Go Back  Offshoreonly.com > Owners Forum > Formula
311 Engine Upgrades >

311 Engine Upgrades

Notices

311 Engine Upgrades

Old 10-09-2020, 12:31 PM
  #61  
VIP Member
VIP Member
Thread Starter
 
TomZ's Avatar
 
Join Date: Feb 2001
Location: Virginia Beach, VA
Posts: 2,559
Received 206 Likes on 150 Posts
Default

Originally Posted by Unlimited jd View Post
9.5:1 is really pushing it with 87 octane without knock sensors and efi
you need to pick pistons before youíll know what the deck height will be, and final compression ratio
dont drain youíre headers until they have cooled down. The water will pull the heat out long after shut down and insulate the outer tube. Dump the water once after running and see how hot the tubes get while sitting. That heat cycling is way worse for the headers. Draining them when shutting off should only be done if you realize you have a leak and donít want the water draining into a cylinder.
You're right about figuring final compression. I'll know more once parts are all together. Would 9.5 and 87 really push it with aluminum heads?

On the header dumps I hear what you're saying. I had considered this but thought (assumed) that with others doing similar this wasn't an issue. I'll need to rethink that a little more. Maybe a much smaller restriction to slowly drain the water? I'm not concerned with leaks since really checking them over, but I had a good amount of water that seemed to make it into the rear ports. I was thinking draining would also limit condensation. I'm open to any and all suggestions on how to go after this the right way.
TomZ is offline  
Old 10-09-2020, 12:46 PM
  #62  
VIP Member
VIP Member
Thread Starter
 
TomZ's Avatar
 
Join Date: Feb 2001
Location: Virginia Beach, VA
Posts: 2,559
Received 206 Likes on 150 Posts
Default

Originally Posted by hogie roll View Post
Not seeing 169621 in the catalog. Do you mean 721? 500efi was a 731 I thought.
721 214/220 .553/.564
731 226-236 .587/.610
741 236-244 .610/.632

731->741 was worth 25hp or 5% at least for Merc. A 721 would give up a lot.

Are your heads full CNC chamber? Getting some duration over .600” lift would appear to be worth a lot of power. Probably 30hp at least going from .550-.600 on its own.
The cam is the one spec'd for the 500 EFI and it's not in the catalog. Grind number is HR-292-2S-14 IG, .598/.610, 230/236 @ 050, 114 LSA. I will probably run this with a 1.8 rocker on the intakes to help get the exhaust in-line some (so lift would be .633 on the intake). Mine have the tulip-Inconel option so the exhaust port will be very aggressive and potentially over-scavenge. Boosting the intake side would help to get after this. From everything I've read, this is a good direction with that head and really close in terms of the recommended split in duration. I know others here have done similar.

The heads are as-cast with whatever CNC work AFR does to them prior to the full CNC option. They would fall under the partial CNC flow sheets though I think the exhaust flows more because of the valves.

Last edited by TomZ; 10-09-2020 at 02:26 PM. Reason: clarification
TomZ is offline  
Old 10-09-2020, 12:59 PM
  #63  
Gold Member
Gold Member
 
badmonkey's Avatar
 
Join Date: Sep 2012
Location: Maryland
Posts: 1,884
Received 159 Likes on 84 Posts
Default

[QUOTE=TomZ;4760964]You're right about figuring final compression. I'll know more once parts are all together. Would 9.5 and 87 really push it with aluminum heads?

Tom, The motors we built for the Monkey were 9:5 with 335 AFR aluminum heads.....I had to run 93 octane fuel...She did not like 87 at all
badmonkey is offline  
Old 10-09-2020, 01:03 PM
  #64  
VIP Member
VIP Member
Thread Starter
 
TomZ's Avatar
 
Join Date: Feb 2001
Location: Virginia Beach, VA
Posts: 2,559
Received 206 Likes on 150 Posts
Default

[QUOTE=badmonkey;4760970]
Originally Posted by TomZ View Post
You're right about figuring final compression. I'll know more once parts are all together. Would 9.5 and 87 really push it with aluminum heads?

Tom, The motors we built for the Monkey were 9:5 with 335 AFR aluminum heads.....I had to run 93 octane fuel...She did not like 87 at all
Thanks Chris. If I have to run better fuel that's okay with me. My only concern is finding it. The place I keep the boat in the summer has 93.

What's the cutoff point with octane and aluminum heads? 9.25? 9.0?
TomZ is offline  
Old 10-10-2020, 07:49 AM
  #65  
Gold Member
Gold Member
 
badmonkey's Avatar
 
Join Date: Sep 2012
Location: Maryland
Posts: 1,884
Received 159 Likes on 84 Posts
Default

[QUOTE=TomZ;4760972]
Originally Posted by badmonkey View Post

Thanks Chris. If I have to run better fuel that's okay with me. My only concern is finding it. The place I keep the boat in the summer has 93.

What's the cutoff point with octane and aluminum heads? 9.25? 9.0?
Do not exceed 9.0 is my opinion. Iím sure others may feel differently however.
badmonkey is offline  
Old 10-11-2020, 08:58 AM
  #66  
Registered
iTrader: (1)
 
Join Date: Apr 2014
Location: North Florida
Posts: 610
Received 85 Likes on 38 Posts
Default

Even at zero you will need 4 cc of dome to get to 9:1 with a 121 cc chamber and a 040 mls gasket. If my math is right. These Wiseco pistons should be close with a 3.8 dome. Part no. PT077H3. Sorry for not having a link. If you go to 4.25 stroke, a flat top will get you a perfect 9.1-9.2 ha ha. It’s only money. Good luck Tom
ph1971 is offline  
Old 10-11-2020, 02:22 PM
  #67  
VIP Member
VIP Member
Thread Starter
 
TomZ's Avatar
 
Join Date: Feb 2001
Location: Virginia Beach, VA
Posts: 2,559
Received 206 Likes on 150 Posts
Default

Originally Posted by ph1971 View Post
Even at zero you will need 4 cc of dome to get to 9:1 with a 121 cc chamber and a 040 mls gasket. If my math is right. These Wiseco pistons should be close with a 3.8 dome. Part no. PT077H3. Sorry for not having a link. If you go to 4.25 stroke, a flat top will get you a perfect 9.1-9.2 ha ha. Itís only money. Good luck Tom
Thanks Roscoe. I believe my heads are 118 maybe a touch under. They need to be surfaced to take care of some corrosion spots because of running on GEN VI blocks with open cooling I was going to take them down to 114 to work with the original pistons per the original plan, but since the one piston messed up and required some boring to fix, I got it in my head to Go higher with the compression, etc. Iím still working on the final configuration.

Iím open to any and all suggestions on this so please keep them coming!
TomZ is offline  
Old 10-11-2020, 02:58 PM
  #68  
VIP Member
VIP Member
Thread Starter
 
TomZ's Avatar
 
Join Date: Feb 2001
Location: Virginia Beach, VA
Posts: 2,559
Received 206 Likes on 150 Posts
Default

My initial rough math based on having the block decked to zero or close to (.001-.002, weíre not final just yet... it may need a touch more than that), using a SRP replacement piston (1cc dome), 039 gasket (FelPro 17048), and the 118 head was putting me at about 9.2. Taking the heads to 114 would put me at 9.4 and change.

Final numbers will be figured out once I have all the measurements in-hand.

Last edited by TomZ; 10-11-2020 at 06:26 PM.
TomZ is offline  
The following users liked this post:
ph1971 (10-11-2020)
Old 10-11-2020, 06:29 PM
  #69  
VIP Member
VIP Member
Thread Starter
 
TomZ's Avatar
 
Join Date: Feb 2001
Location: Virginia Beach, VA
Posts: 2,559
Received 206 Likes on 150 Posts
Default

Any thoughts on my idea of bumping up the intake side with a ratio change? If I go to a 1.75 Crower rocker, I would be at .616/.610 and probably close the duration spread to 232/236 @ 050 (or 231/236).

Last edited by TomZ; 10-12-2020 at 07:53 AM. Reason: I really hate autocorrect.
TomZ is offline  
Old 10-12-2020, 08:14 PM
  #70  
Registered
iTrader: (1)
 
Join Date: Apr 2014
Location: North Florida
Posts: 610
Received 85 Likes on 38 Posts
Default

Originally Posted by TomZ View Post
Any thoughts on my idea of bumping up the intake side with a ratio change? If I go to a 1.75 Crower rocker, I would be at .616/.610 and probably close the duration spread to 232/236 @ 050 (or 231/236).
I would personally would want dry exhaust to safeguard all of the time and money you will have tied up eventually. Keep posting progress, I can’t wait to see how many prop sizes you have to go up.

Last edited by ph1971; 10-12-2020 at 08:21 PM. Reason: Misread the specs
ph1971 is offline  

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.