SU'dCrazy280 Posted January 28, 2007 Share Posted January 28, 2007 My Z is a 76 280 and I just bought a 1979 GMC Sierra Grande from a friend for $300!! The truck is a hunk of *&^%, but the part I love is under the hood. The 6.6 liter 400. I am putting it in my Z, and I think I'll have to put in a different tranny, and do a small rebuild. The engine runs great, and I am planning on putting a big cam in, and maybe do some headwork. The compression looks good, and I don't want to have to mess with the bottom end if I don't have to. The engine has a four barrell carb (probably rochester), and the HEI distributor. The tranny is an automatic, and is most likely a TH400 because the 700R4 didn't come out until later. Would I have to switch the tranny?? I don't want to go automatic, but if the tranny is good I might do it temporarily. Is the tranny itself geared to low to be fast? Or is it the truck's rear end? B/c the truck is not very quick. I am pretty new to domestic engines so bear with me. I can't tell if the mounts are 2 or 4 bolts, I could probably go figure it out but it's cold outside!!! I want to use the JTR kit if I can. Oh, and I'll have to take the giant transfer case off too. Any input or advice would be great because there is not much about 400's on the search function!! Thanks Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted January 28, 2007 Share Posted January 28, 2007 The trans won't work, if it's for a 4wd, so scrap that idea, however it is valuable for a 4x4 rebuild core. If your going to take the heads off and replace the cam, might as well freshen the bottom end as well, new bearings. If the bores are good (not likely), then rebore and install some new KB hypers and new rings. If you don't twist it higher than 4500 rpm you'll be fine otherwise opt for installing ARP rod bolts as a minimum in the stock rods and get them resized on the big ends. Doesn't take a "big" cam to work in a 400. Isky has a nice little 270 mega hydraulic. Works with stock converter, makes good low and mid in a 400. Make sure you get the right valve springs, have the heads set up right too. Top that with a nice little dual plane intake, HEI and you'll be cookin' in no time. Quote Link to comment Share on other sites More sharing options...
Michael Posted January 29, 2007 Share Posted January 29, 2007 First, congratulations on finding a 400 SBC! It is almost universally true that 70’s-80’s full-size trucks have disappointingly poor acceleration, even with large-displacement engines, at least in stock form. Part of the problem is the wear on the engines, part is in inefficiency of the driveline, part is the weight of the vehicle; but the worst part is the abysmally poor breathing capacity of these engines in stock form; with stock intake-heads-valvetrain-exhaust, especially for a truck, net hp ratings hovered around 150. Even the big-blocks barely made it over 200. Volumetric efficiency was poor (70%? 60%?) and peaked at something like 2000 rpm. Even if the bottom end is in decent shape - bearings are not knocking, rings are holding compression, cylinder bores are not damaged, and so forth - you will most likely find yourself replacing the pistons to get adequate compression, and replacing at least the rod bolts to get piece of mind about “high rpm†reliability (I was going to say "high = 5500", but they I noticed that dr_hunt mentioned a 4500 rpm limit!) . If you buy modern aftermarket aluminum heads, it is hard to avoid having to get new pistons. And this means a bottom-end rebuild. I started with a 454 BBC from a 1978 Suburban, and ended up with a complete bottom-end rebuild, though I did retain (after considerable machine work) the stock block, main caps, crank, rods and damper. For a first iteration it is not inconceivable to keep the engine completely stock (in hindsight I should have done the same) while you solve the systems-integration issues of the swap, and become familiar with tuning and troubleshooting the engine. Acceleration won’t live up to V8 hybrid expectations, but it is a good baseline, especially when money/time/tools/resources are tight. Quote Link to comment Share on other sites More sharing options...
SU'dCrazy280 Posted January 29, 2007 Author Share Posted January 29, 2007 Well thanks for the input. Maybe I will go with a manual tranny now that I know I can't use the one it has. This project will probably mostly happen this summer and I used to work at an engine and machine shop so I can use the tools and the boaring machine anytime. The owner will know exactly what to do since he has probably built upwards of 1000 of them. If anyone needs a strong L28 bored .040 over with flat top pistons, a racing cam, then I'll probably be selling it this summer too. If anyone else has anymore input then I'll be happy to hear it, as far as transimissions, clutches, etc. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted January 29, 2007 Share Posted January 29, 2007 The 400's have shorter rod bolts and less stiffness inbetween the rod bolt and the beam. I've seen 'em turn 7K all day in circle track cars using good bolts and rod prep, and my buddy ran stock rods and bolts in his mud bogger. They just didn't last very long. Notice I didn't say all season and I did say all day. If you want it to run longer than one day, you'd better upgrade to 5.7 rods with bolts if you want to stay oem. Better yet, it's been said over and over again, cheap insurance is a set of eagle H beams for $350!!!! Of course you have to rebalance the rotating assembly. Quote Link to comment Share on other sites More sharing options...
SU'dCrazy280 Posted January 30, 2007 Author Share Posted January 30, 2007 Well, thanks for the advice guys! Now all I have to do is figure out a manual tranny! In the JTR manual it looks like the "world class" camaro transmissions are the best for cheap? Are they difficult to come by? I've heard there is a pretty good 4 speed out there too... Quote Link to comment Share on other sites More sharing options...
datsunlover Posted January 30, 2007 Share Posted January 30, 2007 In my exp. it's hard to find the GM T5's where as the mustang T5's are evrywhere... Depends on your area I suppose... I've heard the ford 5 gear can be made to work with a chev (swap bellhousings and use ford clutch disk.. or change input shaft to chev) but its a bit of mucking around. They call them 'World Class' but really they're not that strong.. if you go out and beat on them all day, they'll break. (Like anything really..) I know that Tremec (sp?) makes good tough trannys, but they are pricy. As for a 4 speed, you're probly thinking of a Muncie or Borg warner (T10 I think..) Those are great trannys too, but have the shifter mounted on the side and the linkage may cause you issues with the tunnel/shifter hole. Quote Link to comment Share on other sites More sharing options...
Forces Posted January 30, 2007 Share Posted January 30, 2007 My Z is a 76 280 and I just bought a 1979 GMC Sierra Grande from a friend for $300!! The truck is a hunk of *&^%, but the part I love is under the hood. The 6.6 liter 400. I am putting it in my Z, and I think I'll have to put in a different tranny, and do a small rebuild. The engine runs great, and I am planning on putting a big cam in, and maybe do some headwork. The compression looks good, and I don't want to have to mess with the bottom end if I don't have to. The engine has a four barrell carb (probably rochester), and the HEI distributor. The tranny is an automatic, and is most likely a TH400 because the 700R4 didn't come out until later. Would I have to switch the tranny?? I don't want to go automatic, but if the tranny is good I might do it temporarily. Is the tranny itself geared to low to be fast? Or is it the truck's rear end? B/c the truck is not very quick. I am pretty new to domestic engines so bear with me. I can't tell if the mounts are 2 or 4 bolts, I could probably go figure it out but it's cold outside!!! I want to use the JTR kit if I can. Oh, and I'll have to take the giant transfer case off too. Any input or advice would be great because there is not much about 400's on the search function!! Thanks 2 or 4 bolt mounts? Do you mean MAINS? If so (don't quote me hear) But I think I rememeber reading somewhere that on a 400 block you can tell if the mains are 4 bolt by the amount of freeze plugs on each side of the block. 2 freeze plugs = 2 bolt mains, 3 freeze plugs = 4 bolt mains. Or you could just take the oil pane off. Probably wouldn't be a bad idea anyway, just to check for any surprises you may not be aware of already, and new pan gaskets never hurt. Side note: It's no secret that SBC 400s are prone to over heateing, you might think about a nice electice water pump that pulls modre GPM that whats on the block now, assuing the w/p is stock. BTW, nice find, thats a killer deal, if it runs good and does burn oil. Quote Link to comment Share on other sites More sharing options...
Guest hamlet8900 Posted February 6, 2007 Share Posted February 6, 2007 So you have a running engine with some horsepower? Intelligently install it in the car, make it run and go have fun. If it blows up have it rebuilt stronger and better. Otherwise you'll spend all summer looking at it collecting dust in your garage. Spring is right around the corner. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 6, 2007 Share Posted February 6, 2007 ^^^ Good advice, if you ask me.^^^ Quote Link to comment Share on other sites More sharing options...
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