1970 L47 400 BB Torque and HP chart

[Steeveedee]

Originally Posted by geezer#99

Considering your wife’s need for max 55 mph and quiet running then a swap to 4.10 gear isn’t worth it.
In second uphill you’re turning 3300 now. Switch to 4.10 and you’ll be up to 3900 rpm.
You might not get into 3rd. If you do it might be louder. Drones usually occur at lower rpm.
Best thing to do might be swapping to a lighter trailer.

That trailer is only 4 years old; I'd have to pry her cold, dead fingers off of it to sell it.

The RV store had some of the retro trailers, but she wanted a nice bathroom. That's what really drove her to the one she picked. I don't actually care, except for having to get it safely to where we're going.

[geezer#99]

Do you have any businesses there that deliver your rv to your chosen site. They use their truck.
We have those here on the Island. I know a couple guys that have big trailers and nothing to pull them with.
No muss, no fuss.

[Mike C]

I have recently rebuilt an L36 427 because I had it and it has not been decked and is from a 69 Corvette. BUT, if I was to build a new motor from scratch (and I am considering this for a motor home) I would find a 454 and build a 496. The 427 rebuild was the same price as building a 496.

If it was a low mileage L29 I would probably consider running as-is since they have better compression and large oval port heads already. (Vortex 454 circa 96-2000) Maybe an RV type cam swap. And the headers. For the most part I don’t run headers but for specific goals you mention I think they are worthwhile.

As far as noise, Ceramic Coated small tube headers are fairly quiet. And it is ALWAYS worthwhile to add noise abatement and insulating materials to a 50 year old truck cab…

[Steeveedee]

Originally Posted by geezer#99

Do you have any businesses there that deliver your rv to your chosen site. They use their truck.
We have those here on the Island. I know a couple guys that have big trailers and nothing to pull them with.
No muss, no fuss.

That would be an option, but then I'd be at their mercy for scheduling. I'm also going to look into a rental truck, except that I don't want to have "U-Haul" painted on my tow vehicle. It would be cheaper in the long run than buying another vehicle. Or maybe find a heavy hauler for a reasonable price. Mileage wouldn't be much worse.

[Steeveedee]

Originally Posted by Mike C

I have recently rebuilt an L36 427 because I had it and it has not been decked and is from a 69 Corvette. BUT, if I was to build a new motor from scratch (and I am considering this for a motor home) I would find a 454 and build a 496. The 427 rebuild was the same price as building a 496.

If it was a low mileage L29 I would probably consider running as-is since they have better compression and large oval port heads already. (Vortex 454 circa 96-2000) Maybe an RV type cam swap. And the headers. For the most part I don’t run headers but for specific goals you mention I think they are worthwhile.

As far as noise, Ceramic Coated small tube headers are fairly quiet. And it is ALWAYS worthwhile to add noise abatement and insulating materials to a 50 year old truck cab…

It's a CST, so it's fairly well padded. One can always use more, though. I already contacted Cold Case, as I have their radiator in my truck. They assure me that if the rest of the cooling system is up to snuff, the radiator can handle 500 CI engines. That makes sense, because the radiator in a Cadillac is close to the same size as the truck's and they can have 500 CI engines. And no, I'm not going to put a Caddy engine in it!

[Steeveedee]

I looked at the 496 engines. I don't need a lot of what they put in them, as I have no intention of spinning the engine that fast, ever. Plus a 3k stall converter, etc.

[geezer#99]

Alternate thought!
Do you have an auxiliary trans cooler mounted in front of the rad.

[Steeveedee]

Originally Posted by geezer#99

Alternate thought!
Do you have an auxiliary trans cooler mounted in front of the rad.

Well, it's just below the bumper, at an angle, which isn't the best for cooling, but I didn't install it.

[geezer#99]

At least you have one.
Heat is a trans killer.

[Steeveedee]

True. 4 years ago we went to Randsburg, out in the Mohave desert. Driving the 14 HWY north, the engine and trans (I have an oil temp gauge for it) both were running about 260º, pulling those grades. I know that they both can handle that for short periods, but I'm also sure that they were both heat-damaged. Whatever I do for an engine, I'm going to have the trans gone through, as a matter of course. I have since cured the heating issue (I think- I will be verifying that in late October).

[Mike C]

If you need a trans as well, in my mind it REALLY starts making sense to find a Vortec 7.4l and 4L80E combo running and driving you can swap into your rig. That combined with the 4.10 or even 4.56 gears solves lots of your problems of more pulling power. And better cruising without the trailer.

I regret not buying a rusty Yukon with 8.1 power and 2x4 4L80E a couple of years ago for $1800 in the parking lot of the local supermarket.

[Steeveedee]

Man, you're hurtin me! I suspect the switch would be less than the rebuilds of my current stuff, but I'm kind of allergic to the technology. Funny, because I used to write number crunching code designing spacecraft antennas as part of my job. Haven't done that in 20 years, though. 8.1L, hmm...

[Steeveedee]

So, I got the tach reconnected and ran the truck up a steep hill out of town, in second gear. It turns ~3500 RPM at 55 MPH. It warmed up about 10º pulling the hill, but that's insignificant. I'll have the trailer over to the dealership for a go-back repair in a couple of weeks, and then I'll take it up the same hill as I went up, today. It's not near as warm out as it could be, but I think I beat the cooling issue finally. We'll see. I don't think that I want to change the diff, if I can pull the trailer without overheating. I can hear the secondaries coming on in that RPM range, so it's gonna drink a bunch extra pulling hills. At least it shouldn't get hot, any more.

[geezer#99]

You could tighten up the secondary air valve a bit so it doesn’t flow as much.
Maybe a 1/4 turn more.

[Steeveedee]

I could fiddle with that a little bit, I guess. If I find a 454, the carb will need recalibration anyway, or I'll just buy one for a 454. I could go through the types and figure what jets and rods and springs I needed, but I know for certain that those primary jets aren't coming out of mine, short of stripping them. Once I find an engine, I know a local-ish guy who builds engines, and he has a dyno. Not for top performance, just to make sure that the setup is correct. I'm averse to going to the vendors who only seem to want to make a 6000 RPM monster, when I'm not going to rev it over 4k, even when I'm towing. Though it would be nice to have it already built, complete and dyno'd before I got it. We'll see. If I can tow the trailer up a steep hill without overheating, I could just go with a freshen-up on the current engine. I still have no place but the street for an engine swap, and I really don't want to do that, again.

[burnin oil]

I bet a stock qjet would work on a 454 without tweaking. I recently needed a qjet for a 305HO motor. I walked out to the barn and grabbed one off the shelf and threw it on the truck. Thing had been sitting for years but fired right up and ran like a top once the fuel bowl refilled. That carb was off either a 350 or 400sb. Only thing I tweaked was the idle mix. 2 days later it was hauling 6k pound loads of gravel. No low throttle or WOT problems at all. Only thing it needs is an adjustment to the air door opening. Its a little slow transitioning with a heavy load. I am sure the calibration isn't perfect but the fueling is pretty close. If you think about it the fuel curve is dictated by power output more than engine size in a stockish application. Higher rpm motors will differ due to cam duration and fuel curve from low vacuum. Not saying it's optimal but I am betting that it's in the ball park. After all the potential air flow is fixed and all you are doing is adding a little more or less fuel. Just my thought.

[Steeveedee]

Could be. I'll have to check it out. I do remember when I worked in a parts store, we stocked one part number replacement Q-Jet. When someone came in looking for a new one, no matter what engine they had, that was the carburetor they got.

[burnin oil]

That doesn't surprise me in the least. When you have a broke carb or none at all, a carb that is 95% tuned is definatly an improvement over what you had. The carb is really only allowing a certain amount of gas in with a given amount of air. It really doesn't care if it's a 305 or 454 since we set the initial throttle opening. Most stock engines perform in the same way as far as actual airflow requirements go so the carb keeps the mix going either way. Most tuning envolves correcting AFR via the jets and experienced tuners will try and adjust the timing of the individual circuits. Carbs are stupid simple but terribly irritable. Long story short all a rebuild has to do is make sure the jets are slightly rich along with the accelerator pump and the carb will perform well enough on several engines. Add in the qjets air door mechanical secondaries and it's almost impossible to over carb an engine.