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What years for SM465/NP203 combos.

82355

82355

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Again, I am only talking 1973-1987('91) GM trucks here.

I am 99% sure it was only available in 1974 and 1975. I have been told that it was an option in those two years, not standard. I also read somewhere that the NP203 came standard with the SM465 if you ordered the truck with a V8. I've also heard people say that all 1974-1975 SM465's came with the NP203.

Martin
 
Who cares! :haha:

ba dump ching, martin clutch zinger.
 
Pretty sure mine is a 75 but I only have the tranny and t/c. Heath, you just need a engine with a wide powerband. My truck works great in the sand.
 
It would just be nice to know solid answers to some of these questions.

Martin
 
80' 427 said:
Pretty sure mine is a 75 but I only have the tranny and t/c. Heath, you just need a engine with a wide powerband. My truck works great in the sand.
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I would say it does have a pretty wide power band, I drove the truck around with a stock stall 13" converter for a while and didn't have any complaints. It's not the clutch thats the problem, its how slow the SM465 is to shift, by the time you change your first gear I'm already at the finish line. Slight exeageration but you get the point. If the SM465 would shift like an M22 then I would have no problem with it whatsoever.

Actually I was just joking around because the NP203 sucks, however I realize that you manual truck guys would like that combo to make a nice doubler setup. Although the new magnum doubler is probably a lot better yet but very expensive. I'm glad I don't need a doubler for my type of wheelin, regular 205 all by itself is perfect for me.

Anyway, sorry to hijack with attempted humor, I won't be of any help with the years for the SM465/203, hopefully I'll find some answers for the TH400 thread Martin.
 
I'm not dead set 100% either but '74 or '75 are the years I've heard and seen but cannot pinpoint which year exactly.
 
For some reason, I thought that combo was also available in '76.

EDIT: Ignore me. I just read the factory brochure, and it clearly states that the NP203 was only available with the slushbox that year.
 
folkenheath said:
I would say it does have a pretty wide power band, I drove the truck around with a stock stall 13" converter for a while and didn't have any complaints. It's not the clutch thats the problem, its how slow the SM465 is to shift, by the time you change your first gear I'm already at the finish line. Slight exeageration but you get the point. If the SM465 would shift like an M22 then I would have no problem with it whatsoever.

Actually I was just joking around because the NP203 sucks, however I realize that you manual truck guys would like that combo to make a nice doubler setup. Although the new magnum doubler is probably a lot better yet but very expensive. I'm glad I don't need a doubler for my type of wheelin, regular 205 all by itself is perfect for me.

Anyway, sorry to hijack with attempted humor, I won't be of any help with the years for the SM465/203, hopefully I'll find some answers for the TH400 thread Martin.
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You just need more valve spring so you can spin it over peak power. It makes power on both sides of the curve. In circle jerk we used to spin a 1000 over too keep it in peak power off the corner. Wheel speed is wheel speed.
 
Exactly 74 only.
In 75 you could special order it but no years after that.
As mentionned 76 you could only get the 203 with auto.
 
80' 427 said:
You just need more valve spring so you can spin it over peak power. It makes power on both sides of the curve. In circle jerk we used to spin a 1000 over too keep it in peak power off the corner. Wheel speed is wheel speed.
Click to expand...

If I had more valve spring it would compress the hydraulic lifters. I have the engine just the way I like it. And you ought to know that a stroked big block with a dual plane intake and oval port heads with only 282 advertised duration is going to have a pretty broad torque curve. I like it just the way it is, and I consider it a pretty mild street build.
 
folkenheath said:
If I had more valve spring it would compress the hydraulic lifters. I have the engine just the way I like it. And you ought to know that a stroked big block with a dual plane intake and oval port heads with only 282 advertised duration is going to have a pretty broad torque curve. I like it just the way it is, and I consider it a pretty mild street build.
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I understand, I am just saying in the snow I shove it in 2nd (3rd to me) slip it to get it on top of the gear and hold it wot through the drift. I know it is somewhere around 5500 or so but it is wheel speed that paddles the snow. Once it gets more carb I may not be able to do that. 460cfm will only let it rev so high.
 
80' 427 said:
I understand, I am just saying in the snow I shove it in 2nd (3rd to me) slip it to get it on top of the gear and hold it wot through the drift. I know it is somewhere around 5500 or so but it is wheel speed that paddles the snow. Once it gets more carb I may not be able to do that. 460cfm will only let it rev so high.
Click to expand...

That sounds like fun, I like snow wheelin! I like it when you fly throuhg drifts and snow goes flying every direction and you can't even see where you are going for a moment. And is that on your K30 with the 454 I assume? Yeah thats a small carb, even at 85% effeciency it's pulling 460 cfm at ~4100 RPM. Have you hooked a vacuum gauge up to it, you are probably pulling a vacuum at WOT in the upper RPMs?
 
It is pulling vac, that is why I bought a tunnel ram and a second carb. They make bigger lpg carbs but they aren't cheap. I know it is too small but I like lpg on hills and the fact it is still like 1.86 or so a gallon.
 
I built lots of 500 and 350 cfm carbed stock car motors and know that even the wrong carb will do ok above its depression. It isn't the best way but sometimes you use what you have to use.
 
So do you know how much power you are losing with that cfm rating vs a 750 or so? Obviosuly it can still pull in air just not as efficiently, but I'd be curious to see what percentage of power it's actually losing.
 
No, I don't I do know my qjet on the old motor made alot more tq and hp than the lpg but this motor is different. That is kind of the reason I am going to the dual carbs. The tunnel ram idea is that unlike gasoline lpg will not fall out of suspension so carb signal isn't as important and it will hopefully use the long runners to make more tq down low. We pulled it starting at 1000 on the dyno with the current setup so the next one will get the same. If it does work I will have to cut a hole in the hood but who doesnt' think that is cool?

the current BBC is just junk I had. Gen VI roller short block, merc marine mag cam 228/.485 lift 115 lob sep (35 dollars) and 781 heads with stock replacement ss valves and heavy springs the compression is a low 8 to 1 with a performer intake and the dist curve shortened to about 8 deg of mech advance. Right now the power it done at 4500 which is 500 up from the last 454 I had. My new vaporizers got lost in the mail and I am school again for a quarter so it will be awhile till I am back at it. Plus I may be swapping on a newer cab with less rust but mostly A/c.
 
Kind of butting in here, but I had been doing some playing on desktop dyno 2003 (yeah I know, but I can't afford the various components to test!) with a 350 for the circle track car my family is involved in.

Of course that motor peaks around 6500RPM, so probably just a hair bit more than what you guys are talking about, but an 1100CFM carb vs the 750 was worth 10HP. I don't have the graphs in front of me, just what I had messaged back and forth about.

David Vizard has done a fair bit of work with carbs, and as far as I'm concerned, has pretty much dispelled "overcarbing" as a myth, at least under most conditions. It seems to be more about the carb design and if it's possible to tune it well enough that under various conditions (Idle, cruise, WOT) it's still able to provide good driveability. I noticed that summitracing now lists two different carb CFM's based on their calculator, one street and one racing as I recall.

500 to 650CFM carb testing here, worth a fair bit http://www.onedirt.com/tech-stories...g-part-1-budget-options-for-added-horsepower/
 
I have a 1050 on my 427 and it gained an easy 26hp going from a 750 dominator to the 1050. I didn't choose the carb for the cfm I choose it for the fuel and the cost.

I have a 355 that made 450hp with a 4412.
 
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