I've been a member here for a long time and have read quite a few posts over the years (especially in the C3 section) about how hard it is to make big horsepower out of our older engines. I constantly see threads saying that 500HP out of a small block takes big money and seriously sacrifices drivability yet I'm wondering why this is the case since newer engines can make those numbers easily.

Is fuel injection really that critical to making huge HP numbers?

Why does everyone say 9.5 is about the highest safe compression ratio for pump gas yet new engines often run 11.0 (even pre '71 engines ran higher CR)

What really makes the new LS motors so much better for squeezing HP out of? My Brother in Law got 453rwhp with a cam, headers and milled heads on a stock LS6 bottom (very drivable imo) yet everyone acts like 500HP out of a 383 is so hard to achieve. Does it have to do with lighter parts or higher flowing heads? We have all those parts available on the older engines as well.

Why does everyone insist that 500HP REQUIRES forged internals? Again, LS engines do that regularly on hyper pistons and powdered rods.

Forgive me asking all these questions but I've been wondering this for some time. I figured I'd ask here since you all know a great deal more about motors than I do and I'd love to understand.

 

You have this technology it's called an ECM that constantly monitors your engine parameters. We old school boys have to pay big $$$ for heads that flow as well as a LS3/6/7 head does right out of the box. If the aftermarket EFI builders were half as bright as the hordes of GM engineers that developed your C5/6 systems, we would be in great shape but, they are not.

Millions of $$$$ were spent in research and development of your Vette, they are great cars, anyone can go down to the Chevy dealer and buy one, sometimes with no money down. I on the otherhand have to work cuss and sweat for hours to keep my old C3 running in top form but, my Vette also stands out in the crowd and it's my accomplishment of many years of knowledge.

My next motor here, I'll take on any stock C6 motor and it ran less than a crate LS7 to build but, not by much

 

In a word.....Electronics.

Gary

 

I think you missed my signature where it states I have a '72. Details on your engine?

 

It is 99% the heads. What is amusing to me is to see folks get all emotional about heads being too big on the average 383" motor..but have you ever seen the cross sectional area of what GM sticks on an Escalade or a LS-7 these days?

Good heads allow for milder cams to be used. When folks put stronger cams in..the power increase is much higher due to the better heads. LS motors have incredible heads compared to what was OEM on the old stuff. Heck , right out of the box they flow as well as or better than many aftermarket big block heads!

Then we add in EFI and timing controls. That's what allows 11.0+ compression. It can pull timing in a nano-second if it hears a ping or a rattle. It can adjust for temps, altitude, each gear etc etc. They have spent tons of hours mapping out every possible scenario that it might encounter and provided the best solution. The EFI systems we can buy can do the same thing..but you have to invest the time for YOUR combo to get it perfect. But truthfully, they will get you 95-98% there with their base tunes.

EFI and timing control also allow hypereutectics etc. Less chance of hurting stuff.

Then there are all the little design improvents..but the vast majority is still in the heads.

JIM

 

Amen to that my brother.

 

Block is a production 400SB case now, 4.155 bore. I fitted billet steel splayed main caps myself, if block fails, I now have GM Bowtie as reserve back-up. Crank is 3.500 LJ 4340steel full areo crank weighing 43lbs, with USA made 6.00 rods, the same guys who make the C5/6 pistions made mine: Krauts! My pistons are forged. Compression is 10.8:1 with heads flowing 304CFM@0.550 lift (a little less than a"base motor" LS3 flows.) Rockers are T&D shaft with steel exhaust rockers big ratios, solid roller cam, Isky "OH MY GAWD! do they relly cost that much?" EZ Roll lifters, cam drive is Exceldyne wide belt (OMG! moment again), valves are Manley severe duty, springs Isky "tool room" (again OMG!), retainers are Exceldyne tool steel (lighter than Titainium more EXPENSIVE than Ti but, up side is no silver powder in oil system from retainers and way longer fatigue life.)

Even my valve locks ran about $100 for 32 pieces of metal that look like they should be $32 at most (8mm Super7 locks, thank you AFR for using LS series junk in your heads, if I had it to do over agian I would have gone elsewhere for my heads.)

Intake, ported Super Victor, carb Holley HP Ultra (when a plain HP isn't enough!), Fuel pump CV products billet NASCAR pump, H2O pump Edelbrock, Ignition, MSD crank trigger with a programmable 6AL-2 box, Mallory billet tach drive magnetic distributor for spark distribution (leaving the magnetic PCB inside distributor for back-up if the MSD dies on the road somewhere.) , oiling system was going to be Weiss 3 stage dry sump but, to expidite build, I'm falling back on Melling M select pump with steel billet gears in custom built Canton oil pan-RR baffling/trap doors in circle track pan. Speaking of current engineering Melling now has gone back to steel billet oil pump gears after all the bad press on the powdered metal stuff failing, sometimes trick engineering isn't the best (how are your C5/6 connecting rods doing?)

Power expected will be more than I need. RPM FAR MORE than LS series with juice lifters can attain reliably, Price is $2-3K over budget now but almost done, waiting on KRC for drive components so we can load onto Dyno (Heenan Froude GH490 with Depac 32 channel real time data accqusition of which I might need 12 channels at most.) The dyno I am using is "stingy" with HP figures but the owner keeps it calibrated to SAE specs and it is repeatable within 1% accuracy which is more than can be said for 98% of the installations I have seen being used.

My biggest problem will be getting HP to the ground. My newly accquired Greenwood 5 link should help with that problem.

 

Agree with Jim that heads are key, and the better they are the less cam required to do the same job. Also, agree that electronics play a huge roll as well. Of course, if you prefer your doses of power be delivered old-school style there's always the BB alternative.


As for forged internals being necessary to make big power, they aren't, but IMCO (and many others') the further one pushes things the wiser it is to upgrade such to assure/improve a build's longevity. Raises the adage, "How fast do you want to go? How much money do you want to spend?"

 

What about the mileage they can get with the HP numbers. Amazing.

 

A lot of that is due to gearing.. My LS1 vette got 32 mpg at 70 with the ac on in 6th gear at 1500 rpms. My LS7 gets about 28.

 

engine for engine...the main difference is better breathing....THE HEADS

 

Engine noob here going to ask a question.

You say a lot of this has to do with heads but can you not put better heads on a SBC or do they not make better interchangeable heads for these engines?