like you have a solid plan to make an improvement. That big girl is going to be breaking the 80s when you are done.
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Old 08-15-2020, 09:50 AM
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Thanks Hunter. Weíll see what happens. Iím eager to start the work but of course now it looks like rain for days lol. Figures. In addition to the engine work, Iím also going to tidy-up the bilge as well as paint. The battleship gray has never been a favorite for me. Iím also going to get rid of the ďtrailer-styleĒ harness connections that are buried in the wiring. Iíll probably use ring terminals and junction blocks as replacements. Itíll be nice looking, functional, and remove some of the little electrical gremlins that seem to pop up over winterís layup. while out, the transmissions will get some love too with rebuild with extra plates and a new damper for the starboard engine (port was done last year).

Itíll all be a project and a half but what else is there to do right now?!
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Old 08-15-2020, 10:37 AM
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We just got rid of our 27 contender and picked up a 31 with a blown hpdi on the starboard. Got it all re wired, sound system, plotters, radar, all the stuff done. Waiting on machine shop to finish sleeving the block. We decided to take it to the creek on 1 engine.

You still have 1 good 500hp engine. She should make it on plane with that lol
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