Just wondering if anyone has built any 408 LT1. I would think if u were gonna build a 396 why not go ahead and put the extra 1/8 inch stroke and make it a 408.

 

Been done. Losts of extra cost for questionable benefits.

Few Impala guys did them for nostalgic reasons, round up and call it a 409.

 

Shouldnt cost that much more. If u order the rotating assm. that way it should be about the same from eagle. Only problem would be cam clearance. The way i wanna build one will be more expensive. I wanna run a Callies crank with the 1.88 honda rodbearing jounals, to cut down on rotating weight and to get precious clearance. And i would like to run the 1.5, 1.5, 3MM ring package to cut down on ring tension. Getting the compression down would be the next hurdle. But i was thinking with 11.5:1 compression i could run a cam with around 238/244 degrees at .050 int/exh with an lsa of around 114 should keep the cyl pressure down. I think that would make a pretty wicked street motor that would knock dwn some 10 sec quarters with ease.

 

The extra cost is exactly what you just mentioned - clearancing and machine work.

Have you seen the clearancing first hand for a 396? It is pretty easy to hit water...even a 383 can punch into the jacket pretty quickly with the wrong rod/bolt combo.

You would most likely have to go through more then one block to cherry pick a usable one, shave the rod bolts, clearance the hell out of it, and still have to at least half fill the block...then if you are lucky you'll end up with a usable 408.

1/8" sounds so small on paper until you get in there and realize how much that extra 1/8" clearance would help...it really is not worth the extra cost and risk.

 

MTI in Houston when they still worked on LT1s did a couple, I remember one of them was for a customer in Georgia.

 

yeah what he said, lol!!!

 

How is piston selection????

Actually one of the Impala guys is trying to sell a 416 uses a 4" Cola crank.

 

Well yea ive seen it first hand. Ive done quite a few of them myself. Ive done 383, 396, and 434s and one didnt require hardly anymore labor than the other. Ive only hit water on one 434 setup in the bottom of the cyl next to the cam, and that was my fault. The blocks gotta be machined in the same place in all the stroker setups. Also u have to cut the top inside of the big end of the rod to clear the cam in all of the stroker setups i mentioned above. I cant see where its that much more labor intensive. And yes i know how much difference an 1/8" makes, and your right it does make a healthy difference. Thats why i wanna build one with the honda rodbearing journals. Makes the bigend of the rod much smaller, which equals alot more clearance and less rotating weight.

 

Still comes down to rod selection, have heard of some rod companies just using the same forging and making the hole smaller for Honda journals, no weight or space savings then.

Again how is the piston selection??

 

we got a 402 in one of the shop cars. Mild 447RWHP auto. We have hit it with juice a few times but do not plan on going bigger then 150hp

No rock just block.

pistons were easy as a sanctioning body uses the same pin hight for 362s

 

Naw not eagle or callies compstar rods. We are in the process of building a roundie round motor with a callies crank and eagle rods with the honda rod bearings. The rods are alot smaller on the bigend. And they are a good bit lighter. And as far as pistons go JE makes em. They are a 1 inch compression height, and they would have to be a flattop or dome. No room for a dish. Thats the problem. If they are thick enough in the crown then i may can set em up in the lathe and put a .030 dish in them to get an extra 5 cc. If not i will just run a wider LSA cam to blead off the squeeze.

 

From what I see Eagle sometimes lasts in race applications where the clearances are big enough that the taper from the bad machining doesn't matter. On the street with tight clearances though I have seen a number of bearing troubles with them. The cast cranks guys use in a blind lust for displacement seem to like to crack too. Don't get me wrong I would like a 383 but I wont use a $200 crank to get there, have my eyes on the Compstar Speedpack.

Use the Compstar it is MUCH better stuff.

 

LOL.....

 

There is one guy on camaroz28.com that just finished a 408 LT1. Thats the only one i have ever heard of, its too easy to hit water with a LT motor.

 

Ive never had any problem with eagles H beam rods. They seem to come pretty strait from my experience. And i agree on the cast cranks. The only thing that would justify a cast crank in a stroker application would be a stump puller street motor that never got spun more than 5500 rpms. But even a stroked street engine like im talking about building needs atleast .0025 of verticle oil clearance. Thin oil just cant support the load of a street or race motor with that kind of power. IMO any tighter than .002 clearance is pointless and flirting with disaster on a hot motor.

 

I wont be bothering with a 408 BUT hitting water is not the end of the world, little epoxy and maybe some rock block to hold it in place been done a lot of times by a lot of folks.

fergymoto, why don't you elaborate on those pics.

On the taper I was more refering too the cranks. I know local engine guys don't like Eagle because they say they go out of round after a few torquings.

 

383"
Eagle cast crank, I beam rods with ARP cap screws, KB hypereutectic pistons flat top with valve reliefs. LPE CNCd heads, 224/232 .605/.605 107.5 LSA Bret Bauer cam

4L60E, 3400 2.1 STR Fuddle converter, 3.42 10 bolt, MT ET Street Radials, 3600lbs

.0025" bearing clearance on the mains and rods, 12.2:1 compression, stock intake manifold, 58mm TB, EWP, LT headers, 3" true duals.

I ran this setup for like 700 miles. I got to go to the track with it and it was slow. It ran 12.0s at 110mph with 1.601-1.61 short times. Ran good, it just wasn't fast.

One day I was out cruising in my car and was just driving down the road going ~30mph. I hit the gas and it downshifted to first and began to accelerate and there was a pop and it started free revving. I thought my trans broke, the thing had 117k on it and it was about time. I coasted a little ways with it idling and it was still running fine and what not.

Thinking it was the transmission, I'm like "Well it's about time this thing broke. I'm going to do it in!" So I hit the gas again and it revved and all hell broke loose. I heard parts flying around and looked in the rearview to see a nice trail of smoke following me as I'm coasting down the road. The engine had stalled out.

At this point I still thought it was the tranny and that something had broke and made it stall. I turned the key and it was locked solid. I got out of the car and looked under it and my heart sunk a little bit when I didn't smell any tranny fluid. It sunk a little more when I saw the fluid on the ground was oil and not tranny fluid.

I took it home and pulled the pan off and took those pics. That's it as I found it.

I am sure that the first time I hit the gas the crank sheared off. The second time I hit the gas the crank flexed having no support back there (it broke off the counterweight behind the number 8 rod journal). Then as it was spinning down and flexing it bent the 7 & 8 rods and when it came back up with bent rods it blew the #8 rod and piston into smitherines. The #7 rod did not break but was bent quite sideways, and the piston was cracked.


Any questions?

 

If u ran that motor on pump gas with 12.2:1 compression, that 107.5 LSA cam with that small of an intake lobe, then u most likely detonated that motor to death. Did it beat the bearings outta any of the other rods and mains that managed to survive the storm?

 

Haha i see what killed it. Look in the 4th pic down and u will see ur spiral lock layin in the bottom of the pan. That will kill the **** out of a motor. But i would still bet that detonation played into it with the combinaton u were running. Man that thing had to have a ton of cyl pressure with that 107 LSA.

 

for the additional costs of internals and difficulty of clearancing and machining an extra 12 cubes wouldnt be worth it (for the 408 vs the 396).

personally i would love to see an aftermarket lt1 block with a 4.125 bore like the 400SBC with the LT1 water passages, etc. stroke that out to 434+ cubes. it probably wouldnt be cost effective but it would be badass.