2.5 MFI Engine - Holiday Project

[jbell959]

Here is a sneak peak at what I'll "hopefully" be doing between Christmas and New Years...

Short Stroke 2.5 MFI - Building it to be a fun street motor.

- 77 7R Case
- 66mm Counter-Balanced Crank
- 2.0S Nitrated Rods
- 3.0 Aluminum Oil Pump
- Mod-Solex cams (camgrinder special - profiles between E and S cams)
- Carrera Chain Tensioners
- 90mm Mahle Nikasil Cylinders
- JE Pistons 10.5:1 "RSR Style" (hopefully about 9.5:1 with the 66mm crank)
- RS Spec Heads
- Complete Stock 2.2S MFI setup (well one modification to the pump)
- Single Plug 2.4 distributor

All the machine work being done by Henry @ Supertec.

I'll post some pictures soon..... Merry Christmas

[Henry Schmidt]

Hi John
70.4 mm stroke
90 mm bore
1.0 mm deck
69 cc chamber
28.2 cc dome
equals 10.5 to 1 comp ratio

change only the stroke.
66 mm
90 mm
1.0 deck
69 cc heads
28.2 cc dome
equals 9.9 to 1 comp ratio

MERRY CHRISTMAS TO YOU AND YOURS

[jbell959]

Hey Henry....

I think when we spoke you suggested going to a deck height of about 1.25 which would bring it down closer to 9.5:1. That was the plan. I'm also thinking that JE's 10.5:1 estimate assumes a perfect world and that I wouldn't actually get that.

[Plavan]

When we built my 2.5L we had custom J&E's made because their off the shelf pistons do not always match the CC of your head. We CC'd the heads, and then told J&E what we wanted so we were sure of the compression.

[Henry Schmidt]

All 90 mm JE pistons are custom made. At this time JE does not offer a shelf 90 mm.
As stated in my calculations, all necessary specs to produce the proper pistons are listed.
That is all except valve size.
At this time we are putting larger valves in 2.2-2.7 heads.
Because I know what size valve John is running there was no reason to list valve size.

[Plavan]

I meant when you order them from EBS Racing "Off the Shelf"

[Scott Clarke]

John-
What will the port size be?
-Scott

[jbell959]

I'm going with 36/36 and a stock 2.2S MFI setup. I didn't make as much progress as I had hoped but I'll post some pictures soon.

[Scott Clarke]

John-
It sounds very much like the motor I'll be putting together in the next few months. I'll be using my '70E cams and E pump, and standard sized valves. Otherwise, identical. Why is Henry increasing the size of the valves with 36mm ports?

I'll be very anxious to hear how it runs. My car won't be on the road until August.
-Scott

[jbell959]

He isn't... I'm using stock valves. My heads are essentially 2.7RS spec MFI heads. I think he was just saying that he now offers larger valves for the early 2.2/2.4/2.7 heads. I'm hoping to get this done in the next month or so....

[Scott Clarke]

That's what I thought. Please keep us posted!

[jbell959]

I didn't make as much progress as I would have liked to but here are a few pictures:



My "Assistant" installing the bearings









I'm hoping to get time this weekend to make the necessary measurements to calculate the CR.. More to come

[kenikh]

Nice pistons; what do you expect the CR to calculate to?

[jbell959]

As you can see from Henry's calculation, the theoretical CR will be about 9.9:1 with the 66mm crank using a 1mm deck. I'm hoping to get it down to about 9.5:1 without going above a 1.25mm deck. I'm going to CC everything this weekend and calculate the expected CR and I'll let you know.

[kenikh]

Ah, I missed that part of Henry's post. Why are you trying to back it off? If you are using 2.2 - 2.4 heads, they should be just fine at 9.9:1 even with single plugs.

[Jandrews]

What kind of horsies will something like this make?


JA

[jbell959]

I just want to get the CR down to a reasonable level to avoid detonation. We have some weak gas here in California.

I'm not sure what the HP will be (maybe 200).. Henry can probably help with this.

[Plavan]

Here is the dyno sheet from my 2.5L short stroke with 10.5:1.


More info on this thread:
Dyno Day Pics

[jbell959]

Those are great dyno numbers... What type of gas are you running? Did you measure the CR to see if you got was JE quoted? Very nice motor.

[Plavan]

Thanks. I was also impressed by the work of Aase Motors.
This is my race car so I use 110 octane.
Allan at Aase CC'd my heads and gave a custom order to J&E for a true 10.5:1 compression. Not the "off the shelf" pistons you can buy from EBS or others.
I'm in the process of building a back up Long Stroke 2.5L at Aase's Shop. I want to have one of each