Machining Pistons for 18:1 Compression Ratio

[Chevrolet4x4s]

How much material needs to be removed from 1998 6.5 TD pistons to get 18:1? Anyone have any experience with the 17.3:1 6.5s?

Does anyone have a spare wrist pin lock ring or know where I can get a single one? One of mine flew away :(when removing the rods from the used pistons I got today

Thanks Shane

[john8662]

I took .030" off the pistons I used in my '97 6.5 block, they were the OEM pistons.

I had them ceramic coated after being topped.

If you can't find a lock locally I'm sure I can scrounge up one off an older piston. Yeah, they're known for going on flying lessons (wear eye protection).

J

[Chevrolet4x4s]

Did going to the lower C/R help your economy any?How much boost are you running?These are OEM pistons (extra set that I got today) What exactally is the lock ring called checked advance auto and ebay and cant seem to find one:o it flew some where back towards the most cluttered corner of the garage:eek: Drop me an email to gearhead89 at verizon dot net and let me know how much you want for the lock ring if you can find a spare.The wristpins should be good as long as they are clean go back were they came from and are not worn correct? Also the piston cooling oil sprayers I have heard about,That is the orface in the little end of the connecting rod correct? What year were these first used?
Thanks
Shane

[john8662]

The piston coolers are spray nozzles in the block itself. Look at the block on the main caps. If you have the bearings removed, you'll be able to plainly see the port where the oil travels right to the sprayer. Lookin in the bore you should see it near a main cap.

The hole in the top of the connecting rod is for "splash lubrication" to help lubricate the wrist pin busing and pin.

I did my 18:1 engine simply out of the achieving max power output, I wouldn't recommend running your engine like I'm running mine. Simply because I'm not interested in it running for a lot of miles...

[ogrice]

I machined .030 off the tops of OEM pistons in my 1993. Calculated all the CR's and got the range of 18.7-18.3:1 final CR with all of my calculations. Started with the stock ratio of 21.3:1 because my current engine started out as a NA diesel mill, I also stayed with the conservative calculation of 18.7:1 as my final CR.
Don't know about how the 6.5 will run with anything lower than 18:1. If you were to machine off .040 you would get below 18:1. I didn't coat the piston tops after cutting and my truck still runs strong after 4 yrs and 50K+ miles.

What is your final engine output goal going to be like.?
My truck runs like a monster and I still run a GM-3 series turbo at 12# boost. I have a brand new HX-35w and tubular header turbo manifold in the works.

[Chevrolet4x4s]

I machined .030 off the tops of OEM pistons in my 1993. Calculated all the CR's and got the range of 18.7-18.3:1 final CR with all of my calculations. Started with the stock ratio of 21.3:1 because my current engine started out as a NA diesel mill, I also stayed with the conservative calculation of 18.7:1 as my final CR.
Don't know about how the 6.5 will run with anything lower than 18:1. If you were to machine off .040 you would get below 18:1. I didn't coat the piston tops after cutting and my truck still runs strong after 4 yrs and 50K+ miles.

What is your final engine output goal going to be like.?
My truck runs like a monster and I still run a GM-3 series turbo at 12# boost. I have a brand new HX-35w and tubular header turbo manifold in the works.

I got a set of 20.2:1 pistons the other day that I am going to have milled down.

Here is my plan. Let me know what ya'll think.
6.5 Turbo Diesel
1973-1974 Chevrolet short stepside
Tonneau cover.
Front air dam.
Rear roll pan.
Lowered around 4/5.
Ton sway bars.
Poly bushings.
Aligned real good.
T-56 6 speed.
Synthetic lube in the rear end.
Small mirrors.
Custom built headers for the turbos(plural:D).
GM-8 turbos. may go with one GM-8 and a little turbo off of a daytona or caravan.(which should deliver the best economy).
3 inch downpipes.
3 inch or 3.5 inch NASCAR boom tubes with x pipe daul exit right under the steps no mufflers for as long as I can get away with it.
Daul front mount intercoolers.
Possibly a cowl hood to let air out of the engine compartment better.
Free flowing air intake to the turbos.
Ported intake or maybe make custom Ram Logs similar to this(which should deliver the best economy).http://banksdiesel.com/Dmax-Gallery-images/intake/1_original_sketch.jpg
May go with rear disc brakes.
May do a partial bellypan.
Daul electric fans.
Polish up the exhaust ports a little.
40ish psi in the tires
No A/C (I hate ac in a vehicle..gives me headaches:rolleyes:)
And a slick shiney black paint job:cool:.

Here is the 73-74 grille after I redid it
http://www.hotrodders.com/forum/attachment.php?attachmentid=24798

and what I started with http://www.hotrodders.com/forum/attachment.php?attachmentid=24799

Heres the step by step process
http://www.hotrodders.com/forum/repairing-rejuvenating-restoring-plastic-grille-125972.html

I am hoping for 30mpg plus while crusing with a light foot. Do you think it is possible? Any thoughts or suggestions?
Thanks
Shane

[More Power]

If you're building an economy rig, the 20.2:1 CR would likely be best. Use lower CR for more power and improved durability at higher power levels.

A cowl hood will put air into the engine compartment - unless you make it a functional cowl induction. There is positive air pressure at the bottom edge of the windshield while the vehicle is at speed.

Jim

[ogrice]

Too cool. Your plan is achieveable. You may have to reconsider your turbo combination. You said, "Custom built headers for the turbos(plural).
GM-8 turbos."
GM series turbines are designed to be driven by all 8 clys. The 6.5 will suffer from huge turbo lag with 2 GM-8's being driven in parallel. I don't know about a pair of GM-8's being driven sequentially, both turbos will recieve all 8 cyls just in series and not parallel. A pair of smaller turbos w/ the correct A/R's will serve you better, but you got a lot of research to find the rite combo to run turbos in parallel.
As far as better fuel mileage, you are going to have to run the fuel economy 6.2l heads to get closer to the numbers that you want. There are articles about the differences in the precombustion chamber designs and its direct impact on fuel economy. My rig gets 20ish calculated mpg on summer fuel w/o propane and I've gotten as high as 23.6 calculated mpg w/ propane at a constant 60-65 mph on summer fuel. I run the 6.5TD heads that are made to produce power and not mpg.



Its funny that you're starting with an early 70's chevy. I have a 72' c-10 longbed thats metallic Corvette yellow slammed to ride like a car. I got the pro drop spindles, shocks, control arms, spring combo and leveling kits to drop the truck to about 5 inches of ground clearance at its lowest point. It runs a 350/350 engine/trans with nascar side exiting x-piped dual exh that exits just before the rear tires. The engine is tuned to a respectable 345 hp with what I've put in it. Its about 75% complete to showroom quality. I have some minor exterior and interior finishing to do. I'm going to upsize the rim and tire combo from 225/60-15 to probably 245/40-20's. The new rim/tire combo will raise the truck a couple of inches and will probably fetch a good price with the younger crowds.

[Peter J. Bierman]

If you want a twin turbo setup, look for boost on a budget in the archives, you 'll find the recepe for this setup, custom headers, twin turbo's, dual intercoolers etc, etc,

Have fun, ;) Peter

[76m880]

what about 19.5 to 1? would they be decent for a turbo application

[MaxPF]

FWIW, I achieved my reduced compression in the heads, rather than machining the pistons. I was actually going to post my build here, but I can't post a new thread... :confused: