Many of you have given some great advice for my setup, and I appreciate it. Once more I need to tap into the collective wisdom here at TC. I'm wondering if anyone here thinks that the LS-6 heads would be a reasonable choice at this point. Right now, the '70 will be a street machine (with lots of street time but occasional trips to the strip), around 10.1 CR, 3.73 gears and TKO, RPM intake, and...LS-6 heads. Not sure about the cam. Now I know that almost everyone suggests going with large ovals for this setup. My uncle (very old school-doing the resto) seems to think that the rect's will be the way to go. But I'm not going to be getting above 6500 rpm. He's ornery and when I suggested maybe going with ovals, he gave me a good scorning as only uncles can. Here's the thing, I know very little about engine building (learned much of what I know here and in a few good books) and for me to tell him what's what just isn't right. But I see over and over again that ovals will be a better choice. Now, I suppose price is an issue since the heads are already there. But I'd rather have the 'velle setup right from the beginning than wish I'd gone with something else. Besides, for what it's going to cost, what's an extra $1500? So, do you guys think it's worth the extra $$ for the alum ovals (maybe Brodix?) and try to talk the old man into it? (I know...only I can make that decision). If I tell him it's what I want, he'll do it, but like I said, I feel silly telling a guy who I deeply respect and who's set national NHRA records ('63) how to build an engine. Any advice here is needed and greatly appreciated!
wyatt
I tend to disagree with the majority on this....but what the heck.
As I've said before, myself and 2 buddies all had 70 Chevelles. Theirs were both LS6 engines, and mine was an LS5. All tweaked similarly. We all ran low 12's. I actually made it into the high 11's, but I had raced my car a ton more than they did.
So I think if you already own the heads, use them and be happy.
If you have to buy heads, pick what you want. In my experience....at least with the factory stuff, it's a push.
Ron
As I've said before, myself and 2 buddies all had 70 Chevelles. Theirs were both LS6 engines, and mine was an LS5. All tweaked similarly. We all ran low 12's. I actually made it into the high 11's, but I had raced my car a ton more than they did.
So I think if you already own the heads, use them and be happy.
If you have to buy heads, pick what you want. In my experience....at least with the factory stuff, it's a push.
Ron
The big difference between the factory heads and aftermarket are in the exhaust ports. If you are running 10.0/1, the compression makes up quite a bit for any low end (talking under 2000 RPM) that you may lose with a Rec port. If you have the Rec ports, by all means use them. The guys that have drive the oval/rec comparisons are not talking stock head to stock head. The good performing oval ports a fair amount of money and time invested into them, or they are aftermarket.
It boils down to whether you beleive the potential of an extra .1-.2 sec at the track is worth it. And I mean potential, not given.
What's the 1st gear ratio of that TKO? 2.90.
Let me tell you what your uncle is thinking....if I might speculate..... with a 1st gear ratio of 10.70, then 2nd at 7.4, when you hit it in 1st you'll be at 6500 in a second, l-i-t-e-r-a-l-l-y "one onethous-SHIFT-and".
In that scenario, your rat won't flipping know its got big ports on there, it'll blow past the useful range of the ovals about 3/4 of a second into it!
But they'll move the car quicker in that 3/4 sec, hence the great observation of Ron - it's a push.
Do what I did, max out on DCR or 'push the envelope' ( the number everyone loves to hate), and run a 'smallish' cam well advanced. I would NOT recommend an XE type grind in this app, unless they too lift the intakes quickly off the seats and lay them down gently. I prefer to get my cylinder pressure the old-fashioned way, by static compression, rather than trapping the exhaust to do it. Plus, the exhaust trap must be worse on crappy exhasut ports, which stockers ahve.
Hell use the Lunati 403A3 like I do. It won't know you have 'incorrect' heads on these unless you get very serious about the 60' time. My cam is a small short track cam. Solid. Mint. Look for the same type.
Don't run a 6500 chip, you'll be on it all the time!
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give it some room between shifts to 6600-6700-.
You choose whether the rect/oval battle is worth it to you. To quote Ron, " Its a push ". I wouldn't be dwelling on it imho. Squeeze the mixture well and run a good cam profile in the advanced mode which emphasizes the intake ram effect.
You won't be short on torque my friend! On street tires, you'll be glad you have rects, ovals would be that much quicker to light those hides up!
What's the 1st gear ratio of that TKO? 2.90.
Let me tell you what your uncle is thinking....if I might speculate..... with a 1st gear ratio of 10.70, then 2nd at 7.4, when you hit it in 1st you'll be at 6500 in a second, l-i-t-e-r-a-l-l-y "one onethous-SHIFT-and".
In that scenario, your rat won't flipping know its got big ports on there, it'll blow past the useful range of the ovals about 3/4 of a second into it!
But they'll move the car quicker in that 3/4 sec, hence the great observation of Ron - it's a push.
Do what I did, max out on DCR or 'push the envelope' ( the number everyone loves to hate), and run a 'smallish' cam well advanced. I would NOT recommend an XE type grind in this app, unless they too lift the intakes quickly off the seats and lay them down gently. I prefer to get my cylinder pressure the old-fashioned way, by static compression, rather than trapping the exhaust to do it. Plus, the exhaust trap must be worse on crappy exhasut ports, which stockers ahve.
Hell use the Lunati 403A3 like I do. It won't know you have 'incorrect' heads on these unless you get very serious about the 60' time. My cam is a small short track cam. Solid. Mint. Look for the same type.
Don't run a 6500 chip, you'll be on it all the time!
You choose whether the rect/oval battle is worth it to you. To quote Ron, " Its a push ". I wouldn't be dwelling on it imho. Squeeze the mixture well and run a good cam profile in the advanced mode which emphasizes the intake ram effect.
You won't be short on torque my friend! On street tires, you'll be glad you have rects, ovals would be that much quicker to light those hides up!
Gene,
That was one colorful answer. Now let me provide an interpretation for the lad. Run whatever you have. If you have real GM LS6 rec ports - by all means - run em. Just apply some modern thinking and don't overcam the motor.
Nothing quite like a "real" LS6 big block in a '70 Chevelle. Have fun. And to be quite serious, if my '69 was a stick car (or if one day I get ambitious and convert it) you can sure as all heck bet it will become be a period correct 427/425HP car. Would it be the fastest or best bracket car? No But the big cam rec port high compression 6500 RPM 427's and 454's are a blast to drive on the street.
That was one colorful answer. Now let me provide an interpretation for the lad. Run whatever you have. If you have real GM LS6 rec ports - by all means - run em. Just apply some modern thinking and don't overcam the motor.
Nothing quite like a "real" LS6 big block in a '70 Chevelle. Have fun. And to be quite serious, if my '69 was a stick car (or if one day I get ambitious and convert it) you can sure as all heck bet it will become be a period correct 427/425HP car. Would it be the fastest or best bracket car? No But the big cam rec port high compression 6500 RPM 427's and 454's are a blast to drive on the street.
Hey...GRN69CHV,
The L72 (427/425) was a bad ass combination....period! GM got this one right.
I actually had a 68 Impala Wagon, L72 with a 4 speed, all factory and what a hoot it was.
Documented and gads I wish I still had it.
Ron
The L72 (427/425) was a bad ass combination....period! GM got this one right.
I actually had a 68 Impala Wagon, L72 with a 4 speed, all factory and what a hoot it was.
Documented and gads I wish I still had it.
Ron
Once again, you guys have given some great insight. Thank you all. It's hard not to get carried away with the "this works better than that..." race.
Ron, low 12s is fast! I'd be happy to be close to that. Breaking into the 12s will have me smiling. And yes, I already have the heads. And you're right, I need to quit thinking about it and just be happy with them.
GRN69CHV, do you think 10:1 CR is too much? I was thinking I might get away with a hair over that, but again, I want to be on 91 pump.
Gene, I like your thinking man. The TKO will have me out of first in a hurry. I can't seem to find the Lunati 403a3 anywhere. Do you have a link? And you're right, I'm not going to be short on torque. It's still a 454. By the way, what are your shift points and redline with yours?
Ron, low 12s is fast! I'd be happy to be close to that. Breaking into the 12s will have me smiling. And yes, I already have the heads. And you're right, I need to quit thinking about it and just be happy with them.
GRN69CHV, do you think 10:1 CR is too much? I was thinking I might get away with a hair over that, but again, I want to be on 91 pump.
Gene, I like your thinking man. The TKO will have me out of first in a hurry. I can't seem to find the Lunati 403a3 anywhere. Do you have a link? And you're right, I'm not going to be short on torque. It's still a 454. By the way, what are your shift points and redline with yours?
Wyatt,
The compression issue is as varied as the rec port/oval port deal. For a street driven pump gas type setup anywhere above 9.0 is workable. 10.0 gives you more options on the cam. 9.0 mandates a shorter duration torque profile. Above 10.0 and you have to pay attention to more of the details. I personally would try to stay around 280 adv / 230 @ .050 with 10.0/1 (talking flat tappet hydraulic that is). There's as many cam choices as there are shades of red. For comparison, Chevy produced the LS6 2 years back to back with the same factory solid lifter cam. 1970 LS6= 11.0/1Cr and then in '71 - LS6 had 9.0/1Cr with the same cam. Both were a blast to drive, the '70 has more lower end grunt because of the 11.0/1, but both version would fry the tires at will.
The compression issue is as varied as the rec port/oval port deal. For a street driven pump gas type setup anywhere above 9.0 is workable. 10.0 gives you more options on the cam. 9.0 mandates a shorter duration torque profile. Above 10.0 and you have to pay attention to more of the details. I personally would try to stay around 280 adv / 230 @ .050 with 10.0/1 (talking flat tappet hydraulic that is). There's as many cam choices as there are shades of red. For comparison, Chevy produced the LS6 2 years back to back with the same factory solid lifter cam. 1970 LS6= 11.0/1Cr and then in '71 - LS6 had 9.0/1Cr with the same cam. Both were a blast to drive, the '70 has more lower end grunt because of the 11.0/1, but both version would fry the tires at will.
What did stock LS-6's run? mid 13's,maybe high 12's with stickies? I don't have any money in my current oval port heads,just big valves,the rest is all GM. If you're like the rest of us or most of us, you'll keep wanting to go faster and faster,I'm sure the rectal ports will take you where you want to go,just seems much easier with oval ports when you want to get your big heavy Chevelle down the track. If you're gonna race,its all in the 60ft and you need all the help you can get. After a couple Mustangs blow you off the road, you'll wish you had ovals 
My LS-6 crate motor bone stock with only about 1,000 miles on it ran 3 back to back 12.2x’s in my cousin’s old 70 LS-5 car the first time out. The car had 3.31 gears, headers, a turbo 400 with a mild 11-inch converter and some sticky tires and that’s all. I’m sure with some steeper gears out back a better converter maybe a x pipe and some tuning that same car would have been a easy 11 second ride.
Joe
Joe
Wyatt, 402A3 ..you said you guys will run a hydraulic cam?, then it should be just a schootch smaller than an A3..
http://www.holley.com/HiOctn/ProdLine/Products/IEC/IECC/Chevy7.html
See what Unc comes up with. The cam designer at Lunati, Harold Brookshire, is designing a new generation of cams, "voodo", which should be out top of '05.
Its a 427 Wyatt, 6700 shifts, 6900 redline. A well built 454 should live easily with a 6600 rpm redline.
http://www.holley.com/HiOctn/ProdLine/Products/IEC/IECC/Chevy7.html
See what Unc comes up with. The cam designer at Lunati, Harold Brookshire, is designing a new generation of cams, "voodo", which should be out top of '05.
Its a 427 Wyatt, 6700 shifts, 6900 redline. A well built 454 should live easily with a 6600 rpm redline.
Thanks again for all the replies. You guys are really helping a novice out.
Gene, thanks for the link. We haven't decided on anything re: a cam yet. Do you think the solid would be better choice for this application? I really don't know. I've read a little bit about the VooDoo cams and I sent Harold an email about them, but haven't heard back from him yet. I know he's busy. I can definitely wait until spring for the cam. The body will be on a rotisserie about that time anyway (gotta love an uncle with all the goods). I'm not sure what pros/cons are between the solid and hyd, but I'll go with whatever makes most sense. It's not a real LS-6 car, so as long as what I have performs reliably, I'll be happy. Your car is definitly a sweet ride! With a redline that high, do you still have all the low end you want? I'd love to have a high redline, and I can't imagine low end being that bad with the gears and manual I'll have. Thanks again.
GRN, I know CR is a complicated issue, but from what I've learned, 10:1 should be in the ballpark we'll need.
Gene, thanks for the link. We haven't decided on anything re: a cam yet. Do you think the solid would be better choice for this application? I really don't know. I've read a little bit about the VooDoo cams and I sent Harold an email about them, but haven't heard back from him yet. I know he's busy. I can definitely wait until spring for the cam. The body will be on a rotisserie about that time anyway (gotta love an uncle with all the goods). I'm not sure what pros/cons are between the solid and hyd, but I'll go with whatever makes most sense. It's not a real LS-6 car, so as long as what I have performs reliably, I'll be happy. Your car is definitly a sweet ride! With a redline that high, do you still have all the low end you want? I'd love to have a high redline, and I can't imagine low end being that bad with the gears and manual I'll have. Thanks again.
GRN, I know CR is a complicated issue, but from what I've learned, 10:1 should be in the ballpark we'll need.
edit: Sorry, didn't catch that Gene posted the link.
http://www.holley.com/VoodooCams/VoodooCams.htm
Wes
http://www.holley.com/VoodooCams/VoodooCams.htm
Wes
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