2002 Denali Camping Build
- Thread starter Buggdave
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
OP
OP
Buggdave
Full Access Member
The final piece for my build came today to help with my high altitude horse power. I purchased a new matched set of OEM LS2/LQ9 flat top pistons and balanced crank. I have gen 4 rods to round out the rotating assembly. I am converting my Lq4 into an iron block LS2. The crank is for a 2005 corvette with a 24X reluctance wheel to match my ECU. I tried and failed twice to find used LS2/LQ9 pistons. The first set was mislabel and the measured out to be for a LS1. The second set was from a 44K corvette engine but upon measuring them, the skirts had collapsed and my piston to wall clearance would have been almost 0.004”. Stock PTW clearance with the hypereutectic pistons is 0.0009” - 0.0012”.
I want the OEM pistons because the compression height of the OEM pistons allow me to maintain the 11:1 CR i am targeting. The other replacement flat top pistons are “reduced compression” and they would also need to balance the crankshaft. By keeping the OEM pistons and crank, I am able to maintain the stock balance of +/- 4 grams on the bob weight.
I want the OEM pistons because the compression height of the OEM pistons allow me to maintain the 11:1 CR i am targeting. The other replacement flat top pistons are “reduced compression” and they would also need to balance the crankshaft. By keeping the OEM pistons and crank, I am able to maintain the stock balance of +/- 4 grams on the bob weight.
Attachments
OP
OP
Buggdave
Full Access Member
I am using a Mahle head gasket that is 4.0 bore and a compressed thickness of 0.05”. The OEM piston compression height is 1.336”. I am estimating that the piston will be 0.005 above the deck. This will mean my quench will be 0.045. This should help prevent detonation because i can only get 91 octane in my area. If I had E85, i would be running my 862 heads which would give me almost 11.6:1 CR. I would have to pull a lot of timing with a CR this high and from my research, not the best path to go, so I am going to run my 243 heads.
If you know this already then please forgive me, but it seemed worth mentioning that at higher altitude there is less air to compress, hence why 91 is considered "premium" fuel in the western mountain states. It provides pre-ignition margins similar to 93 at lower altitudes for normally aspirated engines.
OP
OP
Buggdave
Full Access Member
@Geotrash, thanks for the clarification. I understand that the ASTM specifications allows for a reduction of the octane number based upon how high you are above sea level, and agree with the pre-ignition margins as you stated. What I am currently concerned about is how high my dynamic compression ratio is calculating. My cam has the IVC at 32 degrees ABDC. With my static compression estimated at 11.11:1, and using stock rods (6.098") I calculate that my DCR could be 10.55:1. I am researching to see if using 91 (93 @sea level) will cause me to have to pull timing due to knock retard. Since I do not have the ability to use E85 (approximate equivalent octane of 100-105), do i need to adjust my CR by changing my head gasket or going back to my 317 heads. I really wanted to run my 862 heads but i was afraid of the calculated 11.54:1 CR and 10.95:1 DCR and not being able to optimize the tune with the available fuel here. This is why i sourced the 243 heads. I am just chasing ghosts and just run the 862 heads?
OP
OP
Buggdave
Full Access Member
I have been playing with a program called Dynosym5 and have "built" my LQ4 and my proposed build to compare potential gains. I am estimating a 22% increase in my torque @ 3500 rpm and 38% increase in hp at 5500rpm in this re-build. My build is simulated with mild porting of the 243 heads and using the 87mm tb on the TBSS intake with the Vinci MT556 cam. My estimated timing will be about 35 degrees at peak hp. I hope to have the engine out over thanksgiving weekend.
Attachments
OP
OP
Buggdave
Full Access Member
So, I think I have genuine GM lifter trays but after @Geotrash shared his experience I am doing my research. From all of the things I have seen online, I think I have genuine lifter trays. The trays do not have that shiny black plastic that I see on the knockoffs, but are gray in color and do have the correct part number.
Attachments
Looking good. They should be hard to flex as well.
GMT800LUVR
TYF Newbie
- Joined
- Nov 21, 2021
- Posts
- 2
- Reaction score
- 1
love the build im planning a refresh of my 170k LQ4 with very similar specs....do you still have your old torsion keys? think i wanna raise my truck about 2"
OP
OP
Buggdave
Full Access Member
@GMT800LUVR I don’t think I still have the torsion keys as I recycled them when I removed my torsion bars and converted to a coil over front suspension. I did lower my ride hight back to stockish when I downsized to 31.5” tires. I was running about 2” when I had my 33” tires and I liked how it handled most dirt roads. I did add an energy suspension bumper on my lower control arm so that my jounce stops were in contact with the drama as per spec. I went to the factory sized tires when I started towing my camper trailer more. My gas mileage and low end power suffered a little with the 33’s.
