Hey guys, I'm going to get my engine built soon and I was wondering if it's worth leaving the block standard bore or going at least to .30 over? I will be putting in some trw pistons, adding billet center caps, and going to roller. Heads were hand ported and had stainless steel valves added to them. I've read and searched a lot on this forum and has been very informative and thanks to all the guys that share the info. If I should add anything else please let me know. Thanks!
Engine build
- Thread starter c55asleep
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jimmymack87gn
Boost Junkie
- Joined
- Dec 21, 2011
The minimum bore that the cylinder will clean up the better. Get your machinist to check bore taper/out of round.
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Ok, sounds good. When it comes to performance will it do any difference?
pmoore4321
Member
- Joined
- Jan 10, 2010
I believe TRW only makes a standard and .030 over forged piston. Bore size is not going to make a practical difference in power output with the 109. How many miles are on the engine you are rebuilding?
The engine has aprox. 170,000.. It's probably been stock most of its life. It only has an intake and a red Armstrong chip. Engine builder told me it was better to stay stock bore if possible but I wasn't sure. Thanks again
I was referring to the size. The block will be going to a machine shop. He was explaining that after it's been honed and it can stay stock bore size it's better. Not sure if that's a good thing or not. My understanding the more you bore the less material you have.?
If the cylinders aren't round, if they are bell mouthed, if they are tapered, if they have scratches, if there is a low area at the top ring land area.... it HAS to be cleaned up to be right.
If an engine builder says 'stick with stock bore', there's a good chance that person isn't even a good engine 'assembler'.
If you're dead set on running sealed power pistons then, yes, you will have to go .030" over to get a clean round cylinder to build from.
If you have someone competent that knows how to measure and final hone a block you can go less. (but not with a TRW/Federal Mogul slug)
If an engine builder says 'stick with stock bore', there's a good chance that person isn't even a good engine 'assembler'.
If you're dead set on running sealed power pistons then, yes, you will have to go .030" over to get a clean round cylinder to build from.
If you have someone competent that knows how to measure and final hone a block you can go less. (but not with a TRW/Federal Mogul slug)
Ok. It totally makes sense what you are saying. I will be using the trw and will go with .030 over. The engine isn't hurt. I just wanted to freshen it up and make it a little stronger.
C
coach
Guest
I agree 1000% Earl. 170,000 miles and "stock bore" can't be mentioned in the same paragraph, let alone, the same sentence. Depending on oil changes...0.02 might not be possible...0.03 might be the only option. If it needs more then 0.03...toss it in a dumpster in my opinion.
I also agree... I would get a different builder ASAP...before another dollar is spent. These engines are tricky enough without giving it to someone who even remotely thinks a stock bore is possible on a 170k mile engine.
I've seen plenty of 100k stock bores that were only slightly tapered at the top. .010" would easily clean them. I've seen 500 mile engines that had just as much and I've seen engines that had never been driven look like hell
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turbofabricator
Well-Known Member
- Joined
- Mar 7, 2004
I would not reccomend TRW (Sealed Power) pistons. I suggest you order JE, or Diamond pistons in .020" (if the bore is able to be cleaned up). The TRW pistons and pins are extremely heavy. They are NHRA Stock Eliminator legal. The piston is a decent forging but to make up for the heavy assed factory piston weight, they use a wrist pin that literally has a 1/4" hole through it. You could replace the pin with a lighter stronger pin but then you are at or near the cost of JE or Diamond pistons. Give Full throttle a call and order pistons from them. I just ordered two sets.
What are your goals with this engine? If you want to talk in detail over the phone, drop me a PM for my number and I would be happy to help decide on parts and find the right combo and machinist.
About the only advantage to TRW pistons is that you can get away without having to rebalance the rotating assembly. (It really should still be balanced though)
With the right turbo and your hand ported heads it should be able to run deep in the 10's. Providing the machinist/head porter knows what they are doing. If he is not familiar with Buicks, find someone else.
What are your goals with this engine? If you want to talk in detail over the phone, drop me a PM for my number and I would be happy to help decide on parts and find the right combo and machinist.
About the only advantage to TRW pistons is that you can get away without having to rebalance the rotating assembly. (It really should still be balanced though)
With the right turbo and your hand ported heads it should be able to run deep in the 10's. Providing the machinist/head porter knows what they are doing. If he is not familiar with Buicks, find someone else.
I've read for years about the 'heavy' pin and I'm surprised you mentioned that as recently as, well.... now.
Here's a picture of my coffee table I took years ago. Notice the stock 3.8 is the heaviest of all.
The FM slug came with a normal wrist pin and was 30 grams lighter than a stock unit.
I will agree with turbofabricator too. In general usage it's hard to beat most FM products in a 'bang for the buck' sense, but when it comes to hardcore performance, there's other options that are money better spent.
the hyper 4.1s on the lower left are what's currently in my 4.1 and that's the reason I designed a line of 'custom/off the shelf' forged slugs that fit both 3.8s all the way up to 4.2s... One of these days I need to get off my butt and see about bringing the things to market. lol
Here's a picture of my coffee table I took years ago. Notice the stock 3.8 is the heaviest of all.
The FM slug came with a normal wrist pin and was 30 grams lighter than a stock unit.
I will agree with turbofabricator too. In general usage it's hard to beat most FM products in a 'bang for the buck' sense, but when it comes to hardcore performance, there's other options that are money better spent.
the hyper 4.1s on the lower left are what's currently in my 4.1 and that's the reason I designed a line of 'custom/off the shelf' forged slugs that fit both 3.8s all the way up to 4.2s... One of these days I need to get off my butt and see about bringing the things to market. lol
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C
coach
Guest
That's why I said depending on oil changes...could be beautiful or tragic. No matter what...its not gonna stay stock bore.
The engine build started a little sooner than I thought lol. I was going to upgrade the turbo but I was told to freshen up the motor before spending any money on turbos etc.. Funds plus having to do extra things to the block like mentioned above balancing for new pistons and rods was why I opted for the trw. Honestly with 480 500rwhp will be more than enough for me. I rarely use the car. I'm sure it's the most case like others here lol.
