Hello! I'm glad to have stumbled across TC. I'm relatively inexperienced with Chevelles, and I have a few questions for the veterans here. First, let me describe the situation... my uncle is restoring a malibu for me. I don't know enough about restoration to do this job, and even if I did, I'd still want my uncle to do it. However, and I know some people look down on this, it's being cloned into an LS6. Unfortunately, the car is across the country and I won't be there for much of the restoration. It's a '70 malibu, and most of the parts to clone it are there: m22, 4.11 rear, some SS emblems, and of course the LS6 (heads, intake, block, etc.). The engine will have to be put together. I'd like to be able to drive the car on hi-test pump gas, and have a comfortable cruiser...but still be able to have fun with a race here and there. So, my questions are:
1. Recommendations on an accurate resto Chevelle book.
2. Since it's not a #'s matching car, should I make any internal changes to the LS6 for increased power, or just let a good thing be?
3. Can I get by with 92 octane with 11.25:1 compression?
4. Any general recommendations for the project?

Sorry this was so long, but I'm just excited to have a Chevelle on the way! Thanks for the insight.

Sounds like a good project. I have been told that Chevy never had a 4.11 rear, just 4.10. Same in my book, but did not know how far you are going to clone it. As far as the LS6 motor, that may be worth something to someone. If you want to make mods to it internally, go right ahead. Its your car, do what you want. 92 octane at 11.25:1 compression? I believe that is high. I think anything in the 10's is fine, and 11 is the turning point.

As far as cruising, the 4.10's and the M22 will be a helluva ride. It will tach high on the high way, which will cause undo stress on the drivetrain, and cause poor gas mileage. I did not care about it, and its almost the same setup I currently have.

Good luck with your project and welcome to the best place on the interent about Chevelles
Chris

Wyatt, first of all, welcome to TC! There are super people here that will give you great advice and point you in the right direction! To run on 92 octane safely, 10:1 and below would be best. Some new cars have up to 11:1 but they have special ECU management that lowers timing and or fuel maps to richen mixture etc. If car was just occasionaly street driven, mix some high octane racing gas with 92 and experiment to prevent the dredded detonation so you can keep some decent timing. You will have to decide if that hassle is worth it to have 11 plus compression. With those stiff gears a nice cam upgrade would help alot. Amazon.com to fine Chevelle books or Year One! Its great to have such a cool uncle huh?! Goodluck! :D

Welcome!

By my rough reckoning that cam will only allow around 10.5:1 to run on 92. I ran the Crane dual pattern version at 10.7:1 on 93 w alum GM heads. Any chance uncle could have .125" taken off the domes? ( means rebalancing )You'll want to shave a point off compression for safety. And it still may be close.

If you swap to a modern cam, you'll lose the bleed-off of the LS6 grind and have to use a much bigger duration cam to keep it pump gas friendly.

Sounds like it's gonna be a fun ride!

First of all, thanks for the warm welcome! And thanks for the advice on the new beast!

Red, I know the rear end will be geared a little low but I'm like you...I can live with it. What is your current setup?

Blazerbob, I really don't want to worry about 92 octane being too low, so I'll have to consult with my uncle some more on that one. You mentioned a cam upgrade...any recommendations? btw, do you have a blazer right now?

427L88, I'm sure my uncle could take a little off the domes if need be. Is that the only way I'm going to effectively lower the compression with the LS6 heads? And forgive my ignorance, but what do you mean by bleed-off?

Again, thanks for all the help. I'll keep you all posted of the results!

Oh, sorry, those old GM cams have long seat durations ( but not real long .050 durations )and the LS6 is a 114-115 lobe separation angle. Both of those things allow quite a bit of mixture to slip by the intake valve on the compression stroke at lower rpms, which helps keep the engine from pre- detonating or "pinging". Modern cam are more intense, meaning they have less seat duration and more .050 and .200 duration.

EG, the GM L56 has a seat duration of approx 315 with .050 duration of 244. The intake lobe of the Lunati/UD cam I use has 276 seat and 243 .050 duration. ( I think to really compare it to GM it would be closer to 290 seat). Clearly the modern cam is much more intense, meaning it opens the valve much quicker as the difference between seat and .050 duration is much smaller.

A great contribution to all this " will it run on 92" is Pat Kelley's work on DCR, or dynamic compression. Here, read through this ( don't worry, it took me two or three reads before it sunk in..)

http://cochise.uia.net/pkelley2/

Good reading!

Wyatt,

FIrst off, what part of the country are you from? Even 92 octane is slowly disappearing. Second, have you verified what heads you actually have? I know a couple of guys that run 396/375 motors and 427/425 motors. These are pretty much the same spec [11/1 CR & solid cam]. In the summer heat, they have had to turn the timing back and run additives. Typically when rebuilding a motor, the CR comes up a little due to block decking and resurfacing the heads. Personally, I would strongly consider getting the CR to about 10/1 and using a more modern cam profile. If you read enough posts on this site regarding cam selection and performance you will find that the there has been a steady trend towards more manageable compression and more modern cams for torque and not necessarily peak HP.

Originally posted by wyatt:


Red, I know the rear end will be geared a little low but I'm like you...I can live with it. What is your current setup?

454 bored .060 over, unknown internals but rougly 425-450 horse (guestimate), 4 Speed M-21, 4.11 12 bolt posi rear.

In the works: 496cid, 600hp, 100 shot NOS, M22 and 4:11's. We will have to see about this one though.

Pics are in my sig.

thanks again for all the great information. I'm in California for now. 91 octane here. However, I'm not going to be here for much longer. The car is in TN, and it's likely that my wife and I will move back when we're done here. By that time, the car should be done. Even if it's not, I could get by by adding some race fuel temporarily until we get to a more octane friendly area.

GRN69CHV, when you recommend going with a newer cam profile, would you suggest a longer duration?

426L88, would you recommend the setup you mentioned? Shaving some from the domes and keeping the LS6 heads and intake? I'm not opposed to going another route if it makes more sense. I'd like to be able to use the heads though, since I already have them. I'm quickly realizing that it's a fine line to build a road worthy yet powerful engine. I'm just not sure how much sense it makes to reduce the CR with those heads (as opposed to going to oval port, etc.) I've also been considering a Tremec setup with overdrive. I guess I want too much out of this car. But I've already learned a great deal, and I really appreciate all the help from you all so far. I've read about DCR, but at this point, I don't have enough info to make it useful (some dimensions...back in TN). If you guys have any advice for this setup, or can recommend alternative parts, please fill me in. also, the engine is not assembled right now, so this is the time to decide if an LS6 is really feasible. Any thoughts (aside from the fact that I have a lot to learn!)?

HEY, that 427, not 426. I own what would have been a HEMI-EATER, least back in 1968-1971. smile.gif

If you can get the static compression down to 10.2:1, that cam will defintely allow use of premium pump fuel, you can verify this through using Pat's DCR calculator and shooting for 8:1-8.2:1.

IMHO, a modern cam grind that picks up intake port velocity over the LS6 cam is well worth it. My car picked up 4-6 mph in the 1/8 mile when I cut compression 1/4 point and added a modern, pretty intense cam. BUT, if ET goals aren't your schtick, the LS6 cam was much more liveable on the street and would EASILY run power brakes ( 14" of vaccum at 900 rpm idle ).

Shave the domes, rebalance and put it together!

oh wow, i did say 426...SORRY! it was late. smile.gif well thanks for the insight. of course i'm interested in ET goals, but i really will want it to be street friendly. ahhh, decisions. the fun kind though smile.gif . thanks again!