Whisper

iTrader: (12)

I've had my 99 M6 SS for about 10 years and its always remained stock. I recently bought a M6 98 Z28 from a member here that is far from it but I purchased the car to use as a daily driver. My knowledge on cams/heads is extremely limited as I only started looking into them in order to gain some insight on how to tame the car a bit. It has a TSP MS4 cam and GM 88958622 race heads. Compression ratio is 11.2:1. The car also has various engine and drivetrain strengthening parts. The previous owner had the car dynoed at 441rwhp/385ft/lbs torque.

I was already leaning towards going to a less radical cam before I even committed to purchase the car. I was thinking of something with better low to mid range power and most importantly- gas mileage. Fuel mileage is EXTREMELY important to me and I'd be willing to sacrifice some power to pick up close to stock M6 mileage. I talked to Geoff at EPS about some specs after seeing this thread-

https://ls1tech.com/forums/dynamomet...results-2.html

This of course made my eyes light up since I thought it was possible to stay in the same neighborhood of the power I have now with a much less radical cam. And better mileage to boot. But from what I've been reading its best to match the cam to the heads. When I told Geoff what I was after, he mentioned these cam specs 222/230 114 +2. But this is before I could relay him all of the head information other than 'Ls6 heads'.

What I'm after is realistic expectation on what I can expect powerwise and gas mileage wise going with a cam like Geoff suggested with the heads that are on the car. I wouldn't want to lose more than 20 rwhp and with a loss I would expect fuel mileage to increase. I would love near stock mileage but I don't know if that is realistic (the car has 4.10s and I understand thats a major hit to mileage). The post I linked made me think VERY impressive things are possible.

Detailed parts list is as follows:
TSP Magic Stick 4 Cam 239/242 .649"/609" 111 LSA
GM LS6 Race Heads- 61.9cc, 250cc Intake, 85cc exhaust
Yella Terra Rockers 1.7:1 Ratio
PRC Dual Valve Springs w/Titanium Retainers. Previous owner says the springs only have 300 miles on them.
Thunder Racing Hardened Pushrods 7.4"
GM CTS-V Race lifters (GM 88958689)
ARP Rod and Main bolts
Powerband Underdrive Pulley
BBK 80mm Throttle Body
36# injectors
Ported MAF
Jet Hot 1 7/8" Longtube Headers
4.10s

TyCZ28

no matter what you do your not going to gain Milage back with those 4.10's thats whats hurting your economy not the cam. i ran a Tsunami cam in one of my cars and it would squeak out 23mpg highway with ease

JakeFusion

iTrader: (7)

That cam would be fine. Those heads are gigantic... so you're losing some efficiency with those (ported by Lingenfelter).

I'd leave the 4.10s in there. You're only up ~400rpm or so in most cruising situations. The issue is with the MS4 that you have to drop the timing down in the cruising area to get it to behave, which actually causes a greater load on the car, which eats mileage.

HCI2000SS

iTrader: (2)

I'm not trying to sound sarcastic, but with all do respect why are buying a HCI LS1 if you are so focused on fuel economy? I'm just curious more than anything

scotty2000ss

iTrader: (2)

Have you considered selling the cam and heads? Maybe have someone spec you a cam to different heads.

Whisper

iTrader: (12)

Thanks for the info Jake. Can you give any estimate in is it possible to still be around 420rwhp with a cam like what Geoff mentioned? Or any EPS cam that isn't as radical as the MS4? Are those heads designed to take advantage of large cams like the MS4?

When the owner drove the car down to me, he stated the car got 22.5 mpg on the highway. I've been daily driving the car around town and have gotten 15.6 in the city which I guess is pretty damn impressive considering said cam. I'm pretty sure I was only getting 18 in my stock SS around town. What I would like to see is better highway mileage, maybe even 26 if possible. And of course better low and midrange power instead of having to rev the hell out of it like with the MS4.

JakeFusion

iTrader: (7)

I think you'd hit 420.

It might be worth it to sell the cam and head. Go with some Mamo 220s and an efficient cam like a 227/231 114. You'd probably make more power than you have now and get really good mileage out of the car with much better throttle response.

I know that's not what you're looking for, but sometimes when you buy an already modded car, you have to re-engineer it to suite your goals.

And fuel economy and heads/cam are not mutually exclusive. But you may need to start over to achieve the goal.

Whisper

iTrader: (12)

I wrecked my 99 SS years and years ago and once I did that, I didn't think it was worth sinking any money into. So I just daily drove instead of sinking money into it like most Fbody enthusiasts would do. Then I saw the car I purchased. It was just too good of a deal to pass up. It had an SS style hood I lost when I wrecked my SS. It had a clutch and rear end designed to handle the power. And it had low mileage on all of these parts. It had the rims, billet grill, and halos I always wanted to put on my car. And the engine made a **** ton of power. I'm just trying to get the car into a more suitable daily driver status.

So in short, really good deal I didnt want to pass up and had a lot of what I always wanted. And the car was very close. Its just not ideally set up as a DD.

HCI2000SS

iTrader: (2)

I can understand and appreciate your position. You say you are more focused on highway mileage specifically, in which case going back to the stock 3.42 gears would probably help more than a cam change. Of couse the longer gear would work much better with a smaller and better designed cam as well. That's just one thought

Darth_V8r

iTrader: (4)

the cam suggested above would likely work well with the current heads. I tend to think 227 is about the breaking point where you start trading things off in favor of power. Up to 227 you give up very little for the power gains. With that 114 LSA overlap would be minimal, so you'd have a lot less fuel out the tailpipe. You could delay your injector timing and further improve mileage. The MMS220 would certainly be more efficient than the heads you have. Better combination of flow and velocity. The way you drive the car can influence mileage quite a bit. If you go from 4.10 to 3.42 rear gears you might move your mpg by 1. If you went 3.73, you would be almost as good on mileage as the 3.42, but you'd keep more acceleration on tap. None of that will matter if you can't keep your foot out of it. My cam is close to the cam Jake suggests and I'm getting 25/18.

Whisper

iTrader: (12)

Yeah I've thought about it. The other concern is I've heard radical cams can be very tough on springs and other components. I don't mind the chop and I've learned to give the car gas from a stop (lol learning to drive this car from a stop coming from my stock car was a treat, especially in traffic). That's one of the reasons I looked into EPS as I heard their lobes were easier on parts. So the other big factor in wanting a less radical cam is longevity of other parts. And then there is the fact I'm wanting to do this on a budget which basically means sticking to the heads the car has.

I'm also loosely entertaining the notion of keeping the car as radical as it is and pricing Civics for when I want around the town fuel economy. And nitrous for the Camaro way on down the road if I ever want a little more power. But right now I'm trying to figure what I can do to get the car more livable.








Thats what I'm talking about! I know there are people out there getting good mileage on aftermarket cams, they're just probably 1 out of 10 who are speccing/tuning for all out power.

Darth_V8r

iTrader: (4)

That was the reason I posted. My car on the stock cam dyno'd 285 wheels and got 26/19. On the cam I have I dyno'd 370 wheels and gets 25/18. I'm thinking that you get much above 231 and you start dropping faster. What jake speced has less overlap than mine so should do at least that good. With your heads I think you'd still end up around 430.

Those heads with a 250 intake port are screaming "408". I can hear them on this side of the Internet. If you get an opportunity to trade them for some AFR215's jump on it. With a 227 cam you'd be back around 470 and get to keep the mileage.

HCI2000SS

iTrader: (2)

Personally I like your idea of buying a Civic or something as your daily driver, and leaving your setup as is and hitting with maybe a 100 shot. Essentially this is what I've done except my daily is a Kia lol. This way you can have your badass weekend toy without worrying about things like gas mileage, miles, etc....

NAVYBLUE210

If you really want that car to be a DD and mileage and Driveability
Is important then as already said. Heads to Big, Cam to Big, Gears
To Big. I would do MMS 220s, 223*/227* 114*+2, Ported FAST 92,
90-92 TB, 3.42:1 car will easily make 420RWHP, closer to 450,
Plus 26-28 MPG HY ~65-70 MPH much better Driveabilty and
Throttle response = more fun . Sell take off parts and other
Car. Or look for civic daily driver (Focus better and cheaper DD)
Just my .02.