Hello Everyone,

I was wondering if anyone could help me out here. We just overhauled a long block for a 1991 Z28, with a factory 5.7L engine. This new engine is the Pre-86 style block (5.7L), and we're also using pre-86 style cylinder heads as well. We're using this block because it's a 4 bolt main style, but the car is going to be a weekend driver with occasional strip use. What we're wondering is if there's a cam out there that will give us about 300 or so HP without going in to cylinder head modifications? The heads were with the block when we got it, so I'm not too literate of their specs. They have casting number 416 on them, which I think is a 305 head, but I'm not sure.

If anyone could help us out, It would be appreciated, thanks!

 

compcams xe-262-h

218 intake
224 ex 50

462 lift
469 ex

110 lobe seperation


Take your heads, and at least gasket match them, you will see an awesome difference.

Thats the cam I have right now, very pleased with it. I have a pretty mild 350

 

go to performance automotive wharehouse.com a good one for 80 dollars

 

Those heads you have are, indeed, 305 heads from pre 87. 1.84/1.5 valves, and 58cc chambers.

That cam is between mild to aggressive, so I don't know if it will get to 300hp with those heads. That'd be a bad combination. Also, I don't know if your heads will be able to handle it with those springs. You might need some machining.

 

Those heads are KILLING your compression ratio. The cam I suggested works fine with stock heads, its just about the biggest you can throw at stock heads.

I have a set of pre-87 350 heads, if youre interested.

 

Wow lots of replies already, Thanks guys! Now on to my first question haha.
With a 58cc chamber, wouldn't that be essentially better for making power?

Waax the first cam you mentioned, it will work properly with the TPI system?
also, the heads you have for sale, what are the specs, and how much?

 

What about this cam from summit racing? How would it compare?

Summit TPI Cam and Lifter Kits: SUM-G5000 - summitracing.com

 

those heads are just fine. I'm running them on my 350, with a lunati 60103 cam (similar to the compxe268, one step up from the 262 you are being suggested to go with.) It's a beast.
Porting the heads isn't difficult, and really unleashes the beast within.
Use new valve springs obviously, with new retainers and locks, and positive valve stem seals. Check your valve retainer to seal/guide boss clearance during assembly, it should be ok with a cam like that, and new retainers. (Mine was fine, no machining necessary with .535" lift with 1.6 rockers.)

Yes, the 58cc chamber will bump up your compression, but that might be a bad thing if you have milled the block deck, or are using pop up pistons. With stock style dish pistons, stock deck, the 58cc chamber heads are just what the doctor ordered. Personally I had my block decked, and used flat top pistons, so I ported open the chambers a bit to 64cc. 10:1 on the nose. Perfect.


EDIT: don't use a summit brand cam.

 

Guess I should put a little more info here for you guys. Block is .030" over, no decking or milling, running a slight dish piston very similar to factory. I've never "gasket matched" a head before, is it hard to do, or should i leave it to the pros? if I change to a stronger spring, won't I have to install screw in studs for the rocker arms?

 

Hell, that is pretty cheap for what you get. Lucky guys with flat tappet...that kit would cost me 500$ because of my roller cam =/. And for the power received from a stock motor like that...I'd like to see numbers, but I trust summit. Seems legit.

Although those lift numbers are pretty mild...I guess it's the long duration. Beats me though.

 

It is relatively inexpensive, however the cam that Waax mentioned is only $30 more for the complete kit. If it will make more power than the summit cam, then the cost, to me, is not that important. I just don't want to get to the point where I have to re-tune the ECM, etc. to make it run and idle properly.
----------
Sonix I just saw your edit. Would you please explain why not to use a summit brand cam? Thanks!

 

like guitarjunki mentioned; lame ramp rates. The lift is pathetic, given the advertised duration. It also has a very weak duration @.050. They are old grinds, easy on valvetrain, easy on the seat of your pants. Ie, not much power, kills your economy. Pay the extra $ to get a good comp cam or the like. That extra $30 or so, will pay for itself in the first month you drive the car.

 

my thoughts exactly sonix. How does that cam mentioned compare to a factory TPI cam?

 

There are two stock cams that you could be referring to for that 305.
You said it was a Pre-87, so there is 1986 and 1985 camshafts

1986:

LIFT
Int. .350 Exh. .385

DURATION
Int. 178 Exh. 194

LOBE SEPARATION 109.0


1985

LIFT
Int. .403 Exh. .415

DURATION
Int. 202 Exh. 206

LOBE SEPARATION 114.5

--------------------------------------------------

So that cam yo looked at is a big step up from the '86 cam, and a tiny step up from the '85 cam. When Summit tested this package, they more than likely did it on the '86 cam, or one of the like, since there were a few wimpy peanut cam years.

Find out what year that motor is from, and let us know so that we can clear up this cam debocle. It would be absolutely useless to get that kit if you have the 1985 cam, you'd see like 10hp, if that.

 

Should have clarified... the car is a 1991 Z28 with the 5.7L engine. I was curious as to the cam specs for that engine, not a 305. The NEW engine is a pre-87 5.7L block, which has just been overhauled. I'm looking to put a cam in that block that will give me some "oomph" haha.

 

Think of it this way...that cam will essentially give you the same performance as a stock TPI cam (one of the good ones).



And you are putting 305 heads on a 350 block? Idk about that man, don't expect good flow in that respect...I dont even know if that is going to work in the first place...but I could be wrong, someone help me out here.


IMO, that cam, with those heads, will not bring you near 300hp. Maybe 220 crank with those heads, but thats it.

 

The 416 heads were on the block when we got it, didn't really think about changing them at the time. Anyone have the specs on these heads?

 

do a search on 416 heads. Or porting 416 heads. It's a very common thing to do, even putting them on 350's.

Like I said, i'm running that setup. Sitting bull, F-bird'88, mwnova66, Vader etc etc have run them in the ported form, with good results.

Specs on the heads:
also, 160ish cc intake ports stock.


So with that in mind, and a 350CID motor, a compxe262 might be too mild. It's a fire breather compared to the stock cam, but you aren't daily driving it so.... I'd step up to a xe268. My cam is similar to that, maybe a bit closer to the compxe274, and I could daily drive it, no problem. (I car pool, so I don't daily drive it, but anyway...)
300HP shouldn't be difficult. I'd HIGHLY recommend porting the heads, a little die grinder work goes a long way.

 

Okay I wasn't sure if you could swap those heads over. I figured since the bore of the 350 and 305 were different meant that the Combustion chamber wouldnt line up right.

 

well after all this talk I think I'm going to head to a machine shop and get the heads ported. I'll look in to those cams

 

If I do go with one like the xe268, won't I have to get the ECM reprogrammed?

 

you probably want a different prom to make best use of the cam. There is an EFI friendly version of that cam... Look on comps website, and try to find the part #, so you can find it on summit easier. It's got a 114* LSA...

machine shop? You port your heads yourself.
By the time you pay a machine shop to port your heads, you could have boughten aftermarket heads for the cost. The savings and benifit is doing it yourself.

 

could you port heads with a dremel?

 

you could, it'd just take a while.

I used some carbide burrs on my dremel, for the intricate work in the bowls. Works well. Got the bits from carbidebur.com IIRC.

The control is nicer with a dremel, but the sanding drums are more expensive I think...

 

Here is a website I used when I was going to port my heads (i lucked out and bought a used set with what i needed anyway) but I did practice on an old set and when I get the time and money I want to do my own.....but they also sell the stuff you need to grind metal

DIY Porting

 

That engine combo sounds exactly like what I have, except my heads aren't ported, but the cam is kind of aggressive.

224/234 duration at .050

465/488 lift

114 LSA

and yes, the ECM does not run properly. I'm thinking of going down a little bit, mainly because the car's power doesn't really come on until 3000 or so RPM. I'd rather have a cam that came on around 2000.

 

sounds like a familiar grind there quick_trans_am
it was a cheap cam wasn't it? something like this:
Summit Camshafts: SUM-1105 - summitracing.com

That's not an aggressive cam by modern standards. You can get one now with the same upper end power, and keep your lower end power. And no, I don't mean by going to a roller cam...

f-bird'88 posted how to wire up a speed controller for a die grinder before. I bought a die grinder, that comes with a simple on/off switch (most of the lower end ones are like that), for $65, then built the speed controller for $20. Then the burs, sanding rolls, and cross buffs were another $150 or so... (Don't ask, I got royally ripped off...) I also used a dremel for some work.

 

sonic, AKA: mr. psychic detective.

Yes you are correct, that's the exact part number. Chris from CEcoatings hooked me up with it. Are you referring to porting the heads to regain the lower-end power?

 

oh no, sorry. I was talking to the other guys. They can use a die grinder, a cheaper one, and a speed controller, rather then just a dremel...


For you, a better cam is the only way to solve your issues. Your cam is a very *popular* cam, meaning that a lot of people buy them. But that's mostly due to price, availability, etc.... I'm psychic alright, that grind is copied by SO many other manufacturers, it's not even funny. Summit is cheapest however. Search some of sofakingdom's posts, he does a spiel about that cam every now and then Something about a relic from the stone age...

I'd recommend it if you needed to bolt the car together and sell it, but as a long term setup, it's a lame, old school cam, with lazy ramp rates. All the big cam drawbacks, none of the small cam creature comforts. Like vacuum for brakes, fuel mileage, and low end power.
Luckily, due to crazy aggressive ramp rates of new cams, you can have your cake and eat it too!

Example, that cam is quite similar to a compxe 268. 224/230. However, the comp only has 268/27x duration, compared to 282/29x duration of the cam you have. The advertised duration is what gives you the big cam drawbacks.
Anyway, it sounds like, from another thread of yours, that you're tearing down your shortblock? (If i've got my facts straight..) I'd seriously look into the compxe268, or, the lunati version of the same, the voodoo 60103. Crane I think has a Z cam, or powermax (whichever their newish agressive style is), that is similar.

"xtreme", "voodoo", "Z-cams"... They know how to sell cams, the letter x, v, and Z, are the coolest letters. If I could, i'd buy the "mega ultra xtreme Z-style cam"... It'd come in one color only, RACING YELLOW!!!! Just owning the BOX would give you 20HP!
/rant, ok, I just think it's funny the way they advertise these cams. Anyway, they are good cams, end of story.

 

thanks for clearing that up for me haha. I had no idea about that camshaft, I'll search for those posts.
Will that lunati voodoo that you run work with a non-roller style block?
My problem is I'm not literate with cam specs. I know some things, but I don't understand advertised duration, etc. (hint hint )

Yes, as stated in the other thread, I have to tear the block down to change the bearings, so now's a good time for a new cam.
Thanks for the advice

 

I was starting to write a tech article on cams. They are very misunderstood, and complex. I was just going to clarify some terms, etc.
I can email it to you if you want, it's not complete, but will shed some light.

Yes, the voodoo and compxe are both flat tappet cams.

 

Well, if you would, I would appreciate an email or PM with that article. Thanks!

 

ok, rather than email, i'll put this here, and leave it at the mercy of TGO, to correct anything I screw up:


ok, ramp rates are how fast the valve lifts off the seat.

Older cams, factory cams, etc, have "lazy" ramp rates. So, the advertised duration of your cam, (say it's measured at .006" tappet lift), is 282. This is the duration, in degrees, that your valve is off the seat. Leaking air past it, just a little bitty bit. You only start to get usable flow, at .050" tappet lift, hence why you also have a duration @ .050" spec. Yours there is 214*. (looking only at intake, exhaust is similar.).
So, 282-214 = 68*. We can call this number the "ramp". So you have the *big cam* feel of 282*, but the power, of a cam with 214* @.050".
So far so good? (*not all "advertised" duration is @ .006". So it's hard to compare cams if they measure it at a different spec. I think GM uses like .001", so their advertised # is HUGE.*)

So, you get a cam that has less advertised, it'll feel like a smaller cam (as far as drawbacks), and the same amount of duration @.050, and you get the same good points (power).
Now, looking at the compxe268. Advertised is 268, duration @ .050 is 224.
268-224 = 44* ramp.

So, the "old school, lazy ramp" cam, has 68* of ramp, whereas the new style comp xtreme grind only has 44*. The means it SNAPS the valve open faster. The time when the valve can only flow a little bitty bit, (between .006"-.050") is wasted time, only gives draw backs, no power there.
Capisce?

Downside you ask? Yea, it's harder on valve train. Probably won't last 200,000miles. oh well. You also need to use "premium" valve springs. So no bargain basement chinesium $23 valve springs. That's usually not a problem anyway. Comp981s are great for this application, $65 or so, fits stock heads, etc.

oh, side note, a roller cam, because it uses a roller, makes it easier to have even shorter ramps. There is less friction. Anyway, a roller cam is superior for many reasons, one is less friction = more power, but more importantly, the ramp rate can be crazy fast. Hence, more power (lift), without having to shift your powerband up high (duration).

 

i have a comp xe268 in my motor, it is a 305 headed 327, with this setup i have a decent idle (would be better with a 2000ish stall, you will have a much better idle with a 350) and good torque in the 2000-3000 range, 3000+ the thing screams!! i would say the xe268 would be good for you. Good Luck!

 

Very informative.

Will those springs you mentioned work with press-in rocker studs, or will I have to go to the screw in style? Is there a summit part number for the springs?

will a 1.6 ratio roller tip rocker work with that setup?

 

which heads quick?

yea, you can usually use 1.6 rockers. May have to enlarge the pushrod slot, lengthen it.

Press in studs; that's getting dicey. You can pull them out, and tap for thread in ones. You can do it yourself, if you don't feel the need to run guideplates. That's what I did. (mr gasket part, thread in studs, non-collared..)

Or you can pin your rocker studs. That's a nice easy cheap way to do it, and solves the problem. F-bird'88 posted how to do it a few times. I've got a bag of 1000 roll pins in that size if you want some supplies for it.

 

Just the 416 heads that I have, I'm going to try my hand a porting them, so now's a good time to do it.

I appreciate the offer, I may take you up on it yet

 

good choice.
Read all the threads so you know the "sweet spots".
You'll need carbide burrs, sanding drums, and a few cross buffs.
A 6" long burr is needed, and get one with a rounded end for that, not a flame tip, it'll be useless. A short flame tip one is good to have too.

Good luck.

 

Fortunately enough, my dad's got all that stuff at his place, I was looking at it today. Carbide bits, the works. Lucky me!