[Chevelle Doug]

I have the parts to build both L88....or LS7... which one first..?

454 Block 2bolt, can be made 4 bolt.

L88 Pistons
L88 Floated Tin Flashed Rods
427, 396 forged steel crank.

LS7 12.5:1 pistons
LS7 Floated Tin Flashed Rods
LS7 GM NOS Crank in box, factory balanced with tech sheet of part numbers and bob weight....rare. Still in orig cosmolene.

 

[Leadhead]

I vote for the L88🙂

 

[Harris Roc Malouda]

Are you talking about the GM Crate RPO LS7 3965774 with the ZL1 cam?
To me thats the ultimate muscle motor. Most cubes, hottest cam.. max fun

 

[shovelrick]

Man that's a tough call, L88 high revvin or LS7, did LS7 rev like the L88 ? Maybe it didn't need to for the power ??

 

[Harris Roc Malouda]

Man that's a tough call, L88 high revvin or LS7, did LS7 rev like the L88 ? Maybe it didn't need to for the power ??

LS7 with a good aftermarket low windage oil pan.. i think thats just the optimum.

 

[-SS454-]

As cool as an L88 is, I'd go with the cubic inches. More power, better drivability.

 

[gnicholson]

Super cool and super cool

 

[Saltherring]

L88. No externally balanced, long stroke, truck engines.

 

[68Chevele]

Well it depends on what parts you pick out for each combo. Used to be the L88 would make more power and the LS7 would make more torque but who knows these days.

 

[Chevelle Doug]

I like the LS7 with open chamber ovals, have them cleaned up and flowed. I have both 781s and 72 Corvette 241s.

 

[gnicholson]

The LS7 should make more power and torque because they are basically the same engines other than the 30 cubic inch difference plus if I remember correctly the LS7 cam is slightly larger. Other than the weight penalty the later LS7 cast iron heads are slightly better then the earlier aluminum open chamber L88 cylinder heads but that's not an issue for you because you're using the same cylinder heads on either engine and I'm sure you will pick a camshaft particular to each build so that point is also not important

 

[CorvZ061]

I had a crate LS7 in my 69. It was a beast, I vote build one.

 

[Jim Mac]

either one, I'd go with aftermarket heads. something with stock position exhaust ports for ease of installation. jim

 

[shovelrick]

IIRC there was a member a few years ago selling his LS7 out of his 70 (?) Chevelle due to poor driveabilty, Joe? not that means anything, personally I like both, revving like a SBC or brute torque, torque won in my mind and that's the reason for my 489 stroker

 

[Tom Mobley]

if you don't live on an airport neither of these is suitable. Both require 100+ octane.

 

[427L88]

Or at least up to 96.

Ran an L88 in both stock form and in modified ( detuned) form. I'd chose an MJ467 over either. Why? In either case, the TQ peak is up there, I;d guess 5000+ for the L88 and jsut under for the LS7. I prefer it to be at 4000.

Therefore , if between the two, I'd build the LS7. Its still a 7000 rpm mill, but you might find a better, more useable TQ curve w/o the need for a 4500+ stall converter.
Shifting at 7200 is DARN fun! * even 6800 with the "detuned" L88.

EITHER will require a VERY GOOD balance job, the 454's being slightly trickier with the ext counterweight, so the flywheel and/or flexplate have to be included.

PS if you give your parts to a true BBC guru like Mark Jones for machining/assembly, the results will be even more spectacular.

 

[Chevelle 1969]

Are those solid dome Pistons?
If cut the dome so you end up with 10-10.5 in comp.
A solid or hyd roller Valve train and you can have it look like a L88 or LS7 and have 50-100 more hp.

 

[Jim Mac]

there's a guy in town that had a new in the crate l88 he finally installed it into one of his cars. needless to say, the cool factor went away pretty quick when it only runs on race gas just to drive it around. jim

 

[Harris Roc Malouda]

Or at least up to 96.

Ran an L88 in both stock form and in modified ( detuned) form. I'd chose an MJ467 over either. Why? In either case, the TQ peak is up there, I;d guess 5000+ for the L88 and jsut under for the LS7. I prefer it to be at 4000.

Therefore , if between the two, I'd build the LS7. Its still a 7000 rpm mill, but you might find a better, more useable TQ curve w/o the need for a 4500+ stall converter.
Shifting at 7200 is DARN fun! * even 6800 with the "detuned" L88.

EITHER will require a VERY GOOD balance job, the 454's being slightly trickier with the ext counterweight, so the flywheel and/or flexplate have to be included.

PS if you give your parts to a true BBC guru like Mark Jones for machining/assembly, the results will be even more spectacular.

I must side with this opinion..
streetable horses have more value to me than "only" raceable horses.. So i want many horses, but down low, early..
Just for fun i compared the MJ496 to the RPO LS7 (with crane ZL1/LS7-replacement cam)...
And if i would have to find words to describe the difference, i would say the MJ496 is the "street-LS7"

--> +10% cubes, -10% compression, -10% cam duration.. everything else all same... even the cam "character" (= lift/duration split & LSA)
... Well and maybe +10% more power than a well tuned LS7.
--> also:
--> Oval instead of rect port = more low end velocity/torque.
--> & Hyd. Roller instead of Solid Flat Tappet = Less maintenance
--> internal instead of external balancing = easier balancing job

So i would always adjust my build towards this direction. Meaning LS7 over L88 over L78 etc.. above all that a well done 496

	GM Crate RPO LS7 3965774	MJ 496	Numerical main differences
Bore	4,25	4,31
Stroke	4	4,25
CID	454 (7.4l)	496 (8.2l)	42 Ci (+9,3%)
Mains	4-Bolt	4-Bolt
Balancing	External	Internal
Block material	Iron	Iron
Crankshaft mat.	Forged	Forged
Rod mat.	Forged	Forged
Piston mat.	Forged	Forged
Compr. Ratio	12.25:1	9.75:1	2.5 points (- ~10% Hp)
Head material	Iron	Iron
Chamber	Open	Open
Valves (In/Ex)	2.19/1.88	2.19/1.88
Port	Rect.	Oval
Cam	Solid Flat	Hyd. Roller
Lift	.575/.615*²	.578/.608
Timing Adv.	318/330*²	284/294	Diff: -34/-36
Timing @.50	262/272*²	238/248	Diff: -24/-24
LSA	110*	110
	*= Crane Fac. Repl. 131141
	²= ZL1/LS7 OEM Cam 3959180:
	.579/.620
	322/334
	262/273

 

[bracketchev1221]

What exactly are you looking to accomplish? If you are looking to just use the parts you have, that is one thing. The LS-7 was a crate engine, so it really has no value as a street engine and its a really low HP race engine by todays standards. It was an entry level bracket engine, that you could put a roller cam and intake on and be in the mid 10's. As far as compression, I kinda feel either go all in and make it a race engine to NEED race gas or make it a pump gas engine. But 12:1 is kind of on the fence either way. You're not getting the full advantage of high compression, but have the headache of needing to mix fuels at the very least.