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6.5 Optimizer Compression Ratio

Potluckslammy

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Anybody have the scoop on how GEP achieved the lower compression ratio on the Optimizers? Modified pistons...rods....or just a thicker head gasket?
 

Potluckslammy

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Yes, I understand, and thank you for the reply. What I mean is, what method does GEP use to achieve the 20.5:1 compression? Well...I guess the L65 had 20.5:1, as well, so it's not strictly a GEP innovation.
Let me explain what I'm doing, and why I need to know. The L65 in my 99 C3500 gave up the ghost. I ordered a remanufactured Optimizer long block to replace it. If possible, I want to lower the CR another point by swapping out a thicker head gasket.
So...being as this build is eminent...I have opted to cease my lurking, and reach out to the community for input. Is this gasket swap a viable means of nudging the CR a bit lower on this particular project? And, although I had not considered it until this very moment, but I think it is probable the heads have been shaved during the re-manufacturing process...thereby necessarily raising the CR back to somewhere above the factory value! It may be a requirement to swap in a thicker gasket just to achieve something close to the stock 20.5:1 ratio. I would very much like input on this point, as well. Thanks in advance for all comments!
 

Twisted Steel Performance

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A thicker gasket won't get a point drop, I've cc'ed many and that is just hearsay..

You could do one of several things, run it as is, have the top of the piston cut down X amount, buy marine pistons for 18:1, they have the pin bore moved up so the piston doesn't go as high, buy machined pistons like I offer, etc...

Several things "should" be checked in a case where the facts are unknown on a motor, cc'ing them is one of many measurements ..
 

Will L.

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Port you heads for better flow, because its cheap, not hard to do, helps everything in the engine: more power, more mpg, lower egt, probably saves baby whales too.

But when you do it, unshrouding the valves will trim some of the CR also.

Or do what I did, drop the compression down to 18:1 with TSP tricoated pistons with valve reliefs. Or no valve reliefs and 18.5:1.

The pistons are what is different iirc. On going from the 21.5:1 to 20.5:1. I compared heads on the older gm to the newer ones and to my optimizers. I can’t see any difference in chamber area there. But I could see slight changes in pistons. I dont have the older gm stuff here anymore to show pics of difference, sorry.
 

Will L.

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The ten thou thicker gaskets drops something like .1
Or .15 I thought? It is negligible. Dished valves give more from what I remember doing my 400 sbc engines. Does anyone even make those valves for these engines? Haha.
 

Will L.

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  1. Buy reman engine
  2. Complete disassemble
  3. Clean everything perfectly and start measuring
  4. Fix the 7 things you find wrong
  5. Install quality bearings instead of the cheap ones.
  6. Put it together this time with torque wrench instead of an impact like the last guy that did it.
 

Potluckslammy

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If you want to lower compression then Chris @Twisted Steel Performance is the man to talk to. He offers several different ways to lower compression.
I've been ogling his website for this past month as I've considered what to do. Impressive....most impressive!

A thicker gasket won't get a point drop, I've cc'ed many and that is just hearsay ..
See...now this is why I decided to pipe up and ask for help! A body can read till they're blue in the face, and think they know what's what, but it's all bull pucky without a measurement!

My reasoning for wanting to drop the CR is, of course, because I want to chunk the Asthma Attack turbo after engine break-in. And why not plan ahead for full utilization of it's replacement? So I considered all the trick goodies for a rebuild...until I decided, even though the original block and heads showed no signs of cracks, you can't build for strength on top of a weak foundation. That, plus I found the remanufactured Optimizer for less than the cost of rebuilding the stock L65. The drawback was I had to take what was on offer, vanilla.
So, the immediate plan after taking delivery is to install studs top and bottom. I figured this would be an opportunity to go back with the thicker gasket? But apparently the focus should be going back with a QUALITY gasket...which would be which? Fram? Mahle? Cometic?
Is the jury still out on installing a main girdle? Read some that it was the ticket for bottom end strength, short of the P400...and read some that it was yet to be proven useful. Thoughts?

Port you heads for better flow, because its cheap, not hard to do, helps everything in the engine: more power, more mpg, lower egt, probably saves baby whales too.

But when you do it, unshrouding the valves will trim some of the CR also.
Well, if the heads are coming off anyway, maybe I should. But what am I looking at cost-wise, ballpark? I'm having all this done, by the way, in case I wasn't clear on that. Not because my pockets are deep, or because I haven't the desire or ability to do it myself. Fact is I don't have the facilities at hand with my current living situation, and my health is such that I can no longer tackle these big projects. What I DO have is a broke down dually..AND a need for something more useful than a broke down dually!

The pistons are what is different iirc. On going from the 21.5:1 to 20.5:1....
Well okay then, that answers that question! Thank you!

The ten thou thicker gaskets drops something like .1
Or .15 I thought? It is negligible....
Not even close to the full point I had been led to believe. So much for tthatbright idea!

out of curiosity, where did you purchase your reman motor?
I left that out, not wanting to seem as if I were promoting a particular company. But I used US Engine Production...headquarters in NY, factory in WI. Hope I didn't mess up! Checked the webs and couldn't find anything negative...except one pissed-off individual that posted on RipOff Report. But if anybody has any input, positive or negative, let me know now.

Buying a reman engine would scare me. Hope its not the place on the east coast.
New York is East Coast according to Thug Life! But then, so is North Carolina...according to the maps, not the thugs. Which place is the bad place? Do tell!
 

Potluckslammy

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  1. Buy reman engine
  2. Complete disassemble
  3. Clean everything perfectly and start measuring
  4. Fix the 7 things you find wrong
  5. Install quality bearings instead of the cheap ones.
  6. Put it together this time with torque wrench instead of an impact like the last guy that did it.
Now that is some solid advice right there! Would that I could...had I the facilities. Not sure I trust this "mechanic" I've got to be more than an engine installer. But then, I'm not a very trusting individual to begin with.
 

THEFERMANATOR

FRANKENBURBAN
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That is the place NOT to buy from. They've gone by so many names trying to dodge lawsuits it's ridiculous. Cancel the order is the BEST advice ANYBODY can give you. Otherwise roll the dice on when it will let go.
 

Will L.

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Buying from them, you need to. No options, sorry. If we had known in time before you bought, we would have stopped you. So many stories out there. Forget the warranty- You will get nothing.

Before you buy other 6.5 stuff, speak up. Off top of my head also avoid ss diesel supply, a1 custom.

Only run ac delco 60g plugs. Ac delco thermostat, and ac delco sensors.
Harmonic balancer: fluidampr or again ac delco.

Be studious on Bearing clearances, oil pressure is a funny thing.
Melling makes all the oil pumps out there. The other companies are relabeled boxing. Just open the gear cover plate and inspect the gears and body new not used- likely from them. Make sure the pickup tube is secured. Make sure the plastic connector between oil pump and oil pump drive is new.

Imo ditch the factory oil cooler hoses for Leroys kit or have your own made at a local hydraulic shop and get rid of the crap connectors gm used in the block.

Make sure the rocker arm buttons are new and the pushrods are right side up.
Dollar to a donut says your valve springs wont pass weight tests. They clean and resuse old ones all the time. New factory at least, or TSP found some quality after markets some of us bought.

Inspect your rockers and valves- look for cracked heads between valves and check the precups. Minor precup cracking is ok and reusable provided not into the fire ring. Less is better obviously. And if you have bigger turbo plans- post what precups you have in there- might need to swap them.

Measure cylinder wall and ring gap- they just slap in without proper fitting- and expect cheap short life rings.

The list goes on and on. What you bought will not get you 100,000 miles. 50,000 if you are lucky with stock fuel and stock boost numbers.

It takes $$ to make a great 6.5. This just isn’t a cheap to build engine.
 

Potluckslammy

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...If we had known in time before you bought, we would have stopped you....
I got SO lucky! I think, anyway. Checked with the bank and they hadn't taken the money yet. Called the company twice trying to cancel the order...first time got put on hold forever, and hung up...second time I said "cancel", and the instant reply was "free shipping", then got put on hold and the line disconnected. I'll try again shortly. Point is, I avoided an ass raping...and I'm happy about it!!!

Unfortunately for me, I didn't actually sign up on here until after the order was placed. I checked around...search engine and what-not...but couldn't find anything derogatory about them except for that one guy on RipOff Report. However, I started digging a little deeper after I got worried, and found out a whole mess of crap! I won't get into it, but can say there is great sense of relief now that the delimma has passed.

Ok, so this topic is getting way off-track...and thankfully so. Guess what I'll do now is post a new topic asking for advice about whom to buy from. And THEN ask questions about what to do with it, after!

Thanks Will, and everyone else for the help! Starting fresh in a new direction...garaunteed better results than the course where I was headed! Glad to be a part of the community!
 

Will L.

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Start your post with budget, and use. Hot rod, towing, mpg, cheap as possible or want the next 300,000 miles trouble free.
Glad that didn’t turn to a huge extra expense.
If they have used optimizers they haven’t rebuilt that they will sell affordable for you to rebuild- that would be ok, IF you inspect in person.
 

THEFERMANATOR

FRANKENBURBAN
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A friend of mine got an engine from Titan out of Ocala Florida. They use chinese blocks, heads, and from what we could see re-used stock GM rotating assembly. But it ran good, very quiet, great oil pressure, and nothing out of the ordinary.
 
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