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Unread 02-22-2012, 09:36 PM   #1
CadCaman
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4.2 4.0 Head Conversion

Guys, I am in the middle of a 4.2/4.0 head conversion. I found a 7120 head and it is at the local engine shop getting the once over. I also found a Clifford intake manifold that I know will fit the new head.

So..... I am wondering what suggestions you learned folks have for me in regards to an affordable ehaust manifold/header (the donor head did not have one available) to put on (single exhaust pipe) and what would be my best bet for a carbuerator. I think I want a 390 cfm but I am wondering what type of carb I can buy that has the correct jets and stuff and is as close to a bolt on and drive as I can get. I do believe I want a 4-bbl carb but I would like an opinion or two.

BTW - I have a Weber 32/36 now and I believe it is only a 300 cfm and I think I need more.

Thanks, guys.

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Unread 02-22-2012, 09:52 PM   #2
gosupes
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I have the 390 with the Clifford manifold and it ran pretty decent out of the box. Just a little minor jet adjustment is all that I have done in 5 years. I think if I played with it more (PV and secondary spring) I could squeeze more out of it. But I'm fairly happy, runs great, doesn't stumble, plugs are a nice tan color. Some of the truck avenger styles might be better suited, worth looking into. As for header/manifold, I bought one the many knock offs you see around, but back than I paid more than what I see them going for now. The basic stainless steel with the expansion joints on 1 and 6, you know the type. They have Borlas, but you will have to take a hammer to 1 or 2 tubes to clear the manifold, not what you want to do on a new $500+ header. Mine fit like a factory piece and the flange thickness was the same as the intake so no funky washer/spacer issues. No regrets on the exhaust manifold either, no leaks, no cracking, nothing. I had custom single exhaust run all the way out. Been a great setup.
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1986 CJ7, 4.2 w/4.0 head, TFI-HEI hybrid ignition, Clifford manifold w/Holley 390 w/cold air intake, OBA, 4.5" lift, Woody CV shaft and Tattons in front, 4.10 gears - lunchbox in front, Truetrac in the back, twin-sticked, blower upgrade for running topless, trying to keep it simple.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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Unread 02-23-2012, 08:06 AM   #3
CadCaman
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Update: I have decided to go with an APN Header. I hear nothing but good things and a great price. I am still concerned about the choice of carb. Here's my issues with my carb choice.
1. I do not know how tell if I need different jets and if I did I would be concerned about doing it.
2. I don't know what carb will fit on my clifford intake. I know Holley and other carb suppliers have different bolt patterns.

Thanks
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Unread 02-23-2012, 08:10 AM   #4
CadCaman
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Quote:
Originally Posted by gosupes View Post
I have the 390 with the Clifford manifold and it ran pretty decent out of the box. Just a little minor jet adjustment is all that I have done in 5 years. I think if I played with it more (PV and secondary spring) I could squeeze more out of it. But I'm fairly happy, runs great, doesn't stumble, plugs are a nice tan color. Some of the truck avenger styles might be better suited, worth looking into. As for header/manifold, I bought one the many knock offs you see around, but back than I paid more than what I see them going for now. The basic stainless steel with the expansion joints on 1 and 6, you know the type. They have Borlas, but you will have to take a hammer to 1 or 2 tubes to clear the manifold, not what you want to do on a new $500+ header. Mine fit like a factory piece and the flange thickness was the same as the intake so no funky washer/spacer issues. No regrets on the exhaust manifold either, no leaks, no cracking, nothing. I had custom single exhaust run all the way out. Been a great setup.
Supes, do you mind sharing with me the carb (model #) you are using with your Clifford intake? I also want to put the twin stick on my Dana 300. Was that a pretty easy application and where did you get it? I see them in the magazines but I am wondering if you found it elsewhere.

Thanks

Jeff
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Unread 02-23-2012, 08:36 AM   #5
Matt_G
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^it's a holly. they make a specific carb that produces 390 cfm. it's also a four barrel. another option would be the motocraft 2bbl. 1.23 venturi make 356 cfm and 1.33 venturi make 424 cfm. super reliable and easy to tune. but it's a 2 barrel
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Unread 02-23-2012, 08:38 AM   #6
swatson454
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I'd go with the Holley. It has ports for manifold and ported vacuum and a PCV outlet. The Weber doesn't and I don't believe the adaptor does either so you'd have to drill the manifold to accept your PCV and again if you needed a manifold vacuum source.


Shawn
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Unread 02-23-2012, 09:16 AM   #7
titomars
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The Holley part numbers are:
390cfm 4 barrel 0-8007
470cfm T/A 4 barrel 0-90470
If your running a stock cam the 390cfm is a better choice.
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Unread 02-23-2012, 09:30 AM   #8
kaiter
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it's also a four barrel. another option would be the motocraft 2bbl. 1.23 venturi make 356 cfm and 1.33 venturi make 424 cfm. super reliable and easy to tune.
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Unread 02-23-2012, 09:50 AM   #9
swatson454
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If you're going to factor CFM into your decision, you'll have to convert the CFM ratings of the two barrels to match that of the four barrel for a fair test. 1.5 inch depression for the Holley. The two-barrels are rated at 2.5 inches.

For example: a Weber 38 is rated at 390 cfm at a 2.5 inch depression. It flows 302 cfm when rated the same as a Holley four-barrel.

New Pressure (1.5) divided by Old Pressure (2.5)= 'X' (.6)
Square Root of 'X' = 'Y'
'Y' (.7746) times Old Flow (390)= New Flow (302.09)


Shawn
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Unread 02-23-2012, 09:58 AM   #10
gosupes
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Quote:
Originally Posted by CadCaman View Post
Supes, do you mind sharing with me the carb (model #) you are using with your Clifford intake? I also want to put the twin stick on my Dana 300. Was that a pretty easy application and where did you get it? I see them in the magazines but I am wondering if you found it elsewhere.

Thanks

Jeff
What the other said about the carb. Clifford makes different adapters for their manifolds. If the one you are getting has the wrong one or missing altogether, give them a call.

The twin stick is easy to fab but I got mine from eBay. I found a listing for some guy not more than 30 miles from me. I figure if I'm going to spend some money, might as well keep it local if I can.

$130 for that header, can't go too wrong. Looks like people are pretty happy with them.
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1986 CJ7, 4.2 w/4.0 head, TFI-HEI hybrid ignition, Clifford manifold w/Holley 390 w/cold air intake, OBA, 4.5" lift, Woody CV shaft and Tattons in front, 4.10 gears - lunchbox in front, Truetrac in the back, twin-sticked, blower upgrade for running topless, trying to keep it simple.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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Unread 02-23-2012, 12:57 PM   #11
CadCaman
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Quote:
Originally Posted by titomars View Post
The Holley part numbers are:
390cfm 4 barrel 0-8007
470cfm T/A 4 barrel 0-90470
If your running a stock cam the 390cfm is a better choice.
Tito, your everywhere.

Thanks
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Unread 02-23-2012, 01:16 PM   #12
CadCaman
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Decisions are made

Thanks everyone for all your help. Here is the direction I am going:

4.0 Head (7120) being rebuilt now
Clifford Intake
APN exhaust
Holley 0-8007 carb

BTW Tito, my fuel injection plans have changed. I picked up a 304 block not too long ago and I am going to have it rebuilt with a new cam (which will take a lot of begging this forum for opinions) and then I am going to splurge on an Edelbrock MFI system to put on it. I will plan on swapping this during the next winter. I am going with the stock exhaust manifolds so I can keep the exhaust inside the frame (if possible).

Thanks again for everything guys,

Jeff

Couple pics to show my project.
p1010121.jpg   dsc00098.jpg  
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4.0 , 4.2 , carb , exhaust

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