Getting more out of a straight 6.

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sandmann999

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I was wondering if removing the emissions system on a straight 6 is beneficial or not. If so, what all needs to be removed, plugged off, etc... How much of a gain would it get? I'm trying to figure out ways to get more HP out of my straight 6. It's great off road and around town, but out on the highway I have difficulties going the speed limit (65) if the road increases in elevation.

Also, someone was telling me that they know someone who had a straight 6 and replaced the carburetor and manifold with a new one and increased both their HP and fuel economy, mainly because the 1 barrel carb on the I6 isn't the best. If this is the case, which manifold and carburetor is a good one to go with (and where to get it.)

Last but not least, any other efficiency, HP, fuel economy tricks and improvements you all know about.

Thanks!

 
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sandmann999

sandmann999

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I was wondering if removing the emissions system on a straight 6 is beneficial or not.  If so, what all needs to be removed, plugged off, etc...  How much of a gain would it get?  I'm trying to figure out ways to get more HP out of my straight 6.  It's great off road and around town, but out on the highway I have difficulties going the speed limit (65) if the road increases in elevation.
Also, someone was telling me that they know someone who had a straight 6 and replaced the carburetor and manifold with a new one and increased both their HP and fuel economy, mainly because the 1 barrel carb on the I6 isn't the best.  If this is the case, which manifold and carburetor is a good one to go with (and where to get it.)

Last but not least, any other efficiency, HP, fuel economy tricks and improvements you all know about.

Thanks!

PS:  Does anyone make a turbocharger kit for the I6?

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Justshootme84

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Check out Clifford Performance. They offer manifolds and goodies for the 6 cyl. I recommend maintaining the emissions controls so I can breathe :^o

 

351windsorbronco

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yeah when you take off all of the emissions stuff, it starts to make it so you car really smell that carbon CO2 and stuff, although on a V8 it makes it look cool to have a bare engine. Sorry JS84, im making it hard for you to breathe, lol im sorry

351windsorbronco

 
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sandmann999

sandmann999

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Check out Clifford Performance. They offer manifolds and goodies for the 6 cyl. I recommend maintaining the emissions controls so I can breathe :^o
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Thanks for the info. I'm not sure how to make sense of the Clifford Perfomance web site. There seems to only be links to links to links to links and I never end up anywhere. Was it www.cliffordperfomance.com?

Also, I know where to get a complete Fuel Injection system off of a 92 straight six. How easy would it be to install it on my engine? (includes the manifold and everything.)

 

Bully Bob

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1st,

Backyard re-engineering has a 90% failure rate.... That is a "heavy" truck but that I-6 300 is a great eng. Maybe it needs freshing up.

Hi performance & economy are usually found in Hondas, not big trucks.

I would suggest selling as is & buying what you want.

But, a 70-80 mph cruise bronco is going to get around 10 mpg.

 

Justshootme84

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sandman, the intake manifold you want to research is the Offenhauser. I didn't know CP had so many pop-ups on their website nowadays!!! I don't know if it's even possible to convert a carbed 300 I-6 to EFI, as many of the EFI motors went to hydraulic cams & roller lifters and such vs. the old-style flat tappet versions.

And as I stated in the first reply, I can't and won't advise anyone about removing or unplugging the emissions system. But you do need to check your state inspection regs if you want to be street legal. Some states are really strict on any engine modifications and many cities and surrounding Counties do smog testing.

 
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sandmann999

sandmann999

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sandman, the intake manifold you want to research is the Offenhauser. I didn't know CP had so many pop-ups on their website nowadays!!! I don't know if it's even possible to convert a carbed 300 I-6 to EFI, as many of the EFI motors went to hydraulic cams & roller lifters and such vs. the old-style flat tappet versions.
And as I stated in the first reply, I can't and won't advise anyone about removing or unplugging the emissions system. But you do need to check your state inspection regs if you want to be street legal. Some states are really strict on any engine modifications and many cities and surrounding Counties do smog testing.

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Yeah, after your statement the other day, it made me remember that I respect the environment more than my vehicle, so I won't be taking that course of action (even though there isn't any smog testing here in Idaho).

Other than that, I'll look into Offenhauser manifolds.

My main objective is for more ways to get more out of the I6. A good aftermarket carburetor to put on it and aftermarket manifold, etc... My main problem is I don't know anywhere to look, where to start researching, or even what CAN be done. I'd like to rebuild it but don't know where to find a rebuild kit. Needing to know where I can go or who to talk to about some serious tutoring in how to really tune and perfect an engine.

 

Justshootme84

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funny, bm17, very funny. :))

I'll see what i can dig up in my old files on HP mods for the 300I-6. I did some searching last year when I bought the 86, but that project is on hold while rebuilding my 84. But I would aslo like to hear of mods to 'help out' the little six. Try searching some of the early posts on engines for now, I know this was discussed or debated for a while. JSM84

 

LOST1988351

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I was talking to the guy at the machine shop about this the other day .He said you can really just bore them out ,add a cam , match the intake and head (port and polish) and if your fuel injected get better injecters and have your computer reburned. He never heard of an alluminum head for it though . He quoted me $1100 for the engine work, injecters are like $30 each and i guy hear in town will burn the computer for like $50.

 

cjbronco

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I have an offenhauser dualport manifold, holley 390 carb, ****** super compheader and rebuilt head. I removed all the smog and emission controls and have dual exhaust. Quick mods for it would be a cam and what I listed above. Now the cam you pick will affect which carb and intake you get. Also either keep your 300 head and ad chebby 250 inline 6 rocker arms for increade lift(1.7 ration wehre the 300 is 1.6) Or you can swap out the 300 head for the 240 head for a compression jump from~8.4to about 9.5 Just some thoughts. Hit up fordsix.com for more.

 

InfiniteGrade

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Yeah, after your statement the other day, it made me remember that I respect the environment more than my vehicle, so I won't be taking that course of action (even though there isn't any smog testing here in Idaho).Other than that, I'll look into Offenhauser manifolds. 

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Boise requires emissions testing if you were to move down there.

 

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