408W 750HP - what size jets? - Ford Muscle Forums : Ford Muscle Cars Tech Forum
 
LinkBack Thread Tools
post #1 of 4 (permalink) Old 06-01-2014, 07:09 AM Thread Starter
Registered User
 
Join Date: Mar 2007
Posts: 115
408W 750HP - what size jets?

Hi- i have a 408W. 750HP 76/84 jets.AFR205.. solid roller .616/.622... hooker super comps.. full 3" x pipe exhaust.. 34 timing. 3.0 8" rearend (i know ... dont say anything)

Dyno results showed i was too rich 11.67: 1 a/f ratio. This was at 5200 and above. Can someone recommend possible different jet sizes for me..

It started smokin bad at close to 6000. Come to find out after / during the pull #1 intake rocker arm came off too...maybe this caused the smoke??? I couldnt tell it came off during run. It was too loud

Any advice on jet sizes would be appreciated.
hgufrin is offline  
Sponsored Links
Advertisement
 
post #2 of 4 (permalink) Old 06-09-2014, 08:09 PM
Registered User
 
Join Date: Jan 2002
Location: Ontario,Canada
Posts: 6,662
Garage
Re: 408W 750HP - what size jets?

I am no carb guru but a couple of things come to mind..If it was at a higher rpm when it went rich I would suspect the secondaries being rich so maybe try going down a couple of sizes there..Also I am not sure what actual size the 750HP is but if its like the 950HP its much smaller than its name sake..The 950HP is more like 830ish CFM..If the 750 is sized similarly it may be on the small side for your 408 depending on the rest of your combo and what you are doing with it..


1968 mustang 408W Hybrid..Burns gas and rubber!
[email protected] with a crappy 1.72 60ft.
frdnut is offline  
post #3 of 4 (permalink) Old 06-09-2014, 08:19 PM Thread Starter
Registered User
 
Join Date: Mar 2007
Posts: 115
Re: 408W 750HP - what size jets?

I was told to go down a couple sizes indeed. That was before we knew my rocker arm came off... Unfortunately - i dont know how to tell if a carb is too small. I do know the 750 hp i have right now is perfect for the street. I havent taken it to the track yet. THX for your help
hgufrin is offline  
 
post #4 of 4 (permalink) Old 06-10-2014, 02:43 AM
Registered User
 
Join Date: Jan 2008
Location: Seattle, WA area
Posts: 10,299
Re: 408W 750HP - what size jets?

Losing the intake valve operation will cause heavy smoke as it sucks against a closed valve, pulling oil past the rings into the chamber and out into the exhaust.

To know if a street/strip carb is too small for full-rpm flow, measure your current atmospheric pressure. Then read manifold pressure (vacuum) at torque peak and at HP peak. If the pressure drop at peak HP is more than double the pressure drop at TQ peak, you're choking it excessively.

If this were an all-out race-only engine, the spread may be smaller, but even there too large can slow you down if you lose average torque. This also does not apply to EFI, where vacuum is not necessary for fuel flow, and atomization to some degree.

David

-=≡ If it was easy everyone would do it ≡=-
[size=1]HotShotsJava.com Hot Shots Java Coffeehouse, Poulsbo ,WA fair trade and 100% organic. Voted best espresso and coffee![/size]
PSIG is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Ford Muscle Forums : Ford Muscle Cars Tech Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

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:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
what size jets in holley 4barrel #1spudman All Ford Techboard 3 09-20-2012 06:28 PM
408w header size/cam choice? 351stanger Stroker Engines 7 05-23-2006 02:03 PM
flare size on Nitrous oxide jets Matt All Ford Techboard 1 04-16-2005 10:16 PM
jet size 750Hp strokerman All Ford Techboard 3 07-30-2004 09:30 AM
What size carb jets should I run in my 460? Pale Rider All Ford Techboard 3 02-05-2003 06:44 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome