# How hard is it to build an engine by myself?



## str0b3 (Apr 23, 2021)

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## armyadarkness (Dec 7, 2020)

str0b3 said:


> I am new to cars, I got a 1968 Lemans and need a motor for it I'm wondering how hard is it to completely rebuild a motor. I am wanting to buy a Pontiac/Chevy 400 for cheap that needs rebuilt and do it myself if possible. Is there any special tools needed to rebuild an engine that I would need besides basic tools, is there any chance of me completing it and it being a running engine by the time I get done with it... I plan on taking it slow and reading up on a lot of stuff and watching youtube videos for reference as I go along. Also what are some legitimate reasons it would be better to go with a Chevy 400 or Pontiac 400?


You're already over spending, before you even start! Pontiac 400's arent cheap, and Chevy 400's are as rare as dinosaur eggs. If there is no trans mission or it's a manual, I would get a Chevy 350 and build it. If there is a trans then build a Pontiac 350. Those are the cheapest routes.

Chevy being much easier and cheaper.

It's not very hard to build an engine. You just need a torque wrench and solid information. Have a machine shop do the block for you.

All this being said, you really have to stick to budget build plan. The minute you go down the performance rabbit hole, you'll be spending $4000 in your garage or $7000 in a shop.


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## Sick467 (Oct 29, 2019)

It all depends on so much, not to scare you off, however. It helps to have a mentor. That's how I built my first engine (a Pontiac 400). The key to a successful build, given that you can do your research and understand it, is to have a good faithful trusted machinist to make sure the details in the block and heads are spot on. A few thousandths out of spec here or there will cause you to pull the motor and start again. For example, I had this happen with a SBF build once. I did not have the knowledge, at the time, or the proper measuring tools to check the machinist's work. The cylinder bore in two of the cylinders were 2-3 thousandths oversized and cost me the block and some pistons. I did not find this out until after the engine was fully installed in the car. Lesson learned that you can get lucky most of the time, but with a bad apple in the works...the odds are against you.

If I were building a fun street car and did not want to keep it original'ish, I would consider the Pontiac 455 (or the Chevy 454). Remember - there is no replacement for displacement. You can build a 400ci with 400 HP, but a 455/454 will more easily produce the same HP and be closer to a stock build. This means less radical machine work, more stock parts, and an engine that is less likly to tear itself apart (read longer life and take more abuse).

A good piece of advice is to find a motor that was built stock by GM that has a higher horsepower from the factory and follow those specs. This motor has already been "figured out" and will not require much, if any, modifications. Once you start modifying specs...your learning curve gets steeper. For example, you want to mill some low HP heads down to up the compression, now the valve train can no longer be stock and you have to determine what the springs and pushrods need to be. With a stock set of high HP heads...it's more of a matter of ordering stock parts. You can improve upon this stock design with a different cam (no too different), roller rockers, better intake, and headers and get a bit more out of it, along with porting the heads and intake. This would yield the easiest "modified" build and result in a fun car.

I have to give my opinion on using the Pontiac motors...do that if you can afford it! If noting else, it makes it more unique and true to the Lemans. 

Congrats on the 68, you're going to love it!


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## Jared (Apr 19, 2013)

If you go the Pontiac engine route, I strongly recommend picking up Rocky Rotella's book. Read through and see if the entire process looks like something you can do. If not, you may want to start with a short block or have a machine shop/engine builder do the bottom end and build up the top yourself. Another route is you can buy unassembled engines through Butler where you pick the rotating assembly and they provide a machined block, and you put it together. With it coming from Butler, the machine work should be perfect. 

Good luck with the build. There are a lot of resources on here to help you along. I recommend you think hard about what you are trying to get out of your car and make a realistic budget, and then add around 30 - 40% because the little things you don't think of add up quick. Not to scare you away, but these are not cheap to build. I'm doing a 461 build now and my cost is way north of $10K. A close to stock Pontiac 350 would be much less.


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