3door clone

Hi, has anyone got /know of any parts to make up a 3.5 stroker cologne short block assembly, one was on ebay a couple of weeks ago but guy sold it before I had time to go and view it

Stroker

You could start with this http://www.ebay.co.uk/itm/FORD-EXPLO...0AAOSwDuJWwcUI
The pistons would depend on what your plans are ie: N/A or turbo. 2.8 or 2.9 block.
The rest of the short block is just machining/relieving.

3door clone

Hi, thanks for your reply unfortunately that crank is a later 8 bolt flywheel I need the earlier 6 bolt, I'm looking to run N/A, the info I have gathered so far is earlier 6 bolt crank, standard 2.8 or 2.9 con rods and mopar 3.7 flat top pistons which need the gudeon pin holes opened up slightly but not sure what deck height i'll end up with so don't know if block needs decking or pistons need decking or no machining at all

Stroker

Well you live and learn I never knew they made an 8 bolt flange. Must check my spare crank that it's not a 8 bolter.
I used Jeep 4.7 V8 pistons in mine. They are the same as the 3.7 V6 piston but for some reason they are cheaper, plus the extra 2 pistons are good for using for dummy builds when clearancing the block, and believe me you'll be doing plenty of that.
I had to deck my block approx 0.032-0.035" to have the pistons flush with top of block.
I honed the rod small end to free float the gudgeon, the pistons come with circlips to retain the gudgeon.
The biggest problem is getting the compression ratio down to an acceptable level, there's not a lot of meat on the crown of these pistons. So I had a small bowl machined into mine, plus I opened up the combustion chamber.
You could of course run the piston down the bore and not deck the block, but I don't recommend that way at all.
I take it your using 2.8 block with K-Jet injection?









3.5L piston V's standard





Some of the clearancing required to the block

3door clone

Hi Stroker, much appreciate your info, yes I agree with not leaving the piston down the bore as squish is much reduced so mixture doesn't burn as well, have you looked at the mopar 3.3 pistons, there is no picture on summit racing site but there is a drawing on the silvolite piston website, it has a oval bowl about 0.90 thou deep plus the comp height is slightly higher at I think 31.5mm plus these are cheaper than the 3.7 mopar one's at $157 as opposed to $199, yes i'll be using the 2.8 block and the k jetronic fueling which has been much modified, the 4 stacks have been welded around the outside then opened up by about 5mm length and width also the throttle body has been opened up 3mm, the heads are swaymar stage3 6 port items so guess it should breath a lot better than just porting, whats your thoughts on the 3.5 stroker power and torque wise? more torque is what I'm after, I don't mind all the grinding for the clearance, do you machine down the crank counter weights? I've read that they need at least 7mm taken off them.

Stroker

I looked at the Chrysler 3.3 pistons and they were my next choice after the 3.7/4.7 Chrysler pistons. They would require bushing the rod small end to fit the smaller gudgeon. Plus they are 0.020" taller in height so less to remove from deck.
It depends on what compression ratio you want to run. I'll measure the crown thickness of the 3.7/4.7 piston and let you know. I just looked on Ebay and the 4.7 pistons are $119US for a set of 8 including rings, gudgeons and circlips.
The crank needs counterweights machining down, I think it is about 0.500", can't remember exactly as it was done quite some time ago. Also the nose needs machining to take the 2.8 gear.
You may find my thread over at CapriPower forum worth a read in regards to fixing the fuel curve on the K-Jet also has my dyno chart in it http://www.capripower.co.uk/forum/in...-curve-solved/

Stroker

Just measured the crown on the 3.7/4.7 piston and it is 7mm thick.

Also it's the type of piston you use that dictates how much is machined off the crank counterweights. The counterweights don't hit the block but the bottom of the piston and type of piston skirt will hit the counterweights iirc.

3door clone

Hi Stroker, did you use the std 2.8 or 2.9 rods? you said you reamed out the small end to make it a fully floating set up but the std 2.8/2.9 rods doesn't run any bushing as it's press fit did you bush the rod or just leave it unbushed? someone also mentioned using rods from a small block 302 v8 which I think needs narrowing of the width to fit but not sure of its length compared to std rods, with the 3.3 pistons they already have a oval bowl in them so compression should not be excessive, the bowls are 0.090thou but as they are oval compression should not be too low especially if the head bowl is left alone, read up on your thread on fueling and found it very intresting, I to exposed the allen key bolt under the WUR and when mine was set up it ranged from 14-1 @ 2k to 11-1 @ 6.2k so a bit rich through out the rev range but not engine destroying, did you get any power figures while on the rollers? mine is a 3.1cc with a 74mm stroke(2.9 offset ground) and 95mm bore and a piper BP285 cam, power recorded was 195bhp @ 5600 and 210 ft lb of torque @ 3400.

Stroker

Std 2.8 rods. No bushing, just have to give the gudgeon a bit of extra clearance when steel on steel so I'm told. Anyway seems to be working.
Ford SB rods are shorter than the cologne by 0.050" and yes they have to be narrowed along with the bearing. I don't think there is any advantage in using the standard Ford SB rod. The standard cologne rods with ARP rod bolts are said to be good to 6500rpm and with the much lighter stroker pistons they should be good for a bit more.

What sort of compression are you looking for? N/A you'd be wanting to run it fairly high especially with the cam your running.
The power figures for my engine were on the last page of the link I posted. Bare in mind that the figures were taken at the wheels not the flywheel.

Wow 11.1AFR, my motor would be absolutely choking at that mixture. Anything richer the 12.8AFR and my motor starts dropping HP like a stone.
Something that I find quite interesting is my motors peak torque seems to be at a much higher rpm than what I was expecting from my 270 degree cam@4000rpm.
I can't help thinking that the K-Jet control pressure is holding my engine back and controlling my whole torque curve.

3door clone

Ok that's good then that the rods don't have to be bushed, I take the big ends are fine and just require the correct size bearing to bolt straight onto crank journals including mains (no line boring required) yes mine pulls right off idle right upto max rpm with no hesitation or flat spots and plugs look pretty good colour considering it's a bit rich but the rollers adjusted it to a happy medium if he leaned off topend then bottom and mid were lean so he went for richer top end as it wouldn't be there all the time, maybe mine would make over 200 if it was leaner top end but then bottom and mid would suffer, often think about going to carb as jetting it would give a better fuel ratio throughout, I don't have the knowhow and patience to be experimenting with the k jet as you ( compression doesn't have to be that high as the 285 cam despite it's name only runs 276 duration so 9.5/10-1 should be more than adequate.

3door clone

By the way Very impressive power @ the wheels Stroker especially as it's 4WD


also did you get the crank assembly fully balanced once bells and nose were machined down and if you did did you have to have weight added to the flywheel and front pulley?

3door clone

I see what you mean about the prices of the pistons, I found two sets that use the global shipping programme which is cheaper to ship worldwide, one set at $108us and one at $119us only problem is both sets are 93mm only no oversize the cheapest set I found was $149us that uses global shipping so still cheaper than summit racing and their sets don't include rings.

Stroker

What about http://www.ebay.com/itm/321501225923?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITAlso read the add with ones saying they are STD quite often near the bottom of the add/description some tell you what over sizes are available and it's just a matter of leaving a note on the purchase order.

Yes the big ends and mains on the 4.0L crank are the same dimensions as the 2.8.
Without seeing your actual fuel curve it's hard to say at what stage your motor starts to over fuel. But I'd say it's a pretty safe bet that it would break the 200HP mark by leaning off the top end. If you can do it without leaning the bottom end as well.

Yes you have to add weight to both the flywheel and the front pulley. I had a steel flywheel made with counterweight for mine, but you can just have a piece of steel machined and bolted to the flywheel and front pulley.
My front pulley is similar to the image I PM-ed you.

3door clone

That's one light looking flywheel

Stroker

12lbs IIRC

3door clone

As the 4x4 is a relatively heavy car is it not worth going a bit heavier to help launch it?

Stroker

170ftlb torque@1800rpm at the wheels, launching isn't to much of a problem.

3door clone

When I had my turbo engine in I asked my daughter to get something out of the glovebox for me then when she leant forward I nailed the throttle and she got pinned back in her seat, obviously that joke only worked once on her

sp1x

Hi.
I want to get 3.5L with my BOA Cosworth engine.
I plan to use 3.7/4.7 Chrysler flat top pistons. But standart pistons have dish with valve reliefs.
So should I I deck my block to have the pistons flush with top of block? I'm afraid that valves will hit pistons in this case.
What compression will I get without decking the block? Standart compression is 9.7

Stroker

I'm sorry but I haven't had any experience with the BOA engine what so ever, so I really can't answer any of your questions.
You may find some useful info over here..... BOA Stroker

Stroker

Thinking about your questions last night and I think the 3.7/4.7 pistons may not be your best option. I really think you will struggle to get your compression down low enough, there isn't a lot of meat on the piston crown for too much cutting of valve reliefs and combustion bowl.
I think another better option may be the Mitsubishi 6g74 piston, have a look at the DOHC variant of the 6g74. They have a bowl and valve cutouts already in them. Whether the cutouts line up with your cosworth valves I have no idea. You will also have to do your own research on what your compression would end up being. These pistons have a smaller gudgeon pin, so the rod small end will need bushing. I did look at these pistons when I was deciding how I was going to build my 3.5.

sp1x

Thank you so much for this information.
I don't need to reduce compression exactly to 9.7
Up to 10.5 will be ok.