The question 400 or 350???

[84 400]

Well since i bought my 84 i have wondered this and since i got some free time tomarrow i would like to lay this one to bed once and for all. When i bought my truck from a guy in texas it had 3 thousand miles on a new motor. The motor was purchaced a while back when the guy was stationed in Georga (in the army). The motor was bought for his then camro project which he sold before the move and never put the motor in. so it was brought from GA to Texas with him and his family. The 84 had a 305 but the guy he bought it from had put a 383 stroker in it. and rebuilt the th350. Eather the 383 went bad or the guy i bought it from did not like it for one reason or the other so he had his buddy pull it out and drop in the current v8 and in return the freind of his got the 383 . Come to find out the guy i bought it from had a fight with the engine builder down in GA about the size of the motor. He ordered a small block 400 from the guy but thought the guy shafted him and gave him a 350. I have done an oil change but found out that the filter for a 350 aned 400 are the same. So were can i get the numbers from to lay this down once and for all. i want it to be the 400 because every one and the mother have 350's (not that they are bad but it is nice to go to a cruse in and say it has a 400.) Also this thing has some power. put the pedel 1/2 way and it will just spin from 0 to 30 mph. It pulls hard and if it is a 350 i wonder what the builder put in it. i would love to have built it my self but i bought the truck for less then the guy paid for this motor. so were do i look for the id code and were can i trace it ?

Thanks
ian

[magnethead]

i it's internally modified, the block numbers will reflect what it was origionally, not now. You'll have to pull the pan and/or heads to see what it really is.

[piecesparts]

Is there a flat spot on the block (just in front of the head on thepassenger side of the engine)? If so, take the numbers off of there and see what the dealer will cross reference them to. In reality, Anyone can build a dang responsive 350 or 400 motor. The motors are basically the same with the difference being in the crank's "throw". the 400 has a longer stroke than the 350. That is how 383s are created, a 400 crank in a .030 bored out 350 motor.

[Slonaker]

Well, if it is a 400, that is a factory displacement, and would be indicated by the numbers on the block. You can pull the numbers off the back of the engine (at the very back of the block, behind the heads, by the distributor, I can't remember which side) and run them at www.mortec.com.

Displacement on smallblocks is hard to determine without looking up the numbers. As magnethead said, sometimes (like with a 383) you can't even go by the numbers because the engine is made from one kind of block and another kind of crankshaft.

Because of this, it is easy for sellers to lie about what is in their vehicles when they sell them to try to raise the value. Some folks aren't telling lies, they are just repeating what they were told when they bought it.

In other words, don't be surprised to find out you have something besides a 400. If you don't, hopefully it will be a 350 and not a 305 or an old 307 or something. The best way to look at it is that you have a good, strong running smallblock regardless of what it is.

Slonaker

[b454rat]

Look at the balancer, is there a groove looking thing on it?? It could be internally balanced, so that theory is out the window. If it lights the tires up that easy, it's a least a healthy 350.

[84 400]

alright thats for the help. i will get the numbers when i get a chance. I hope to hell it is not a 305 and if it is it is the baddest one i have ever come accross. It has to be at least a 350 cause the filter on it matches up with the 5.7 code from napa but that same code applies to the 400 and i think the 305 as well i bet i will find the block is a 400 or 350 and if it comes out that way then if it is a 350 block i will guess it is a 400 crank in it cause i am not about to drop the pan. when i get the numbers i will let you know at any rate it is a nice motor i am only wondering because when i go to shows and people ask me what it is i can only say it is a very strong small block. once i get the numbers then i will know what the block is and then i could say it is a 350 or 400.
thanks for the help guys

[scotto0609]

Tell them it is a 305!! It will leave them guessing when you destroy them at the first light!!!!!!

[AirMale]

If it is a 400 you can tell by looking at the flexplate. It will have a weight on the inside of the toothring. As far as telling if it's a 350 or a 305 you have to decode the block code.

[84 400]

Originally Posted by AirMale

If it is a 400 you can tell by looking at the flexplate. It will have a weight on the inside of the toothring. As far as telling if it's a 350 or a 305 you have to decode the block code.

it is not easly acessible right?
Thanks

[AirMale]

very easy.....drop the the inspection cover in the front of the trans (4-bolts)?

[magnethead]

yes, 4 bolts hold the cover on.

[84 400]

and then look up at the flex plate and search for a weigh?
Thanks agian for the help

[bigarmzz]

isnt there "3" freeze plugs on the side of a 400, v/s only 2 on a 350 or 305?

i was always told that was the quick and easy way to know for sure if it was a 400

[MylilBowTie]

They have 3 and 2 freeze out plugs on 400 blocks. I would try to get the suffix code off of the front pad on the block under the alternator area. I would also take the valve covers off and see what kind those are as well. The harder of all of them is the casting stamp in the main rear on the driverside. Using all of these will get you a pretty good idea of what it is.

If you really want to know what size the crankshaft is you can pull the oil pan. The crankshaft if it is a gm or maybe even aftermarket will have a casting number also.

[82c10]

IMHO, i would just look at the numbers behind either of the heads, turns out the 305 that was in my truck was actually a 350.