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302 4V Heads on a 289 2V

Mosesatm

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Jan 18, 2005
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It's my understanding that the 1968 302 4V heads are identical to the 1968 289 2V heads except they have smaller combusion chambers.

A smaller combustion chamber creates higher compression and thus creates more horsepower. Pretty simple so far.

Now for the part that confuses me;
Since the higher compression should create a more powerful explosion it seems that those heads would be more efficient than the lower compression 2V heads. With that in mind would the 302 4V heads also increase MPGs? More horsepower AND better mileage!

Any thoughts or experiences with this idea?
 

rvrtrash

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Lots of variables here Arlie. Speaking only from a hypothetical standpoint, because I've never done this head swap, if you run higher compression, you would also have to adjust your timing and run a higher grade of gasoline, both of which would effect your mileage and performance. Additionally, if you run that 4V only at partial throttle, you are using smaller venturis than the 2V, basically a smaller carb, and increasing your mileage. If you run at wide open throttle, you are putting more fuel into the engine (such as 600 cubic feet/min instead of 450-500 CFM), which increases your performance at the expense of mileage. Never discount the human factor. My right foot is heavier than my left, and I have weak ankles so my right foot tends to hold the pedal to the floorboard, making any scientific comparison impossible. :grin: Ask Joe. It runs in the family. :wink:

Steve
 
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Mosesatm

Mosesatm

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Sorry, Steve I wasn't clear enough. Same carb, just different heads.

I agree that the question is a bit unreasonable when the human factor is added. No one is going to drive the same after they acquire added horsepower.

But let's assume super-human willpower and everything being the same except the heads. I'm thinking about making the swap one of these days but if I can get better mileage out of the deal 'one of these days' may get here a little quicker.

Whatever illness Casey and Joe have seems to be spreading!
 

Midnight Special

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Hey... Watch out. I resemble..er, I mean ...I resent that remark. I choose to think of it as a positive characteristic, not an illness. :wink:

I Stand behind you on that Joe!
(...damn sure as hell wouldn't stand in front of you ;-)
 

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joedls

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Hey... Watch out. I resemble..er, I mean ...I resent that remark. I choose to think of it as a positive characteristic, not an illness. :wink:

I also forgot to mention that I inherited this "positive characteristic" from my Dad. :grin:
 

68gt390

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Never discount the human factor. My right foot is heavier than my left, and I have weak ankles so my right foot tends to hold the pedal to the floorboard, making any scientific comparison impossible. :grin: Ask Joe. It runs in the family. :wink:

Steve

Steve;
I totally agree with you. I tried that very theory while in California with Tim's car and it worked very well. :grin: :grin:

Now as for my own car, Instead of swapping heads to gain more compression, I swapped the whole engine (428CJ for the 390) and found that I ran into the same problem I had with Tims car. Heavy foot and weak ankles. :rofl: :rofl:

Arlie; I've never seen anyone do it that way (4V heads and 2bbl carb), You'll have to let us know how it does. I've seen folks swap out their 2bbl manifold for a 4bbl manifold and 4bbl carb but, leave the 2V heads on the motor. Talk about a waste of fuel and performance. And then they wonder why their car doesn't run well. :frust:
 

joedls

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Steve;

Arlie; Your going in the right direction. I've seen folks swap out their 2bbl manifold for a 4bbl manifold and 4bbl carb but, leave the 2bbl heads on the motor. Talk about a waste of fuel and performance. And then they wonder why their car doesn't run well. :frust:

Also, Arlie, at a minimum, I would port match the exhaust ports before installation. Those ports are horrible from the factory.
 
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Mosesatm

Mosesatm

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Geez, I guess my writing skills still suck.

Right now I have a Holley 4V carb and an Edelbrock intake sitting on '68 289 2V heads. I am thinking of switching to '68 302 4V heads to get away from the 8.7 compression ratio the 289 heads provide.

As Don noted, the engine feels like it's being strangled but the 302 and 289 heads use the same valves so I'm not sure the engine will breathe any better with the 302 heads, unless I gasket port them as Joe mentioned.

From what I've been able to research all the 302 heads do is raise the compression due to smaller combusion chambers. I don't know if the intake chambers are the same size. That'll take some more research to find out.

Of course, to pick up compression I could just get the heads milled.

The overall goal is to maximize power with out destroying mileage and I was thinking the 302 heads may be a win/win on both ends but the more we talk about it the more doubt I have.
 

68gt390

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Arlie;
I thought you still had the 2bbl on your car. Sorry. With 2V heads your dumping a lot of raw gas into your heads that isn't being burned effectively. I would think by going to 4V heads you'd burn the fuel better thus picking up some better fuel economy as well as added power. Not knowing much about the small block heads, I'm not sure if the exhaust ports are the same size on the 2V 289 heads vs the 4V 302 heads. I know there is a difference between the 390 GT heads and the 428CJ heads when it comes to the exhaust ports.

Don
 

robert campbell

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All,
Arlie is correct. There is absolutely no difference in valve or port sizes between a 2V and 4 V 289/302 heads in 1968. To go a step further, there is really no difference between the valve and port sizes between a hipo 289 heads and 4 or 2 barrel cars in the early years. So putting a 4 barrel head on a 2V motor in 1968 is fine and the only difference is compression.

The installation of the 68 4V head with the smaller combustion chamber will increase your compression ratio. Now will that equate to more power? Yes. More gas miliage…. Hard to judge.

Steve is correct in all the other variances involved. Timing, carb size, are just a couple. Gas combustion characteristics… I could write a whole thread on the difference between old Chevron Custom Supreme 101 “white pump” vice today’s 92 octane. We could talk joules of energy and stuff. Quickly get way over our heads!!!

So, will this increase gas mileage? Doubtful you could measure it. Yes, it will make more power tuned correctly. But not a ton more.

Do you have a set of 4V’s on the bench? They are hard to find. If I was buying I would head (no pun intended) into the aftermarket world!

Rob
 

@Holmes

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Dec 22, 2006
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McAllen, Texas
Well the main consideration for carb size is your cam rpm. The standard calculation for this is cubic inch divided by 2. In your case with standard bore would be 151 times the max cam RPM (stock would be 5000. Max hp of a J Code was rated 230hp at 4800 RMP) divided by 1728. So if you have a 5000 cam it would be 151 x 2.89351 = 436 CFM. The 68 Autolight 4300 was rated at 440 CFM.
You could use a 2100 but you will flat line around 4000 RPM and never reach the full potential of your cam. If you want beter perfomance and great MPG consider a 2100 tripak from Pony Carbs, its pricy, about 1900 bucks (http://cgi.ebay.com/ebaymotors/Ford...mQQcategoryZ34198QQihZ015QQitemZ250050646659). If your goal is to build a stock sleeper go with a cam that has a lower RPM range that your 2100 can handel. All 68 2100 were rated at 356 CFM except the C8AF-AK and the C8ZF-G were rated at 287 CFM. If you have a 356 CFM your Max RPM would be aprox 4000 RPM if my math is right.
SOO you need 4000 RPM cam with at least a 112 Lobe Separation AND no mor than 220 lift at exh and intake or you will lose vacume which will result in poor idel. Also consider roller rail type rockers. A cam to look at would be http://store.summitracing.com/partdetail.asp?part=SUM-K3600&autoview=sku. This would go well with an auomatic with a standard stall converter.
Lassiter
 

rvrtrash

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Arlie, I think I know where you're going now, so let me try again. My 302 has the "F" code heads which gave 10:1 compression. When I rebuilt the engine, I used a different piston to drop the compression ratio to 9.3:1, on the advice of my engine builder. The higher compression was meant to use premium gas, which in 1968 was 98 to 101 octane and he felt a slightly lower compression was better for todays 92 octane. I'd keep the heads you have for this reason. As to the mileage part, again hypothetically, if everything else stayed the same-carb,intake,fuel quality,exhaust,etc., you might get marginally better mileage, but not enough to justify the expense of the swap. I would imagine you could do just as well with a low restriction muffler. Hope this is what you were looking for.

Steve
 

nates68

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Nov 7, 2007
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169
On the 4bbl heads they also used Flattop pistons to achive the 10:1 comp.
My J code came this way. Mine runs fine on Prem. Chevron gas.:rolleyes:
Nates68
 

rvrtrash

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I believe all the '68 302 pistons were flat top, regardless of compression ratio, heads or 2V/4V.

Steve
 

robert campbell

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Arlie/All,
Steve is correct on the pistons. Same same on all 68 engines. I also agree with him on the effect on mileage. Minimal at best. Not worth the investment if increased mileage is your goal.

What is your goal? If more power is the goal and mileage a possible benefit, you may get where you want.

I have been dying to talk compression and octane. I am no chemist, but rely on yesterdays engines reaction to today’s gas. So here goes.

Today’s gas octane rating is a relative figure. The mixture and the additives (lack of lead) have no correlation to the gas in 1968. Lead was the primary anti-detonation (read slow down the burning) for engines with higher compression in the 60’s. The amount of lead was increased to raise the octane rating. In my mind today’s gas rating has no relation to old rating system. Today’s gas has no lead as we know. They are using other chemicals and compounds to reduce the combustion characteristics of “gas”. Does 87 octane gas react differently than 92 in today’s or yesterdays engines?? Yes. 92 will reduce ping in an engine that pings on 87. But I have found that 92 reacts very similarly to 99 or 101 from the days of old. My 3 cars, which 2 have iron heads, all run high compression. My 67 runs around 13 to 1. My 57 Wagon with the 428 Cobra Jet runs 10.7 to 1 or stock. My GT/CS runs 10 to 1 with aluminum heads. All run great on 92 octane with no booster our additives. Tuning is a major part of this, although they are not far away from stock timing.

Let’s talk about gas a bit more. Hot Rod ran an article about a year ago and used a 360 mopar engine with 10 to 1 hotted up to about 400 HP as a test mule. The ran 6 pulls on 87, 89, 92, and some race gas more like the old days with lead that were rated at 101 and I think 113. Each pull was at a different “total” timing. 38 degrees total is the industry standard for all naturally aspirated engines whether today or yesterday. Total timing is the addition of initial timing, plus vacuum advance, plus centrifugal timing. The total timing measure at above 2,500 RPM for the engine. Need a degree tape or a degreed damper to measure.

The results of these pulls demonstrated something I have felt would happen. Today’s gas ran fine at the 38 range and made good HP. The more they dropped the total to say 32 or 34 total on this engine the less power it made on today’s gas. The interesting thing that happened with the “old type” gas is that the engine actually made more power as they reduced the total timing. Down to 30 and below. The old gas was more “volatile” or burned quicker and liked less total advance. I will go way over my head next in my education….. One explosion or power stroke on yesterdays gas produced more “joules” (yes I said that) of energy or heat than a power stroke on today’s gas. The test mule made the most HP on the old gas!! I was not surprised.

Today’s gas burns slow and will run in high compression engines, but it does not make as much power. So you can tune your 4V 302 or 390 to run just fine on today’s. You need to adjust your engine properly. Now if you wish to add additives or run aviation gas or whatever you have to be consistent. If you tune it to run on the hot stuff, of course it will run differently on today’s gas.

Another thing that factors in is camshaft overlap. Believe it or not a hotter cam with more overlap actually bleeds off low speed compression and aids in elimination of mid-range pinging. If you measure compression of a stock engine and then install a cam with more overlap with no other changes, the compression measurement will be less across each cylinder. Would love to explain cam “overlap”.

Another area that can really help on a stock engine is the proper adjustment of the vacuum advance. The early vacuum advances have the ability to unscrew the end and use different shims and springs to adjust them. The later stamp steel models you can insert an Allen wrench in the tube where the vacuum nose plugs on and adjust it. I took an old one and cut in open to see how it works. This simple adjustment can tune away mid-range pings. I can go into that.

Make your choice on the fuel you will burn. Stay consistent and tune it to match. If you want the most power, get the old fuel. But you can make great power and run just fine on 92 with your old engine.

By the way, don’t get me started on hardened seats due to “unleaded” gas. Unless you are pulling a huge trailer or running a boat, hardened seats are unnecessary. Also, when you are putting so few miles on an engine, it will never factor in. Don’t tear into your engine just to put in hardened seats.

Not speaking for Paul with the miles on his car, but most of us put so few miles on the car. How many years will it take some of us to put 50k on our car? Forever….

Rob
 

nates68

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Nov 7, 2007
Messages
169
4v heads

Arli,I suggest you invest in a book called Ford v-8s on a budget,pg 66 gives
good details on the 4v heads. I also agree with Rob,Steve. Rob is so right on
hardened seats. Th:icon_ecst ey gave you good advice. Nates68
 
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