I considering doing another block and have owned a couple of 396/398 motors with the current being a 383. Trying to figure out why the 409 ci combo isn’t more popular. They were winning a lot of street races a couple of years ago but hear nothing about them now. Guess I’m looking for a little bit more torque and to be different.

What are the disadvantages of the 4’ stroke vs. 3.85? If any.

Again, this is just hearsay, but I’ve heard using a 6” rod will cause the piston to be very short causing excessive wear. Any truth to this?

What is the best rod length? I’ve heard the 5.85 rod is best with a 4” stroke due the length (shortness) of the piston (CH).

Who has pistons for the 4” stroke and 5.85 rod? I understand Eagle make a 4” crank and for $150.00 you can get it ground for 5.85 rods.

Or should I just sit down keeping my mouth shut and do another 396 and get it over with?

Denny

 

Denny-
409 is not popular because you are hitting the big time curve of money/pain in the ***/wear and tear vs power after a 396 for an LT1 block. but yes, I would recommend a 5.850 with a 4" stroke crank..

How much power do you want to make? Having built 3 blower cars over the last year.. and building a turbo setup for my self, I think for your use you would be much happier with a SQ trim on a nice little 383. you would be able to make 550rw+ on pump gas easily, pass emmisions, and have more drivability. Of course there is more to "go wrong"... but I still thinks its less of a hassle than a NA/solid roller combo.. because you can run a small hyd and still make big power.

if you only wanna make <420rw, then you are best off stickin NA.

but if I know you.. 420 isn't gonna be enough! you ever ridden in a 550+ rw blower car? its fun

 

Thanks Jordon.

Finally out of the closet and what I’m trying to do is come up with a reliable 450rwhp (or more!!) combo if possible. Was hoping with enough ci, great heads (I’ve not ruled out the 215 AFR’s raised runners), electric water pump and a sensible (236/242 or so) hydraulic cam, I could come pretty darn close. No more solid lifter cams for me after breaking those darn liters all the time.

I used to drive Pat’s supercharged 383 on occasion and it was powerful no doubt. My concern living here in Dallas is overheating in summer. Plus it seems like most of the people I know with supercharged cars sooner or later break pistons. Maybe it’s just me or perhaps Pat’s old car, but the throttle response was slower giving the subjective impression of being not as quick as it really was.

On second thought, if overheating is not an issue, a supercharger with different pistons for my current 383 block/heads/cam may even be cheaper and certainly does produce effortless power. All I really need is lower compression pistons, larger injectors and the supercharger. Which supercharger do you recommend? What compression? Also, don’t they like 5.7” rods? I tearing down the engine no matter what.

Thanks again for the input. Let me sleep on that one as it has real merit.

Denny

 

One vote for a mild 236/242 cammed 396 stroker with AFR 210's and a HydraRev kit topped with a Nitrous Express Fogger and some smallish 250hp jets...possibly a Comp Nitrous HP grind camshaft??

Just my .02 from one Denny to another.

 

I always respect what a Denny has to say. I've found them to be bright, charming and good looking. Real studs in every sense of the word. In adition, experts on cars by all means.

Actually my ship is sinking some on thinking about doing a 409 motor and may end up just like everybody else owning another 396.

Believe this particular list probably has the best technical expertise on the net and I'm not getting any responces in favor of the project. The guys on the Vette list jump up and down that "bigger is better" but don't seem to have the technical expertise to explains the pro' s and con's nor have they actually done one. (Think that may tell ya something)

Is anyone running the raised runner 215's on the street? I haven't e-mailed Mark Monvaleo for a while, but my understanding he sells the adapter plates so you can use a regular LT1 intake. The only kicker is Jensel rockers.

Again, I done jumping through hoops and may end up with a 396 with 210 AFR heads, but sure do like the sound of a 410 ci motor and 215 raised port heads though.

Thanks!

 

Jordon, I'm curious, why a 5.85" rod with a 4" stroke? That puts the rod ratio down to 1.46, instead of 1.5 with a 6" rod. Is it a physical limitation, clearancing issues, with running such a big stroke? I know rod ratio isn't the end all be all, but it would be nice to know why the 409 isn't more popular. I had always presumed that people wanted to stay above a 1.5 r/s ratio. With the reduced rod ratio there is more side-loading on the pistons, and reduced longevity, right? Maybe its to make it have peak power a bit lower in the rpm range? A better rod ratio would have characteristics of a higher reving engine, so you are effectively limiting high rpm efficiency I would guess. Then again, the stock pcm only goes to 7000, so its not a high rev option unless you go standalone. Ok, I'm through rambling for now.

 

i for one think it would be cool
....and also not a good idea for a engine that sees lots of miles
13 more cubes isnt a huge deal, but having something different i think is pretty cool, i say go for it

 

brain-
rod/stroke ratio is just a number.. it means very little. about all you wanna do is run the longest rod you can, and still have a decent size piston there.. and IMO, 6" rod doesn't leave enough piston

Denny-
a really good set of heads(215RR would be great) and a hyd cam in that range should make your desired power easily. the 215RR heads will need a hogans sheet metal intake however. there is some talk that you COULD use an LT4 intake, but it would become a major problem area...


As far as blower cars, the reason why they feel slower at low RPM is 2 fold, 1) its so friggin fast up stairs.. and 2) you generally run lower compression, which reduces low end(say 1500rpm-2500rpmish). However, you will be running a much smaller cam, which will give you more off idle response.


A properly built blower motor/combination should NOT ever hurt pistons... think of all the turbo/blower cars coming from the major automakers.

If you keep the HP low(say under 550rw), which would probably take around 10lbs of boost with good heads, I don't see why you would have any problems with pistons breaking, as long as you don't skimp on the fuel system.

This also gives you more room to grow, in the future if you decide you wanna put the car in "kill" mode, you can up the boost.

overheating should not be an issue.

with a 3.750 stroke, you can use a 6" rod. I built a blower motor for a car last xmas that uses a semi-custom SRP piston, 24cc dish, for a 6" rod. worked great. car makes over 500rw, with very little $ invested.

 

This is hearsay, but I heard Mark M. had an adapter plate he was selling to adapt the LT series intakes to the 215 heads. Guess I need to e-mail him to find out for sure.

The word I’m getting on doing a 4” stroke with a 6” rod is that the compression height of the piston is very low/small which puts a lot of strain on the sides of the piston. That’s why people are using the 5.85 rod instead. Again, this is also just hearsay and I’m trying to get some feedback from someone whom actually has a similar combo. There has got to be someone on this list who owns a 409 and can explain why they did one and if they would do anothe?.

Just can't believe doing .015" more stroke makes a night and day difference in the wear factor. I realize that when you push the edge things do happen faster, but shouldn't be that much faster. An 1/8th of a inch just isn't that much compared to the overall stroke.

Just being very cautious as a believe it or not, I was one of the very first to do a solid roller 396. Pretty amazing as to how many problems I had back then vs how common they are now.

 

The 409 wears a lot more, because you have the added stroke, AND you must run a shorter rod.

FYI, mark m at one point had 6" rods in his 4" stroke motor.. althought for continuos street use, he would prolly recommend a shorter rod.

 

It's not a 409, but I still have the Excell spec sheet where Mark Montalvo did a 421 and used a 5.85 rod.

Just ah 1/8th" really does cause a lot more wear? well.... all I can say is "damn". And, I had my heart so set.

What about the guy in Houston whom is running a 412ci Impala using a 4.15 bore and 3.85 stroke. How in the hell do you pull that trick off?

 

Start with a 400 block?

I get 416 CID with a 4.15" bore and 3.85" stroke, so it must be a 3.8" stroke if it's a 412 (411.2). That's an awfully big overbore if it's an LT1 block.

Mark tried two different combinations to end up with 421 CID. The first was a "big bore" (4.090" bore) with a 4" stroke (420.4 CID). His most recent 421 has a 4.125" stroke crankshaft, with a 4.030" bore (420.9 CID), I believe.

 

Coincidentally, it was the 409 LT1 built by TPIS and featured in the July '98 issue of Vette magazine that got me started thinking about a stroked LT1 for my project. The numbers (523 hp @ 5750 and 528 lb-ft. @ 4750) were what hooked me. Of course I sort of passed them by in both respects with less cubic inches, but that 409 was what started it all.

They used a 3.875" stroke crankshaft (with 5.85" rods) and a 4.100" bore (biggest I'd ever heard of for an LT1) to arrive at their 409 (409.3) CID, according to the article.

 

I hear what your saying about the 4.15 bore and a 400 block. My assumption is he is running a LT series engine because he talks about having a "hot" cam in the car. Actually he calls it a 409 and e-mailed me saying it was actually 412ci.. explaining the bore and stroke.

Jeez..... the more I know about these things, the dumber I seem to get.

 

thats just because there are so many combinations, cant really talk about a 409 like there is only one type, though what you have in mind sounds more common

so what are the limitations for bore on lt1/lt4 blocks? i'm trying to think if i ever even hear of 4.060" over the usual 4.03/4.04"

do LTx blocks from certain cars/years withstand higher bore? isnt it extremely rare one that will safely hold 4.06? how do you tell?

i really like LTx based engines merely on the fact that they are reverse cooled, think its a great starting point for a small block
but i thought they were limited to much less than 4.1" bore simply because there arent any reverse cooled 400 blocks