I asked this question the other day in a general sort of way - didn't get any responses. Will ask in a more specific fashion...


Putting a crate LS7 in my 70 Z28. Advertised @ 505 HP/470 tq. I keep hearing about "simple" bolt ons to get 500 rwhp.


Two questions: I am adding a set of 1 7/8" ss headers up front. How much will that add?


What other "bolt ons" will contribute to this 500 rwhp milestone?


Thanks.

 

Headers, a good flowing exhaust, 4" intake setup, UDP, and a good tune with put you at 500whp add a ported ls7intake in there for good insurance if you want. although that also depends on the rear. if your spinning 4.10's in a 12 bolt, with an auto and 19" wheels dont count on being close to 500

 

Thanks redbird - still learning the LS platform - liking what I'm seeing so far. UDP?

 

under drive pulley

 

Just don't use any underdrive pulley ....invest in a ATI unit

 

Ahh....thanks.

 

fix the exh valve guide issue and port the heads at the same time. ported ls7 heads on a stock ls7 will make around 500 rwhp. thats what mine did.

 

"fix the exh valve guide issue..."


Would you mind elaborating on this a little? Is there some sort of design issue on the exhaust valve guides?

 

Big time!! I've seen street driven LS7s with only 16K on them with 12 out of the 16 valve guides already worn till they were out of spec. As suggested above get the heads ported at the same time you get the valve guides fixed and you'll be over your 500 rwhp mark in hurry and you'll have a reliable engine.

 

Sorry for the continued questions, but what is the issue, alignment? If so, how is it corrected? Do you install a blank guide and re-bore?


Just curious because I have not bought my engine yet and wondering if the newer crate engines have corrected this problem...


thanks.

 

Port the heads on a LS7? WTF! They are already CNC machined from GM......while I know they can be improved, there isn't too much wrong with them from GM. I would do the headers, intake, trunion upgrade on rocker arms and maybe a cam....definitely a cam before porting the heads. If it's a GM crate motor with a warranty in effect, I might just leave it as is for a while. There are instances of rocker pads being mis machined and valve guide wear....you should look over in the Corvette Forum in the C6 Z06 section for more info. I owned an 09 Z06 and loved the car but, I did notice some slight valve train noise at 23K miles and circumstances made me sell it, still had 32K miles left on a GMPP warranty if anything went wrong. Seriously check out the Vette Forum for good LS7 info.

 

Yep, I am planning on leaving it stock for awhile for the same reason you mentioned. I am just trying to get up to speed on the LS7 platform and trying to learn some of the more common upgrades...


Thanks for the tip. I'll check out the corvette forum.

 

yes port the heads. I know they come cnc ported from the factory, but there is much left in them for improvement. My heads have bronze valve guides, Manley Severe Duty SS exhaust valves and tumble polished stock titanium intake valves, with a Frankenstein Racing Heads CNC port job. all this was done at 14K miles, kind of a preventative maintenance and knowing that if there were to be an issue, that its already taken care of. Just reading up on this it kind of a 50/50 thing if it will be covered under warranty. yes its not cheap but in the grand scheme of things its not that expensive compared to if it actually did drop a valve and destroyed the motor. plus you get the performance of a ls7 with better heads

 

Hi LC,

At the risk boring you I personally have had a lot to do with the LS7 engine, and still do, we [V8 Supertourers New Zealand] have run these engines in our race cars, for the last 4 years as a "control" engine, meaning thats what you have to run, and as such we have some 30 plus LS7 engines still in the category.

We started off running virtually out of the box crate engines, the only thing we changed was dressing the front with an ATI damper, repositioning the alternator, and adding an additional pulley wheel to increase the wrap of the drive belt. We even ran, and still do, the Factory headers into a fabricated dump style U bend that runs into 3.5" primaries that run through a merge collector and then out to a hand fabricated muffler.

We bench dyno'ed the first 24 engines and they were all within 5 BHP and 3 Ftlbs of each other. We then numbered and sealed them and allocated them to the teams by lucky number draw. The engines made an average of 554 BHP and 526 Ftlbs at the flywheel with our locally manufactured LINK ECU's on 98 Octane pump fuel.

The first issue we had was created by allowing the engines to run to a 6,800 RPM soft cut and a 7,000 RPM hard cut. We ran several races with elevated oil and water temperatures, and a couple of engine failures before we discovered that, above 6,300 RPM the standard twin grotor crank snout mounted pump cannot scavenge sufficient oil to stop the factory dry sump pan from filling up with oil to the point were the crank counterweights are literally smashing through a trough of oil, heating and aerating the oil, which in turn raise the water temperature via the factory heat exchanger.

In an emergency move we lowered the hard cut to 6,500 RPM. and removed the heat exchangers as a band aid measure and there was a significant improvement in the reduction of both the oil and water temperature.

We then worked with Bill Dailey, of Dailey Engineering who makes the worlds best dry sump systems, to design a bolt on [USA passenger side] integrated 3 stage dry sump pump and pan, which cured our problems instantly and allowed us to go back to the 6,800 RPM soft cut, plus picking up more crankshaft vacuum than we wanted, and a handy 10 BHP and 10Ftlbs of torque.

Since then the only thing we have changed is allowed our engine builders to blue-print the engines because GMs tolerances are that lousy that we lost engines due to ridiculously low main bearing, and wrist-pin clearances etc.

OK if you still with me. We have recently been doing quite a lot of R&D work on some of the LS7 engines that have been sold out of the category pool and powering other categories with greater engine freedoms, and as such we have tried several camshaft, in conjunction with a 92 mm throttle body and been staggered at just how much power and torque the engine will produce with a completely standard inlet manifold. With a set of aftermarket 1.875 bolt on primary headers the engine easily make's 700 BHP at the flywheel and some 575 Ftlbs of Torque.

So, my advice to any LS7 engine owner is not to spend any money so called porting the inlet manifold or spending money on after market inlet manifold's, a good cam and matching springs, CHE rocker's, a 92 mm throttle body, and some decent bolt on headers make big gains providing you can re-map the engine to get the fuel and ignition curves we they need to be.

Cheers,

Mark.

 

Thanks Mark for sharing. That is surprising and disappointing at the same time about the tolerance issue from GM. The way they advertise the fact that a special team of people hand assemble the LS7s at a unique location would seem to suggest otherwise...


Have you seen any of the valve guide issues mentioned earlier?

 

Hi LC,
We have seen some engines with badly worn guides, but the majority are good, and when they are blue printed and rebuilt, most are not replaced.

I guess its because our engines see comparatively low milage, less than 4,000 miles are year, even though they are racing miles, we just don't see worn guides as an issue. Whilst we have never seen a failed rocker trunnion however, we did go with the Brian Tooley trunnion upgrade simply because it an affordable form of insurance.

I also meant to highlight the fact the our recent R&D program has proven beyond all doubt that the stock standard CNC ported LS7 cylinder head is capable of well over 700 BHP at the flywheel, so to me it makes no sense to spend good money porting the stock head unless you are running a very serious cam and intake manifold etc.

Cheers,

Mark.

 

Yes fix the heads first. They are junk from the factory. Get new guides/valves/etc in them.

500rwhp depending on drivetrain is nothing but a tune/headers away from a stock ls7. c6z have done 500rwhp time and time again with intake/tune/headers.

Don't buy a crate GM ls7. That is a colossal waste of money. You can find used short blocks in great shape for $3500-4000, or used motors for $7k-7500. Pop the heads off, spend $2k getting them fixed/ported/milled, throw a mild cam in, do headers, and enjoy a nice solid 550rwhp setup.

I sold my factory 18k mile short block to a guy that was on his 3rd engine. Dropped a valve at 20k and another on a new engine at 15k. When he got my motor he made sure to do the heads since it already cost him $25k+ in factory engines.

 

Unreal.

I don't mean to be offensive, but your comment about the LS7 heads being Junk from the factory, etc, is simply not true. If you read my post's above, with over 30 LS7 engines in our category pool, we have seen an insignificant number of valve guide issue's. Maybe, as I have also said that's because we don't do high milages, but unless you are going to put a lot of milage on the engine as a daily driver, you are wasting your money spending money on the cylinder heads. The right camshaft is all you need to wake up a bog standard LS7, and CHE rockers will give you some piece of mind.

Cheers,

Mark.

 

You are talking about being good/bad from a making power perspective. They are great at that. Done several ls7 cars with nothing but new guides/valves that have made 580-590rwhp. I do agree that port work is not a good way to spend money. I'm talking about them from a reliability stand point. I've seen over 40 sets pulled. Only 1 wasn't completely worn with almost all the valves shot and guides 3-4x the service limit. I've seen exhaust valves with radial cracks forming. I've seen 2 ls7s drop valves right in front of me. I know countless others that have popped because the head issue wasn't addressed. So yes, fix the junk heads from a reliability stand point then they will make power just fine.

It should be the first thing any ls7 person does, that or an extended warranty unless you have $12-15k laying around to replace it when it pops.

 

I really appreciate the continued dialogue, I am learning more all the time. I encourage others to post with opinions.


"I've seen over 40 sets pulled. Only 1 wasn't completely worn with almost all the valves shot and guides 3-4x the service limit."


This statement seems a little disconcerting to me. It would suggest that almost everyone who has bought a 2014/2015 Z28 will experience valve guide issues in the near future. Is this not something that has caught the eye of the General? What is GM doing to address this issue or am I missing something here?