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Old 04-17-2019, 01:44 PM   #1
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454 Head Swap Worth It?

Im starting with a 1986 Winnebago Chieftain 33, with 24,570 miles (happen to know because it just got inspected), for which I paid $3600 (I think somewhere around there.)

Havent had time to do much with it since buying it last October, but enough to convince myself that its a keeper.

Were about to put our house up for sale, and I have a commitment from my wife of $10k of the proceeds for my stuff on the motorhome suspension upgrades all around, headers (1973-91 GM / Chevrolet 396-454 BBC Pickup / Suburban / Blazer (2wd) Tri-Y Headers (7/8) and exhaust for sure, dual-plane manifold as well beyond that still plotting Oh yes, I scored a low-mileage Jacobs ignition module on Ebay, so thats in the cards as well.

My wife and I lived aboard a 1916 sailboat for many years, so while weve never lived in a motorhome, we are pretty confident we can make it work, at least in limited doses.

Or goal is to be able to get away from the harsh winters, and freeload off old friends across the land 8^)

I am cognizant of the fact that I will never put enough miles on it to pay back any potentially mileage-enhancing modifications, at least not in terms of dollars. What I want is reasonable performance, acceptable economy, and above all, efficiency; and what I mean by that is I just want this engine to be operating optimally for this application, reasonable?

Also, I am capable of doing most, or all of the intended upgrades myself, if need be, however, I also have two friends who are professional mechanics, both of whom I trust, willing to assist, or be assisted by, me only problem neither of them has a bay that will accommodate the coach, but neither has balked at the prospect of doing the work in their lots.

So again, headers/exhaust and intake are a given, as is the ignition module, and probably an upgrade distributor.

Next in order of likelihood is a strong RV cam; probably hydraulic roller. At the moment Im leaning toward this one:
COMP Cams: Xtreme Energy, XR252HR: Cam & Kit
but subject to revision.

Ive done this job before, with the engine in the vehicle, and thats one reason its on the second tier of to-dos, however, I really know that as part of the entire upgrade package, the right cam will result in a synergistic improvement.

{Parenthetically, a B&M 4L80E 4-speed OD transmission, lock-up torque converter, aftermarket controller, shortened driveshaft, etc. are also in the cards.}

Arriving at last to the topic at hand, heads:

I have no issue with the ability of the peanut-port heads to flow just as much as I am ever likely to demand, and with the availability of a well-matched manifold (https://www.summitracing.com/parts/w...2wnd/overview/) specifically for the peanut heads, I would probably be very happy with the results.

On the other hand, unless I am mistaken, a set of closed-chamber (100cc) oval-port heads (iron or aluminum) will combine with my flat-top pistons to yield a 9.0:1 9.2:1 compression ratio, which is much more in the range that I would target if building a performance street engine.

My question then becomes not: is it economical? so much as: is it advantageous?

There are several aspects to this question.

My understanding is that the lowering of compression ratios, among other factors, reduced combustion efficiency, necessitating the addition of air injectors to promote post-exhaust combustion. If this is accurate, would this not be one factor that contributes to the premature exhaust manifold/gasket failure to which these engines are purportedly predisposed?

Now, I know that compression translates to horsepower, but the next part of my question regards how valuable this power is going to be in my application. I mean, these engines are going to make tons of torque regardless. Will I even notice the difference between a properly set up engine with the stock heads versus a similarly configured engine matched (as necessary) to the replacement heads?

Final data point has to be: what do I want?

Well, I want it to be as much fun to drive as anything that size is going to be. Id like to be able to merge with traffic without coming to a full stop waiting for a space, and Id like to be able to climb moderate grades without becoming a hazard to navigation.

And when all that well-designed, well-tuned mechanical efficiency is not contributing to performance, I would like it to deliver some improved fuel economy.

Im not so much concerned with the cost to fill the tank(s) as the ability to even reach that next gas station in a pinch. Call me paranoid, but I remember gas lines for miles, hot tempers, and even people shooting each other back in the late 1970s, and that is whats really in the back of my mind when I consider fuel economy. [Or maybe getting beyond range of marauding zombies, or invading aliens ]

Anyhow, we originally planned on selling the house, getting another, and putting $15-$20k into a modest motorhome or trailer and tow vehicle, but then this came along, so we grabbed it. So now weve upped that a bit: I get $10k for man stuff and my wife gets $10k for her stuff (nicer fridge, range, carpeting yada yada yada )

No, its never going to be a wiz bang diesel pusher, but from what Ive seen these past few years, Id be hard pressed to find such a vehicle for the $24k (including the new tires Ive already installed) I have earmarked for this.

Thoughts?
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Old 04-17-2019, 01:55 PM   #2
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Or you can leave the engine alone if it has good compression and runs well.

If it doesn't have one maybe add a vacuum gauge at he dash.

Seen to many good engine go bad from a pulled up head bolt etc.

What fuel deliver system on this bad boy ?
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Old 04-17-2019, 01:55 PM   #3
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I think youd better off with MarkV or VI 496 crate motor.
Tryin to combine older quench type chambers and high cyl pressures on anything but 93 octane is tricky. Especially on a large cyl (that will also have temp variations from the lower portion of the cyl - not to mention few ideally placed knock sensors) that has lots of 'time' for some other combustion process autoinitiate at some point during the cycle. Sometype of closed loop fuel control is mandatory IMO.
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Old 04-17-2019, 05:57 PM   #4
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I’m assuming it has a 3 speed auto. If so I’d get a gear vendors overdrive. That would probably give you your biggest boost.
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Old 04-17-2019, 06:50 PM   #5
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Ok, way back when I had 3 who just like you purchased, i ran them as rentals, solid chassis other than the front air bags inside the coil springs,once i replaced OEM bags with aftermarket problem never came back, had a chassis lean installed spacer blocks that wbo supplied. E fine and trans, decent performance and good fuel economy, renters were reporting 11-13 on a gallon , no overdrive . Sold all 3 in 89 2 had 90k one had 110k, never a problem bone stock. My take is i can buy a lot of fuel for the price of the engine upgrades and i am a gearhead and retired Ford field engineer. There is a YouTube where some gearhead swapped engine and trans in a 80's who i think it was a Chevy ls and 6 speed auto trans out of a wrecked Camaro or vette.
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Old 04-17-2019, 06:52 PM   #6
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Originally Posted by avfordguy View Post
Ok, way back when I had 3 who just like you purchased, i ran them as rentals, solid chassis other than the front air bags inside the coil springs,once i replaced OEM bags with aftermarket problem never came back, had a chassis lean installed spacer blocks that wbo supplied. E fine and trans, decent performance and good fuel economy, renters were reporting 11-13 on a gallon , no overdrive . Sold all 3 in 89 2 had 90k one had 110k, never a problem bone stock. My take is i can buy a lot of fuel for the price of the engine upgrades and i am a gearhead and retired Ford field engineer. There is a YouTube where some gearhead swapped engine and trans in a 80's who i think it was a Chevy ls and 6 speed auto trans out of a wrecked Camaro or vette.
Auto correct who should be wbo
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Old 04-17-2019, 07:02 PM   #7
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First off You don't sound like your in the US - Just me !
With all the power adders - You'll Gonna have to address the Cooling System at the Same time- Bigger Radiator- Cooling Fans ECT ! And Maybe a Trans Cooler too !
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Old 04-17-2019, 09:14 PM   #8
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Sorry but I think you are nuts doing all that to a 86 Winnie with a 454! I have a 88 Winnie I bought 4 years ago for 2k, put 3k and my labor into it , new 5row radiator, brakes with all new lines, master ,etc. Drove it 4000 miles on our 1st trip got 10-11 mpg with a stock 454 keeping my foot out of it , got on it when I needed to! It sits in my driveway fully insured and plated, we bought a 2006 Itasca with 2 slides and a 8.1 (496) and a 4l85e trans. It is parked in front of my house waiting for my buddy to rebuild the rear with 58000 miles on it took it to Florida about 4500 miles , got 7-8 mpg, boy I miss the 454! Good luck but i'd spend my money making it more comfortable and suited to you and your wife! Wish I had instead of spending 30k on that gas eater!
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Old 04-18-2019, 05:38 AM   #9
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Quote:
Originally Posted by Chief Alen View Post
Or you can leave the engine alone if it has good compression and runs well.

If it doesn't have one maybe add a vacuum gauge at he dash.

Seen to many good engine go bad from a pulled up head bolt etc.

What fuel deliver system on this bad boy ?
Well, truthfully, that's my inclination with everything except the fuel system and the headers.

Right now, everything is stock.

I elaborated in another thread, but basically, the previous owner died, and her family just let it sit from 2002 until I bought it in 2018. We put a battery in it, pumped it 4 times, and it started up on the second try. Didn't run all that great, but got me home, and since I changed the plugs and it's loosened up a bit, starts right up every time.

All of which is to say that I've done this enough times over the years to not be too anxious to open up a properly running engine.

I'm inclined to keep the stock Rochester carb because ... well, it's working well, I've always liked them, and I kinda know my way around them (only been 40 years or so since I worked on one, but ... like riding a bicycle ... right?)

I think headers are a given, and a dual-plane manifold doesn't incur many risks, but beyond that, I plan to proceed with caution.

Past experience (last vehicle I 'built' was a '73 F-100 4WD/4-speed with a 420 SCJ) suggests that the right cam would be the next big performance jump, especially moving to the kind of lifts available with a roller cam. That's a tedious job, but one I'll probably do just because the payback is so big, even in light of the effort involved.

So, given that I want to go that far based on what I am confident it will do for drivability, economy, and performance, I started asking myself whether I would be sorry if I got that deep into it and didn't take that last step, if the result would be justified, or even beneficial, and THAT was the essence of my question:

All else aside, if I were building a new big block for a motorhome, would it be preferable to go with lower compression, smaller ports, high velocity flow, or higher (but still moderate) compression, coupled with a port design that might be somewhat less suited to very low RPM flow, but would nevertheless deliver tons of power across a usable power band.

If it's not obvious, part of this is admittedly a late-life crisis thing -- will undoubtedly be my last opportunity to build a super-cool machine -- re-live my misspent youth, and all that ....
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Old 04-18-2019, 05:44 AM   #10
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I'd work on optimizing airflow below 4500rpm . long small,tube primaries and cold air. And this

https://www.cjponyparts.com/holley-s...FI9/?year=1987
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Old 04-18-2019, 05:51 AM   #11
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Keep in mind this is a truck and not a race car. The modifications you will be making are not really for long term high load conditions and will generate a good amount of stress and heat. Even just adding headers can add a ton of unwanted heat in an already cramped engine compartment and the cab of the rig. I would keep it mostly stock and make sure everything is in good working order.
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Old 04-18-2019, 06:38 AM   #12
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If you are going to add headers , take a look at the Banks System. Those headers have long tubes which help produce power a t lower RPM's. A cam will make more of a difference on performance , especially if you get one for low end power. The intake will not give you much gain except for higher RPM's . Since you have to remove the intake to replace the cam it would be a good time to change it. Heads are a toss up. You will get more power , but with the higher compression , you will have to run premium fuel and may run into detonation problems.
I would scrap the carb and present distributor and look for an aftermarket fuel injection and computer controlled ignition. It makes tuning so much easier .
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Old 04-18-2019, 07:41 AM   #13
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Im assuming it has a 3 speed auto. If so Id get a gear vendors overdrive. That would probably give you your biggest boost.
100 plus agree
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Old 04-18-2019, 08:36 AM   #14
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I think youd better off with MarkV or VI 496 crate motor.
Tryin to combine older quench type chambers and high cyl pressures on anything but 93 octane is tricky. Especially on a large cyl (that will also have temp variations from the lower portion of the cyl - not to mention few ideally placed knock sensors) that has lots of 'time' for some other combustion process autoinitiate at some point during the cycle. Sometype of closed loop fuel control is mandatory IMO.
Probably right, but an engine swap is just a bit further than I'm prepared to go.

Am leaning toward leaving the heads be, but biting the bullet and doing cam, headers, and an intake manifold under the stock carb.

In any case, the suspension upgrades will come first, and in the meantime I want to put some miles on it, if nothing else than to shake out 16 years worth of deterioration, an also to establish a baseline.

I've been thinking about all this a bit, and have concluded that a big part of my enthusiasm us due to the fact that it's been a LONG time since I owned a vehicle that I can understand and maintain myself, without the need for digital logic analyzers and suchlike. Heck, I'm (almost) tempted to install a breaker-point distributor and just lay in a stock of matchbook covers (for all the youngsters, that's what some of us would use to set our point gap when no actual feeler gauges were at hand ....)
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