Offenhauser and Holly upgrade?

Since I am always looking for new performance upgrades for my 69 Jeep CJ5 V6, I would like to know by replacing the stock manifold and the Rochester 2bl carburetor with an model # 6035 Offenhauser manifold and a Holly 8007 390 CFM (I wish the Holly had a manual choke), what additional performance on and off road could I expect, and will I get better gas mileage than the stock set up I have now?





jeep toss


:v6:

 

I did this. I did it because my 2gc was trash and i was tired of piecing together junk to try and make it right. I have no idea what my gas milage is. This is not even a thought for me. I just wanted a no problem solution. it was either buy a remanned 2gc for 300 bucks or a new holly for 415 on sale. I DID have issues. The first carb was faulty. Summit replaced at no charge or issue. even free shipping to and from them. they sent out a new one before I even mailed out the old one.

When i mash the right pedal going up hill in high gear and the vacuum secondaries kick in, wow. Totally worth it for me.

The electric choke kind of sucks though. It works really well when its cold, does exactly what its supposed to. Problem is that when you turn it off the bimetallic spring gets cold eeven f the engine is warm and there you go.

I am totally satisfied and excited every time I drive it and I have no carb throttle shaft galling or random idle problems or any other wore out carb problems.

 

If your looking for a night to day sort of performance gain just a manifold and carburetor will not do that unless what you currently have is junk. Those motors are only about 155 Horsepower, a nominal gain of 10-15% which is appreciable is still only 15-20 HP.........I would first work on the basics, like doing a compression test or leak-down test to truly find the condition of your motor, ring seal & valve seal........bolting anything to it without first knowing the condition of the heart of the motor would be a waste of time.
Then perhaps Ignition , maybe headers and with a better camshaft then a Manifold and better Carburetor may get you some small gains.

 

^15-20 HP is a noticeable "seat of the pants" gain, especially in a small lightweight vehicle.
I put a 4bbl on mine too and like the way it runs better than the stock 2G.

 

Over the past months I have had the engine totally rebuilt including having the exhaust ports throated. I bought a set of Sanderson Header along with Flowmaster Super 40's, an DUI distributor, the brakes are being upgraded to 11" drums in the rear and disk in the front along with a new Master Cylinder and new AGS NiCopp brake lines. I am installing an electric fan for additional cooling and an American Eagle radiator. I am looking at replacing my original stock spring with BDS springs. So if I add the Offenhauser and Holly Carb are installed I would assume I maxed out just about everything I could do for on and off road performance for my Jeep.

 

There's always more you can do. :twisted:

Speed costs money. How fast do you want to go?

 

Here is a link to a manual choke conversion kit. I am running a Offenhauser and a Holley. The Jeep runs great.

https://www.holley.com/products/fuel_systems/carburetor_components/choke_components/parts/45-225

 

Do you have the part number for the headers? Did they fit good? Do you like them?

 

Tom,
I think these are the headers that Warloch and Novak (the company) had a hand in.
i have a coated set in a box waiting to on on when I mount the engine and trans, etc. back in the jeep.

they look good. I'll be going dual exhaust also, not sure if I want to try Warloch's super trap setup, or go with the flow masters or something else.

 

Thanks for the info on the headers. In the past I have great luck with Spintech Mufflers. They are smaller than Flowmasters and I have found them to be quieter with a better sound. Take a look.

http://spintechmufflers.com/

 

I can across someone on the net and he had posted that he installed the Offenhauser manifold but used a Holly 0-90470 470 cfm on his 69 Jeep. My question is, is 470 cmf to much air for the 225 cubic inch engine, if not does it increase mileage or additional performance over the 8007 390 cfm? The features on the 90470 are:

• Gold Dichromate finish for extreme off road environments
• Single feed fuel inlet for ease of installation
• Optimized off-road calibration that works out-of-the-box
• Factory preset electric choke for easy startups
• Vacuum secondaries allow use on a wide variety of vehicles. Quick Change vacuum housing cap allows you to tune for performance or fuel economy (springs included)
• One piece off-road vent tube eliminates fuel spillover during extreme maneuvers
• Intended for off-road/off-angle use. Unique metering block designed for flood free operation up to 40º while climbing and 30º during side hill maneuvers & “nose down” decents
• Limited lifetime warranty - Guaranteed to be free from defects in material and workmanship for the life of the product!
• 100% wet-flow tested by Holley technicians to assure it arrives ready to run! My next question is about a base mounting plate and gasket for either the 90470 or 8007. I thought I read there are not to many readily available for the Holly to mount on Offenhauser. No, I am not looking to race the Baja 500 or anything like that. I am just doing some upgrades that I have always wanted to do and have fun doing it. I appreciate everyone who takes time out to help me with my questions.

 

I have a 225 with cam, Offy 360 dual port, 10:1 compression, Sanderson headers, and some porting work. I asked this question of a Holley tech guy - 8007 390 or truck avenger 470. After several questions and some hemming and hawing, he said, "Go with the Truck Avenger 470. You probably won't get into the secondaries very often anyway." No comment on the performance if I do get into the secondaries, but it sounds like a little too much CFM for the little motor?

I'm thinking a 390 with some off-road mods will work best for me. That or TBI/CFI.

 

Seems there was a thread around here that others went into detail recently. all were very informative on the cfm volume max the 225 can swallow and digest out of the box.

Something about the cid, max rpm, and volumetric efficiency (80% being the average, or something close)

Iirc, the 470 wasn't optimal (too much).

im hanging with my original boat anchor intake and the 2g carb for now. Had plenty of go with the 4.88s I'm turning, with the 30" tires... Stopping is an issue with my 10" brakes... Converting to 11"...

A little Google foo and I found this Cfm calculator : http://www.buicks.net/shop/reference/carb_cfm.htm

However, there are some guts you can add that change the equation pieces (example: http://www.flatlanderracing.com/iskycamsbuick.html and taperformance.com). This is a deep rabbit hole, lots of shiny baubles and trinkets but I'm not sure how far you can push the HP for the cost benefit ratio.

Say $600 for the isky kit, $600 for the carb; Pistons, rings, Crank, machine work, and I see lots of Benjamin's...

For me, I'm being gentle on mine... not sure how tight you want to twist the rubber bands on our little 225, but I'm thinking a safe zone likely near 4500 max, but not as a WOT on reg basis (old motor, unknown condition, nothing special innards). if it flops at some point, I can dump a pile of cash into it rebuilding it, or go 4.3L.

others have magic horses under theirs and they are neat...

and then I pick up an old book on juicing these things up and ... I want for cool factor.

 

The 390 CFM is more closely sized to the 225 both in cubic inch , CFM and breathing capacity needs..............both carbs have vacuum secondaries which means unless the demand from the engine in air flow volume required exceeds the needs of the primaries , which would only happen at high RPM ranges its doubtful the secondaries will see much activity in either carb. The Primaries of the 470 are 1.500" bore and the 390 are 1.438" bore.............The 470 is nicely set-up for 4-wheeling right out of the box whereby the 390 will probably require some additional work in venting and spring loaded floats if your Jeep will see serious off-roading..........Neither carb. should be considered a direct "Bolt on and forget" on a 225...........both will require some tuning to get them correct and Holley by far has the best support in parts to customize them..............Either one will work................Simply, I would base my decision on where the motor RPM & Jeep will spend it's most time.

 

I'm running TA 470 on mine...at 6000 ft above sea level!