Here's another article that has some info about higher ratio rocker arms...

http://www.boyleworks.com/t.../psp/RockerArms.html

Concerning the debate between roller tip and non-roller tip, Dave over at tripleedgeperformance.com tells me he has seen 3800s running aftermarket cams for 5-10K miles using stock rocker arms and the valve tips get worn pretty bad; more miles and he has seen them cupped, and that is with using synthetic oil. I've personally seen a few 3800's and a lot of other engines (mostly V8s) with this same problem when using aftermarket cams with stock (non roller tip) rockers.

Who cares if you lose 5 HP with a full roller at same ratio because of the math/dyno; we don't like the wear aspect (all that metal has to go somewhere) and it doesnt occur with full roller rockers. Stainless valves help, but how many guys who are using aftermarket cams have stainless valves?

Of course if you are one of those guys who doesn't care about trashing a perfectly good engine because you can just go down to the local pick-and-pull and get another one for $100 and then don't care about wasting a weekend swapping it out, then I guess it makes little difference how long stuff lasts.

quote aftermarket cams for 5-10K miles using stock rocker arms and the valve tips get worn pretty bad

This type of deductive logic is so flawed. Why would a stock rocker last 400k miles in a stock cam.. and have over 400 times higher wear due to 15% increased lift?

The answer has everything to do with the fact that every single 3800 out there right now running a xp cam and stock rockers is seeing .570 peak lift assuming you have a 130/LS6 valvespring... Guys running 105 springs are probably closer to .585. It is quite easy to run into binding issues at this point on stock heads.... although it is not typically that severe... I have never heard of rocker arms falling apart personally... I have worked on many cars running xp/s1x cams for 50k+ miles.

quote Originally posted by darkhorizon: This type of deductive logic is so flawed. Why would a stock rocker last 400k miles in a stock cam.. and have over 400 times higher wear due to 15% increased lift?

Because a stock rocker used with a stock cam and stock valve springs has less pressure being applied to the valve tip than an aftermarket cam with higher lift, higher ramp rates, and higher spring pressures (required by the aftermarket cam) perhaps??? Seems logical to me. The only constant between the two situations is you aren't changing the hardness of the valve tip. But with the aftermarket cam and springs, you are putting more of a load on it. And don't forget the higher the valve lift, the more the tip of that rocker is going to move across the valve tip as well. Faster ramp rates built into the cam lobe will increase the speed at which the rocker tip swipes across the valve tip. So not only is there more pressure, it is swiping across that tip farther and faster. Seems to me right there it would wear more quickly. Don't you think?

After all, if you have done nothing to increase lubrication at the valve and rocker tips nor if you increase the hardness of the valve tip, how could you say there wouldn't be increased wear with the increased loads and movement when using the bigger cam and stiffer valve springs with stock rockers and valves???

[This message has been edited by Darth Fiero (edited 12-06-2011).]

Ok, I think the rocker debate has gone on long enough. I will be using roller rockers in this build like it or not. that is the great thing it is mine and I can build it any way I want

Moving on!

[This message has been edited by 30+mpg (edited 12-06-2011).]

quote Originally posted by Darth Fiero: Never said anything about stock rocker arms falling apart. We are talking about valve tip wear here. I don't care how many cars you've worked on. If you don't know what you are looking for (or what you are looking at), I'm not surprised you "haven't seen anything wrong".

And moving right along.......

It's a good looking build Dean. Sent you a pm, just checking if you saw it.

-Joe

Sounds good to me Dean, and on the troll thing is there a way to block post from trolls.

This

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Turbo 3800 E85 5spd spec5
11.54@132.7

Ok, so I have a few little parts on the way for the build and the heads are almost done being ported. once that is done it will be off to the machine shop to get the hardened seats and guides installed. the block should be done next week at the cryo and then it will be going to the machine shop as well. I still need to find rods for the build but I may have a line on that now I will let you all know once I know more.
D.

quote Originally posted by whodeanie: Ok, so I have a few little parts on the way for the build and the heads are almost done being ported. once that is done it will be off to the machine shop to get the hardened seats and guides installed. the block should be done next week at the cryo and then it will be going to the machine shop as well. I still need to find rods for the build but I may have a line on that now I will let you all know once I know more. D.

I'm looking forward to the rest of this build. I'm interested to see what you will do about rods. Keep up with the updates!

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'04 Mazda RX8 Build Thread
'88 GT- 3800 Turbo 11.367@121.03mph (Sold and gone now)
GM Tuners

so with a lot of research and a few fittings I have found the rods I will be using. I have been talking to Bill Miller of BME and they are going to make me a set or rods for my build.
I have a set of rods for a V8 already so they are going to be sent back to be reworked to fit the 3800. after a lot of measureing and fitting we came up with a plan that will make the motor a 4.2L in the end with a little longer stroke than stock. we will be keeping the compression low because of boost it will only be 8.25 - 8.5 - 1 depending on how much I will need to take off the deck to get it flat.

I ordered a set of Manley SD 2 valves 1.90 intake and 1.57 exhaust we will be installing them with bronze guides and high nickel hardened seats.
the rest of the valvetrain will be this, custom 3/8 hardened push rods, yellow tera 1.7 rockers, 150lb springs and comp roller lifters. the cam will be custom and we have figured out that with this setup I will be just under 600 lift this will make sure everything works like it should.

more to come....
D.

offset grinding a crank, or is there something else special in store?

How are going to get another .4L from this engine? Not saying it can't be done, I'm just curious. Not sure if your aware, but the stock internals put the piston 0.020" above deck at TDC, so keep that in mind when selecting your rods and pistons...and head gasket thickness (if using mls gaskets).

There are quite a few 4.2 liter 3800's running around. Do your research.

Swan sells a stroker kit for the 3800's. DH said they weren't worth anything, so I didn't research them further.

http://www.3800stroked.com/

quote Originally posted by L67: There are quite a few 4.2 liter 3800's running around. Do your research.

So to obtain 4.2L, you have to run an even SHORTER connecting rod? These rods are short enough already. The side load on the piston is gonna be huge.

And thanks for your friendly reply. I gave you a +....just kidding

quote Originally posted by ricreatr: offset grinding a crank, or is there something else special in store?

ZZP did this awhile ago... They sold them with the disclaimer "do not use with boost/nitrous"

Remember that extra displacement does not make the heads flow more, nor does it "help" the turbo. Other than some slight octane tolerance extra displacement offers little gain in a 3800 turbo platform.

My little ST2 cam is making roughly 580 lift on stock heads, stock lifters, stock pushrods, stock rockers, it works pretty decent, and you should not need anything custom to achieve this.

[This message has been edited by darkhorizon (edited 12-09-2011).]

quote Originally posted by darkhorizon: My little ST2 cam is making roughly 580 lift on stock heads, stock lifters, stock pushrods, stock rockers, it works pretty decent, and you should not need anything custom to achieve this.

Ha Ha ... my cam is bigger than yours...

quote Originally posted by darkhorizon: ZZP did this awhile ago... They sold them with the disclaimer "do not use with boost/nitrous" Remember that extra displacement does not make the heads flow more, nor does it "help" the turbo. Other than some slight octane tolerance extra displacement offers little gain in a 3800 turbo platform. My little ST2 cam is making roughly 580 lift on stock heads, stock lifters, stock pushrods, stock rockers, it works pretty decent, and you should not need anything custom to achieve this.

So, here is the question. If someone built two identical engines with identical levels of boost, but one was stroked, would it not make a difference at all? Wouldn't the displacement allow for some gains? Or is it just that the gains wouldn't justify the additional expense?

[This message has been edited by mptighe (edited 12-10-2011).]

quote Originally posted by mptighe: So, here is the question. If someone built two identical engines with identical levels of boost, but one was stroked, would it not make a difference at all? Wouldn't the displacement allow for some gains? Or is it just that the gains wouldn't justify the additional expense?

"levels of boost" is not a term to reference anything by. Airflow is airflow, "boost" is a measurement of restriction.

You really need to stay out of the turbo threads.

quote Originally posted by darkhorizon: You really need to stay out of the turbo threads.

Why, his question was completely legitimate. Ignore the mis-nomenclature and answer the question.

quote Originally posted by mptighe: So, here is the question. If someone built two identical engines with identical levels of boost, but one was stroked, would it not make a difference at all? Wouldn't the displacement allow for some gains? Or is it just that the gains wouldn't justify the additional expense?

Bigger displacement will give gains. The old saying "there's no replacement for displacement" is true. When it comes to changing the stroke, things can get tricky. Longer stroke will give more displacement, but requires shorter connecting rods or custom pistons that have a shorter distance between the pin and the dome. The shorter the rod, the more friction there is on the piston skirts. Some engines can take advantage of longer rods to reduce the side loads on the pistons, but longer rods don't change the displacement. Longer rods usually require custom pistons too.

quote Originally posted by 1fatcat: Bigger displacement will give gains. The old saying "there's no replacement for displacement" is true. When it comes to changing the stroke, things can get tricky. Longer stroke will give more displacement, but requires shorter connecting rods or custom pistons that have a shorter distance between the pin and the dome. The shorter the rod, the more friction there is on the piston skirts. Some engines can take advantage of longer rods to reduce the side loads on the pistons, but longer rods don't change the displacement. Longer rods usually require custom pistons too.

Not sure if it matters with a turbo charged engine. I don't think the heads are going to flow any more just because there is a larger hole beneath them. If your heads are big enough to where there is no restriction then I could see a larger cylinder taking on more air and fuel creating more power.
_______________________

Would decreasing the stroke for more RPM create any more power? ...or are the heads still the limiting factor?

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Turbo 3800 E85 5spd spec5
11.54@132.7

quote Originally posted by whodeanie:

those

where did you get those rods and how much would a set cost me?

[This message has been edited by etofun (edited 12-11-2011).]

quote Originally posted by 1fatcat: Bigger displacement will give gains. The old saying "there's no replacement for displacement" is true. When it comes to changing the stroke, things can get tricky. Longer stroke will give more displacement, but requires shorter connecting rods or custom pistons that have a shorter distance between the pin and the dome. The shorter the rod, the more friction there is on the piston skirts. Some engines can take advantage of longer rods to reduce the side loads on the pistons, but longer rods don't change the displacement. Longer rods usually require custom pistons too.

The biggest problem we have with these Series 2 and 3 engines is the shorter deck height (at least shorter than Series 1 and older 3.8L V6s) and that these Series 2/3 engines already have pretty short connecting rods and pretty short pistons to begin with; which gives them a pretty poor rod-to-stroke ratio (compared to other "popular" engines). To "stroke" one of these engines would only make the rod-to-stroke ratio worse, which will increase piston skirt side-loading and decrease the amount of dwell time the piston will have at TDC.

INCREASING piston dwell time at TDC helps keep the combustion event area size small & contained for a longer period of time (in relation to crankshaft rotation) which can help reduce the odds of abnormal combustion (like detonation) from occurring. In short, the longer the piston dwell period at TDC, the more powerful and octane-tolerant the engine becomes. Which is something you would want when running boost. Increasing the stroke on this engine would only result in the opposite of this effect, which is not something I think you would want to do.

While you can make more power by increasing the stroke of an engine, I would not think it to be a viable option if you are turbocharging. Why? Because you can always use a bigger turbo and/or turn up the boost to make more power that way, instead of "stroking" it to make more power. If your engine was not boosted and you had no intention of ever putting boost on it, then "stroking" the engine would certainly be an option for increasing displacement and making more power.

-ryan

[This message has been edited by Darth Fiero (edited 12-11-2011).]

ok, so I guess I am explaining it wrong. I have the formula at work so I can not post it up now.
the motor will not have a longer or shorter stroke on the crank. it is going to have custom rods that are a hair longer than the stock 5.68 measured center to center of the stock rod. and the pistons are custom made for this as well. we have set it up this way to prevent piston slap.
the bore will also be .020 over this is were we get the 4.2L. I have seen the stroker kits from Holden and I like others do not see any advantage to running on a boosted motor maybe an NA would be cool with it.

keep in mind that I have done my homework and I have built several of these motors as well as other very high HP motors. this is going to be a test car for the shop so that we can test parts we will be selling as well as well as have a blast building and driving it.
after all if it is not fun, why do it

I love the feed back even the odd ones here in the thread


so, the heads are now ported and waiting on the valves to get here so we can have the hardened seats installed as well as new guides . they look great and should flow fantastic.
the progress will be slow due to other work but fun all the same.
D.

[This message has been edited by whodeanie (edited 12-11-2011).]

quote Originally posted by whodeanie: the bore will also be .020 over this is were we get the 4.2L.

a 3.820 bore over a 3.800 bore is going to increase your overall displacement by a 1.5% percent. 3.8L x 1.005 = 3.86.

Close to 4.2, but not quite

quote Originally posted by Darth Fiero: The biggest problem we have with these Series 2 and 3 engines is the shorter deck height (at least shorter than Series 1 and older 3.8L V6s) and that these Series 2/3 engines already have pretty short connecting rods and pretty short pistons to begin with; which gives them a pretty poor rod-to-stroke ratio (compared to other "popular" engines). To "stroke" one of these engines would only make the rod-to-stroke ratio worse, which will increase piston skirt side-loading and decrease the amount of dwell time the piston will have at TDC. INCREASING piston dwell time at TDC helps keep the combustion event area size small & contained for a longer period of time (in relation to crankshaft rotation) which can help reduce the odds of abnormal combustion (like detonation) from occurring. In short, the longer the piston dwell period at TDC, the more powerful and octane-tolerant the engine becomes. Which is something you would want when running boost. Increasing the stroke on this engine would only result in the opposite of this effect, which is not something I think you would want to do. While you can make more power by increasing the stroke of an engine, I would not think it to be a viable option if you are turbocharging. Why? Because you can always use a bigger turbo and/or turn up the boost to make more power that way, instead of "stroking" it to make more power. If your engine was not boosted and you had no intention of ever putting boost on it, then "stroking" the engine would certainly be an option for increasing displacement and making more power. -ryan

Everything is a compromise. A longer stroke will increase piston speed, and reduce RPM capability. It can add torque. The shorter stroke will reduce piston speed at a given RPM, but will let you run more RPMs which means you can increase the amount of air that is pumping thru, given equal displacement. Short strokes also lead to reduced pressure on the skirts. You gain here, you lose there. There is a reason why the Japanese hyper bikes use large bores and small strokes. Add to that the multiple valve technology and serious power can be made. I wouldn't bother stroking a 3800 because, as Darth put it, it's most likely not worth it. The top end may be the only real place for improvement.

[This message has been edited by weaselbeak (edited 12-11-2011).]

Thanks for taking the time to explain. I had read that stroking would potentially generate more torque but didn't know if it was a moot point with a turbo or not. Make a little more sense now.

engine displacement bore x bore x stroke x .7854 x number of cylinders

quote Originally posted by engine man: engine displacement bore x bore x stroke x .7854 x number of cylinders

Where .7854 is ~1/4 pi since you need r² not diameter. Interesting.

3.8 x 3.8 x 3.4 x .7854 x 6 that comes out to 231.35999 going with a .020 over bore might get you 3 more inches but is not going to get you to a 4.2 you would need to gain about 20 inches

[This message has been edited by engine man (edited 12-12-2011).]

quote Originally posted by engine man: 3.8 x 3.8 x 3.4 x .7854 x 6 that comes out to 231.35999 going with a .020 over bore might get you 3 more inches but is not going to get you to a 4.2 you would need to gain about 20 inches

If you were willing to resleeve it .200 over, you would net 4.2l.

I know where I can get a NASCAR buick v6 for less than $1000

quote Originally posted by whodeanie: the bore will also be .020 over

The other thing I forgot to mention is if you are planning on running a LOT of boost, you want as thick of cylinder walls as you can get. If I was building a "hardcore" 3800 and planned on running a turbo with a lot of boost; I would try to build an engine using a standard bore if I could. I know removing 0.010" of matieral from the cylinder wall (= net: 0.020" over) doesn't sound like a lot, but it can make a difference when you are running A LOT of boost and making a lot of power.

Didn't someone build a 8000rpm 3800? At that rpm the hp is a little over 1.5 x the tq rating. Resleeving to 4.000 and the hp number just jumps (assuming th tq rating increases at the same rate as the displacement). Then you could get by with significantly less boost for the total/peak power.

quote Originally posted by Xyster: Didn't someone build a 8000rpm 3800? At that rpm the hp is a little over 1.5 x the tq rating. Resleeving to 4.000 and the hp number just jumps (assuming th tq rating increases at the same rate as the displacement). Then you could get by with significantly less boost for the total/peak power.

If they did they did ALOT of homework.

The biggest gains that you could make on a "hardcore" 3800 are not even being discussed here... its pretty sad to watch in all honesty.

ZZperformance made the claim. Unfortunately this video ( http://www.youtube.com/watch?v=w_OE3GLYac4 ) doesn't prove it.