steven74

Hello Rennlisters,
I have been following Shawn and Sid's experiences with the 2.5 hybrid stroker build and would like to copy their design. I prepped the water jackets and poured the Moroso block filler as Shawn described and let it set up for a week.
Today, I dropped the short block off at the machine shop and explained again what I wanted done and the machinist was very concerned about using a short fill of the block filler on the street.
He said that the filler continues to cure and an engine prepped and honed with filler can leave with straight bores and after a few races will return for teardown and the bores will be distorted from the filler. He advised to use a different block with no filler.
My intent is to build a mostly street engine putting out about 350 to 400 crank hp. My question is two parts:
1) is there any real concern using the block filler with 1.7 inches below deck height and sleeves if using stock radiator and larger oil cooler on k28 hybrid water/oil engine with a/c. I am in Houston and see ambient temperatures above 90 regularly.
2) is the block filler an essential part of the hybrid build with sleeves or can it work as well without the filler? I have an extra block I could use if needed.

Chris White

I ran a 370rwhp engine for years with no block filler - I would skip that unless you are going for big hp - and then I would tell you to get a 3.0 block!

gruhsy

2.85 engine I am putting together for my neighbor is sleeved by Michael Mount.

No block filler for this one. He advised to make sure it has a good tune of course.

Shawn has posted his success using it but, it does not mean you have to using a 2.5 crank.

edit: I should have added this motor is not going to be a high hp motor, just a better replacement for a stock motor running standalone.

steven74

My original block from my car was prepped and filled with block filler per Shawn build on his website. I also have a second block with no filler in similar condition. I dropped off the filled block at the machinists today but no work has been done as of yet. I am not sure which is the better choice for my goals. The machinist is advising against the filler like what Chris White posted. Howe very, Shawn shows good results with the filled block. By the way, it was filled to 1.7 inches of deck height with no obstruction of the water pump area in front of number 1 cylinder.

rlm328

I would not use the block fill. Cooling is hard enough with these things, especially in Houston. I have converted my car to Evans Waterless and will take it to the track on the 20th, so will have more on that at a later date. You will also want RL Steam Vent Kit.

Who is doing your block work in Houston? The HP you are aiming for is doable with a normal engine set up. Whose sleeves are you using?

If you are worried about cylinder movement I would get a cylinder girdle.

V2Rocket

I would go with what your selected and trusted machinist is recommending because he's the one who will have to answer for any issues down the road, and he knows it.

People have made a lot of power on stock 944 blocks for a long time before the block filler concept was introduced around here - it's a clever trick to stabilize the cylinders IF you are worried about cylinder movement...now that will beg the question, what kind of boost and timing are you going to throw at this engine?

steven74

It seems the consensus is to use the unfilled block. I am having the machine work done at Faermann Racing engines in Houston on Pinemont. Dennis Faermann said they have done a number of 944 engines over the years.
I have been assembling parts for a while and currently have a stock 2.5 liter bottom end with plans to sleeve and offset grind the rod journals for the Mitsubishi rods with sbc pistons per Shawn and Sid's 2.85 liter build.
I also have a speed force racing ported and o-ringed n/a head, Tial 38mm wastegate, speedforce .57 trim hybrid t04e/k26 with machine #8 wheel , Lindsey racing 3 inch coated turbo back system, and plans to run a system similar to the rogue M tune with 80lb injectors. I may go with Vems from Raceboy or try megasquirt similar to O'Donnell's setup. I plan to run the stock cam and coat the crossover piping to turbo since I don t have ceramic ports in the exhaust anymore. I hope to keep boost around 16 to 18 lbs on pump gas with possibility for e85 if needed.
I mostly plan to use it on occasional street and de events. I want to keep my Fuchs and am running a 245/40r16 rear tire with lsd transaxle.

refresh951

I have several comments:

- Yes, block filler is an essential component to the Hybrid Stroker (straight cast iron sleeves) unless you run a deck plate. It works fine. We have built a lot of these and have history. I am on year 5 on my car and all is well with regular 400+ hp use, thousands of pulls and many DE events. I have built quite a few motors and the one motor I did not fill had sleeve issues (the only motor I have ever had problems with). Fill the block. It works and it stabilizes the block a great deal. I know this by examining head gaskets.

- On a 2.5 Block I would always use a straight sleeve rather than a flanged sleeve. The straight sleeve anchors at the bottom where it is much cooler and sees a less hostile environment. A flanged sleeve must be used on the 3L block but the block is far superior from a structural standpoint.

- Filling the block as Sid outlined does not change engine temps at all. It has no effect, I have done a lot of logging. I am sure this is why Porsche changed the blocks later. If you track the car you should run a bigger oil cooler no matter what. For several years I ran my HS with just the stock oil cooler (including several track events at 13 psi on cooler days). Eventually I ran into warmer weather at the track and saw 240F oil temps and decided to make a change. I live in Atlanta and we see pretty high summer temps and I had no issues sitting in traffic for LONG periods of time with the stock oil cooler.

refresh951

Were they dry sleeving them with $25 cast iron liners? If I was using expensive Darton interlocking sleeves I probably would not fill the block

Humboldtgrin

Didn't the very rare (like ten made?) 650 HP 87 944 turbo GTR's have a half filled block? They had some major short block changes for being a 2.5L with that power. Or were they cast half filled like the 3.0 blocks and super rare like the turbo 3.0l 8V ceramic exhaust posted head that MM has posted photo's of before?

sherry66

Shawn , any pictures of bottom of liner in cylinder sleeve showing how much material is left in place please ?

V2Rocket

I'm sure some were...I was talking about big power stuff going back into the early 90s and beyond, when dinosaurs like Broadfoot, Gomez, Milledge (and Garcia ) roamed the earth...


TO clarify, I was not trying to argue AGAINST filling or put it down, I think it's a good idea, but its use is to stabilize the cylinders if there is possibility of significant movement. From your testing "we" know that the cylinders can and do move but I wonder at what point of boost and ignition timing does that become a real issue versus a much more conservatively-built car (stock 951s blow HGs from coolant corrosion, not dancing barrels, for example)

Voith

How does filling compensate aluminum expansion? Top it up with molten aluminum would be interesting

Humboldtgrin

It's not the expansion that is the issue. Filling a 2.5L block half way holds the cylinder walls better and it helps from the cylinder walls egg shaping from the pistons rocking which results in piston slap. That's why a 3.0L block is preferred over a 2.5L block on high HP builds. On the 3.0L block the cylinders are connected, not floating like the 2.5L block, and the block is already cast with half the depth of the coolant valley from the 2.5L block.

steven74

With all the positive support for the filled block, I think I will continue along Shawn's original design path. I have already filled my block and dropped it at the machine shop. At this point, I think I would like to proceed with the standard dry straight sleeve in the filled block. Another benefit of the filled block is it also blocks cooling supply to the oil cooler housing section, thereby eliminating any possibility of mixing coolant with oil in the troublesome housing area. At the least, if there should be any unusual problems with the block design, I do have a second block available to proceed with and possibly use the crank that has already been reworked for this block.
Is there any reason for concern of the block filler continuing to hard and expand, causing cylinder roundness problems in the future? My thought is the filled area is high enough to not really cause skirt or ring seal with the stiffer cast iron sleeve encased in the original aluminum cylinder base.