I'm sure I'll catch a lot of flack for this but this method of stroking has been around for decades and was real popular amongst hotrodders..

You don't neccessarily HAVE to find a shop that deals strictly with imports or the VQ specifically, only one that has a lot of experience in working with crankshafts. For that, it would be beneficial that you try and find a shop that does cater to the hotrodder bunch as most of these guys really turn out good precision work for not that much $$$$.

What's odd about this set-up is that you'd use SBC (small block chevy) rods which are very close in measurement to the stock VQ35 rods as you'll see a little further down. Another benefit to using SBC rods is that there are just so many of them out there. Billet, forged, cast, aluminum, steel, light weight, ultra light weight, etc., etc., etc. AND they can be had for fairly cheap!! Also custom pistons will have to be machined which according to a quote from Arias should be about $145 per piston ($20 additional if buttons are used). Of course you'll have to choose your comp. ratio (11.5:1 for NA or 8.5:1 - 9.0:1 for FI).

I kinda took the liberty of finding all the neccessary specs and playing with the numbers thus coming up with conservative measurements that shouldn't require too much block clearancing or machining(hopefully) .

Stock VQ specs we need to be concerned with for stroking:
Deck Height = 8.464" (215mm)
Stroke = 3.205" (81.4mm)
Crank Throw (stroke/2) = 1.6025" (40.7mm)
Rod Length = 5.677" (144.2mm)
Rod Big End Diameter w/bearings = 2.165" (55mm)
Compression Height = 1.168" (29.67mm)
Deck Clearance = .025" (.635mm)

First thing is to have the crankshaft rod journals offset ground by 2.5mm. This will increase the stroke by 5mm total bringing the final number to 3.40" (86.4mm).

Now that you have offset ground the rod journals by 2.5mm you have essentially reduced the diameter of those journals the same (2.5mm). The new diameters will be 2.067" (52.5mm).

The SBC rods you'd use are the standard size 350 with a length of 5.7" and a big end diameter (w/bearings) of 2.100". You can see that the rod journal diameter is smaller than SBC rods big end diameter by .033". To bring the rods closer to journal diameter you'll need .040" undersized bearings. Federal Mogul, Clevite, etc. all make any kind of rod bearings you can think of for any application you can dream up.

With the new undersized bearings you're basically reducing the diameter of the rod big end by .040" to a final diameter of 2.06" (52.32mm). Now the journal diameter is actually larger than the rod big end by .007" and can be finished / polished down to size.. All done with crank grinding and really shouldn't be more than $500.

As far as pistons go the compression height has to be lowered to prevent the piston from coming too far out of the bore. Very simple task!!! You've increased crank throw by .098" (2.5mm) from crankshaft grinding and you've also increased rod length by .023" (.58mm) from using longer SBC rods. Essentially this just means that if you put stock pistons back in with stock comp. height they'll extend beyond the blocks deck by .121" (3.07mm). Thus, on the new pistons, the comp height has to be reduced by the same amount to prevent that, bringing the new height to 1.047" (26.59mm). Also the piston pin bores need to be machined to fit the SBC rods small end.

That's all there really is to it in general. I know it may seem like a lot but again it's a very simple and inexpensive alternative to stroker kits. For a bulletproof NA motor with high comp pistons I'd be figure anywhere between $1800 and $1900 for everything if you build the engine back-up yourself. Little bit more if you have a builder do it for you.

 

Intresting....

Any ideas as to the decreace in engine life????

 

Sounds very intresting actually. Are you planning on attempting this?

It would be fun to lock you and Tilley up in a machine shop with a ton of different motors and see you would come out... Probably some monster that will rule the earth.

 

well im excited, please do this and get some before and after numbers.........and can u state in english what it is your actually doing?

 

cessna,
I really don't believe the engines longevity would be adversely affected by this. So long as you build it to match your power output goals..


Actually Oleg I plan on going FI next year sometime and really didn't plan on cracking the motor open for a rebuild unless I was going to stroke it. There was a belief I had about machining the crank and having to weld up the journals that steered me away (long story). This is up until I discovered using the undersized bearing trick Now it looks a little more feasible for me to do. So in essence, yes I plan on attempting this.

 

mario60185,
I know it's kinda "Greek" but check out this link to help you better understand it a bit http://www.fordmuscle.com/archives/2...er/index.shtml

 

Seems like a good and inexpensive way to increase displacement but i'd rather put my money on increasing bore with darton sleeves/new forged pistons. Much better alternative to my motor IMO.

 

thanks for the link, so whats going on? are you ready to try this? you say its around $2,000.00 ? is that with your motor already pulled out?

 

Zexy,
I hear ya bro.. If you sleeve the block, open the bores up to 100mm and run the stroker, man you'll be pushing 4.0L.

Not yet, soon though.. Still talking with a few machine shops.. Also, as I mentioned I'm planning on FI next year and if I got this done now I'd be running around with 9:1 compression Definetly wouldn't be taking full advantage of the mod until then. Decisions Decisions

 

[QUOTE=atlsupdawg#2]cessna,
I really don't believe the engines longevity would be adversely affected by this. So long as you build it to match your power output goals..
QUOTE]


Correct me if I'm mistaken, but I thaught that if your boreout a block, that it will always have an adverse effect on its lifespan?????

 

This would make a nice little set-up for either NA or FI. Can't find lightweight aluminum rods for a Z anywhere can ya??

PDQ Engine and Machine, INC: Offset grinding, finishing and polishing $300

Summit Racing: Manley 7075 T-6 Aluminum I-Beam rods w/ARP cap screws. 515grams, 850HP rating, 8,500RPM rating. $66.50ea

Clevite77 P-Series Tri-Metal .040 undersized bearings, high rpm app. $30

Arias: Custom 11.5:1 or 9.0:1 Pistons $145ea

ForgedInternals: ARP Main and Head stud kit $380
***Grand Total*** $1980 + associated parts to finish motor.

Average forged internal set-up is about the same price, granted you use top of the line stuff ie. Pauter, CP, Arias, etc.

EDIT: Also wanted to add some rough HP estimates for NA if one were to go this route.

The increase in stroke should yield about 25HP
11.5:1 compression should yield about 7HP
*12.3:1 (w/water injection) should yield about 11.5HP*
Set of cams ie. JWT, Nismo or Tomei should yield about 15-20HP

Total increase not including exhaust, plenum's, CAI's, hi-flow cats / pipes, pulley's, lightened flywheels, A GOOD TUNE, etc. = 47HP - 56HP

 

whats your expeirience in this stuff, im just curious?

 

I think this'd be a great inexpensive way to buld the engine with stronger internals to allow a higher rev limit, while still keeping the same bore...maybe 7500rpm or so with appropriate cams. That extra 500+rpm (depending on what you're already running) would probably be good for 5whp on the dyno with the right cams...........at least.

 

first off, want to say good work on your figures. there is still really alot of stuff that would need to be done though. never use aluminum rods in a street motor you want to have last a long time. they start getting impacted over time and can start to rattle. perfect for racers who tear the motor down alot and replace, also they are much larger, and it is still speculation on the rods even being able to spin in the block, let alone massive aluminum ones.
something like this would take a ton of trial and error to do. also, are the journal widths the same for the vq as the sbc. a small amount could be removed from the sides, but well you see where i;'m going if it wasn't done correctly and were not in the center of the bore.
don't get me wrong, i would love to see it done, but i'm not sure the word "inexpensive" is where you would be at upon final completion. unless you have access to all this equipment yourself. but rod consideration would be the key to making it all work. oh ya, and to make sure federal mogul DOES have the bearings you need, or a size you could atleast modify a little. good luck.

 

i have done my own hybrids, but they were all in proven territory. hell if ya get it figured out i may be willing to try on my next rebuild.

 

oZ1,
Glad to have you chime in on this thread.
I don't have much experience dealing with aluminum rods other than knowing that they eventually stretch a bit. Now that you mention it and I looked at those rods again, they are pretty thick. Eagle H-Beams are actually a bit cheaper and can handle a good amount of power and higher revs so that's a plus.

I've been trying to find a good machinist out here, to no avail, that can do cranks in house as opposed to sending them out. So, I've been pretty much talking to a guy in MN at PDQ engine and machine who do volume work for many engine building shops. He's been pretty helpful and quoted me a $300 price tag for all the journal work and finishing. Forgot to ask about knife edging and balancing however. Yet and still, I figured between $500 - $600 for crank work so my estimation including the additional work should still be in that "ball park" range.

As far as the journal widths are concerned, I did think about this but without an extra crank handy I can't take any measurements. Shaving or adding a bit material shouldn't be much of problem though but may add to the price, which I DON'T wanna do. What I think I'll do is give SGP a call and see if they wouldn't mind giving me those numbers. I'll also see if they can give me the rod end to block clearance so I'll know if any additional shaving is neccessary. And, I'll try and dig up the widths for some of the popular SBC rods ie. Manely, Lunati, Eagle, etc.

I do believe that a lot of trial and error (more $$$$) can be avoided if the numbers were so much more easily available and consistent. Though I'm pretty dead on with the stock VQ numbers, it's still kinda nerve wrecking working from numbers that one person gives to find out that someone else has measurements slightly different. You know as well as I that in this engine building game even a .020 - .030" variation could mean more $$$ in parts and machining. I'm definetly willing to do this so others can benefit as well.

We'll see though..

 

The new capacitiy with this mod would be 3711 cc.
The increased stroke would probably foul the oil squirters but could be overcome the same way AEBS do, by drilling up the center of the rod from big end to the little end.

 

i have both sbc and vq35 rods up at my shop. i will be heading up there tomorrow and could take a look at the widths for ya. i remember i did put a stock sbc rod by the stock vq rod, and laughed. our rods are a joke. i think the rod in my quad is thicker, lol. i build all my own motors and always have, even my current vq, just have the machine work sent out. i do not remember the clearance on the outside block rails or bottom of piston bores as to how close it was exactly. but i do remember it being VERY close already. typically you want to see around 0.040 around the rod bolts and beam, or whatever other area you might run into. i have run closer though.
the vq crank is internally balanced, and they didn't have a prob balancing it at all. but it may get more complex as the weight moves farther out from crank centerline.
one thing to remember too, is that as stroke gets longer, piston speed gets faster, putting more strain on rod bolts and brings down possible rev limit.
i think it might be alot more trouble to do than the extra 13-15 ci (based on your figures) would be worth. if you are planning a turbo for f/i, it gives alot of bottom end anyways, so traction will be your worst problem instead of torque.
don't get me wrong, not trying to talk you out of it, but i just feel the word inexpensive will not be what you write in your check book by the time it is done, hahhaaa. would be nice to have access to this type of machinery and experiment with though. unfortuneatly, you would have to pay a machine shop to do all the refiguring, and it would suck to have them make a mistake and get most of it done and say "impossible". aahhhhhh.
i would say better money to be spent on sleeving the block and hit high boost. guarranty you won't be disappointed.

 

oZ1,
That would be great if you could afford a little time to check that out for me. I found out that the SBC rods are around .940" in width so hopefully the VQ rods aren't too far off.

Also I was off on the stock rod lengths. They are actually 5.669" and not 5.677". S**t like that can cause me to lose a set of pistons.

Anyway, the machinist is gonna try and get back to me with some block clearance numbers but your .040" does sound safe and that's what I'd want to maintain. I found out that the JUN 3.8 stroker kit does require a little block work to run their set up and they're running +6mm increase in stroke. So, I'm pretty sure I'll have some to do as well. Another thing I need to check into is how short of a piston skirt Arias, JE or Wiseco can manufacture.

 

Spoke with the machinist, JE Pistons and Sean from SGP (thanks for those measurements) and everything seems doable. I do still need to get the clearance for the rods and block. When I change my oil this weekend I'll drop the oil pan and try to get up in there for some quick measurements.

Couple things that turned out to be a plus: You can actually increase the stroke by another mm to bump the displacement up to 3.8L using 96mm pistons. Using the same length rods (5.7") and moving the crank throw out that additional mm would still maintain a decent compression height. According to JE they don't recommend going less than 25mm on the comp height because the ring packs would be too compact and the ring lands too thin. Not good for a FI application!! With the above measurements the comp height stayed above 25mm. As well, the pistons can be manufactured with shorter skirts to avoid contacting the crank counter balances.

Also there is no need for undersized bearings, as SBC rods come in 2.000" big end diameters also. Offset grinding the journals down that additional mm brings the journal diameter to 2.04" so that's perfect! The additional .004" - .005" can be easily removed when finishing and polishing.

Flip side to this is that the SBC rods are a bit wider than the stock VQ rods (.940" SBC / .824" VQ). So, an additional .060" has to be removed from each side of the rods big ends. According to the machinist it'll take no time at all and no real jump in price. There will definitley have to be some sort of grinding to the inner portion of the block but I'll know this for sure, and possibly how much, when I drop the oil pan..