carb jetting (4160) - Hot Rod Forum : Hotrodders Bulletin Board -- Hot Rod Forum

Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 07-22-2005, 02:45 AM
Last photo:
Join Date: Dec 2004
Location: Issaquah, WA
Posts: 288
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
carb jetting (4160)

Ok so this is my first time messing with the internals of my carb. I have a Holley 4160 750cfm carb. I think I have been needing to change the jetting because it has been running awful rich. Today i pulled the bowls off, I see two jets on the primary side bowl and none in the secondary (just a plate thing). This is a newb question, but are both jets in the primary bowl for primary or is one secondary? How does that work?

Also, the two jets were both 72's... what number jets should I switch to? It ran ok, but stumbled a bit when I floored it at low rpm in higher gears, also lined the combustion chambers of the heads with black sut as well as header ports.

To add to the equation, while the engine is apart im upgrading from the regular edelbrock performer to the performer RPM manifold as well as gasket matching and home-porting the heads. The heads were from a 305 for higher compression and didn't notice the intake runners didn't match the intake manifold's runners until now. I am considering upgrading to 1.6 ratio rockers as well to get a little more cam lift. I don't know if this will be enough of a difference so that the engine will actually be able to use the #72 jets or if I should still use smaller??

Here's my engine's specs:

Holley 750cfm 4160 (vac sec)
Edelbrock performer rpm intake
Comp XE274 cam, 230/236, .490/.490 lift
#450 heads, 64cc chambers, 2.02/1.60 valves, home porting
Comp ratio 9:1
Manual 5sp tranny (NV3500)

Thanks guys,

Any tips?

Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 07-22-2005, 06:06 AM
Deuce's Avatar Moderator
Last wiki edit: Choosing a trailer
Last journal entry: Jan 13 2013
Last photo:
Join Date: Aug 2002
Location: Deuceland USA
Age: 68
Posts: 5,657
Wiki Edits: 6

Thanks: 0
Thanked 10 Times in 9 Posts

4160 series Holley means only 1 metering plate with changeable jets. The rear is a plate ( which can be changed.......complete plate for plate )

Holley sells a kit to convert your 4160 to a 4150. The kit has another metering plate for the secondary (rear) side with changeable jets. I did this to mine.

I would just convert the 4160 to a 4150, drop 2 jet sizes and try it....

Holley also sells a jet assortment box...for about $40...with 30 sets or so
Lot less expensive than buying them at $5 a set


"I won't be wronged . I won't be insulted, and I won't be laid a hand on. "

Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 07-22-2005, 06:15 AM
TurboS10's Avatar Moderator
Last wiki edit: Auto Terms and Definitions Used in Modern Engine T... Last photo:
Join Date: Sep 2002
Location: Texas
Age: 38
Posts: 3,463
Wiki Edits: 2

Thanks: 0
Thanked 0 Times in 0 Posts
I agree. Just drop two jet sizes and see how it reacts. Then you can go down one or two more if it needs it. 68 is not an uncommon primary jet to run.

I would also offer a word of caution on the head porting. Dont do anything extravegant. Search for "pocket porting" or "bowl porting" on this site and you will find lots of information. That and the gasket matching are all you want to do without a flow bench. Just hogging out the ports could end you up with a real dog or useless heads.

Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 07-22-2005, 12:48 PM
Last photo:
Join Date: Dec 2004
Location: Issaquah, WA
Posts: 288
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks guys. I'm not going to have the money to convert to a 4150 right now because of the rest of my engine I had to throw money into rebuilding but I will check everything out in there.

People keep telling me that 72's arent that big and pretty standard, so I dunno but from the get-go I always figured the 750 was a little big for my combo anyways so maybe thats why its running rich. I'm hoping my little mods here and there will allow me to pick up some extra power and put that 750 to use.

As far as the porting goes, ive done quite a bit of reading about it. I don't plan on hogging out the runners at all, a light polish on the intake side and a smoother polish on the exaust. My idea is cleaning out the port a little, grind enough to match the intake runners between intake manif. and heads (top of head runners come in and are actually smaller), and deshroud the valves as well as polish up the bowl. The heads were from a 305 so when the 2.02/1.6 valves were installed they have a good bit of shoruding
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 07-22-2005, 09:18 PM
New Member
Join Date: Jan 2005
Location: WA State
Age: 61
Posts: 17
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
RE: Carb Jetting

I know you were asking about carb jetting but after looking at your engine specs I think you should go in another direction. If the # of your head is 367450, my books show that is off a 75-76 262 ci. It is for a very small smog engine, the port volumes are so small they will never move enough air to take advantage of the cam you picked. That cam runs from 1600-6000 rpm with a healthy duration, cyl heads and cam is where you want to spend the money for performance. Those heads were designed for a very small bore, I assume you are building a 350, so those chambers will over hang in a 4.00 or 4.030 bore. Also since you have a manual trans, forget the 4160--get a 650 or 750 DP which will make more power, but I would replace those heads if it was possible.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 07-23-2005, 07:58 AM
Last photo:
Join Date: Jan 2005
Posts: 3,706
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
Those heads will work fine if you open the runners up, raise the roof of the port as much as possible for the entire length of the runner, narrow the port divider to 1/8" and work in from there being careful not to cut into the headbolt hole, leave the port floor alone except for blending to short turn into the bowl, match your intake to the new roof height and divider width. Unshroud those valves out to the bore line not gasket line. Blend your lower cut below the seat into the bowl. They'll work fine and probably end up at a 170ish intake port volume. The set I did the chambers CC'd at exactly 64 after the deshrouding and a .030 mill. I did spend a ridiculous 30+ hours on the ports though . If you do the port work make some go/no go guages out of heavy wire so you can check dimensions as you cut- this way the ports will be more equal when done.

The 750 VS carbs do seem to have a really rich idle circuit and with your cam the overlap isn't helping much. I bet if you open up the secondary throttle blades just a tad with the setscrew adjustment in the baseplate and readjust your air/fuel mixture screws the richness will drop quite a bit. If this problem is related to rpms below 2500rpms I'd say it's more than likely an idle circuit problem. Make sure your idle mixture is on before making jet changes. JMO's Bob
Reply With Quote Quick reply to this message

Recent Engine posts with photos
Gear in this thread - Powered by O'Reilly Auto Parts

Quick Reply

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


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 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
carb gaskets...poor idling...holley 4160 oldmako Engine 4 07-25-2010 10:58 AM
Holley 4160 carb on 400 SBC. Silver_Camaro Engine 3 05-14-2005 11:22 AM
Carb Jetting Starting Point camaro 68 Engine 3 04-13-2004 03:55 PM
Holley carb jetting, help please... Jare Engine 1 05-24-2003 08:06 AM
HOLLEY 600 4160 CARB QUESTIONS? mr_chickenhead Engine 3 05-22-2003 02:57 PM

All times are GMT -6. The time now is 12:41 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright 1999 - 2012. All Rights Reserved.