Tech Stuff

Time- and money-saving tips from technicians

General Motors’ pre-2003 LS engine blocks require two different primary head bolt lengths. The short 8 mm bolts are used on all LS heads as the inboard “pinch bolts.”
<p>General Motors&rsquo; pre-2003 LS engine blocks require two different primary head bolt lengths. The short 8 mm bolts are used on all LS heads as the inboard &ldquo;pinch bolts.&rdquo;</p>


When servicing or rebuilding a GM LS engine (which includes the LQ series), cast iron or aluminum blocks, be aware that there are two versions of cylinder head bolts, based on the design of the specific block.

2003 and later blocks require 11 mm x 2.0 x 101 mm bolts for all 11 mm locations. Pre-2003 blocks require two different length 11 mm bolts, including 101 mm and 155 mm in length. This is due to the depth of bolt hole locations in the block. These are referred to as long style and short style blocks.

Also, all OEM head bolts are torque-to-yield style and require a torque-plus-angle tightening. Some performance aftermarket bolts (such as ARP, as an example) do not require angle tightening and require only a torque value. If you’re using aftermarket head bolts, be sure to follow the bolt maker’s tightening specs. Aftermarket bolt makers will usually specify two different torque values based on thread lubricant… one spec for oil and a different spec for moly.

Rob Holland

Holland Auto


A Ford truck that features a two-piece driveshaft will feature a carrier bearing. If the carrier bearing wears out, and/or the U-joint behind it starts to seize up, the customer will complain of a droning noise that sounds like the truck is being driven over a road surface that has just been graded. It’s not uncommon for someone to first suspect the transmission.

Check the carrier bearing and driveshaft U-joints first and save yourself a bunch of time and aggravation. Also be aware that there are several different part numbers of carrier bearings for the Ford trucks, so save the original for a match-up.

Bob Young

Bobby Y Automotive


Some of the cast aluminum cylinder heads installed on Chrysler PT Cruisers were very poor castings with weak spots. If a spark plug literally blows out of its port, taking the threads with it, a cheap fix, as opposed to replacing the head, is to replace the threads using a kit that Goodson Tools offers. It allows you to restore the threads without removing the head. Naturally, care must be taken to avoid debris being dropped into the combustion chamber, but it is feasible. I’ve done a handful of these repairs with total success. One customer’s engine blew a spark plug out of the head after only 10,000 miles. After the repair, he now has over 150,000 miles with no problems. It takes a few hours, but it will save the customer a load of cash as compared to replacing the head, or pulling the head to perform a thread insert fix.

Eric Pullman

Greber Repair


If you have a customer who wishes to install a mechanical or aftermarket electric oil pressure gauge onto a GM LS engine, an easy way to make an adapter is to use an old OE oil pressure sender. Cut off the plastic connector flush with the metal base, and then drill out the center using a 1/8-inch NPT tap. The 16 mm thread OE sender base will thread back into the block in its original location. The 1/8-inch NPT port will then allow you to connect any oil line with a 1/8-inch NPT fitting. No modification to the block is needed.

Scott Gressman

Gressman Powersports


This is an old trick, but it works. Whenever you encounter a frozen threaded plug in a cast iron engine block, use a torch (using acetylene only) and heat the plug until it’s cherry red. Then touch a chunk of pure wax to the plug. The wax will liquefy instantly and will migrate into the threads. Nine times out of 10, the plug will walk right out, but be sure to remove the plug while it’s still hot. Don’t let it cool down first, as this might allow it to seize again.

Naturally, this should only be done with the block removed from the vehicle. And obviously, be sure to wear eye protection and heavy gloves. Cheap candle wax isn’t the best choice. Buy a chunk of pure, non-colored wax or paraffin.

Bob Fall

Fall Automotive


Be aware that the flywheel bolt holes on the rear of the GM LS/Q series crank flange may be open to the crankcase (open to the back of the reluctor wheel). If you don’t apply thread sealer to the flywheel bolts, you may have a nasty oil leak that will at first glance appear to be a rear main seal leak.

Before you bolt the flywheel or flexplate to the crank, make sure that the bolts have a good thread sealer, either a traditional sealing compound or a thread licking compound that also seals.

Brian Goodman

Great Valley Auto


Be aware that some Chrysler vehicles equipped with the 41TE automatic transaxle (PT Cruiser, for example) may feature a transmission oil pan with a drain plug that faces the rear.

The inside protrusion of the drain plug bung can interfere with the transmission oil filter, preventing a good pan seal and potentially damaging the push-in plastic dowels of the filter.

A replacement pan is available from Dorman Products that features a drain plug at the bottom floor of the pan to avoid this problem. This pan is also a good replacement for original pans that never originally featured a drain plug.

Greg Burgy

Alderman Specialties

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