I have a pair of Jet Hot 1.75" tube headers still in the box from 10 years ago, never used. Are the primaries too small for big cube LT1's let's say, 410 ci?

 

What valvetrain?

 

What size are the exhaust valves? If they're less than 1.75", (which unless it's a big block they're going to be) you have nothing to worry about as the exhaust valves cannot outflow the bigger primaries.

 

No idea what valvetrain. Recommend me one for a 410 ci LT1. Streetable, M6, daily driver.

 

That should be fine.

 

1 5/8" is 1.625" so you are arguing that nobody with a 23degree LT1 needs anything over 1 5/8" headers and that if anything they are a little overkill?
Even the AFR 227s the biggest available LT1 head the exhaust valve is only 1.600.


The real world says that your valve size/ header diameter argument is completely invalid.


If you do a 355 or 383 RIGHT the torque is unusable on the street so to build a 410ci motor for the street is just foolish. Spend less on that bottomend and more on the topend and you will have a nice setup. Keep your displacement blinders on and you will likely endup with a failure to make a good runner.

 

I hope you have a LTx Bowtie block if you are going for 410ci...

 

I agree with you 100%. If a car is mostly for the street, stall/geared cars have trouble putting down the power they are making. Let alone a 410ci motor. He would need to spend at least $1700 on a new tranny, $300-$400 on a new driveshaft, $2000 on a new rear end and about $350 on a set of DR's just to be able to use any of that power on the street. That's not even including any costs whatsoever on the engine or any other bolt on's or suspension components, which would total thousands upon thousands of additional dollars.

I think we're talking about a upwards of a $20,000 buildup to do everything right and ensure that the power is usable on the street and nothing breaks.

 

I don't have Pipemax on this computer, and more info would be needed to run it anyway. But 1 3/4 should be ok, in general.

 

Well there are a few members here with a 400+ cubic inch engine that's why I was asking. I mean if I were really to go big cube I might as well deck plate and sleeve the block for even higher dispacement. That is IF I were insane and wanted to waste serious cash on bragging rights.

Although I've heard of LT1's being sleeved but not deck plated...

 

I say go for it. Everyone here (as well as other forums) seems to be stuck on the "go with what works" bandwagon. If everyone that ever worked on cars did that then hot rodding would not exist. My plans were to build a streetable 408 LTx but I've since been convinced by a good friend that the LSx swap is a better alternative. Since I'm not really biased either way, I'm gonna save some money in the short term. Then again when I get to do my LSx build.....I'm thinking 454 with a Eaton style blower.....Can you say 1000+ RWHP and DD manners?!?!?! I say go for it build a 410ci. LTx and shut all the haters up. What's the worst that happens.....motor breaks.....can't take money to the grave with you so you might as well have fun with it while you can!!! That's just my outlook though...

And if you're looking for max power....look for some 1 7/8" headers or look into making or getting 2" primary headers made.....Those little 1 3/4" will choke it on the high side...

 

10 years ago, they were selling LT1 409 short and long blocks - but nobody bought them. One of the FORMER members here built two different configurations of a "421" LT1. There's another guy that sleeved and built a 427 LT1. Its all been done.

 

Interesting that a post about big cube LT1's should pop up again. The last time we talked about this I mentioned that I had acquired an "LTX" block, and was going to do a large cube blown engine for the street!
I said that I would post updates on my progress, which unfortunately has been sloooww!

Anyway to recap. The block is supposed to be one of only ten, LT1/4 based blocks produced by Chevy's high performance Div. It has a finished bore of 4.125, 4 bolt steel billet caps on 400 mains, and .250 raised deck. I'm using 3.875 stroke crank with a 5.850 rod for 414ci.
The heads are Dart Pro 1, 215's with 2.55 I & 1.60 E.
The blower will be a Pro Charger D1SC with the dual intercoolers.
Cam. is a Lunati custom grind, for this engine.

Before anyone asked were using the 5.850 rod so that we'll have plenty of room for the rings on the custom blower pistons.
The "short block" machine work is complete, the pistons have been coated, and the custom plates have been made for the end seals and heads. These were obviously necessary because of the raised deck. Not going to do a sheet metal manifold. Heads are being ported as we speak. I only have a couple of pictures, if I remember I'll post those tomorrow.

So what's this have to do with the post? We're going to use 1 3/4" headers, at least to start with. "WE" think they will be adequate. If not, as has been suggested, we'll upgrade later.

Still have a few dozen decision to make, particularly what ignition to use.

 

Post pics please!

AND, what heads do you recommend for a 410 NA setup with the stock LT1 manifold? AFR 227's?

 

Here's the link, only 8 picts. so far.

http://s886.photobucket.com/albums/a...ORR/LTx%20414/