Building a 427 - options and ideas

**Tobynine9** · 08-08-2008, 10:12 AM

Ok, within the next few months I plan on beginning a build up of an LS-powered AC Cobra replica. My first thoughts for power were to just find a take-out LS1/T56 from an F-body, swap the heads and cam, along with other little upgrades, and use that. That would make more than plenty enough power to drive a 2,100 lb car and would be relatively cheap.

I got to daydreaming recently... An LS-427 sure would be fun bragging rights in a "427" Cobra... I don't want to spend $14k on an LS7, though.

So, here's what I was thinking. This is where y'all come in and say, sure, that would work or, NO, that won't work well and here's why...

LS7 bare block is $2,450 from GMPP.
Eagle rotating assembly part B12826125 is $2,400 from Summit. Balanced with +4.5cc pistons and a 4.00" stroke.
L92 heads from Texas Speed with dual springs installed and hollow intake valves are $1,630.
L76 intake manifold and a cable-driven throttle body, approx. $800.
(LS7 heads and intake would add too much $$ - I'd have to pony up for the pricey titanium valves if I use the high-lift cam I want)
LS7 lifters $130.
LS2 timing set $90.
GM rocker set $250.
Plus $1,500 for completion parts like sensors, hardware, covers, etc. (tell me if that's too low)
Custom camshaft $400. The cam profile I like is a spec by a fellow on tech. 223/227 - .636/.639 at 110 with 0 advance. Loads of mid-range torque.

That puts the grand total around $9,500 for parts. Plus, I have to put it together myself. And I've never built a motor. I've done heads and cam before but I've never actually gone through a build up of the bottom end.

From Texas Speed, an LS7 long-block with intake mani, cable TB, covers, and LS7 heads WITH the pricey titanium valves is $12,150.

Either way, it's a crap-load of coin. So, without considering more options, between those three - what do y'all think is the best bet? Also considering that if I build or buy a motor rather than a combo, I still have to find a T56 and bell housing.

LS1 with H/C and be done? Build by own L92/L76/LS7 427 hybrid? Or buy a long-block LS7 already built?

**Mr. Luos** · 08-08-2008, 10:15 AM

While the 427 is a great idea...what about a 402/408?

**cam02ss** · 08-08-2008, 10:46 AM

Quit listening to Mr. Pusspants and do an LSX 454

**Mr. Luos** · 08-08-2008, 10:50 AM

Originally Posted by cam02ss

Quit listening to Mr. Pusspants and do an LSX 454

I was looking to save money....not spend more.

**Y2KArcticSS** · 08-08-2008, 11:01 AM

572..........................

**cam02ss** · 08-08-2008, 11:04 AM

Originally Posted by Mr. Luos

I was looking to save money....not spend more.

Are we building an engine or going coupon-shopping at the local grocery store with the wife??

**Mr. Luos** · 08-08-2008, 11:19 AM

Originally Posted by cam02ss

Are we building an engine or going coupon-shopping at the local grocery store with the wife??

Fill me in on why you have a 408 then?

You have any coupons to share?

**JHayesLS1** · 08-08-2008, 11:23 AM

3.8 V6 :d

**cam02ss** · 08-08-2008, 11:56 AM

Originally Posted by Mr. Luos

Fill me in on why you have a 408 then?

You have any coupons to share?

I was a hasty bastard and should have waited another year

**Tobynine9** · 08-08-2008, 12:17 PM

Geeze... we should re-name this forum from LS1.com to Tangent.com

y'all can't keep a train of thought going any longer than i can keep a woody with janet reno in the room.

The chassis/kit I'm buying for the Cobra is VERY light and based on C5 Corvette forged suspension bits. I want LIGHT. So no iron blocks.

I've thought of a 408 but the expense for a LS2 bore motor isn't much less than a 4.125 bore block. Plus, it would be cool to tell folks, "yeah, it's got a 427," then lift the lid to display an LS.

**Bottesini** · 08-08-2008, 03:14 PM

Just a couple of things to point out. If you are going to be doing all the work yourself remember you are going to have to pay for quite a bit of machine work.

Now something that might save you money. I am not sure, but I believe the LS3 block can be made into a 427 fairly easy and should be much cheaper then an LS7 block.

**Tobynine9** · 08-08-2008, 04:58 PM

If I use a brand-new block and all new components sized to fit the OEM machining, why would there be machine work?

**Bottesini** · 08-08-2008, 05:09 PM

Originally Posted by Tobynine9

If I use a brand-new block and all new components sized to fit the OEM machining, why would there be machine work?

With luck it should be minimal, but I would always suggest when making an engine from the ground up to at least have a machine shop check everything out. Not to mention at least you will want everything balanced out.

**Tobynine9** · 08-09-2008, 07:22 AM

is there a "how to build an LS from a box of parts" book out there?

**txz28** · 08-10-2008, 07:14 PM

Originally Posted by Tobynine9

is there a "how to build an LS from a box of parts" book out there?

Auto Zone has a book. I think its called .."Building a High Street Performance LS-1"
I skimmed threw it I went there lookin for a hanes book on my 2000 Z but they didnt have one anyhow I found that book and like I said just skimed threw it its brokin down into horse power ranges ( 350,450,500, and i think 550 and above was the last section) 20 bucks or so for the book.

**jimmybling31** · 08-10-2008, 07:49 PM

Originally Posted by cam02ss

Are we building an engine or going coupon-shopping at the local grocery store with the wife??

haha that's great

**Tobynine9** · 08-11-2008, 06:57 AM

Having never built a motor, do y'all think it's too big of a task considering the expense I'd be putting into parts?

The more I think about it, I'll likely just use a H/C LS1 as it'll come with everything already, wiring, coils, covers, etc.

**shady milkman** · 08-11-2008, 07:17 AM

i personally think its tooo big of a task to do yourself..never building the bottom end ect.. if you have a friend that has..ask him for help and start to work on it. You mess something up on the bottom end..its only a matter of time before you grenade the whole engine.

**99transamC/FIA** · 08-15-2008, 02:32 PM

If you never built one look at some of the short blocks available.For what you are trying to do you are not looking for anything that cant be bought put together.Putting together a new motor (even if its a brand new block) with out checking clearences with a BORE GAUGE ,not plastic crap, is just stuip!!!!
Why spend all that money and have one little thing go wrong a tear up all sort of shit.
You can find 427 in LS for around 6000+ top half, and be under 10,000 still.
I urge you PLEASE atleast let someone take a look at it if you do decide to do it yourslef.

Also you could run a 4.065 bore block(ls3 l92) with a 4.100 stroke and come out with 426 cu in and just tell youeslef that it is 427 inches.

If you really what to make that thing a true tire smoker build a custom piece, i have build lots of ls stuff and 500-600hp is pretty easy to do for under 10,000, and will go low 11's (smoking the tires)at the track, and will whip corvette's bad.

What kit is the Corba, I have put together a few of those kit car. the ones i did were made by Kurkum( i belive).They are really nice.And they had 400 in 600hp fuel injected small blocks, and would roast the tires at 80mph. What a fun ride.Send me some pictures when you start to get it going.I will dig up some pictures of the ones i did and send them to you.
Just my to cents
PM me you you what to talk about something.
Good luck sounds like a great build