400 rebuild or 290hp crate 350

[lapranch]

havn't decided if I should have my small block 400 rebuilt or go with chevy 290hp crate motor. The crate motors run about $1700 for a long block.
Anybody run one of these crate motors? they seem like a good deal to me.
or would I be better off upgrading my 400?

[Billla]

For price, it's hard to beat a crate engine. You could definitely build that 400 into a torque monster, but likely for closer to $2500 depending on what you find during teardown.

IMHO, the choice is more around price and the amount of work you want to do vs. which engine is a better choice. If you can deal with the down time, it might be worth tearing down the 400 to see what you have to work with before making a decision. In any case, someone will want the 400 if you don't

[lapranch]

have had many chevy cars and trucks over the years. They've always had 350's.This is my first 400 so I'm not up on all the pros and cons.
It's the original motor in my 79 Jimmy with all smog junk. a lot of miles on it but truck still gets up and moves.

[Billla]

The 400 has a few shortcomings; the bores are "siamesed", meaning they're joined without water circulation between them. This means that the bores will never be completely round, and the engine can overheat more easily if the cooling system is marginal. The main webs are also weak, oddly enough the 4-bolt blocks are weaker than the 2-bolt blocks due to the shape of the crank caps. The stock rod length is 5.565, which is not great for bore/stroke ratio.

The upside is 50 more cubes, which is always a plus and easy upgrades to stroker cranks and longer rods. Bottom line is that you can easily build a very strong engine from the 400 that will make more torque (and lower) and more HP than a comperable 350 build.

[lapranch]

thanks for info
I am curious about the 290 horse crate engine compaired to the 350 "goodwrench" base engine that runs about $500 less but comes with a much better warranty.
Any input on these two motors would be appreciated.

[Billla]

The 350 Goodwrench engine is a GM OEM replacement; the 290HP is a "General Motors Performance Parts (GMPP) engine and is considered an "aftermarket" engine - hence the difference in warranty. The spec comparison is pretty clear. There are other more powerful GMPP engines as well - the 330HP is really a nice street engine.

Another option for you would be to buy a GMPP shortblock and put a good 4x4 cam and some stock Vortecs - another torque monster for a reasonable price.

[jimfulco]

The only difference in the two GM engines is the camshaft, which is the same as the old 350hp350/L-82 cam from the late '60s & '70s, pn3896962, and which has too much duration for the low compression ratio.

[Pyrotechnic]

The only difference between the 260HP and 290HP is a cam, and I've heard that the cam was poorly selected for the 290HP in that it's too radical for 8.5:1 compression. [EDIT: jimfulco beat me to this by a few minutes.] I always thought it would just be better to get the 260HP stick a more suitable cam in it and end up at the same numbers with a better power curve, but the downside is that you lose your warranty doing this. I think these motors are a very cost effective choice if you want something thats not a race truck but has good power.

However, if your 400 block will clean up with a .030 or .040 overbore, and your crank is solid, I would get a set of 5.7 inch rods for it and the pistons for this application. I recommend the rod upgrade because you will have to get new pistons if you bore the block, and 5.7 rods are very common and very cheap. Have all this internally balanced and you got a winner. Though more costly, you'd have a quite a bit of torque and power in the end with this combo.

[Ricks1971]

I would go with the 400 myself. If you have a 509 block casting, the cylinders are not siamese. Like PYROTECHNIC said you can change the rods to a 5.7 rod. The cost of building a 400 right means becouse its a externally balanced motor which means you need to balance the motor. (crank,harmonic balancer and flex plate) it costs abit more.

[MylilBowTie]

I would use an internal balanced crank in the 400 if you plan to make some power. They cost a little more but what good is a broken crank and trashed block?

[streetstar]

The 260 and 290 horse GM crate engines have their hp's measured at the crank, not the driveshaft, --- The 400, with a well planned, conservative build, should have more grunt than either one of those engines.

290 hp for 1700 sounds good, but those motors are not even in the same league as some of the engines GM has put in , say, a 3rd Gen IROC that were rated at a much lower power level (net power) --
but they would be a good reliable foundation for a truck anyway though

[lapranch]

I crawled under my very greasy engine and confirmed It is a 509 casting by seeing "509" embossed on side of block.
I assume this is good one to have. I'd kind of like to rebuild it. Mainly to keep the jimmy original and to have something a little different.
Any advice would be welcomed.

[Billla]

Budget, always budget

A performance overhaul will run $2000 or so - how much more than that do you have to spend?

[Billla]

Originally Posted by Ricks1971

IIf you have a 509 block casting, the cylinders are not siamese.

I don't know of any stock-block 400's that aren't siamesed bores. They all have the same bore centers and bore...there's not enough room there for water all the way around. Source of your information?

[Zoomad75]

Originally Posted by Billla

I don't know of any stock-block 400's that aren't siamesed bores. They all have the same bore centers and bore...there's not enough room there for water all the way around. Source of your information?

Ditto on that! Where are you coming up with 509/400 blocks don't run siamesed bores? I've been around a few and read up on the subject and have never heard of a non-siamiesed bore 400. I can't imagine GM tooling up two separate castings for the same size engine The way I undersand it, there's no way to fit the 400's bore size in a conventional small block wrapper without eliminating something. In this case they dropped the water jacket between the bores to facilitate the large 400's bores while maintaining the same bore spacing as every other small block made.

I'm not sure how the giant World blocks get 427/454 CI out of thier small blocks but they aren't stock GM castings for sure.

I'm not trying to start a flame war I'd just like to know where the info is on non-siamesed bore 400's are.