Choosing a small block for my truck

[hirschdalechevy]

Would I be able to tell by looking at the piston what type it is? I guess that would only help if it's flat topped, if it were domed or dished we'd be guessing how much? I have a camera that would fit down through the spark plug hole. Also thinking of doing timing set with gears, or should I stick with a chain?

Looking at the piston my help , but you still wont know how high in the deck they are or how thick your head gaskets are. Most 400's stock , the pistons are way down in the deck , ( I have seen them .035 down). The only way to really know what you have is pull the heads. The first thing a cam tech line will ask is , (whats your compression ratio) and you wont know. But if you dont want to go that far you could just find out what cam you have and pick a smaller cam and go with it. You should also run the numbers on the heads to see what cc they are as well.

If it was me I would pull the heads then you know what pistons you have , find out how low in the deck they are and you could pick the new head gaskets with the thickness you need , figure out the cc of the heads and then you will know your exact compression ratio . Then you can pick a perfect cam for the rpm power you desire.

 

[Sublime]

Do you know anyone that has a compression gauge that you could borrow?

 

[Green79Scottsdale]

I agree mostly with what all the others say. If you are pulling it out of the truck, yank the heads so you know exactly what you have. Then your parts selection can be that much better. And if you are changing the pan and all that, look into a one piece oil pan gasket. I have heard good things about using them in the older originally two-piece engines.

 

[KnockingDiesel]

Most tools I own, including a compression gauge.

I was going to ask if was a good idea to pull the heads and reseal the engine. Intake and rockers gotta come off any way

I intend to drive the truck as long as possible so labor is no trouble at all, the budgets not really a problem either. It's just time, I have built small blocks before but nothin fancy just stock work horses. I have a small garage at home but have access to a large shop if need be.

I can pull/install an engine in a few hours but I honestly don't know how long it would take to do everything. And then I'd have to order a cam/lifters/pushrods/maybe rocker arms while I'm there?

 

[hirschdalechevy]

Testing cranking compression wont help you find out what your static compression is , (thats the problem you have now , to low cylinder pressure from a long duration cam). Cranking compression is changed by the cam , (static compression and cam equals dynamic compression) , so the longer duration cam makes lower cranking compression and a short duration cam makes higher cranking compression. Cam lift can change cranking compression as well , but very little.

High static compression motor's need longer duration cams to keep the cylinder pressure in a range that is pump gas friendly. So low compression motors need a short duration cam to keep cylinder pressure up so you make good power at the rpm's you run at , (low end).

If everything is good in the motor you have it seems to me that the person that built it threw some pistons in it that said 9.5 to 1 on the box , (which that means nothing) and never checked how far they were in the hole , threw some good heads on it and picked a wild man cam and called it a day, no cylinder pressure , over cammed.

When you take it apart you will know.Also when you know your exact static compression ratio you will be able to select a perfect cam for what you have and how you intend to use your truck.

 

[KnockingDiesel]

Due to time constraints and parts, I decided to sell the 400, I order the GM Goodwrench 240hp engine should be here soon. Thanks for all the replies! I honestly would not have the time to properly tackle the 400 sbc or the 350 I already have, I will have maybe one weekend off in May. I'll update with pics when I get it on a stand

 

[KnockingDiesel]

Also I ordered all new parts for the long block, so it should look good when done.

 

[84c10Tony]

Way to go TJ, I liked the stock 350 idea with 5k miles, but a new LB is even better, keep the 350 for a backup!, wish I still Had a backup lol, ****, wish I still had a garage...
Also later, if you want more torque, just change the cam. Remember the zddp if it is not a roller on the oil changes.
Good luck and waiting on good pics too.