4.00 Stroke?

Has anybody been able to put a 4.000" Stroke crank in an LT1 block? I am getting ready to sell the 383 to help pay legal fees and figure that when I recover I want to either try something 'new' or start with an LS1. I was thinking of a 4.000" stroke on a 5.7" rod and 12.0-12.5:1 CR. that is all I have thought of so far. Not sure what heads yet and when I decide on heads I will get a cam to try to match them. Right now I was just wondering about the crank Combo. If it will work, will the block need a little more than just some 'massaging', or will a Grinder take care of all the clearancing I would need?

Well you can get one in a SBC block, but the depth of the LT1 cylinders will make a 4.00" stroke a bit of work. It has been done, and you would have to get a setup to work to fit everything in the block.

The Eagle 435340006000 crank needs 6.00" rods and a 1" compression height piston to work. That also means that the counter weights are going to be hanging out there so it's going to be an even tighter fit.

As I have said before I don't think the $ per HP are worth it when you go from a 383 to 396 to 408 are worth it.

Bret

Actually, I considered a 6" rod at first. I thought that there may be a problem with the long rod and long stroke and the piston stalling for too long at the top and Bottom of the stroke.

or if you got to go big 3.85 stroke and sleeve the cylinders. that would allow for a lot larger piston. and you would still have you 400+ cubes.

One of the engine shops was selling an LT1 409ci short block... 4.00X4.030, but they no longer show it in their online catalog. Makes you wonder why.

A former member here claim to have built a 4.00x4.090 "421" and a 4.125x4.030 "421", so it has been done. There's also someone that posts here occasionally who claims to have a sleeved 4.00x4.120 LT1 "427".

Its just a matter of how much effort you want to invest in it for the unique ability to say "I have an LT1 4XX cubic inch engine."

Originally posted by Injuneer
One of the engine shops was selling an LT1 409ci short block... 4.00X4.030, but they no longer show it in their online catalog. Makes you wonder why.

A former member here claims to have built a 4.00x4.090 "421" and a 4.125x4.030 "421", so it has been done. There's also someone that posts here occasionally who claims to have a sleeved 4.00x4.120 LT1 "427".

Its just a matter of how much effort you want to invest in it for the unique ability to say "I have an LT1 4XX cubic inch engine."


I read effort as money. :)

Put the money in the heads and valvetrain rather than trying to go that big. You will get more bang for your buck.

Rich Krause

I just did not think that the cost would be 'too much' more for a larger stroke Forged crank over a Stock stroke Forged crank. I am pretty sure the price is near the same. I figured most of the added cost would be in clearancing or extra machine work.

Originally posted by Deadcarny
I just did not think that the cost would be 'too much' more for a larger stroke Forged crank over a Stock stroke Forged crank. I am pretty sure the price is near the same. I figured most of the added cost would be in clearancing or extra machine work.

And custom pistons, less choices when you go beyon 355 and 383

Hmmmm. I guess I was figuring that the pistons might be only 50-60 bucks more than a normal 3.850 stroke piston set.

I have a 4" stroke crank in my new motor (LT1). Easy when you use the right parts and costs no more than a 383/396.

...................well tell the folks at home more about it Johnny. Seriously.............im curious about this 4 inch stroke. How did you make it work jason. Thanks Prorac1

Use 383 pistons for 6" rods, but back off to a 5.85 rod... then get a 4" crank and some copper gastkets.

The slug will be 0.025" out of the hole, and some 0.065" gaskets will get you great quench.

Going 30-over, with the 4" crank you'll have a 408ci LT1, using off the shelf parts (assuming you have a 4" crank).

Clearancing will be a PITA, and you may even end up trying a few different sets of conrods...


The big question of course, is: what heads will you get to feed it?

I'm gonna have enough problems hoggin out LT1 castings to feed a 383 I'm building... fortunately I'm going with a small backup plan (Weisco pistons with reliefs to fit 23 AND 18* valves).

Power's in the heads... smart money's there to start.

Originally posted by Steve in Seattle
Use 383 pistons for 6" rods, but back off to a 5.85 rod... then get a 4" crank and some copper gastkets.

The slug will be 0.025" out of the hole, and some 0.065" gaskets will get you great quench.

Going 30-over, with the 4" crank you'll have a 408ci LT1, using off the shelf parts (assuming you have a 4" crank).

Clearancing will be a PITA, and you may even end up trying a few different sets of conrods...


The big question of course, is: what heads will you get to feed it?

I'm gonna have enough problems hoggin out LT1 castings to feed a 383 I'm building... fortunately I'm going with a small backup plan (Weisco pistons with reliefs to fit 23 AND 18* valves).

Power's in the heads... smart money's there to start.

there is the point, power is in the HEADS!

Nothing wrong with a 1.00" compression height piston really and it's much better than the piston sticking way up into the gasket. I'd rather have a really thin gasket and the piston in the hole.

Bret

I know of more than one LT1 block where clearancing for even a 383 (3.75" stroke) hit water. I think that if you didn't hit the water jacket when clearancing for a 4" stroke, no matter what rods you had, you were lucky. And even then, I think you would some pretty thin metal there. The Lunati Pro Mod rods seem to have good clearance. They are better in that respect than Eagle H-beam and Crower rods. The best rods I have seen for clearance are the Oliver billet I-beam rods. Most motors don't need these, which is good considering the price. But on my new motor I am using a set and they required very minimal clearancing. Almost none in some places.

In an NA motor the relatively high revs needed to make power will come into play when considering a long stroke motor. At 7,000rpm a 4" stroke and a 6" rod will produce a max piston speed of 4,648f/s and a max acceleration of 119,384f/s^2. With a 3.75" and 3.48" stroke and a 6" rods the numbers are 4,357 and 110,174 and 4,043 and 100,489 respectively. For a street motor these differences are significant.

I think a 4" stroke is too long. Jason, and other knowedgable people obviously don't think it's an issue. But if I wanted a 4" stroke small block I would use the lightest pistons and stongest rod bolts I could find. And definitely a 6" rod, though the difference in acceleration is small I think every bit may help.

Rich Krause

Rich,

I didn't want to get into all of that really because I have gone into the depths of velocity, accleration and force in relation to stroke before but THANK YOU. That was a great post.

To me it doesn't make sense to build a motor which will have higher engine speeds and compound on that with a long stroke motor.

Now I realize this is not as much of an issue with the lighter weights of a SBC vs. BBC and the higher mass components used in those motors. The problem is we are physically limited to the size of the parts in motors with tighter packaging problems.

On a side note:

Your Oliver rods are some of the BEST designed connecting rods on the market. There is a good story about the design by the late Carrol Smith comparing them to the contemporary H beam used by Eagle and Carrillo. I know it's one of those old things where guys think Carrillo is the best but I firmly belive that Oliver is one of the best connecting rods compaines out there along with Arrow Racing Components. They both have exellent contacts in the materials and racing industry.

Bret

4" stroke is alot and I dont know if it will be better or worse for what I am looking to do but i figured it is something different to try in my naturally aspirated quest.

Only 4.0" stroke ~4.0-bore motor I've seen in person was Chuck Riddeck's. When I was at his place last year, the engine was basically a dyno mule but it was putting better than 600hp to the crank with LT1 heads. As I understand it, he never intended to keep the engine in his car for more than a year or so anyways.

On that note and with regards to longevity, I just don't see it being a problem. Most guys who build something of this caliber aren't planning on getting 50k miles out of it. They rebuild every couple of years. So piston/cylinder loading, acceleration, lala, la (not to sound like an a$$) but... WHO CARES?

I definitely wouldn't but thats just me.

I'd just go to an aftermarket block at this point.... hello, Dart, WP and company.

-Mindgame

Mindgame: I am glad you are back posting again.

Rich Krause

Mindgame, I second that.....good to hear from you :) How is that motor running....love that thing.

Originally posted by Mindgame
I'd just go to an aftermarket block at this point.... hello, Dart, WP and company.

-Mindgame

I agree.

Long time...

Actually the longer the rods the less rpm you will have at any given piston speed and the easier the rod bolts will have it because rpm is far more important than piston speed in the loads that the rods see. Turning 4700 FPM with a 3.000 inch stroke will put the rod bolts through hell but with a 4.000 inch stroke they are taking it easy.

With a 6.000 inch rod and 4.000 inch stroke the rod bolts see 3800 Gs at TDC at 7100 RPM.

With a 6.000 inch rod and 3.000 inch stroke the rod bolts see 4760 Gs at TDC at 9450 RPM.

With a 6.500 inch rod and 3.000 inch stroke the rod bolts see 4690 Gs at TDC at 9450 RPM.

So you can see that even with a huge 2.17 rod ratio the smaller stroke engine is tearing the rods and pistons which also see this load up! The reduction in friction is also sometimes evident when doing testing on the larger engines even with short rods even though most people think they have more!

.....now turning the SAME rpm the smaller engine DO have less stress and friction but you're also now making way LESS hp too so they are no longer comparable. You can again do the larger engine and come out way ahead in reliability at this newer lower hp rating too if you run the larger engine slower to match the smaller engines piston speed and power and you'll come out ahead again usually.

You only have so much room however and the 4 inch stuff starts hangining out the bottom of many SBC blocks which I don't like depending on things. Overall bigger is always better if it fits!

Originally posted by racer7088
Actually the longer the rods the less rpm you will have at any given piston speed and the easier the rod bolts will have it because rpm is far more important than piston speed in the loads that the rods see.


Yep, 33% more rpm increased the piston gs (and rod load if masses remain the same) about 24% in your example.

8.3% longer rods decreased the gs about 1.4%
My conclusion is rod length has very little to do with rod bolt loading. As you said, it's RPM that counts.

Are you sure that rod length affects average piston speed?

Avg. PS = rpm x stroke / 6 if I remember correctly. Maybe you didn't mean average piston speed?

Thanks for the welcome gentlemen.:)

Jason,
How are ya?
The "motor" is running beautifully! I wish I could say that for the transmission. It's a goner thanks to my last trip down the 1320. So, I'm looking to either put the beef to another T56 or go with a stick-shift alternative. Following some leads posted in AT here a while back about strengthening the T56 so we'll see where that leads me.
On another note, these cars are a little different suspension-wise and I'm having a time getting the car to ET like it should. I think I need to send a bit more money to BMR, then maybe I can pull off some times *close* to what our buddy Joe Overton is running. The mph is there.... the rest aint yet.

-Mindgame

What about that 472 SBC they did on Horsepower TV? Couldnt you do a setup similar to that?

Didn't see the HPTV 427. But yeah, you could build an engine based on the Gen1 small-block and have anything from 350-500 cid. Then you have to make it work in an f-body. That'd require some fabrication skills but it's been done.

The gentlemen I mentioned in my first response, is/was running a 434 ci Gen1 in his car. 700+ hp na and to my eyes, ears and buttometer... very streetable, so not too shabby... or inexpensive for that matter.;)

-Mindgame

Mindgame, stay with the M6! I am amazed at how the cryo treatment of the mainshaft really has withstood alot of great 60ft times in some of the more stout M6 cars. That may be something you want to look into.

Did you get any better passes than that 10.4@137 with your setup since then? I can only hope that my car will trap 135+ NA....certianly *should*.

Thanks

Oldstrokerss,

Right, the average piston speed never changes with rod length just the peak.

MG, curious, what breaks the most often on the T-56? Is it the input shaft? Also, do you have a similar problem to what a lot of the mustang crowd has with the car not going into gear? I know a lot of guys convert to pro-shifted stuff. It also looks like a lot of the LS1 crowd is going that route as well. I wasn't sure how much street time your car got, and everyone's opinion of "streetable" varies, but for some reason, I could see you dealing with it. :D

I don't know much about the stang's T56, except that it was used on the Cobra R and the 2003 Cobra (w/blower ;)).

If there's a problem with getting into/out of gear it may be a shift-pattern problem, or the way those damn mustangs put the shifter half-way up the dash (just feels wrong when comparing it to my Pro 5 w/Lou's Short Stick).

The stangs probably upgrade their input shaft a fair bit as well... I belive they use a 10-spline shaft, while the Fbody/Viper unit uses 26 or 29 or sumthing much higher.

In most f-body failures it's actually the other end that goes... the output shaft. There's a few companies out there that will machine the Fbody housing to fit a Viper shaft (and more importantly, the thicker output shaft bushing). D&D performance does this for ~$700, while those with a bit more inititive can get the machining and parts for ~$500 (but I belive the D&D kit comes with extra pieces like a 16-tooth reluctor wheel).

To my knowledge the T56 is pretty damn solid up to ~600hp or so (when in a 3000 to 3400 lb Fbody).

MINDGAME!!

i have been tring to get ahold of you for monthes!

I have all my 18* stuff but never found you so I decidedt o just go with stock LT1 stuff for now and save it for a SBC 427 in a motown block. Making all the parts now ;)

Glad to see you are back!

Hey Ellis!

My apologies. When I left here, I also left two other message boards behind. Same e-mail addy for all those sites. Had only a little to do with an individual on this board but mostly it was due to time management... I was just spending way too much time browsing the internet. Being the anal-retentive manager I am, I decided to call it quits and take on some other projects I'd had on the back burner for some time.

I went back to check e-mail some 3-4 months later and my box had become a haven for spam. After scrolling through pages of "Hi I'm Amber, wanna see me naked", "2 wet4 U", etc., I just deleted the whole damn thing and only recently went back for another cleanup. So, I regret to say, I probably deleted your message along with many other important ones. May they rest in peace. *insert Taps here*

I'm all for helping as much as I can. Just PM me with any specifics and we'll go from there.

Jason,
The car has gone as fast as 138.6mph. Not bad for something I could drive every day of the week if I wanted to.:)
The 60' times are still not too great, 1.72 being the best so far and 9.82 secs. If I can get the chassis worked out, the car has some potential to go a little quicker, I don't think she'll see much more mph but I'm very happy with the tuning so far.

Yep, Ken just sent me a link that I'm about to investigate further (T56 builders). I talked with a guy earlier this week from One Cryo, they said they've had excellent results with their cryo-treat on race engine parts, especially gears, splined shafts and other high-load components. Yeah, he's a good salesmen and I understand the industry but looks as though you've heard some good things as well? That is reassuring! One Cryo will be getting a few parts here soon.. albeit, beefier parts than stock.

I've pretty much made up my mind to stay with the M6. If this were a drag car (and it won't ever be) then I'd go auto but that to me, would just take all the fun out of driving this car. Not to mention, I'd need to rethink my cam selection a bit.

How's your project coming anyways? Last I heard you were still considering an intake and dealing with clearance issues??

Brain,
Don't know what all is wrong with mine yet. My work schedule right now is keeping me away from my hobbies.
One thing I can tell you at a glance is I have a nice helical-spline. She didn't break but she's twisted like Chubby Checker.;)

Later,
-Mg

Originally posted by Mindgame
The car has gone as fast as 138.6mph. Not bad for something I could drive every day of the week if I wanted to.:)


If you can make it to the Thunder Shootout I will buy you dinner for being such a pimp! 138.6mph? :bow:

Back to lurking in this forum...
Ryan

I would love to make the Thunder Shootout get together but there just aint no way that is going to happen this year Ryan. I put in for two weeks at the first of this year as I had planned on at least making the HR Power tour but my request was shot down on the spot. Here I am a senior manager and I can't schedule any time off til near the end of this year. Needless to say... we are really working our tails off right now. Considering the number of jobless in my sector of the industry, I have no room for complaints.:)

Maybe next year!

-Mindgame