Hot Rodding an A4 - Page 2 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Gas > Atomic 4
 Not a Member? 


Like Tree6Likes
Reply
 
LinkBack Thread Tools
  #11  
Old 11-03-2011
jay grant's Avatar
Junior Member
 
Join Date: Nov 2011
Posts: 8
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
jay grant is on a distinguished road
Roger that.

This is the 2nd site Ive been on in as many days where some people just like to argue. Dont answer questions directly . Ive been trying to find the owner of an fx-inshore mainsail and gotten feedback on who to vote for and how to name my children. Know what I mean? Your rundown on proper rebuild was spot on.
SloopJonB likes this.
Reply With Quote Quick reply to this message Share with Facebook
  #12  
Old 11-03-2011
tommays's Avatar
Senior Member
 
Join Date: Sep 2008
Posts: 4,282
Thanks: 1
Thanked 29 Times in 29 Posts
Rep Power: 7
tommays will become famous soon enough
It already makes 30 Hp at way to much RPM (3600) to have a long life and you burn a ton of fuel compared to going along at 5.5 knots and 1400 to 1500 RPM as we are pushing displacment hulls

The cam thing is pretty much a no go because any more aggressive grind will cause Water reversation which is and ongoing battle in high performance boats and even low performance motors with waterlift mufflers

The crank is NOT all that strong or well supported
__________________
1970 Cal 29 Sea Fever

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

1981 J24 Tangent 2930
Tommays
Northport NY


If a dirty bottom slows you down what do you think it does to your boat
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #13  
Old 11-03-2011
bljones's Avatar
Senior Member
 
Join Date: Oct 2008
Location: South Coast Ontario
Posts: 8,192
Thanks: 33
Thanked 74 Times in 67 Posts
Rep Power: 8
bljones has a spectacular aura about bljones has a spectacular aura about
Quote:
Originally Posted by RobGallagher View Post
Nothing like a tranny with a good rear end.
__________________
It's 5 o'clock somewhere:


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #14  
Old 11-03-2011
CalebD's Avatar
Tartan 27' owner
 
Join Date: Jan 2008
Location: NYC
Posts: 4,616
Thanks: 4
Thanked 92 Times in 85 Posts
Rep Power: 7
CalebD will become famous soon enough
blj,
I thought about that yesterday but thought I'd wait and see if someone else would take the bait.
If a tranny does not have a good rear end what does he/she have going for them?
__________________
"The cure for anything is salt water~ sweat, tears, or the sea." ~Isak Denesen

Everybody has one:

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #15  
Old 11-03-2011
SloopJonB's Avatar
Senior Moment Member
 
Join Date: Jun 2011
Location: West Vancouver B.C.
Posts: 10,926
Thanks: 58
Thanked 56 Times in 53 Posts
Rep Power: 4
SloopJonB will become famous soon enough
Quote:
Originally Posted by tommays View Post
It already makes 30 Hp at way to much RPM (3600) to have a long life and you burn a ton of fuel compared to going along at 5.5 knots and 1400 to 1500 RPM as we are pushing displacment hulls
I agree, that's what I had in mind about the cam grind - possibly lowering the torque peak RPM. I'd imagine the stock cam is just a "bump stick" without a lot of sophisticated design behind it. A sharp cam grinder can really change the performance characteristics of an engine by playing with the lobe angles, the overlap, the advance or retard of the events etc. They can move the torque peak up and down the RPM range, sacrifice power for torque (which is what really matters in a boat) and so forth. It's not always just about "higher and longer" like it is in most high performance cam applications.

Quote:
The cam thing is pretty much a no go because any more aggressive grind will cause Water reversation which is and ongoing battle in high performance boats and even low performance motors with waterlift mufflers
I don't understand this - does it have something to do with the overlap of the intake and exhaust events?

Quote:
The crank is NOT all that strong or well supported
I've never seen the bottom end of an A4 - is it 3 main bearings?
__________________
I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
Reply With Quote Quick reply to this message Share with Facebook
  #16  
Old 11-03-2011
SloopJonB's Avatar
Senior Moment Member
 
Join Date: Jun 2011
Location: West Vancouver B.C.
Posts: 10,926
Thanks: 58
Thanked 56 Times in 53 Posts
Rep Power: 4
SloopJonB will become famous soon enough
Quote:
Originally Posted by CalebD View Post
blj,
I thought about that yesterday but thought I'd wait and see if someone else would take the bait.
If a tranny does not have a good rear end what does he/she have going for them?
Since we're talking hot rodding - a rigid front end?
__________________
I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
Reply With Quote Quick reply to this message Share with Facebook
  #17  
Old 11-03-2011
tommays's Avatar
Senior Member
 
Join Date: Sep 2008
Posts: 4,282
Thanks: 1
Thanked 29 Times in 29 Posts
Rep Power: 7
tommays will become famous soon enough
Only two bearings with four pistons in the middle


You are pretty limited on any marine inboard with wet exaust the A4 is not as bad because most have a good size dry section

Even the new big outboards have to be carefull about shutting down to drift fish in a big swell as water can reach the lower cylinders as the boat bobs up and down
__________________
1970 Cal 29 Sea Fever

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

1981 J24 Tangent 2930
Tommays
Northport NY


If a dirty bottom slows you down what do you think it does to your boat
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by tommays; 11-03-2011 at 08:44 PM.
Reply With Quote Quick reply to this message Share with Facebook
  #18  
Old 11-04-2011
PaulfromNWOnt's Avatar
Senior Member
 
Join Date: Aug 2010
Location: Fort Frances, ON, CA
Posts: 342
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 5
PaulfromNWOnt is on a distinguished road
Quote:
Originally Posted by Arpegecap View Post
Car engines are designed for light load. Pushing a boat under power is like driving a car uphill forever. That's why automotive engines are "marinized" using heavy duty truck engines. I'd stick with a real marine engine myself.
Prop it, gear it, and govern it. You can tweak the requirements into the entire driveline.

Lemme splain:

Electronically govern the RPM to slightly over half of it's max. Use a reduction transmission to cut the revs to a point where a good prop can make use of them. If you add the right prop into the mix, the engine won't be working excessively, but just enough to keep things tight. All you need is enough to push these bad boys up to hull speed into a moderate headwind.... we're not trying to win races here.
Reply With Quote Quick reply to this message Share with Facebook
  #19  
Old 11-04-2011
NateKing's Avatar
Member
 
Join Date: Dec 2010
Location: Fairway, KS
Posts: 36
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
NateKing is on a distinguished road
Quote:
Originally Posted by SloopJonB:793192

What I'm thinking of is this;

First, stripping it for a rebuild
Next, adding the Moyer stuff - electronic ignition, oil filtration etc.
Next, shaving the cylinder head and block to raise the compression to, say, a whopping 8.5 to 1.
Then, having the mains line honed.
Then, cleaning up the intake and exhaust ports with a carbide burr and die grinder (port & polish). Since it's a flathead, I expect relieving the area between the valves & combustion chamber may be necessary. Also, matching the intake & exhaust openings with their respective manifolds. Also as part of this process, checking and matching the volume of the combustion chambers.
Next, having the rotating assembly carefully balanced.
In other words, basic balancing and blueprinting.
Next, painting the inside of the engine - all non machined surfaces, with Dolphinite to promote rapid oil return to the pan.
Last, possibly having the cam reground to increase its lift & duration a little. A good cam grinder will know how to shape the lobes to maximize low RPM torque

I don't know what any of this means, but it sounds bad Ass.
SloopJonB likes this.
Reply With Quote Quick reply to this message Share with Facebook
  #20  
Old 11-04-2011
SloopJonB's Avatar
Senior Moment Member
 
Join Date: Jun 2011
Location: West Vancouver B.C.
Posts: 10,926
Thanks: 58
Thanked 56 Times in 53 Posts
Rep Power: 4
SloopJonB will become famous soon enough
Quote:
Originally Posted by NateKing View Post
I don't know what any of this means, but it sounds bad Ass.
Yeah, I want make the nickname "Atomic Bomb" really MEAN something.
__________________
I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
Reply With Quote Quick reply to this message Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



All times are GMT -4. The time now is 04:43 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.