Here is just something I've been wondering and as often is, is probably pretty silly thing to be pondering.

Looking to hear from those who have an Offy intake with the 390 Holley (or some other carb mounted to it I guess as well like 500 etc.)

What MPG are you getting with one? Also, is your speedo accurate? Just note that from experience in the Mini world. People swap engine and gearbox assemblies or diffs and claim mpg numbers with never getting the speedo dialed into the combo.

Obviously, if you have your foot in it all the time then MPG will go down. Just wondering if the install is strictly a performance thing or if it can be put together as an MPG enhancer? OR, is the design of the carbs available etc. such that you are naturally going to use more fuel regardless.

I guess if you post it would be helpful to know what car you have, engine size and mods, rear gear, tyre and anything else you think is important.

Been looking for a complete Super Six setup every time I can make it to the U Pull, but in almost 12 months or more no luck in finding one. So, know this is a bit more, but at least can buy new pieces if wanted to.

As a final piece of the puzzle, wondering if it would be flat overkill on a bone stock 225, 904 auto, 3.21 rear, 225/60/14 tyre car? Not looking to race, just nice reliable transport that can pull good MPG numbers and have a bit more welly if needed. Also not looking to pull the engine down, shave the head, put a cam in it, headers etc. Might increase the pipe size and put a good muffler on it though. You get the idea.

Looking forward to hearing what you have to say and your experiences! Please don't blast me for such a silly question perhaps.

Cheers

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From Mopars to classic Minis and back to Mopars in 19 years flat!

Will work for roast chicken crisps!!

For MPG I would stick to the super six set-up. Talk to SS Dan he has NEW carbs for the converstion.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

I've been running the Offy on basically the setup you are talking about.
It can help with economy out on the road, so long as one keeps out of the power valve and secondary circuit at cruise speed.
With the 390 Holley and the 600 I get about the same economy cruising at 55-65. Somewhere around 22-23 MPG.
Once I clear 70, that all goes to Hades in a Hand Basket with the 600. The trip to Vegas was made in the 70-80 MPH Range for an economy of somewhere in the 16mpg range for the whole trip.
Around town and combined driving with the 390 came in around 18 mpg. With the 600, make that 12 mpg.

Your rear ratio will help with the combined and town economy. I have 2.76's. Nice on the freeway, lousy at the strip and in the city.

My head has a street port, and the distributor has been recurved to the engine. For this trip I noticed that my vacuum was down slightly. The engine is very worn, and I drove it to Vegas with the sole intent of abusing it heavily. My compression is 8.0:1 Just lucky there. Stock compression varies widely, and 8:1 is the minimum for using the four barrel set-up. many stockers were clear down at 7.5:1

So Apples and Oranges.

For a stock engine, follow 66aCUDA's advice; Go with the Super-Six. It will work much better where extensive compression modification is not employed. It will perform better as well with a stock combination. The Holley 600 at WOT at any engine speed will drop engine vacuum off scale low. A big rolling donut. Zero. The BBD will work much better where oversized valves and high compression are not going to be part of the equation.

CJ

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Part of Tyrde-Browne Racing

http://tinyurl.com/5veaaq
http://tinyurl.com/66gzjv
I have one of the super sixes forsale. Let me know. $250

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Hi moparbrit,

Ok, you ask an opinion borne of experience..here is mine, but recognize others may have other expereinces.

First, I have found modifications should be made as a group with an objectie in mind, and darn if every ole slant vehicle isn't different! Second, I think you are asking the possible outcome and wisdom of putting a 390cfm Holley on a Offy 4bbl intake....on a stock engine with automatic tranny.

In my opinion, to be blunt about it, such a swap will give you insight into the problems of manifold and linkage swapping and may soothe the ego as regards looks, but I can't forsee any other positive results. This kind of swap is closely akin to putting different hats on your head hoping your blood pressure may change. The reason I am so negative about this limited swap is because I don't see the objective. The carb is very good when the engine can breathe. Having a 4 inch pipe running water into a 2 inch pipe while not forcing the water through the system will not get more water into a small pipe faster just because there is a big pipe to start.

I am very pleased now with my third incarnation....on a heavy truck. I wanted low end power, good breathing, and a 3.91 rear end on 28 inch tires. Yes, my speedo is very accurate. I got the right speedo gear for my tranny and tire combo and checked them on speedo dyno. I didn'tt really care what mileage was, I was building for pleasure. Still, on the road it is about 18 mpg at 65 mph with my 727 automatic, and was only about 20 mph in overdrive when I ran an A833OD (about 2200 rpm at 70). I imagine my truck has more rolling resistance than a lighter car, but never matched it up against a car.

I milled the head .100, bored engine .060, over size valves, 340 springs, Erson cam, balanced crank, roller timing chain, dutra duals into a custom built and tuned exhaust with one Flowmaster muffler, Holley 8007 modifed to use two metering blocks, recurved distributor, MSD ignition, complete primary circuit rewiring, and the offy intake. It all works together....as my friends say listening it idle..."I NEVER heard a 6 cyl sound like that!"

Why all the worK? Well to start with I wanted an Offy and the Holley. Then I found a "few" other things had to be done in concert or my truck would't even wiggle. Getting that big mass moving fast takes torque. Just breathing well isn't torque...it needs to aspirate air and fuel and combust them at an optimal time in the cylinder at a compression that will extract some horsies. If you do all these there is no doubt you would run better than stock and I bet you would get better mileage than I do, since you just aren't moving the same weight. It would be fun to pull my engine and pop into your car and find out! But you also would need the right rear end and tranny splits.

So, plan ahead, if you get the Holley and Offy at a good price and stash em as part of your plan, (I held mine 3 years til I needed em), put on that super six and upgrade your ignition to HEI first....and see what happens!

rock
'64d100

My car is a Super 6 with a stock exhaust manifold and big single exhaust (2 1/4" with a 340 Turbo muffler)

I have big valves, swept chamber, pocket ported and milled 100 head....decked .60 block.

Its about 9.25 CR The Cam is a 280/270 Erson (lots) I have a 5 speed and 3.55 ratio and 25"tires.
The car really scoots.....I can finally use a bigger carb.....just.

The BBD on a Super 6 is a very good combination for a stocker or mild hopup. ....Id say better than the OFFY/390 given the price difference.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

OK, I will bite - why do stock compression ratios vary so much? I know there have been production changes over time but I don't think that is what we are talking about here. I have read several entries that say, mill the head .100 and you are good to go- you will be at 9 or 9.2:1. When I build my slant (street engine) I would like to see 9 to 9.5:1. I am glad I am not ready yet - seems I have alot to learn! Thanks for your help.

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66 Lil' Red Piggie Valiant (Mater Crusher) - Thanks Zilla!!!!! 72 Demon (Number 1 Son's)

You need to measure YOUR combination to find your current CR....then you can calculate what you need to do to achieve your target CR.

You need to measure chamber volume and piston to deck height. You also need to know your gasket compressed thickness.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

To get 9.5CR I took some off the block and the head. I took more off the 74 block to take out the twist, (about 060). My 78 head was off a truck and it was twisted the other way so it took about .060 to clean it up and level it out so the chambers were closer to the same size. Then did the pocket porting and gasket matching and opened up the intake runners.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Great info all!

Got a chuckle out of the hat and blood pressure comment, har!

Thanks also for the offer on the Super Six setup. I've emailed you on it.

Seems from the comments I've gotten and the PM's that the 4 barrel is really more performance oriented for at least those that have gone this route. Some have done more mods that others, but in general that seems to be the concensus.

Sounds like for my purpose getting a Super Six is probably a wiser plan as I don't want to get into doing engine stuff at the moment. If I had a spare 225 laying around then maybe I consider tinkering a bit, but again nothing to radical. A bit of extra power so that the car can get in and out of traffic when needed and not fall on its face on long hills or something would be nice, but MPG is probably primary.

Cheers

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From Mopars to classic Minis and back to Mopars in 19 years flat!

Will work for roast chicken crisps!!

I am glad everyone is so helpful to you here.












What's a chicken crisp?

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

Sorry, did not see your post until today.

Roast Chicken Crips are an adiction. Crisps would be potato chips in the US. Wish I could find them here other than occasionally at an import store. Smokey bacon flavour are a close second.

Super Six arrives Monday! Thanks Brennan.

Cheers

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From Mopars to classic Minis and back to Mopars in 19 years flat!

Will work for roast chicken crisps!!

We have crackers here that a called "Chicken In A Biscuit." I can eat a whole box by myself.

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

YUUUMMMM.... Chickeny, salty. Can someone come take this box from me. PLEASE.

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225 .030
.020 off the block .100 from head
Comp 264
904 Tranny
New Ebre-ting

http://s78.photobucket.com/albums/j103/edrod01/

What RPM's are you turning at 65? You have a 904 tranny, right?

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225 Cubic Inches of Iron-Head American Muscle

225 bored .040 /.100 off block, Schneider Cam 224@.050~ .480 lift - Stock valves, blended bowls, Offenhauser intake with 500 Edelbrock carb