thermactor hole plugging update

Reply Subscribe

Thread Tools

Search this Thread

Jan 19, 2005 | 06:39 PM

hey_beaver

Thread Starter

Freshman User

Joined: Nov 2004

Posts: 38

Likes: 0

thermactor hole plugging update

well i went to a machine shop to see about plugging thermactor holes in my 351m heads. the machinist took them and simply welded the holes that flow into the intake closed. took 10 minutes and cost me 20 dollars hope i did it right. I trusted the machinist cause i couldnt get any responses to my previous post on this subject. I'm sure I'll have several people tell me how to do now but thanks anyway. but if there is a problem with this method would appreciate input on it

Jan 20, 2005 | 04:51 PM

TxBrokenarrow

Senior User

Joined: Sep 2004

Posts: 263

Likes: 0

From: FLOWER MOUND,TX

hi...might be dumb question,but why would you do that??just asking because i'm fix'in to have my heads r&rd..

Jan 20, 2005 | 05:46 PM

hey_beaver

Thread Starter

Freshman User

Joined: Nov 2004

Posts: 38

Likes: 0

because if your running an after market intake and carb with no emissions junk on it, you dont want the hot air from your exhaust passing through your intake and heating it up. the cooler your fuel system the better. so i'm told anyway. the purpose of the holes is for your factory choke system I believe. the heat from the motor tells it when to shut your hi idle off. i have a manual choke 750cfm holley double pumper so its not helping me.

Jan 20, 2005 | 06:36 PM

Bill_Beyer

Posting Guru

Joined: Aug 2000

Posts: 2,416

Likes: 4

From: PacNW

The purpose of the holes which go from the intake to the exhaust ports are to allow fresh air from the A.I.R. pump to be injected into the exhaust stream. I really don't think that it'll make a huge difference in the intake temp if the exhaust gas runs backwards through the system as long as you plug the port in the intake but it can't hurt.

Jan 20, 2005 | 08:31 PM

TxBrokenarrow

Senior User

Joined: Sep 2004

Posts: 263

Likes: 0

From: FLOWER MOUND,TX

Bill...as long as you plug the port in the intake ....are you talking about the pipe thread holes on the intake???i'm fix'in to install a weiand 8010...thanks

Last edited by TXBROKENARROW; Jan 20, 2005 at 08:33 PM. Reason: miss spelling

Jan 20, 2005 | 08:55 PM

hey_beaver

Thread Starter

Freshman User

Joined: Nov 2004

Posts: 38

Likes: 0

your thinking of the egr valve i think which the thermactors holes flow to there but the hot air still goes into your intake you need to block it where it enters I believe

Jan 21, 2005 | 04:08 AM

Torque1st

Posting Legend

Joined: Sep 2001

Posts: 30,255

Likes: 37

There have been other recent threads on methods to plug the thermactor ports. You can find them with the search function.

Here is one from just a couple of weeks ago:
https://www.ford-trucks.com/forums/s...d.php?t=327831

10 Ways Ford is LOSING to the Competition

Joe Kucinski

Top 6 Best Deals Available on New Fords & Lincolns Right Now

Brett Foote

This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level

Verdad Gallardo

Top 10 Fords at 2026 Carlisle Ford Nationals

Joe Kucinski

3 Best / 3 Worst Parts of Modern Ford Ownership

Brett Foote

10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches

Pouria Savadkouei

Every 2026 Ford Engine Explained

Brett Foote

10 Ugly Ford Trucks That We Still Kinda Love

Joe Kucinski

10 Things Every Truck Owner NEEDS (2026 Edition)

Michael S. Palmer

Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath

Verdad Gallardo

Jan 21, 2005 | 08:26 AM

Torque1st

Posting Legend

Joined: Sep 2001

Posts: 30,255

Likes: 37

Blocking the thermactor holes is a problem unless you run a heated air intake with a stock type airbox. Running a properly functioning heated air intake gives you the best performance in all conditions. The exhaust crossover can cause carb percolation and vapor lock. It also cokes the oil on the underside of the manifold if you don't run a valley pan. The additional heat on the incoming air is bad in the summer. Running an open element aircleaner is bad most of the time, they work fine on trailer queens tho.

You can find descriptions of airbox modifications etc in the 73-9 forum as well as this one. I run a dual snorkel unit on a Mopar airbox with a modified thermostatic vacuum switch.