ElkySS

iTrader: (6)

ok so we have all seen the news about dart making this new block right? lets talk about its potential. what kind of parts need to go into this motor to make the most out of 427 cubic inches? im not aware of any lt1 heads above 215cc, and im not sure that will feed a motor that size very well. what kind of pevs would we be dealing with. could you rev a motor that size to 7k and still have decent low end torque? im talking about a strict street car motor. one that can be driven everyday and even sit in traffic. im thinking 550-600 (maybe more) n/a rwhp with a 6-speed. if you think this is possible, post up your ideas for a capable motor. lets make sure we all know how to build this motor right before we get a bunch of sub-par builds.

marc97taws6

iTrader: (6)

I wouldn't know myself but I am curious to see the outcome of this thread...

SUBSCRIBED

1badzee

iTrader: (12)

I have the answer..

http://www.youtube.com/watch?v=DDmKr8slxmk

But on a serious note, I'm subscribing too. I'd like to see the outcome of this

FASTFATBOY

iTrader: (23)

AFR makes a 227 head that in the right porters hands could feed a 427 to 7000 rpm. But would need a worked single plane and a 1300cfm TB.


As far as low end torque, hell yes....depends on the combo of parts. Mine has huge heads, single plane intake, huge headers, moderate solid roller(big to some here) and makes 400lb feet of torque by 3100 rpm, peaks at 436 lb feet of torque has a nice arc on the chassis dyno from 3500 to 6000 rpm where it goes back to 400 lb feet.

94Z28rag

iTrader: (10)

How high do you spin yours?

badfbodyz

iTrader: (3)

i thought afr was soon coming out with 235 cc lt1 heads?

Puck

iTrader: (17)

They are. I think TFS are coming out with 230+cc heads as well. The as cast runner size of aftermarket heads does not mean a whole lot though since they usually are the same castings as the smaller ones, and therefore have the same porting potential in the hands of a good porter.

duh

iTrader: (16)

See, I was thinking do the 427 rotator, AFR 227 LT4 heads(of course opened), open the intake to match, and a Monoblade. I figure that'll make one hell of a street motor, have tons of bottom end and still have a decent top, once I got the cam figured out.....Cam would most definately be bigger than the little 847 I had in my 90

Advanced Induction

iTrader: (2)

The output of any build is primarily going to be dictated by the top-end regardless of the size or quality of the short block. The average guy going from 383 to 427cid, essentially running the same head & valve train, will realize a small increase in power & a moderate increase in area under the curve. For most guys with a decent 4" bore short block there will be more gain to be had by investing in superior heads & valve train than in cubic inches.

Numbers like that are thrown around often, but are extremely rare in reality. That said, the NA goals you propose are certainly feasible and should be easily met provided the budget and expertise is there. The average $10k build is still going to be in the 4XX's in all probability. Our last 383 LT engine managed over 550rwhp SAE from 6550-7300rpm. That was through a non-lockup converter, 4l60, 9", and on 93 octane pump fuel. Were it a converter that could lock up, the #'s would be closer to a manual drive train & well into your goal power range.

http://www.advancedinduction.com/dyn...3octA4-SAE.jpg

At 427cid it should only need to manage around 1.5hp/cid or 64Xhp to be at ~550-580 w/ an auto or manual gearbox. The 427 will help to offset the deficiency of simply running a large inefficient head, but always at the expense of area under the curve. In any case, entry level heads & valve train are not going to get people into that power range. To be done consistently and reliably, it will not be cheap whether HR or SR. We have heads that will certainly manage 550-650rwhp with 427cid & retain drivability for street use. They are out there & are available.

As an alternative, at the price point required to reliably generate a streetable 600rwhp, it is difficult to exclude moving to the LS7. If you feel a hydraulic roller valve train is a must, it is hard to beat. With a factory PCM and support software that is vastly superior to the LT unit, as well as weight savings, is worth heavy consideration at the ~$20K level.

In any case, it is great of Dart to allocate the resources towards a quality replacement for the GM part. As capable as the GM piece may be, we'll now have the displacement available to begin to utilize some of our racier head designs.

OutlawZ

iTrader: (4)

I have hand ported AFR 227's (the old castings) and my car makes power all the way to 7600 RPMS with a big solid roller.... and 383 cubic inches....

I'm sure the new eliminator 227's that are hand ported or CNC ported could support 427 cubes and 7500 RPMS with the right cam and valvetrain....

FWIW, I shift my car at 7300 cause power peaks right around there.... but even at 7600 i'm down like 5hp....

1SlowFormula

What size valves do you have in there now? One of the advantages ofgoing with the big bore LTX block is that fact that you can take good flowing heads like yours and open them up even more and adding bigger valves to increase flow, and still be far enought from the cyl wall to also increase the flow. not much more work to the heads and you get a ton more potential out of them. obviously this is not to say stock castings will get the job done, but the heavy hitter aftermarket stuff can now get a little more work done and easily support a big bore LTX...

duh

iTrader: (16)

Way back when I remember one of the car rags doing a build off a 400 block with a 327 crank to make the "350 GM should have built". If I recall the thing made like 450-500 hp with a "stock type" cam (meaning LSA in the 116-118* range). Now if someone were to do a 350 that way, you'd probably be able to spin it a lot higher and still have longevity. Now I think that would be something wicked to have in an LTx seeing as you can spin it nice and high to make some decent hp #'s. I think this new casting opens up a whole new aspect of combo's that the LTx world has yet to see. Imagine a big bore LTx with a relatively small Ci. spinning to 10K rpm. Defiantely different which is what the LTx crowd has been well known for embracing by keeping the LT platform in the car.......

Just my .02

FASTFATBOY

iTrader: (23)

Gets done shifting 6800/6900

joelster

Here's some information. A guy on this other forum built a 427 SBC with AFR Eliminator heads out of the box. He used a Vic intake and an 850 carb. It made 640hp at 6400rpm, and 600 ft/lbs at 5000rpm. Compression was 11.5-1 but it should still be fine on pump gas, especially if it was reversed cooled like our LT1's, lol. All of the comments that follow are interesting to read too:

http://speedtalk.com/forum/viewtopic.php?t=9911

Or how about this 427 SBC. 628hp and 585 ft/lbs both well under 7000rpm, and it's a freakin 210cc out of the box head:

http://forums.corvetteforum.com/c3-t...ally-done.html

YngBird

this is exactly what i want to do. i would like to see how this turns out.

Puck

iTrader: (17)

That first build is impressive because of the small cam it was done with. 240/245 .68x/.68x 112LSA is tiny for a SR, that must be a true streetable 628hp .

Now I am even more unsure if I should stick with my current low 24x/24x cam or go bigger on my ported AFRs, and shot both AI and LE emails last night for some opinions .

joelster

I REALLY think your cam choice should be whether or not you are sticking to the factory pcm/opti, than anything else. You can run a pretty big cam and make it peak at/near 6500rpm or so. That's what those 2 builds are peaking near. If the car is going to be an all-out drag car, then go bigger, but a street/strip car will be fine with the opti. You can always whack it with some nitrous. I'd be willing to bet half of the guys interested in purchasing these blocks and doing 427 builds don't have their cars anywhere near ready to handle 650hp and 585 ft/lbs of torque.

I am going to run my AFR's box stock, not sure what displacement I am going to run though.

Corey @ Clayton Racing

I'd be willing to bet half of the guys interested in purchasing these blocks and doing 427 builds don't have their cars anywhere near ready to handle 650hp and 585 ft/lbs of torque.

You have a great point, 9 times out of 10 this is what we see. All the thought goes into the motor and none into the car. You always find the next weakest link, and you start breaking alot of stuff until you get it up to par too.

spin the tires, put on stickys.
break the rear, fix the rear
break the clutch fix the clutch,
break the axle, fix the axle,
break the driveshaft, fix the driveshaft,
break the trans, fix the trans.

There is a lot of stuff that needs to be thought of.....

duh

iTrader: (16)

Don't forget the brakes, everyone who wants to go fast never remembers that you need to stop eventually.....preferably under your control and not the sand pit

engineermike

I really believe a base-case problem with the LTx stuff vs SBC and LSx is the runner location. It's too low, especially when combined with lots of cid and the other geometric constraints such as pushrod location. It will always be handicapped as long as the runner is ON the deck surface. I would be most interesed in a 427 cid LTx with converted Brodix -18 STD X heads. It would be very comparable to a LS7 in many respects then.

Mike