Patro46

Jerry....I was SO kidding on the 73 mph in 1st. I do believe the final drive in 4th gear with a 1 to 1 final drive ratio the Rockcrusher had, with 3:73's, I was running around 3800-3900 rpm @60 mph. That kept me cruising any distance to between 55-60 mph, and that wasn't really "comfortable". With this build, I pulled the 3:08's and put 3:70's in the rear, except this time, I'm running a 4L60e with a true overdrive. Talk about being able to have your cake and eat it too!...

Vortecpro

The last 1970 LT1 I rebuilt, made 390 HP with the factory carb with headers.
The last ZL1 I did made 592 with headers, 850 Holley.
The last L72 in pure stock trim made 530s through the Chevelle exhaust manifolds.

7t9l82

the LT-1 and L-88 were from different engine families and shared NO significant parts as big block rods pistons crank etc are completely different from the small block.

'71LT-1Stingray

Lol...I'm soooo gullible to have bought that. But in my defense, I stand behind my 1st reply about 1mph for every 100rpm in 1st gear. I don't plan on taching it to the 6500 red line though, it's an incredible roar at 5000rpm and that is as far as I plan on taking it...shifting into 2nd at 50mph was good enough for me. I like to drive the car easy or normal and mainly cruise around, shifting in the 3000 to 4000rpm range still puts out an awesome sound and lets me rest easier knowing I'm not teetering on abuse. Haven't even made the 1st payment on it...lol.

I think I'm in the 2500rpm range doing 55-60mph in 4th. Way more comfortable than the upper 3000's that's for sure.

chevymaster1972

1970 ZR1 ( Not to be confused with the 90's ZR1) was a road race package that included stiffer bushings, radio delete, I believe an aluminum radiator( No Fan shroud) various brake upgrades( Not sure what they were) But the LT-1 was the same as any other LT-1 Corvette or Z/28. The 1970 ZR-1 did come with the M-22 4 speed, so in a distance way, it would be SLIGHTLY comparable to the L88 cars in suspensions , brakes, exhaust, lack of creature comforts but without a big block. I believe the 1970 ZR1 was as close to what Zora envisioned in the Corvette, a powerful great handling car for it's day No offense, the Big Block chevy is heavy, made the car nose heavy, even with aluminum cylinder heads.

Steve Matz

I owned a 69 coupe with an L88 Engine back in 73. It was not a very Streetable Car unless you had 4.11/4.56 gearing. The Compression ratio was not for a Street engine either(12.5-1) If you didn't have a Sunnoco station in your town than you either had to run an octane booster or back your timing off or it would knock if you ran more than 34 degrees They didn't put a Fan Shroud on from the Factory so you ran into overheating issues quite easily if you were lugging around in intown traffic.

The cam lift wasn't that bad but the duration was much to long for street application. Remember this was a purpose built race engine and race profile cams don't like restrictive exhaust systems. I was on the fine line of having a legal streetable exhaust back then. I had a set of Hooker Headers with the side Pipes(Chromed of course) Hooker back then offered 2 different muffler inserts for the sidepipes. One was an actual muffler and the other just a glasspack insert. When you have that much compression it doesn't take long to burn up the fiberglass and before you know it your running an almost open exhaust. I could hear it get louder almost daily and people that knew me said they could hear me blocks away. Luckily I never got a ticket the whole time I owned it for too loud of an exhaust. Cops didn't carry decibel meters back then, so you could argue your point on what was OEM for exhaust.

It was definitely a Monster when you were on the Cam which didn't really come on til about 4000rpm. I was really leary about the 10 bolt rearend too. They never changed anything from any other Application except your gearing. Why Duntov or another designer didn't come up with an IRS Center Section that used something similar to a DANA 60 i'll never know. Guys had to be breaking rearends if they were Drag Racing or even Slalom racing. The yoke was tiny compared to what came later on Borg Warner T10 type Trannys when they didn't have any real power.

One other thing you had to be super careful about was removing any kind of bolt,cap screw,Sparkplug, etc. from the Aluminum heads. You wanted to make sure those heads were cold or you'll pull the threads out quite easily when hot. I'm sure there are a bunch of L88 Heads that have heli-coils and oversized bolts in them. The downside of Aluminum/Alloy.

If I knew that these Muscle Cars/ Engines were going to bring the kind of Money they do today; I would have kept the Vette as well as some other toys I had in the Late 60's and early 70's. I remember LS6 Chevelles sitting on the showroom floor in 70 not selling because the kids that wanted to buy them couldn't afford the insurance on them even back then. Why Chevy went ahead and put the 450hp rating right on the Aircleaner didn't help your cause when your insurance agent looked at your car engine. Should have put 300hp decals and saved yourself a ton...

The L88 was Fun for a While but it is definitely not a Street Car.They deleted the Radio, No heater/defroster/air conditioning,etc. They were trying to avoid the kids buying these Cars, thus the HP rating trick verses the L71 option. They also didn't get the 5yr/50 thousand warranty that every other Chevy muscle car got back then even after you paid over a grand for the engine option. If your buying one for an investment Fine, but stick with an L71/ L72 or L78 for a streeter. There are a lot of things you can do to those engines at low cost to pull even more power out of them...s.m.

Bad Bird

Rubbish. No C3 Corvette is particularly nose-heavy due to the radical engine set back.

Steve Matz

Forget about those HP Numbers on the Sales Brochure and Air Cleaners. That's for Marketing and Insurance Companies. Engines don't go down the Road without a Chassis,so forget BHP Numbers;whats at the rear wheels is what counts and Why Mfger's of Muscle Cars don't use them because they are a far cry from the Advertised HP and wouldn't appeal to the Young Crowd who were buying these Cars. Our infloor 500HP CLAYTON DYNO tested 100's of different cars and probably at least a half dozen 1970 LT1 Vettes. The most RWHP we ever got out of one was right at 280 at 6200rpm. This was exceptional as most were in the 265 range. This engine was OEM but the Valves had been relashed to .008 int .010 exh (those .022/.024 are for warranty safety;these muscle cars still had 5yr 50thousand warranty then) The distributor was also recurved to 14 degrees in the Dist and Full advance all in at 3000rpm. Carb was also rejetted for our 3300"ASL altitude...You can do the same to your OEM LT1 and gain 10+HP....

The most RWHP we ever got out of a Stock RPO Muscle Car was a 1970 LS6 Chevelle that had close to 2500 miles on it. Best Dyno run was just under 325RWHP at 6000rpm.
Impressive HP Numbers sell Cars to Kids. The MFGers knew this. Those BHP numbers as I mentioned before are basically false Advertising and Marketing Strategy. If you don't believe me take your Factory Mega HP (on the aircleaner) to a Dyno shop with in floor water filled Rollers and you will leave pretty disappointed....S.M.

Alan 71

Hi Steve,
Are you SURE the L-88 cars that left St.Louis didn't have the usual new car warranty and also heater/defroster systems???
Regards,
Alan

Steve Matz

You are correct Alan; I was actually referring to the General Chevy Muscle Car of around 68-70....The L88 or at least the 69 that I had only had a 90 day warranty. Same went for the ZL1 Option; since there were only 2 vettes with that Engine; they probably still would have cut you a break if something broke. The 69 ZL1 Camaros also got the limited warranty.

The GM 5 yr/50k warranty was actually a pretty generous move for GM.Many of these Muscle Cars that were HS Graduation Gifts to Kids back then were abused to the hilt. In my Town back in 68 a prominent Doctor gave his son a new 68 Stingray for a Graduation Present. It was a 390hp 427 Coupe. Another Arrogant little Jerk that never had to work or pay for anything in his life. He blew that car up 3 times in just over 2 months. The last time he brought it in for warranty, the Chevy dealer replaced the 427 with the lowest HP smallblock they had in Stock and told him this was the last warranty Job repair they were ever going to get of this Dealership.

The valve lash I mentioned in the last post is no Joke. No Solid Lifter or OHC engine ever used extreme lash settings like that. I have built both Racing Motorcycle & Automotive Engines since the 60's; some with extreme lift and duration profiles and never have ever needed more than .008 on the int or .010 for the exhaust. The valve lash and carburetor Jetting done by Chevy for these Muscle Engines was intentional and a Safety Margin for them. Chevy knew that probably more than 50% of these Cars would ever come back to the dealership for the recommended periodical valve adjustment. If they had set the valve lash at the numbers I spoke of then they more than likely would have been doing warranty pay outs to their dealers for burnt valves after the valves seated and the lash receeded.The cars were also overly rich on the 780cfm Holley 3310 based Carb. Chevy didn't want to being doing warranty work on burned pistons for too lean carb jetting. Remember most of the Engines had 11-1 static compression ratio.

This was actually a bummer for the Guy that was tedious about following instructions for Engine Maintaince. As the valve lash clearance was closing up after putting a fair amount of miles on his Car;he probably was noticing a little performance gain. However when he took the Car to the dealer and they re-adjusted the lash back to .022/.024 He probably lost some performance. I have adjusted many L78-L72-L71 and LT1 engines that had over 10,000 miles on them where you are going to have almost nil valve seating any longer to .006 and .008 clearance and had no issues of burnt valves or loss of performance.

Also the distributor modification makes a big difference. People don't seem to realize how important they are in the performance dept. after all they are delivering what is firing your air/fuel mixture to give you the most efficient power stroke you can give with OEM Parts. A minimal amount of money can get you some real performance in these old OEM MC Engines. The only real money that you may have to put out is for having the distributor put on a SUN or ALAN Distributor Tester for Recurving and rpm advance. If you have a Friend that has one then your only cost for that is buy a couple packs of distributor advance weight springs which should be only a few dollars. Go for it Muscle Car Owners,you will be more than pleased at what you will gain in performance and still have reliability. Also a bonus, your valve train noise will be suggnificantly reduced so you will have think you are using a Hydraulic lifter cam....

cv67

Clayton water dynos only seen one out here Bob Jennings has one

I took my Camino over there many yrs ago to have him fine tune it
new 10:1 350 Isky 280 FT cam 462s with 2.02 intake no porting Holley 300-36 intake 1-5/8 headers 750 VS carb
Turbo 350 w/cheapie 2800 stall that slipped

Car ran great but was avoiding returning calls to my buddys about "getting it on the dyno!" Sure are humbling the Claytons

Made 180/2xx tq at the tire.

RickyBerg

The ZR1 was basically a L88 chassis but with the LT1 engine.
The ZR2 had the same chassis but came with the 454 LS6 engine.

To call a bigblock Corvette C3 "nose heavy" is to pull it a bit far i think and i don't agree a bit on that.

Steve Matz

Don't believe that to be true. My 69 L88 Coupe had the same Front end height from my driveway to the lower spoiler as a friend of mine's 69 Smallblock. Never looked up the Front Spring PN's between the 2 though...

Steve Matz

I remember a couple 65 Mustangs that we did with the 289 High Per engine(271 hp) Manual 4 sp......When you do a Dyno Pull,the car has to be in 4th gear or 1 to 1 Rearend Ratio. These Mustangs even after they were strapped down had a heck of a time trying to get the Rollers turning and they resembled a Pro-Stock car with severe tire shake. They did put out in the low 190 numbers though. These same Mustangs could stay even up with a GTO in a Drag Race...

RickyBerg

I think it had been wise to know the spring rate to get substance behind the height of the cars.

The difference between a full iron SB and a full iron BB is about 110lb after what i have dug out so the difference in weight between your L88 with alu-heads and a stock SB would be next to nothing.

Vortecpro

Chassis dyno's numbers usually mean nothing, but could be useful as a tuning tool and I guess some R&D work. In my world 100 MPH quarter mile @ 3600 pounds is 281 crankshaft HP

LT1driver

lotta BS and LT-1 (original) bashing and guessing etc. by people who looked up data, were not there and on and on. I will say this, regardless of hp the LT-1 was a screamer and if you have one and limit yourself to less than 6500 rpm you are missing what the car is all about. I have now (70 LT-1) and had in the day a 70 454 and several 70 350/350 and 454 torque made it the winner every time in a 1/4 mile race, even with a 3.08 rear and m-20 trans. Enjoy whichever you have.

Little Mouse

They were all weak as wet toilet paper compared to the 302 chevy i was there lol. Extremely strong below 4000 rpm used to hook it up to tree stumps pull them out. Out ran the gassers and the rail jobs with it to, little GTO. No wait a minute it was the 18 wheeler i pulled the stump out with.

Steve Matz

Even the pink color coded Rods used in LT1's aren't really up to
being turned 6500-7000rpm on a continuous basis. The Rod itself is strong enough; it's the same thing I mentioned earlier about OEM Bolts.The L88 had BORON STEEL Bolts but they were 7/16" and I don't remember them offering any smaller size Rod bolt for the 3/8" BB or SB Rods. When I was rebuilding Rods back in the 70's, ARP wasn't on the Scene yet and we used Bolts supplied by Mr. Gasket. They were certainly Stronger than OEM Bolts back then but compared to an ARP 2000 Bolt; tensile strength is no comparison. I saw a good number of SB's using the Pink Rods but not changing the OEM Bolts out and they do just what the BB's did when buzzed frequently in the 6000+rpm range. They spin bearings due to stretch....

Steve Matz

I'm taking this as a Joke;right Little Mouse. The Z28 was a winder but it's Torque was Nil. You needed 4.11's or more to feel anything close to what a BB felt even with Low 3 gearing. We Dynoed a couple of those back in the Day and the numbers were still comparable to the 289 Ford HiPor. I remember the 1st Z28 that came to our town in 69. In the Trunk was a set of Headman Headers supplied by GM/Chevy that were supposed to be a Dealer Option Installl. They really woke the little 302 up especially if you had them full open. The Cops didn't give too many Tickets back then for Loud Exhaust. But they would give you one in that Car with Open Headers; Pretty Radical Cam...