Will an LS7 head support a 1.550 O.D. valve spring ... can they be milled without hitting water or weakening the head ? The plan is to use a shaft rocker setup ... will the head support an increase in valve spring pressure at the rocker stand attaching points ?

 

Can it be milled from 1.3 to 1.5? Probably. Will it weaken the head? That’s the question everyone faces. The GM casting has its faults and in my opinion the rocker stands are flexing at rpm. I’ve seen bigger springs actually break the stand completely off the casting. It’s common on raised runner castings such as the LS7. Makes for less material above the ports for needed strength in the stands and valve spring seat area. If you decide to utilize the GM casting for this venture (aftermarket castings are better in every way) I would have the stands machined down and use a true shaft setup like a Crower to stabilize the stands. I had a set machined and used a Crower shaft setup on it many years ago and it worked well. In my opinion, unless your going with longer valves for .800+ lift camshafts, you really don’t need a larger diameter spring. Lots of guys here including myself are using 1.3 diameter springs with .725+ lift solid roller cams on Oem valve lengths (TrickFlow castings) without issue. Always use as little valvespring as possible to positively control your valves. Adding more spring than necessary is costing you power and undue wear on valvetrain components.

 

Just go buy a Brodix big spring head and be done with it. It is designed for the big spring and I would be concerned about what Mr. Chevelle said above.

 

I've been running an LS7 with OEM castings since 2014. 40,000 miles later (and worn out guides and new hollow Ferrea intakes, with solid stainless exhaust valves (not my choice), and it's been OK.....So far. BUT-I'm running 1905 PAC dual springs, and about .640 lift. 160lbs seat, 420lbs over the nose. I'm pushing my luck with 40,000 miles on them, and plan to change them this late Spring/early Summer. I'd listen to Che70velle. Ive heard of, but not yet seen for myself, guys who broke some rocker stands. With my lift and springs, I'm probably OK. I'm not a young guy anymore. If I was, the OEM heads would be up for sale. When it comes to engines, I hate the words "might be", "probably", "pretty close", etc. I'd recommend going with aftermarket heads if starting from an oil pan on up build. I personally like the Brodix BR7s. I also like the AFR 245s if going cathedral, and unless you're shooting for NHRA national records, those AFR 245s are some great heads, and will probably feel faster by the seat of your pants, and will make more power than most drivers can take advantage of. My .02. worth .00!!

 

..... Mine is a dedicated drag car ... my gen one sbc building/racing experience is weighing heavily upon my parts speccing and choices ... I have read of the valvetrain failures that are commonly blamed on the heads , the valves , the rockers , etc . but am actually amazed that there hasn't been much blame assigned to the drivers who believe that 450# of seat pressure (or less) means that you can safely rev a hydraulic valve trained engine to repeated 7000+ rpm levels without consequence ... But so-and-so does it all the time ... Oh yeah , it will spin much higher but its just a matter of time before reality , physics , and that hollow stemmed valve come crashing into the top of a fast moving piston (stroker cranks and all) ... if I lose a little power to spring pressure so be it ... I'm simply asking if the spring pockets on an LS7 head can be milled to 1.550 without causing or creating other hazards .....

 

I disagree. My Camaro has 108g solid stainless intake valves with a 232/234 .600/.600 and TSP 660 springs (made by PAC). 160lbs of seat pressure and probably not even 400 open at .600" lift, TSP's website says 415 lbs pressure at .660" lift.

I revved it to the rev limiter at 7000 rpm more times than I can count over the last 12,000 miles, and I ran them to 6600 repeatedly for the 10,000 miles before that. I even asked PAC racing if these springs would be enough before I changed my setup and wanted to rev higher, and they told me the 660 springs would do just fine.

I think part of that though is that cam technology has come a long way in the last 10 years. Most cam manufacturers have moved away from aggressive violent cam lobes to more gentle more stable lobes that often have more lift. LS engines also have a larger base circle than SBCs which also makes it easier to keep the valve under control.

 

Can they be? Yes. Should you? That is the real question. I honestly think the LS7 heads are pretty much at the limit of reliability the way they come OEM. Call it fragile. IMHO, if you really must run 1.550 diameter springs, I think you should go with aftermarket heads. The OEM heads have a questionable reliability record. I'm hoping people chime in who've actually run springs that large, so we can get a better idea of how feasible 1.550 springs are. I truly believe the LS7 heads reliability record would be even worse if everyone was putting 12,000 miles yearly on their Z06s. Corvette owners obviously don't do that often.

 

Are ALL of GM's heads unreliable ? Or is it only those that are used on higher performance / higher horsepower engines that are backed by a manual transmission ?

 

Quite the opposite. The LS7's have issue's and that's the only one I have ever heard of other than the early Casteck heads that leaked coolant.

 

Why 1.550" OD? There are so many solid roller spring options in the 1.300" and under.

 

They're ALL very reliable, EXCEPT the LS7 heads, and a few 2002-? LS6 heads had some bad OEM springs. I'm with TurboBuickv6. Why you need springs that large? I bought some 1905 dual PAC springs and Ti retainers from him, and they go 7,000+rpm, going on 9 years and 42,000 miles. Absolutely no issues.......

 

..... Solid Roller ? ... specs ? .....

 

Check with Mickyinks on here. He is solid roller and drives it a lot. Had multiple failures, but still going. I agree w/ Chev70elle, you really do not need the spring diameter so much. JMO, I would drop the factory head idea and do something better. I am in the process of building a solid roller pumpgas motor and the only thing factory is the block and it is sleeved. The oem LS3 heads are way better if you must run a factory head. Otherwise chop off the LS7 rocker pedestals and go shaft. By the time you spend all that $$, you could have went Brodix or CiD and gone faster. I am spending the same $$$ myself and have owned 4/5 sets of oem LS7 heads and would not touch another set.

 

Hyd roller. .640"/.646" lift, 238°/242° duration@.050" lift, 114LSA

 

Mickey is running Mamo 265’s, which are TrickFlo castings like many of us here. He’s also using 1.3 diameter springs with his solid roller, again like many of us. Again going larger diameter valvesprings….even with a solid….isn’t necessary unless you need a longer valve for .800+ lift camshafts. A larger diameter spring is necessary when you need more head room for coil bind, such as you would encounter with a .800+ lift camshaft which would need a longer valve. The 1.3 diameter springs are plenty for any solid roller under .775” lift…maybe even a tad more.
I simply would not waste my money or time, on a GM set of LS7 castings with all of the problems they inherently have and the amount of money it will require to machine them to make a true shaft setup work, as Dave said above, and I posted earlier in the thread. No need to take our word for it. Contact Tony Mamo, or Mast, or CID heads and ask their thoughts about GM LS7 castings.

 

Just wanted to add some important details about the "failures".....LOL

He drives the pants off this thing making close to 700 RWHP with my MMS 265 LS7 heads. The failures he has experienced have been lifter related both times.....axle wheel issues using the same brand of solid roller lifters.

We are going with a premium set of Jesel lifters now that are just gorgeous.....DLC coated lifter body's that almost slip out of your hand. Their QC is second to none and naturally you pay the price but after two previous failures we don't want to mess around any more and decided to put the best that money can buy in this third go around

Micky will also be upgrading to my larger lighter valve package and is sending the heads to me to freshen up and install the larger Ti intakes and hollow stem exhaust valves. New Manley Nextek springs going in as well at the same time.

Anyway.....just wanted to mostly clarify the issues Micky was having.....hoping the next round not only makes more power but offer him alot more in the way of longevity.

Regards,
Tony

 

What kind of failures have you personally had with the OEM LS7 heads ?

 

Tony , How much $$$ for a pair of MMS 265 Heads ?

 

Very wide range of pricing based on porting options, valve material options and valve spring package options.

Most heads I could say the same but with the LS7 stuff its just more to choose from

My Stg 1 heads which will smoke any OEM ported LS7 heads by a large margin in both flow and performance (especially airspeed and "efficiency") sell for only $4350 !

When you factor in what you can sell a set of OEM heads for (versus paying to port them) the Stg 1 heads are really a bargain IMO

They come with custom hollow stem Ferrea lightweight intake valves and a solid steel exhaust valve. They both weigh about 100 grams (which is light).

Want more flow, high lift premium valve springs, additional porting options and larger titanium intake valves and larger hollow stem exhaust valves (the "Mac Daddy" package.....LOL) and your going to spend in the high 6K range and anywhere in the middle based on a combination of some of this optional equipment. I offer a package for $5450 that's very popular.....it comes with all the porting upgrades, premium springs for high lift aggressive cams, my CNC + (hand finished chambers bowls and exhaust ports)....basically everything with the exception of the Ti intake/ hollow exhaust upgrade and these heads make a bunch of power (630 - 650 RWHP when parked on top of an OEM C6Z06 shortblock).

See pics attached but your best bet if your interested is to get on the phone with me and we can go over your build and select the best way to build them to optimize your particular combination and budget






Cheers,
Tony

 

I think most of the issues with the OEM LS7 heads have been with valve guides wearing out (just go over to C6 Corvette Forum). They have seen it on stock heads and of course modified ones. I think some of the issue with the modified heads is the valve spring pressure gets over 400 pounds it compounds things. The OEM pedestals are raised pedestals whereas on say Brodix BR7 it is a blob of aluminum and a pedestal cut in it - thus less flex. My Brodix head weighs 29 pounds the OEM head was 24 pounds so 5 pounds of aluminum all over the place for extra support the deck being a big factor (.400 vs .750) but you can also see in the pedestal area too. Tony's heads above have no pedestal a blob of aluminum and a short rocker arm piece that goes across the top. Also the scrub of the factory rocker arm (versus roller tip) probably also come into play as spring pressure get up there. Depending on what you are doing - a typical 1.30 spring is probably fine and less weight too. Like I said you need to bigger spring go buy a head like the BS285 from Brodix that is designed for it. I can not make my regular BR7 a big spring I need to buy the BS head that they move stuff around so a big spring can fit - so that might be a clue there for you. Call Brodix they may shed some light on it for you.