I am looking at a car with the following motor. Only have limited details right now. Just wondering if this motor will be tame enough to drive on the street or am I looking at a life of octane-boost and additives:

1970 LS6 454ci Chevrolet engine, roller motor, approximately 500hp, 635 lift roller cam, roller rockers, ported closed-chambered 427 Corvette heads, rebuilt transmission w/shift kit and 3000 stall converter, 10 bolt rear with 3:90 gears, 3 inch exhaust Ultraflow mufflers

Thanks,

nacho

 

Depends on the duration of the cam. I would hope that a roller 454 with that kind of lift and good heads would make more than 500 HP. iwould hope to be closer to 550 to 600 depending on the cam and head work. Anything is streetable. If you want a daily driver probably not. A weekend warrior yea it sounds pretty good. What is the compression of the motor also.

 

No, this will not be a DD. Not sure of the compression. I'm awaiting response from the seller. Only have the description to go by at the moment. I want something to cruise on the weekends, but I don't want a headache when I get home!

 

Sounds like racing fuel territory to me. But if the roller cam is ground properly to keep your dynamic compression where you need it you could try Amoco Ultimate and back the timing down a little. If it don't ping you got it! You could run Aviation fuel and Premium mix if that don't work. Silvolite has a Dynamic compression calculator to figure dynamic compression but you need detailed engine information and cam specs. You are not driving an economy car anyway.

 

That's what I'm worried about. Can the motor be "de-tuned" by changing the cam? Or am I opening a whole new can of worms?

 

Yes, Cam specs can make or break it, Aluminum heads will also help with octane problems. You can run a lot more compression with aluminum heads on pump gas than iron. And the 427 Corvette heads that are on it if they are rectangular port closed chamber will probably be able to be sold and almost pay for a new set of aluminum heads. Nice matched date heads like this will bring a premium price. Might be able to easily sell them here on the forum or maybe trade for aluminum

 

AN original LS6 is 11 or 11.25-1 compression, I would guess that the 427 heads would have even smaller chambers..not sure but either way 11-1 is way too much for pump gas.


I would get lots of pics and faxes of paper work on the engine/trans if this is an ebay special. BE WARE ebay cars...

 

The 1970 LS6 is 11.25 to 1 stock. It did come with closed chamber heads so the 427 corvette heads are probably the same as the stock heads unless they have been milled. But you could run it on pump gas with the aluminum heads and the right cam selection. You could always drop the compression a little with an aluminum head with a larger combustion chamber. A custom grind cam should be available to help resolve your problem and compliment the change in compression, retarding the timing a little will help a lot. There are a lot of guys out there running there late 60's High performance, Iron head 427 cars on premium gas by backing down the timing. It will cost you HP but you can drive it.

 

A few years ago I was running a flat top pontiac .030 400, it had 72cc iron heads and the compression was around 10.5-1. Always ran the timing around 36* total. Car ran well but after 5-6k street/strip miles, the car started slowing down, compression was still good though across the board. I tore it down and it had major detonation damage. Scuffing on the crowns of the pistons, one of the pressed pins actually pressed out of the piston and had been rubbing the cylinder. The rod bearings were copper. The motor just had too much detonation eventhough I NEVER heard a ping and always ran good quality 93 oct and it was jetted fat. After I rebuilt it, I mixed fuel for about a year and eventually switched to 88 cc heads which killed power but ran well on pump gas until I sold it. Lots of testing has shown just because there is aluminum heads, doesn't necessarily mean you can run higher compression on pump gas. Quench, cam timing, fueling and fuel quality all matter. The reason all new cars are running 10 or 11-1 comp. is not because of the aluminum heads, its because of the advanced engine management systems, knock sensors and very good head/chamber technology.

Do your research on your engine combos but 11-1 on an LS6 will not get you very far for long.

 

Tough to say if it will run on pump gas. Sounds like it's maybe will maybe will not. Take it for a ride. Empty the tank, which should not be hard to do by driving it, and fill up with 92 octane. Check the timing to see where it's at. The owner may have it retarded. If it runs fine, bump it up to where it should be and see how it goes. If the owner has the timing where it belongs and no ping, you're all set to go.

Calling the engine an LS-6 means very little. It's not an LS-6. Roller cam is a dead give away. Who knows what else was changed. If it's only 500hp, it may be tame enough for the street. In my opinion, what makes an engine unstreetable is when it will not run somooth enough at 2500-3500 rpms. In other words, you got to keep it running at higher rpms. An 800hp Nascar engine is streetable if you want to drive it at 5000 rpms minimum.

 

DON'T waste your time or money on actane boosters. They don't do anything and they sure do NOT boost octane up to the levels they advertise. NO WAY IN H*LL will they boost pump gas up to 104octane like they try to tell you they do. At best they may boost it up about a 1/4 point.

If you have a radical enough motor that requires high octane, go buy racing fuel of around 108 or 112 octane and put 5 gallons in each time you fill the tank with premium pump gas. THAT will boost your octane level enough to keep the motor happy. Those boosters and additices they sell are nothing more than BS and the only people that benefit from them are the people selling, them not the people using them.

 

I don't buy the arguement that all octane boosters are snake oil. Moroso used to sell an octane booster back in the late 70's at $28 a gallon. If they sell the same product today, it would probably be close to $100 a gallon. I'll agree that some 12oz bottle for $1.99 of the 104+ octane booster will do very little.

 

Although ... part of the reason is due to aluminum heads AND closer attention to how efficient the heads' coolant passages are. Some of the newest designs include direct injection which also helps chamber cooling ... piston crown shape (in conjunction w/ above-referenced chamber design) also aids chamber cooling. Been looking at newest 2 liter turbo motor for saturn roadster ... marvelous.

 

Well when you're mixing it with a 20+ gallon tank of gas it doesn't do jack, obviously. However, I accidentally put 87 in my bike once and noticed it was missing some power. Put a bottle of octane booster in it and it perked right back up. When you're only mixing it with 4 gallons of gas it can help.

 

Sure it`s streetable! Is this a Vette, or something else? You just mentioned car.

 

Below is a unit we delivered yesterday, it was dynoed last week. The post was placed over on the "Team-Chevelle" website earlier in the week. I would assume you have the same type heads on the one you mentioned. "Good Luck". Thanks Gary in N.Y.

(Quote) This post is "aimed" at the many up here that follow HP/Torque numbers with respect to "stock" and "stock appearing" units. The unit was first tested with our carb and headers and came off the dyno with 510 HP @ 5700 RPM and 500 Ft.Lbs. Torque @ 3900 RPM. This was with open headers. We were happy with those results. Using the customers carb and our headers it did 495 HP/500 Torque, same RPM's.

After installing his cast iron factory exhaust manifolds and leaving his carb in place, our final "as-delivered" numbers were 464 HP @ 5800 RPM and 484 Ft.Lbs. @ 4200 RPM. The exhaust's here are the "restrictor".

What we've concluded from this test on this particular unit is the fact that the stock "square-port" intake, #3963569, IS capable of producing past the 500 HP number, unlike the recent LS-5 "oval-port" test where the "open-headers" made absolutely no HP difference. We estimate we could possibly get 550 HP through this particular intake. We have to make certain we don't have a vacuum issue for accessories! A slightly larger cam along with headers would have made a significant HP increase.

This is a "pump-gas" unit that runs fine on 93. The specs are 10:1 C.R., 238/248 @ .050" x .550"/.570" x 112L/S. This is a solid lifter unit with a set of "Probe" pistons, a +.250 long rod, and stock valve sizes with .375" stems.

The #291 heads, in at 99 cc's did receive a decent amount of "bowl/runner" work, but NOT a "full-port". We felt that extensive cylinder head work would be wasted using the stock intake setup! It's topped off with a set Comp Cams #1320 rockers and will end up with the stock valve covers in place.

It was destined to be at Englishtown for the "Fast" race today but obviously didn't make it on time. It posed no problem however. It's headed into a "numbers matching" 1970 Chevelle.

Below is a shot as it was delivered. The valve covers/breathers are for test only! Thanks, Gary in N.Y.

P.S. When you are ABSOLUTELY "locked-in" to stock appearances you will find that the HP numbers are difficult to deliver. This unit is in "contrast" to the 396 pump-gas one a few months back, using the "Winters" (open-chamber) heads, 10.5:1 C.R., a step or two up on the solid lifter cam, and an old "Torker" intake, that was delivered with over 500HP on 93! That was with a "Holley" and open headers. (End quote)

 

Hard to say without the cam specs, and the only other thing that will make it a bit interesting is the converter. I ran a very similar combo in a '64 GTO, and it was fine for weekends and the occasional drag strip pass (12.80's on 7" cheater slicks), but it was rough on the THM 400transmission running around town. I had to service it often to keep clean fluid in it. I'd say as long as you run a cam that bleeds off some static compression, it should work on 93.

Hans

 

If you want a true octane boost and are not running cat converters, you can still get Tetra Ethyl Lead (TEL) to mix with your pump gas. It's not well known, but a company called Kemco Industries makes a product called Octane Supreme 130 http://kemcoindustries.com/product_info.php?pId=61. We all know TEL works to boost octane because it has been used since the 1940's.

This is the same product and according the the packaging, you can go 16 points higher if you want to....just don't think anyone here will need to. It has a chart on the bottle that tells you how much to add per gallon for octane boosts from 2 points to 16. Because of it's poisonous nature, you need to be careful using it, but it does work. I've been adding enough to get 93 pump gas up to about 98 and have been running 36 degrees advance on 10.8/1 CR with iron heads without a problem. That may be more than I need, but I like the valve seat lubrication too and I'm running the old double humps with larger valves.