I Am Building A 408 For My Truck

[Quik]

Krambo, it is a shop that will build the engine but I want to keep control over the parts that will be in there because so little people know that much about the SSS. Just to give an idea, I find my truck a bit unideal for DD BUT I don't really have a choice since I practically have some engine damage. I just find it money wise to go 408 since I have to do all this anyway. The stall is going to stay in there until the new tranny failure that is for sure, a new cam isn't out of the question but I have so many thing that broke that I have to be careful not to blow "the budget" . BTW Eagle pruducts has a nice application page for their kits : Eagle Rotating Assemblies

 

To go for a 11:1 ratio would only require to have 68CC LS6 "Style" heads from Patriot

2035 Assy. 2.08"/1.60"/68cc

 

I thought that the 408 had more torque on the bottom end than the 6.0 is that right?

Still wondering why i'd have to go higher on the stall. It just gets on my nerves sometimes...

stall speed relates to rpm band when launching. as in drag racing you want to launch at peak torque or where it flattens out. this is why a 3k stall is even good for a stock motor. i think a stock lQ9 peak torque at 4500. i suggest 3500 cause anything less and you wont get off line like you should. now if truck would never see the track and be a tow setup then i would suggest a different route. i have 1320 thoughts thats why i suggested what i had. you can run your heads just get a different headgasket thickness. something like a .040 will help get you close. compression will give you power thru the entire range, some ppl are afraid of it but with todays motors 11.1 is normal. for ever .5 in cr either +/- youll see a difference of 15-20hp. and that is thru the entire rpm range!! which is important.

 

ive driven and delt with large cams with traffic and etc. they arent as bad as some think they are. a good dialed in tune will cure alot of issues ppl have with larger cams

Edited December 27, 2007 by Quik (see edit history)

[zippy]

I say keep your current cam. I've driven a 408 with stock heads and a 212/218 cam. That engine still had very good power and drove around like a stock 6.0L, except with alot more torque and hp coming in sooner. I'd certainly stay with the cam you have and you'll be suprised with the power it makes. Cam selection is based on power level desired, drivability desired, and the parts surrounding it. There are too many head choices out there to give much recomendation since so many are just as good as the others. As for the converter, stay with what you have already or go to a 2600. A 2600 should stall to around 2900 behind the 408 and the 3000 should stall to around 3400 behind the 408.

[Simon]

We are getting somewhere, I think this is what i'll do (same cam, same stall) but I will bore it at 4.125 because my ring cylinder is quite damaged and I don't want to have surprises when boring at only 0.030. I could always throw my TBTC which still layin' around in my garage but even then I think my Yank is way better than my jobber TBTC.

 

2bseen got a setup similar and runs 12.14 from his sig as quoted by him : "Well right or wrong this is the cam I got for my 408. Comp xer 230/234 595/601 114. I had my shift points at 6300 with the old motor and will be alittle higher we this one. I am running 2.05/1.60 valves with 10.8 to 1 compression.

 

2003 Chevy SS blue with a few other colors 11.49 at 117.29 mph Old setup/ New motor 12.14 n/a at 109mph. Showing hemis the tailgate soon. Check the vin its a 6.0."

 

Still gotta decide on heads though.

[Krambo]

2bseen got a setup similar and runs 12.14 from his sig as quoted by him : "Well right or wrong this is the cam I got for my 408. Comp xer 230/234 595/601 114. I had my shift points at 6300 with the old motor and will be alittle higher we this one. I am running 2.05/1.60 valves with 10.8 to 1 compression.

 

2003 Chevy SS blue with a few other colors 11.49 at 117.29 mph Old setup/ New motor 12.14 n/a at 109mph. Showing hemis the tailgate soon. Check the vin its a 6.0."

 

 

Keep in mind that 2bseen ran the 12.14 not with the 408 but rather a well built 427 (I believe it was a 427 from conversations) in N/A form. Ric (dounome) bought his old 408 and was able to muster a 12.6 which was the fastest that motor went in an SSS. I was there when Ric ran the 12.6 at Atco. It was a stout motor no doubt.

[zippy]

I don't think you'll be able to get an LQ9 block that far out. I know with an LS2 block you can by resleaving it, but I've never heard of doing it with an LQX block. You could go .040 over like Benkey did.

[Simon]

ok...I knew there had to be something lol it seemed too easy.

I gotta know before I buy my kit... how much oversize max can we do with the LQ9 block???

I was just about to order the rotating assembly, it should be here within 7 days...

Edited December 27, 2007 by Simon (see edit history)

[zippy]

.060" over is the most I've heard of. I personally wouldn't go more than .040" though.

[Simon]

Here is what the cylinder looks like, only one got damaged. Their only high compression kits are for a 4.005, 4.030 and 4.125 bore. I just wanted to go bigger because of the scratch but how much you guys think i'll need. I know it's not easy to see but I gotta know before I purchase. My idea was to have the biggest bore in hand before I take it to the machine shop so we can clear that mark for good.

 

[Black2003SS]

Guys, can he mill the heads so he can order a larger oversize bore and get the same compression?

[Quik]

We are getting somewhere, I think this is what i'll do (same cam, same stall) but I will bore it at 4.125 because my ring cylinder is quite damaged and I don't want to have surprises when boring at only 0.030. I could always throw my TBTC which still layin' around in my garage but even then I think my Yank is way better than my jobber TBTC.

 

2bseen got a setup similar and runs 12.14 from his sig as quoted by him : "Well right or wrong this is the cam I got for my 408. Comp xer 230/234 595/601 114. I had my shift points at 6300 with the old motor and will be alittle higher we this one. I am running 2.05/1.60 valves with 10.8 to 1 compression.

 

2003 Chevy SS blue with a few other colors 11.49 at 117.29 mph Old setup/ New motor 12.14 n/a at 109mph. Showing hemis the tailgate soon. Check the vin its a 6.0."

 

Still gotta decide on heads though.

isnt that something. a setup you just looked at is similar to what i said to run?... i said 11.1 10.8 is close. i said 230s cam, guess i havent done this

 

but your not going to bore a 6litre block past .04. if you do youre going to have to sonice test it to see what you can go. find another block if you can. you score is pretty bad

[zippy]

That is what he looked at, but most 408's are built with cams in the 236 to 242 area for cam duration so it's not like he found some wierd or special combo. Most N/A 408's are also around 11.0:1 to 12.2:1 compression. I'd agree that the compression should be around 11.7:1 or so. Both dounome and 2bseen built their 408's around that type of setup with good results performance wise. Gas milage and idle issue's might be another thing. Gas milage in the real world of 3.60 per gallon is important on something you might drive alot. Idle is important, try idling with a big cammed truck in big city rush hour traffic for an hour or so. Remember that he's building another engine because he broke the last one. He's not doing it just because he wanted to go faster. You're telling him that with more cubes, he needs more converter than he's currently running and he was happy with on the 6.0L??? That makes no sense at all. You're also telling him the he needs more cam, just because he's going to more cubes. If he did nothing more than replace his short block, he'd still be quicker than he was with the 6.0L that he was happy with. His 6.0L had stock heads and stock intake. Just replacing the heads alone would have been an improvement on that and I'm sure he'd have been happy with that. With the 6.7L, the same cam and a good flowing head will make alot more torque in a wider powerband with better drivability than his 6.0L had. The more parts you change from your setup at once, the more problems you'll have. Honestly I'd just replace the short block and build it more from there after he's gotten it tuned in and some miles on it. Since the heads are bad, I'd make a change there simply because they need to be replaced anyway. I'd go to the CNC ported GM LS2 head, Dart 225's, or do an L92 conversion.

 

That bore looks like it might clean up at .030".

[riddle]

It would be nice if you had another vehicle to buy you some more time to re-search this engine build,

 

But, I can give you my set-up and Opinion wich may be helpful?

 

I'm running a 408ci, with CNC ported LS6 heads, (243'),(Z06 heads) and a 2002 z06 cam.and 42 lbs injectors.

*heads are about $900 per head

I am at 9:1 compression, cause I usually run a blower, (wich I am not running currently)

 

this head and cam combo Idle sweet, drives fine and has Tones of power! My truck feels way faster non-supercharged 408 w/low compression, then the stock Lq9 with vortech blower.

 

BTW, I have a TCI 3000rpm stall, and I think it is a bit big for a DD, especially if you lived in a big city! (IMO) you have to use both brake and gas, and pepper the throttle to get it movin slow,(tight parking spot will drive ya nut's, LOL

 

any way, here are some Dyno #s per SA Desings.:

 

6.0 liter, 10.362:1 Compression, Shorty headers, stock air cleaner housing,w/water pump, no Alternator or power steering, LS6 Heads and Cam, 94 octane fuel.

 

401hp @ 5700 rpm.

407ftlbs @ 4600 rpm.

 

the heads are pretty impressive from everthing I have read, May be worth lookin into?

 

~Danny

[Quik]

That is what he looked at, but most 408's are built with cams in the 236 to 242 area for cam duration so it's not like he found some wierd or special combo. Most N/A 408's are also around 11.0:1 to 12.2:1 compression. I'd agree that the compression should be around 11.7:1 or so. Both dounome and 2bseen built their 408's around that type of setup with good results performance wise. Gas milage and idle issue's might be another thing. Gas milage in the real world of 3.60 per gallon is important on something you might drive alot. Idle is important, try idling with a big cammed truck in big city rush hour traffic for an hour or so. Remember that he's building another engine because he broke the last one. He's not doing it just because he wanted to go faster. You're telling him that with more cubes, he needs more converter than he's currently running and he was happy with on the 6.0L??? That makes no sense at all. You're also telling him the he needs more cam, just because he's going to more cubes. If he did nothing more than replace his short block, he'd still be quicker than he was with the 6.0L that he was happy with. His 6.0L had stock heads and stock intake. Just replacing the heads alone would have been an improvement on that and I'm sure he'd have been happy with that. With the 6.7L, the same cam and a good flowing head will make alot more torque in a wider powerband with better drivability than his 6.0L had. The more parts you change from your setup at once, the more problems you'll have. Honestly I'd just replace the short block and build it more from there after he's gotten it tuned in and some miles on it. Since the heads are bad, I'd make a change there simply because they need to be replaced anyway. I'd go to the CNC ported GM LS2 head, Dart 225's, or do an L92 conversion.

 

That bore looks like it might clean up at .030".

yes but its known that large cubes eat duration up. look at the difference between a 4.8/5.3-5.7-6.0 youll see differences. i drove my 240 cam and played with others in PGH traffic. i had no issue what so ever. my 408 combo i built idled and drove just like my stock 5.3!!!!!!!!! now my 6litre was alittle different that was also before i learned and got this far in tuning. my 408 was so tame that my girl was able to drive it. it idled rock steady, as steady as my blazer does. it pulled away off idle. i could load thta motor down to 500 rpms in 6th and be able to creep. we are talking 244/248 duration with a 112+2 with 11.1 cr. the only issue i hated about my last combo was my heavy ass clutch. as i stated drove like my 5.3 till i hit about 4k then from that point till 7k it was pure tire shredding. could break loose 305/40/20s at 100 shifting into 4th but driving daily was simple. now for the first few days it was hell even getting it to idle and etc.

 

thats why i firmly believe a 230s cam will give him what he wants. a 3k stall is so small, hell most 4wds stall 2400 from factory. ive been in atleast 5 4wd Gms that stall all around that rpm. my blazer, my ex's blazer, 01 6.0 sierra, 02 5.3 silverado and 00 4.8 silverado. point im saying 3400 isnt a large converter at all. i drove my 4k daily now i wouldnt recomend that for a DD whatso ever for him but a 3400 wouldnt be bad. would be a good mixture of race and DD

[Simon]

I have no problem idling or driving in traffic with my Yank 3000. Actually, you gotta run about 100 miles before everything gets in place but after that I just let go the brake and start moving forward. It depends how bad the traffic is...hell if my yank stalls at 3400 behind the 408 it's even better (plenty for me). It's also good to know that a low CR 408 feels faster than a supercharged 364!

I will know around jan 7 if i'll be ok with the 0.030 bore and start picking parts from there. It's kinda hard to build a motor between Christmas and New Year's but gives me time to think about the setup which is nice. I didn't know that I could go that high with the compression ratio 12.2:1 that's alot!

 

Quik, how was your gas mileage with you 244/248 combo and 11.1 cr? I was also considering a set of Dart heads.

[riddle]

Ohh, sorry I must of missed somthing in your post I thought you were asking how the high stall was, Yeh, I like mine too. some of these post are so close you get kinda mixed up, LOL

 

Anyway, yesterday, 12/28/2007, after I replied about the truck feeling faster, I used my G-Tech to see what was really going on.

(*I am not saying G-tech's are accurate, but I do use mine for a basline for tunning and modification and it is fairly accurate for comparison, IMO)

 

So, Per the G-tech, my truck ran a 13.37 in the 1/4 @ 102.2, and 0-60 in 4.68 w/ tire spin.

 

My stock Vortech Blown set-up, Ran, 13.89 in the 1/4 @ 102. and 0-60 in 5.20 w/o tire spin.

 

So, yeh it is definately faster. ( note: the stock set-up did not have a high stall )