Blown 944 Hybrid Stroker DIY Guide
#198
Rainman
Rennlist Member
Rennlist Member
I measured the thickness of the rod when I built my hybrid stroker.
see
https://rennlist.com/forums/944-turb...l#post11115908
see
https://rennlist.com/forums/944-turb...l#post11115908
Are you using small-end bushings or running steel-steel?
So taking Eagle rods to 0.944 (24mm) should leave about 0.1475" minimum "wall thickness" (for lack of a better term) at the small end.
#199
Burning Brakes
#200
Rennlist Member
Thread Starter
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.
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.
#202
Rennlist Member
Thread Starter
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.
#203
Rennlist Member
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.
#204
Burning Brakes
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.
#205
Rennlist Member
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?
#206
Drifting
Join Date: Aug 2009
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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.
#207
Burning Brakes
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.
#208
Rennlist Member
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
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 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.
#209
Rennlist Member
Thread Starter
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.
#210
Rennlist Member
Thread Starter
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?