View Full Version : Ls7 454


Southern72
04-17-2006, 08:48:15 PM
While at a friends house i discovered he has a real LS7 454 that he bought brand new years ago.He took the original iron heads off and put gm racing alluminum heads on. He was planning on drag racing the motor but never did.This motor is 12-1 compression.And has been sitting in a garage for a long time but has never been run. He took out the original LS7 solid cam and replaced it with a bigger one but still has the stock cam.What do i have to do to this motor to run it? I will put a smaller cam in maybe the stock LS7 cam but what compression can i run on premium pump fuel. Keep in mind this car will never be a daily driver.

kirbi69
04-17-2006, 08:51:56 PM
i thought the ls7 was a 427, from the late 60's vette and the ls6 was the 454

Southern72
04-17-2006, 09:01:53 PM
From what i read the ls7 was scheduled to replace the 427 vette motor but emmisions stopped it mid production. the motor option even made it in the vette brochure.chevrolet then sold them as crate engines.

pdq67
04-17-2006, 09:06:04 PM
The 454 was both, an LS-6 and a never sold in a car, LS-7.

LS-6 was 11.25 to 1 CR. with just the .520" gross lift solid cam in it! The LS-7 was 12.5 to 1 CR. with a big .560"/.600" gross lift solid ZL-1 type cam in it..

Can you say 600+ hp uncorked and ready to boogie!!

pdq67

Southern72
04-17-2006, 10:38:28 PM
He said it was good for over 600hp as is. I would like 500hp and pump gas friendly with a cam that is streetable.So how much compression do i have to lose to make it live on 93 octane.

theflash
04-17-2006, 10:42:29 PM
12-1 compression is not pump gas friendly. At least not todays gas, back when that motor was made you could still buy 100 octane gas.

ZS10
04-18-2006, 03:58:36 AM
I would like 500hp and pump gas friendly with a cam that is streetable.So how much compression do i have to lose to make it live on 93 octane.
Everyone will have their own opinion on this, but mine is 500hp is easy to get with a 9.5:1 454. No need for exotic anything. Flat tappet hydraulic cam, a decent alum dual plane, (or single plane if you need to kill some bottom end). Stock oval port iron heads with a decent valve job and maybe some port work. Great street manners, runs on regular and be thankful its cheaper, you're going to burn lots. When you get bored with the power, put some nitrous into it.

70RS/SS396
04-18-2006, 08:40:31 AM
Keep the engine as is it, onley change pistons to a little more pump gas friendly. You will still problably have 500-600 hp, depends on the camshaft. If you takes the original cam you have at least 500++ hp.

BIGBADBOWTIE
04-18-2006, 08:57:37 AM
There was also an LS5.....

camrs73
04-18-2006, 09:13:16 AM
There was also an LS5.....

yeah 454/390?hp hyd cam, more of an A/C car motor i believe

BIGBADBOWTIE
04-18-2006, 11:16:14 AM
Yeppers... my father-n-law and I restored a 70 Chevelle with an ls5.
Hydraulic cam with big O port heads. Still ran strong with an RPM intake/cam.

Southern72
04-18-2006, 11:25:54 AM
I have A/C and power brakes.I almost hate to modify this engine. I have access to the original iron heads. The shortblock has never been run only the heads have been used. I could have a real #'s correct new LS7 but what could i do with it at 12.5-1 compression?

camrs73
04-18-2006, 11:38:17 AM
given your options, maybe consider selling it, definatly get some good $$ for it. if it were me, i'd keep it and find something to put it in with the high compression and go racin :)

Grumpy 427
04-18-2006, 12:42:12 PM
The good 427 was the L-88, the LS-5 was kind of a pollution motor? the LS-6 was a good performance 454, and the LS-7 was the race motor you could buy right from GM. With good heads and a big solid cam guys were making 700-750 Hp with them back in the day.

BlownBigBlock
04-18-2006, 12:56:08 PM
The good 427 was the L-88, the LS-5 was kind of a pollution motor? the LS-6 was a good performance 454, and the LS-7 was the race motor you could buy right from GM. With good heads and a big solid cam guys were making 700-750 Hp with them back in the day.

The big differences between the LS6 and LS7 was the cam and compression. The LS7 used the same cam as the 427 ZL1 motors.

The LS5 (Corvette wise) was basically the same as the 427 390 and 400 hp big blocks except for the longer stroke. The 400hp version was a tri-power setup but still with big oval port heads.

The LS7 was designated for the 70 Corvette to keep the car as it's top performer, but GM dropped it late and the Corvette was stuck with a LS5, whereas the Chevelle was already being made with the LS6. Engine was to be equipped with aluminum heads, I believe all LS7 engines bought over the counter were iron heads.

The engine is not gas friendly, best word to use is compromise, I'd retard the timing a tad, and keep my foot out it. Very sloppy on the bottom end, car really wasn't fun to drive till around 3000+ rpm.

70RS/SS396
04-18-2006, 01:21:19 PM
Some LS7 engines were original equipped with alu headdes. I know 2 of them. The others had 990 headds.

Bruce Sherman
04-18-2006, 04:58:01 PM
Some LS7 engines were original equipped with alu headdes. I know 2 of them. The others had 990 headds.

If it were a totaly original LS7 it would have had the 6260482 cast iron heads.
You had to ask for the aluminum headed one, LS6 was the same.

Southern72
04-18-2006, 06:28:36 PM
Yeah this motor came with iron heads he pulled them and installed alluminum heads and bigger cam to race but the motor never made it in a car. The price I believe is good if i want to go the big block route ,cam and piston swap and i should be ready to go.

muscl car
04-18-2006, 07:44:17 PM
if you have a honest #'s matching unmolested LS-7 BBC i would not do anything to it at all :) . if i were you i would look at selling it since there are alot of collector car owners that need engines like this . go over to http://www.yenko.net and inquire about it ,i guarantee you will have alot of potential buyers for it and could get alot of money for it .

BobB
04-18-2006, 08:14:51 PM
70 LS-6 =Closed chamber heads 11-1
off road LS-7= open chamber heads 12-1


I would cut the domes down on the pistons to a more friendly size.

Bruce Sherman
04-19-2006, 09:35:20 AM
70 LS-6 =Closed chamber heads 11-1
off road LS-7= open chamber heads 12-1


I would cut the domes down on the pistons to a more friendly size.

If he could find them, he could swap out his pistons for the closed chamber LS6 pistons part #3963550 or #3976031 they would give ya 10.2 compression with the LS7's open chamber heads.

80'427
04-19-2006, 09:47:16 AM
Run E-85 it will work with 12 to 1. Wouldn't have to change pistons

RacerRick
04-19-2006, 12:01:24 PM
Figure out the dynamic compression.

With a big ass cam, it might bleed off enough cylinder pressure to run good on pump gas.

Bruce Sherman
04-19-2006, 07:23:47 PM
Figure out the dynamic compression.

With a big ass cam, it might bleed off enough cylinder pressure to run good on pump gas.

I ran teh ZL-1 (LS7) mechanical cam in a 11-1 454, and from 3500-what ever you wanted to turn it, it pulled like crazy. Idled like a modified stock car. I had 215 cranking pressure with it, and it ran fine on 91 oct.

If you want to keep it all stock (using stock parts), I would recomend the pistons I mentioned earlier, and the GM cam, part #6272989 its only .500 lift (both sides), but it is a awsome street cam. It is there marine cam.

pdq67
04-20-2006, 10:48:10 PM
it may not be, but I have a feeling that the .500" hy-cam Bruce mentioned is really the old '65 Chevelle Z-16, 375hp/396 cam....

The difference between the Z-16 and the later 375hp/396's was the hy-cam it ran...

pdq67

jforb
04-21-2006, 03:02:57 PM
If you can get decent gas where you live, such as 104 at a special pump at some gas station, and you put it in a car that's set up to work from 3500-7500 rpm, then you'll have a screamer....stock....

If you want to tone it down, there are lots of choices. Smaller cam, pistons with less dome, rebalance it and set up the valvetrain to work with the cam you pick (correct springs, etc).

Last I checked, still in the crate LS-7s were going for well over 5k.

I got mine in 1989 for $2700 from the local dealer.

pdq67
04-22-2006, 05:49:46 PM
Back about the early summer of '74 after I got out of school and got a REAL job, I got to ride in a guy I worked with's '67 'Vette ragtop with a 435hp/427 motor, 4-speed and posi!!

Stock sidepipes and all! You talk about a hoot!

It was the motor that had trips on the rect port headed 425hp/427 short block!

GM made the trip motor 435 hp b/c they didn't want Dr. Daddy's little boy's buying the full boogie, 430 hp, L-88 RACE motor over the 425 hp one!!

5 MORE HP sorta deal for guys that didn't know better and that just checked the box with the biggest hp number in it sorta deal here is all.....

Those were the days, imho..............

pdq67