How To Torque The Head Gasket On A Chevy 350

‍What's special about the Chevy 350?

The Chevy 350 is an engine featured in Chevrolet sports cars and is frequently featured at vintage car shows on vehicles like the Corvette. The reason why one would want to know how to torque the head gasket on this particular engine is that automotive enthusiasts often rebuild and modify their vehicles.

Why do torque specs matter?

It's easy to blow off the idea of torquing bolts in a specific manner, at specific pounds. The reality is that especially in a sports car, bolts that are not tightened evenly can distort the head gasket and head. The head and head gasket are very important parts of the vehicle, especially in an original, and it isn't easy to make the metal head original again.

You can also cause your engine and head to overheat because of excess friction. You don't want that. Overly tightened heads can cause damage to the gasket, cylinder head damage, and the stripping of threads in the head and bolts.

What are the torque specs?

Here we go! Tightening the bolt is relatively easy – it's just a matter of tightening each bolt in sequence up to 3 times with different amounts of torque each.

Start with your torque wrench at 25 ft-lbs of torque. Set your torque wrench to 25 pounds or change your adjustable wrench to the right amount, first. Considering there are something like 18 bolts to tighten, the sequence becomes more important to maintain the right tightness and torque across all bolts.

A couple of other things to note: for blind holes, you should apply some engine oil or lubricant. You should also apply a sealant to any holes that will reach the other side and penetrate.

The instructions are well put like this: As the block has three rows of bolts, you can assign a letter, like A, B, and C to each row. A is for the top, B is the middle row, and C concludes with the bottom. Numbers are then included with 1 being furthest left and 8 being the furthest right.

The specific sequence is B3- A3 - C5- C4- A2- B4-C6-C3-B2-A4-C7-C2-A1-B5-C8-C1-B1. Remember to start with 25 ft-lbs of torque so you don't overtighten right away either.

The next step is to adjust your torque wrench or use a different torque wrench that does 45 foot-pounds of pressure. This is almost double the previous pressure. You'll want to retighten all the bolts in the same sequence as 25 ft-lbs of torque.

Finally, you'll want to do the same sequence after adjusting your wrench to 65 foot pounds or otherwise grabbing a torque wrench with the correct weight.

Can I re-use the original bolts?

You can if you still have them. Many owners try to maintain originality but the bolts can become rusty eventually.

Do engines have the potential to be different?

LT series engines built before 1995 have a little bit of a different approach. They tend to ask for slightly more tightening in the shorter bolts (hold the side of the bolt by side and you'll know what we mean) just a bit more to 67 degrees while the longs get 80 degrees.

Can bolts be different?

Bolts can indeed use different metals which have different tolerances. TTY bolts have their own instructions for LS engines which involve turning in sequence by 90 degrees, then turning the middle rears by 90 degrees again.

Should I look up torque patterns specific to my kind of bolts and year of engine?

While we can provide a base instruction on how to torque your head and gasket, it is a good idea to look up nitty gritty specifics. If you are changing the types of bolts or have a later year engine, look up the specifics for that combination, as there are many ways to complete this successfully.

How long will it take to torque the bolts?

If you are good with a torque wrench and follow instructions quickly, you should be able to torque the bolts in less than a half an hour. Torquing the bolts will probably be the easiest part if you are replacing a head gasket or doing something to replace or modify the head.

Should I take my 350 into the shop instead?

You can – but you can tighten bolts in the garage with the right equipment and the right research methods. The advantage to bringing your vehicle into a shop is that they are liable for any issues you have with the bolts, but it also means you'll be paying for labor – which can be considered for head gasket and head work in general.

Why do I need a torque wrench?

A regular wrench won't do. Your engine will face lots of vibration, and getting just the right tightness for that vibration is critical to avoid loose bolts, which can eventually loosen the head and cause serious problems. Torque wrenches are unique in their ability to be set to a specific amount of torque rather than that provided by your arm, and because they can be found at the right length for your vehicle.

Marking bolts

Given that we provided a sequence and it's esay to get distracted, consider adding a mark to your bolts as you go. You could use a marker or something to indicate that a bolt has already been tightened, especially if you can't quite feel the difference.

You could also use a torque measuring tool to indicate how tight the bolt is sitting.

In regards to marking and remembering where you were – just go slow. It's more important to get the torque amounts right. Naturally, you can just redo bolts by screwing them back out in the event one is over-torqued.