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I have seen a few guys on Facebook building 2.85L HS motors. Pretty cool but I have noticed a few things. First, some are planning fairly high power without filling the 2.5L block or incorporating a deck plate. I think this is a mistake. Some have questioned filling the block. It works and we have done it several times. It is not difficult and should be done.
Second, I question the use of flanged sleeves vs straight sleeves on a 2.5L block. Flanged sleeves must be used on the 3L blocks but the 2.5L blocks can use straight sleeves. The flanged sleeve anchors at the top and the straight sleeve anchors at the bottom of the cylinder. Sid's original 2.85L and both my HS motors used straight sleeves. I think anchoring the sleeve at the bottom is a better approach if possible. Less heat and pressure at the bottom of the sleeve not to mention flanged sleeves are about 4X more expensive than straight sleeves. Just my 2 cents.
Shawn did you hone the sleeves after install? Or are the sleeves ready for the pistons as is? I never read that anyone ever post that info.
Final bore prep is done after install of the sleeves. I have been having the sleeves installed, then fill the block, and then return to the machine shop to have final bore prep including honing done.
I have seen a few guys on Facebook building 2.85L HS motors. Pretty cool but I have noticed a few things. First, some are planning fairly high power without filling the 2.5L block or incorporating a deck plate. I think this is a mistake. Some have questioned filling the block. It works and we have done it several times. It is not difficult and should be done.
To those that may be unaware, filling the block provides additional stability to the cylinders and is an effective upgrade to the 944/951 blocks. It only applies to the 2.5 block since the 3L blocks are already 'filled' via a revised casting. Note that filling the block must be done BEFORE any cylinder reconditioning; whether simply honing oversize or machining for sleeves. This is because the filler material distorts the cylinders as it sets up. So those who are not planning any cylinder reconditioning, avoid the block filler to keep the cylinders round.
Final bore prep is done after install of the sleeves. I have been having the sleeves installed, then fill the block, and then return to the machine shop to have final bore prep including honing done.
My block was done the same way. It has straight sleeves supported at the bottom. The sleeves were initially bored but not honed. Then I prepped the water jackets and filled them. Let it cure for 3 days, then sent it out for final honing and to set the clearance between piston and wall. BTW I used .0045" PTW since I was using pistons with a coated skirt.
Info for posterity;
Most of the water jacket is 90mm deep. It's deepest at the front by the water pump and rear next to the bellhousing at 110mm. The area between cylinders is shallower at 37mm deep.
IMHO a 90mm water jacket is excessive for an engine with a 76mm stroke. Many modern aluminum block engines have water jackets that are shallower than the length of the stroke. For example, the 4 cylinder 2.3 EcoBoost has a 94mm stroke with 82mm water jackets. BMW N54 has a 89mm stroke with 70mm water jacket. These are also open deck engines.
Is it possible that part filling can increase temps as it reduces circulation of the water cooling effect? Plus even though the block is part filled, can't the top of the cylinder still vibrate which seems to be the main reason for gasket failure? Shawn and others, have you pulled the head on your builds thus far and seen any negative effect on the gaskets still occurring?
I asked this question to Dave on FB, I will post here too because I think the idea is very interesting. The Honda drag cars fill the block water jacket with salt, then pour the block filler on top of the salt to harden which creates something similar to a closed deck. Of course, they then flush the salt out with water.
Is it possible that part filling can increase temps as it reduces circulation of the water cooling effect?
The bottom of the water pump is blocked by the filler, the top passage remains open. The top of the cylinders are the hottest part so you don't loose much cooling effect. I supplemented the cooling system by adding an upgraded oil cooler since oil helps cool the bottom of the pistons and cylinders.
Originally Posted by 333pg333
Plus even though the block is part filled, can't the top of the cylinder still vibrate which seems to be the main reason for gasket failure? Shawn and others, have you pulled the head on your builds thus far and seen any negative effect on the gaskets still occurring?
I haven't removed the head on my engine yet, it's been nearly two years since it first ran and it's been my daily driver for 1.5 years. Yes the top of the cylinders can still move slightly, but filling the block reduces this movement. This is an important step when building a hybrid stroker out of a 2.5 block since the longer stroke increases side loading of the piston against the cylinder wall when the piston is halfway down. It's also the reason I like the idea of a deck plate aka cylinder support system. They add support at the top of the cylinders to give the headgasket sealing surface the best stability.
I asked this question to Dave on FB, I will post here too because I think the idea is very interesting. The Honda drag cars fill the block water jacket with salt, then pour the block filler on top of the salt to harden which creates something similar to a closed deck. Of course, they then flush the salt out with water. Attachment 1148166Attachment 1148167
Geez, you wouldn't want to get distracted at the time when you need to remove the straws...just sayin'
Originally Posted by Dave W.
The bottom of the water pump is blocked by the filler, the top passage remains open. The top of the cylinders are the hottest part so you don't loose much cooling effect. I supplemented the cooling system by adding an upgraded oil cooler since oil helps cool the bottom of the pistons and cylinders.
I haven't removed the head on my engine yet, it's been nearly two years since it first ran and it's been my daily driver for 1.5 years. Yes the top of the cylinders can still move slightly, but filling the block reduces this movement. This is an important step when building a hybrid stroker out of a 2.5 block since the longer stroke increases side loading of the piston against the cylinder wall when the piston is halfway down. It's also the reason I like the idea of a deck plate aka cylinder support system. They add support at the top of the cylinders to give the headgasket sealing surface the best stability.
I like the idea as it's cheaper than a deckplate. Plus I think in a mostly road car any inefficiencies won't show up. Perhaps in a track car too but I haven't seen anyone do this yet on a purely racecar.
My block was done the same way. It has straight sleeves supported at the bottom. The sleeves were initially bored but not honed. Then I prepped the water jackets and filled them. Let it cure for 3 days, then sent it out for final honing and to set the clearance between piston and wall. BTW I used .0045" PTW since I was using pistons with a coated skirt.
Dave - Thanks for the input. What is your preparation process to prepare for filling?
Is it possible that part filling can increase temps as it reduces circulation of the water cooling effect? Plus even though the block is part filled, can't the top of the cylinder still vibrate which seems to be the main reason for gasket failure? Shawn and others, have you pulled the head on your builds thus far and seen any negative effect on the gaskets still occurring?
We have seen no adverse effects in terms of temps when half filling the block. I do think a larger oil cooler is a good idea however if you track the car. I pulled my head when I installed the new head and bigger cam and it is obvious there is still some movement but I would contend that it is greatly reduced with filling. Jet 951 had a thread a couple years ago stating that he changes his Cometic every year do to some movement and that is with his 3L 16V motor (3L block with raised floor and joined cylinders). I would say that anything over about 350 hp would be questionable with a 2.5L block without a deck plate or filling, but that is just a guess however.
03-09-2017, 10:37 AM
