Is it really worth the extra work to build a 383?

[jim_in_dorris]

Well, the marine stuff is out, not only after 1project2many's comments, but my research. The 302 idea would work if I saw high rpm's, however using my handy dandy self made excel spreadsheet, with my 3.73 gears, 700R4 and 265/70/15 tires, at 2350 rpm in 3rd gear I am doing 55.5 mph, 80 in overdrive (not that I would tow in OD). if it kicks down to second, 3500 rpm is 51 mph. I need torque in that kind of range. The 406 was a torque monster on DD, but I give up a lot when I switch back to a standard flat tappet cam. The trailer loaded is going to be somewhere just under 5000 lbs. loaded, so I will need lots of torque. I guess my real question is with the 350, I get about 415 #/ft of torque from 2000 to 4000 rpm. Will that work? The 383 gives me 450 #/ft of torque from 2000 to 3500 rpm. obviously this is DD, so results may vary. My question is mainly if I have over 400 #ft of torque at the flywheel, will it do the job towing? BTW, thanks everybody for chiming in, I really appreciate talking to people that aren't trying to sell me something but have real world experience with the kind of motor I am interested in building.

[1project2many]

Relax! :)

Youre trying to build an engine with more torque than most production engines. It will pull your trailer ok. You've got more to worry about in the driveline, trans, cooling system & etc. After all, you're increasing factory torque by what... nearly 100%?? And you're expecting to apply that force for long periods of time. Torque breaks stuff!

If the 406 is your cup of tea then don't sweat the roller cam. DD makes assumptions about roller cam profiles that aren't correct for many of the street hydraulic rollers. It's not uncommon to find a street roller with a profile like a flat tappet cam... mild ramps and small duration at the peak. Not what a roller's about but nice and quiet and doesn't wear out guides. A retrofit roller is available if that's what you need, even though it costs a fair amount. DD also makes big assumptions about exhaust systems with headers. Can be hard to figure out a real world duplicate of their model. If you really want the roller cam block accept the limitation of a 4" bore and call it a day. DD also has old design turbo maps, or at least my version does. The information to properly map the turbo in DD isn't always available and the ones they offer often look very unappealing on mild engines.

If I can find it, I'll try and dig out my DD 600hp 302 turbo build when I get home. IIRC power was all in by 6K and the torque curve wasn't too bad. Parts combination was fairly mild.

[jim_in_dorris]

1project2many, thanks. I have already rebuilt the 700r4 to handle more power, rebuilt all the driveline with new stuff (hopefully that works) and will be upgrading the cooling soon as I have a coolant leak at the filler neck of the radiator. Yes it is a lofty goal of increasing torque. Part of the reason for asking all the questions is that I completely understand that DD doesn't always make good assumptions. Does Comp-Cams software do better or worse? I suspect worse because they are trying to sell something. The bottom end of the engine isn't that much rocket science except for getting quench right, but the cam selection and heads make up for it in sheer numbers of variables. If DD is way off on torque specs for this roller cam, maybe I do want to look at flat tappet cams. I just want lots of torque down where I would be using it. Thinking about it, the shape of the torque curve has a lot to do with what I want. I tend to like flat torque curves not peaky torque curves.

[1project2many]

You're putting this kind of torque through a 700!!!??? <whistles> Get a big cooler. Get a beeg, beeg, beeeeg cooler. Also consider using fittings from a later 4L60E (if they fit) to use 3/8" cooler line.

Does Comp have engine dyno software? I've used their cam selection software to pick cams before. It worked ok but cams have come a long ways since the '90s. I use Engine Analyzer Pro for modeling but it asks for a lot of variables that aren't always available if you don't have parts on hand to measure.

DD makes assumptions about the lobe shape that may or may not match a real cam. If you're looking at a spec card for a cam use the cam math section to enter as much data as possible and generate a more accurate model. Last I knew DD couldn't even model asymmetrical lobes. The way I see it is this: If DD gives numbers you like, try to ensure you can get a cam that matches DD's model.

[RobertISaar]

IIRC, the software used by comp is more or less a spinoff of desktop dyno.

engine analyzer pro? last i knew, that was not cheap....

and that kind of torque while towing, i would be looking at 4L80s(if staying automagic), just saying.

[gregs78cam]

CamQuest has a very similar feel to DD, and they seem to be very close on the numbers. If you can get actual head flow numbers they can be 'more' accurate, but it's all relative. I would look into a stroking a factory roller block.

A 700R4 should be ok, as long as it's not setup to shift hard at greater throttle openings, that is what breaks parts, more line pressure is ok, and more of what you want than hard shifting. But I agree with Robert, 4L80E.

[jim_in_dorris]

Nobody loves my 700R4 Boo Hoo LOL. I am hoping that the tranny builder (who has done a couple of trannys for me and really knows his stuff) is right when he said he built it to handle 500 hp.
I have been looking at flat tappet cams and kind of like the Lunati Voodoo 60101 cam, I think I might forgo the roller cam just to save the money to put into better heads.

[1project2many]

If your trans survives this trip, I swear I will sacrifice a Honda in it's honor. :)

Too bad the Bowtie Vortec's aren't an option. The small port version is ideal for your engine.

[jim_in_dorris]

I can't even begin to tell you how may 700r4's I've scattered across the pavement. I think we went thru 9 in our first s10 blazer. The 2.8 V6 just couldn't support it. I plan on flogging the truck after the initial break in period with lots of local towing, we have a few 6% grades around here that are pretty brutal on tow vehicles. If it even looks like I am having a problem, I might have to learn $0E code. And I am just barely getting a handle on $0D. And be sure and make a video of the Honda sacrifice, I would watch it over and over and over...... LMAO!

[1project2many]

History lesson. GM's Hydramatic Division designed transmissions from the early '60s to 1990 They sold transmissions worldwide to customers such as BMW, Jaguar, Rolls Royce, Daewoo heavy equipment, and many others. They designed nearly legendary transmissions such as the Powerglide, THM350, THM400, and 4L80E which are still in use in many applications today. They know their stuff.

in 1979 Chevrolet executives looking for a new four speed automatic told Hydramatic to pound sand and proceeded to design one of the most problematic and expensive transmissions ever released by a GM division. Chevy spent 6 years trying to fix it but it was eventually given to Hydramatic to straighten out. Hydramatic spent another 4 - 5 years working it over and in parallel, designing an electronic version of the trans. It took until 1992 to achieve "not too bad" status and other than the name, there aren't many parts shared between the early and late transmission. I have a list at home of all the updated parts beginning in the original trans and ending with the last 700R4. There are 2 1/2 pages of part numbers.

Also, don't forget that the torque converter provides torque multiplication and the gears do the same. If you are fully loaded in 1st gear you could be providing 400ft/lbs * 2.25 multiplication through converter * 3.06 1st gear ratio = 2754 ft/lbs of torque produced at the driveshaft. Yep, 2754. Hang on, baby. :)

[1project2many]

Jim... I just wanted to mention this. I was talking to a very good transmission man the other day who mentioned that for a short time you could get dual stator torque converters for 700R4 applications. Where typical torque multiplication is around 2 - 2.5:1 these were good for 3 to 3.5X. The problem is that they worked. 4.3L engines making 250 ft/lbs at the flywheel were destroying the cases of stock trannies as they'd produce nearly 900 ft/lbs at the input shaft of the trans. Now I don't know if this is is a warning or if it means you should try and locate such a beast for your own application, but I do know that I'm considering a 4L80E swap.

[jim_in_dorris]

Holy Cr@p if I make 420 FT/LBS with a 3.5 multiplier Torque converter I would be hitting the input shaft with 1470 Ft/Lbs. That will break stuff. I guess I could go all billet. There goes a years budget.

[RobertISaar]

be great for us small 6 guys though. :D