Engine 99 GT Engine Build - Questions and Advice


New Member
Sep 22, 2018
I'm thinking about tearing into my engine and giving it a rebuild, or maybe getting a new block altogether for my 99 GT. I'm less asking questions and more looking for advice. If I was going to build the 4.6 up, being an extremely inexperienced engine builder (0 experience to be exact), should I get myself another engine and work on that and try to forge it myself, or would it be better to pick up a pre-assembled shortblock with forged internals. So far the only two shortblock providers I've found myself interested in are MMR and Modular Headshop. Any recommendations for other shortblock providers and does anyone have experience with these two providers? At this point I'm just looking to be efficient with both my time and money, and am in no rush because this is planning for the future within the next year maybe. Any insight is appreciated and if you have questions about what I want to do with the car or anything else feel free to ask. Thanks :)
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SN Certified Technician
Aug 14, 2009
Houston Texas
GM V6 3.5 VIN "N" RPO LZ4

Just wondering. Do you have any engine builders or engine machine shops in your area? Consider paying them a visit to see what you can learn about their operation. How's the quality of their work? Talk to some customers.

I recently built my first engine from individual parts. A GM V6 3.5 VIN "N" RPO LZ4. This was to go into a 2007 Pontiac G6 hard top convertible. Through a series of mis-adventures I ended up with three motors. None were usable motors. Basically three big buckets of parts (cores).

With the help of a local machine shop:
  • Gave me information that I needed to know HOW to label and organize the parts before disassembly. Before hot tanking everything has to be removed. I didn't fully understand that everything meant everything. Where the supporting parts that are not part of the long black came from needed to be documented, recorded, and organized for re-assembly.
  • Measured and inspected the parts to figure out WHICH series of parts were the best to use.
  • Hot tanked and cleaned all parts.
  • Fresh coat of paint on the block.
  • Machine shop rebuilt both heads. The idea is have both heads ready to bolt on (whatever they needed).
  • Measured all parts to confirm "standard" sizes.
I assembled the motor using:
  • New bearings.
  • New pistons rings
  • New gaskets
In this way I felt I was getting the best value for my time while giving me the greatest chance for success. IE use the professional for the professional tasks. Add my "sweat equity" where practical.

Lessons learned from the experience:
  • The whole assembly process was way more "fidgety" than I imaged. Taking a lot more time than I imaged. They make it seem so easy on the TV shows.
  • IMO the services of the machine shop were vital to the rebuilding process. There's no way I could have known that the parts would have fit together with the correct clearances. Nor could I afford all of the special measurement tools.
  • The overall cost was higher than I expected.
  • I was not as organized as I should have been. Wasted time looking for parts due to a lack of organization.
  • I took what I thought were a bunch of pictures. In the end it turned out that I didn't take enough.
  • It was more difficult to keep everything clean than I would have thought.
  • For all intents and purposes I ended up with a zero mile motor.
  • I used every torque wrench I own. I did have to buy a torque angle gauge.
  • The tapered piston installation tool does make it easier to insert the pistons.
  • Priming the oil system was kind of a PIA. I even managed to "smoke" my power drill.
Regarding your question about buy or build, it seems to me that the decision should be based on things like:
  • Do you want/need a guarantee?
  • Your money or time? Which do you value more?
  • Who is doing the work? Yourself or a professional?
  • How quickly does the job have to be done?
  • Do you have the tools needed for the job?
i might suggest starting off by simply swapping in a salvage yard motor. This will give valuable experience. Research Windsor to Romeo swap. Search car-part.com for some sample prices in your area. Consider using a salvage motor from a 2003+ Grand Marquis, Town Car, or Crown Vic.
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New Member
Sep 22, 2018
Thank you for the thoughtful reply wmburns. I was hoping I could do something like what you said, where I would have the professionals do the professional stuff and add in the ‘sweat equity’ and do as much as I could on my own, but after hearing your reply it honestly sounds like something I’m not ready for.
To answer some of your questions, I would rather spend more money but have things done professionally and safely rather than try to save a buck by doing things half assed on my own.
Second, I would want the job to be done relatively quickly, but I figured time wouldn’t be as important if I had an entire separate block that could be worked on while I still drove the car. I will look into engine builders near me and see if I can give some input back with that.
More input is appreciated, I know there’s a lot of you smart Modular men out there.
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