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Old 08-12-2012, 01:02 PM   #1
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All Things 454

I'm starting this thread with a specific purpose in mind. Most of us have 454 gas engines in our MH's. We all struggle to get as much performance and gas mileage out of our coaches as possible and some of us even struggle to get our MH to pass emission standards in those states that require such. We all have a wide range of skills and experiences and I believe this thread could help us all tremendously. I can turn a wrench pretty well myself but it's always a struggle to figure out what is really beneficial for the 454 in a Motorhome.

I have spent countless hours researching "performance" mods for the 454, I usually come away disappointed. The 454 is probably second in line to the 350 as one of the most successful engines produced by GM. It has a wide range of capabilities and I believe it is an excellent platform for the Airstream Motorhome. But herein lies the problem, we are using this platform in a Motorhome not in a race car or high performance boat. Almost all the information available today on 454 performance is directed towards high performance street engines that require high horsepower and rev to 6000 RPMs or higher. The highest I've ever gotten my 454 to rev is about 3800 RPMs. For a Motorhome, we need lots of torque and our RPM range is probably around 2000 to 4000.

I'm always amazed, not in a good way though, at the Internet arguments out there by all the "experts" on the correct performance mods for the 454. Again most of this is geared toward street rods. Very little is directed towards truck engines and almost none is directed towards use in a Motorhome. I'm not even sure that which is relevant to a truck engine is relevant to use in a Motorhome. A pickup truck weighs 3000-4000 pounds and our MH's weight 14000 or more. Using high rise manifolds, cathedral ported heads, high performance Excel distributor modules, high volume water pumps and on and on and on are all great for producing large amounts of horsepower and torque at 6000 RPMs but do nothing for us that need lots of torque at 2500 RPMs to get our 14000+ pound coaches from that highway on ramp onto the highway and well out in front of that 80,000 pound 18 wheeler that would rather run you off the road then to bother to move over and let you in.

Another issue that I have here in California is that I am now required to have my MH smogged every year. Last year I barely passed and that is in a county with the least restrictive emissions. Anything I do for performance has to be weighed against meeting the emissions requirements.

I know there is a lot of knowledge in our community and it would be great to hear from those that have actually built or tuned engines for use in our applications!
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Old 08-12-2012, 10:28 PM   #2
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The big block chevy is near and dear to my heart, ran one in a drag boat for years. Put a 8-71 huffer on with a bird catcher and run alcohol you'll have the fastest MOHO on the block.
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Old 08-12-2012, 11:14 PM   #3
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Originally Posted by 195Pilot
The big block chevy is near and dear to my heart, ran one in a drag boat for years. Put a 8-71 huffer on with a bird catcher and run alcohol you'll have the fastest MOHO on the block.
I can see that blower sticking up through the dog house right now LOL . I'd love to see an Airstream doing a burn out!
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Old 08-12-2012, 11:17 PM   #4
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After a while everything wears out.
Valves, rings, bearings get loose and with water (ethanol) in the gas, carbs gum up too.
Getting the air in clean, mixing it well with the gas, sparking it all up and flowing the fumes out without restriction are the obvious high points.
Tire pressure, driver gas pedal control and dumping the 1,000 extra pounds of fluff are gravy.
So what do you want to do, add fuel injection?
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Old 08-13-2012, 12:07 AM   #5
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Quote:
Originally Posted by fastrob
After a while everything wears out.
Valves, rings, bearings get loose and with water (ethanol) in the gas, carbs gum up too.
Getting the air in clean, mixing it well with the gas, sparking it all up and flowing the fumes out without restriction are the obvious high points.
Tire pressure, driver gas pedal control and dumping the 1,000 extra pounds of fluff are gravy.
So what do you want to do, add fuel injection?
I think FI would be awesome but only if I could do it for free! I think it is important to show some ROI on anything that I do. I couldn't justify the added fuel economy and performance againt the high cost of adding FI. On the other hand, I sometimes will replace or upgrade something not for the ROI on fuel economy or performance, but for the added reliability. The cost of breaking down on the road or let's say out in the desert could be staggering. For example, I just replaced my ignition switch and headlight switch not because they had failed but because I can't afford for them to fail out on the road.
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Old 08-13-2012, 02:51 AM   #6
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Hi, My Mac Tools truck weighed about the same as these motorhomes and was a P-30 Chassis. It came with a 350 engine that failed twice at around 20,000 miles each. On the last engine, I bought an RV cam shaft for it and it did help. For some reason it felt like the stock cam was made for a car or pick-up truck. My GVWR was 14,000 lbs, but I weighed it at 16,750 lbs. Quite a load for a 350. Anyhow, I would suggest an RV cam shaft, a cam shaft from the biggest truck that ran a 454, or one from a 366 big block truck engine. These should all give the low end torque that your motorhome should have been built with.
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Old 08-13-2012, 06:43 AM   #7
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On my previous Airstream Moho with a 454, I installed a "Jacobs Electronics" ignition system, which unfortunately is no longer available. It consisted of a high voltage coil, a computerized control unit and a small uphill module. The power increase was remarkable, I can only imagine what it would have done with a banks system.
On one trip, I took that Moho over four 10 000 passes, which it handled most beautifully. I remember one the signs on the way to Silverton: Molas Pass 4 miles, no pull outs. Yikes!!
Has anyone installed one of the other ignition systems available?
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Old 08-13-2012, 08:46 AM   #8
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Quote:
Originally Posted by dadstoy View Post
For example, I just replaced my ignition switch and headlight switch not because they had failed but because I can't afford for them to fail out on the road.
Smart move on your part. I would be smart to follow down this path but unfortunately I'm somewhat of a procrastinator which is not always a good thing .

Brad
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Old 08-13-2012, 04:08 PM   #9
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If you are gonna stick with the BBC....
Everything you do should be torque biased.

Short block:
Make sure you are building on a 4 bolt main block.
1/4" stroker crank brings you to 496 with a 0,060 overbore, but I would stick with a 30thou, and leave some meat in the cylinders. Its almost as cheap to put a stroker crank assembly in as a stock one..
Forged or hypereutectic pistons for better heat and detonation resistance.
Coated pistons for friction reduction and heat resistance.
match your pistons to suit the head you are planning to use(Open or closed chamber).
RV cam, with true roller dual timing chain.

Heads.
GM 781 or 049 head castings have the larger oval ports than the "Peanut Ported truck heads. They loose a little torque off idle to the smaller posts but I gather that by 2000rpm are all square and make more power in the midrange.
I would also look at putting bigger valves in too.
Aluminum would be good, as long as the ports are on the smaller side, to aid low speed flow, but the cost is prohibative.
A good set of roller tip rockers is wise, in 1.6 or 1.7 ratio... adds power and lowers friction.

Top all that with a good intake, like an Edelbrock performer, and you will have about 400hp and 500+ ftlbs of torque...

I have heard good things about MSD 6AL CD Ignitions on the BBC...

Personally, if I have to pull my 454 out.... I would so put a 5.9 Cummins in tho...
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Old 08-13-2012, 11:09 PM   #10
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The older blocks have been said to have thicker walls and are almost always successfully bored .060 over. Most builders also say that 454s under 600hp/625torque are fine with two bolt mains. The peanut port heads came out in the late '80s so hopefully mine are the oval port heads ('81).

I'm really curious as to the emission effects of an RV cam and if they could pass in Calif. I think my compression ratio is 7.9/8.0. I don't think one would want to go anything above 8.5 today...what do others think?

Also knowing that the MH 454 will never rev above 5500-6000 rpms, when I tuned up the engine last year I installed a new stock coil and didn't buy a hi performance HEI coil or module. Old coils can become weak so I replaced mine to be on the safe side.

I'm waiting for a very large tree to fall on my buddy's new Chevy or my brother's late model Dodge pickups (with no one inside of course) so that I can get their diesel engines for free to stuff in the MH, otherwise I just don't think upgrading to that extent is very feasible.
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Old 08-14-2012, 12:11 PM   #11
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I have an RV cam in my 454 powers suburban and it flew thru the CA smog with no difference between before and after on the readings... I will try and find the printouts to post, and the spec of the cam.

Whilst I agree with you comments about 2 and 4 bolt mains, I want to add something.
I am sure a 2 bolt main cap is fine for the power you mentioned, but its not the whole story.
A car or light truck under power and full throttle, will spin thru its rev range, from idle to redline, and be lightly stressed in real terms.. Our M/H motors need to be able to run WOT on an incline for miles, at, or close to its max torque output.... with 8 tons on its back! Thats what happens, thats the real world life of a Motorhome 454.... all that torque or twist is centered on the crank and mains... Thats why all of the HD 454's have 4 bolt mains...

Oh, here is a pic of the bottom end of my 454 Suburban motor with 150k miles under its belt...



Here is a pic of the crank journal, and its bearing cap... pretty good for 150k miles and it was used to tow a huge boat for a good chunk of that..




Also I have squirrelled away a pair of "781" casting large ovalport heads....




Good reading on adding a Banks kit here...
Motorhome Performance Upgrades - Intake & Exhaust - RV Magazine
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Old 08-14-2012, 07:15 PM   #12
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Keyair, do you know what the specs are on your RV cam? Also, do you know if there are any marking on the outside of the heads to tell what they are? I'd sure like to know which ones I have.
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Old 08-14-2012, 08:37 PM   #13
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I see a lot of scoring and pitting on those mains. I see definite signs of oil film breakdown under hard loads. Not uncommon and not unusual for the miles and usage, but not the cleanest bearing surfaces I've seen over the years. The rest of the internals look good though. Good typical honey color you'd expect from regular oil changes.
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Old 08-14-2012, 08:39 PM   #14
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The important advantage of FI is not fuel economy, but longevity & reliability.

1] The instantaneous engine starts (no choke problems)

2] Instantaneous altitude adjustments

3] No cylinder washdown in cold/rich conditions, as well as at idle

All of which adds up to "like new" performance for tens of thousands of miles longer than a carb'd engine.

Better performance

Longer life

and some better fuel economy.

Ironically, the better FE is much the result of warm-up and adverse climate/terrain advantages accruing to the FI systems. The on-road, level Interstate FE difference between FI and a well-sorted QJet is low (that's a great carb). But the tenths really add up on a heavy vehicle.

I understand the OP's concern about the difference between hot rodding and RV performance. I spent more than 30-years searching the details in countless articles, advertisements, etc (for CHRYSLER motors, in main).

A 454 is a half-decent big block. A good ways down the list from the ones better designed (the Ford 460 was the best, the older 440 Chrysler would have been second; the 454 lacks the deep skirt and mains reinforcements, poor rod/stroke ratio, bore/stroke ratio, etc), but the huge aftermarket makes building one to any sort of spec the easiest and cheapest. The advantage to Chevy having built the most big motors.

The limiting factor isn't simply weight, but the low compression ratio needed to accommodate a motor always on the verge of detonation. That limits what camshafts can do. One would do well to read up on dynamic compression ratio for a deeper understanding.

In the end I never saw that any more than a true compression ratio of 8.8:1 was realistic. Even with the best heads and head work (that's where the power -- and money -- really are) there are reasonable limits on cam duration. But cam lift for an RV roller cam can be quite high (relative to flat tappet cams).

Maximum torque numbers always sound nice, but the torque profile (dynamometer readout) that comes in early and stays late is the way to go, IMO. May not have the high peak of other types, but power in a moho is about power recovery after the shift. One cannot rev so high as with the hotrodders, so the point at which the engine "comes back in" (rpm) after a transmission shift is completed, is vital.

One must work from a cam builder sheet:

- Tire height
- Drive axle ratio
- Torque converter slip
- Transmission gear ratios
- Vehicle weight
- Anticipated road speed

These are the limits. The camshaft that works with the limits is the one to have (and custom cams can be done, almost a requirement for cylinder heads properly "flowed" for low and middle range power [backcutting valves and proper seat flow a huge improvement; percentage flow gain at low valve lift]).

The engine built or modified with this in mind is more easily fitted by formula. Fuel delivery must work with primary and secondary ignition advance (this is where most attempts fail, as finesse is involved; both science and art. Luckily, dynos can capture problems and suggest solutions when exhaust gas monitoring is done).

I'd copy the intake and exhaust of the BANKS offerings, overall. Packaging is always the problem on engine air intake and exhaust. An infomative article on the latter (by David Vizard, anything he writes is gold, and for our purposes, the best data laden) Auto Exhaust Science

The rest will take some work. For example, a cold thermostat is the wrong way to go. I've changed to hotter ones (185F to 195F) and found better FE as well as better all around performance. But one must search out the best water pumps, radiators, etc. Shrouding and air flow control. Fan clutch data. Fan pitch. Etc.


Start with a weight scale ticket representing total moho weight as well as side to side variances; then on to individual wheel position. Correct any large weight imbalances and look to the springs, suspension bushings, etc, before any power additions (as these can, literally, suck up a lot of horsepower; power not properly transmitted to the ground). A good set of anti-roll bars is worth horsepower, as are best shock absorbers (KONI FSD) as a vehicle faster in transient steering response will burn less fuel, will require a bit less horsepower, etc.

A sloppy transmision is inexcusable. Have it tested out per the FSM as the second round of things. Setting shift points correctly is worth every minute of work. And good firm fast shifts are important.

Brake drag, steering wander and alignment are next. Less than perfect is unacceptable. The A/S moho sits on a crude, wandering & wallowing chassis. Make it work!! The world of big trucks pays more attention to fuel economy than any other sector. All of the above [non engine] is straight from that world.

The 454 engine, and cam, are literally the very last things . . . .


.
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