350 Upgrade Help/Suggestions

[Rogue67]

Hey guys, I'm new to the forum and just had a quick question. I have a 67 camaro with a sbc 350 as well as a 350 tranny. It's out of a 86 1500 Silverado, it's all refreshed but with stock parts minus a new edelbrock intake and 650 carb. I am looking to do a little cam swap including the comp 270 h magnum cam, magnum roller rockers ( non aluminum), air gap intake, new valve stems and springs etc, and possibly porting the heads a little bit cleaning them up ( stock heads, non vortec). Has anyone used this cam combo or anything close to it, and does anyone have a suggestion on another cam they have used? It's mainly a street car, I have some suspension done to it and looking for a little more power and sound on a budget while I continue to upgrade the suspension?

Thanks , Dylan

[Ron Sutton]

Hi Dylan,

The 270H Magnum "was" agood street cam back in the day. We used to build small block & big block street performance engines with this cam in the late 80's. It's an older single pattern design, meaning the lobe shape, lift & duration are the same on intake & exhaust.

A more modern design would be a dual pattern cam. They tend to perform better, where the intake & exhaust lobes are each optimized for the job they perform. A good dual pattern cam in a similar rpm range as the 270H would be Comp Cams "Extreme Energy" Series: XE268H.

An even nicer cam dual pattern cam, but more expensive, would be a hydraulic roller from the Comp Cams "Extreme Energy" Hydraulic Roller cam line: XR270HR
* This cam & lifters will cost more money.

You can see the specs for the XE268H here:
http://www.compcams.com/Company/CC/c...x?csid=86&sb=2

and compare them to the specs of the Magnum 270H here:
http://www.compcams.com/Company/CC/c...x?csid=78&sb=2

The specs for the XR270HR Hydraulic Roller are here:
http://www.compcams.com/Company/CC/c...?csid=187&sb=2
*Even though the duration at .050" is smaller on this cam, is puts more air/fuel into the engine due to more aggressive ramps & lobe shapes.

Before you pick a cam, 2 factors to consider are your rear gear ratio.
1. Depending on rear tire height, I suggest you run a 3.36-3.55 rear gear ratio, or lower (numerically higher), for either of these cams.
2. You can get away with a stock stall converter with these 3 cams, but just barely. Again, gear ratio plays a role here.


Another suggestion ... non cam related ... is while you have the engine apart, getting a new intake, etc ... You may want to consider upgrading to a set of Vortec heads. I assume if you had the budget, you'd add aluminum heads. But since you didn't mention that, you can pick up used, stock, steel Vortec heads inexpensively. Port them slightly to clean up flashing & the valve bowl area ... match the intake runner ... and have them freshened with a valve job, correct springs for the cam, etc ... and you'll pick up some nice power over the 1986 heads (stock or ported). This has been a low cost upgrade many street guys & Street/Stock racers are doing, as the heads are plentiful & cheap.

[Rogue67]

I have stock gears In the rear but looking at 3.83 gears in the near future, and with the converter I have a 2500 stall I'm going to throw in. Now wouldn't this cam theoretically give less sound/power since the lift and duration are different? ( I don't now much about cam specs and info) what is the benefit of having the intake/exhaust different? I have been looking into vortex heads but if I was to upgrade heads it would be too aluminum so I'm kind of skeptical on spending the money now when I really want aluminum.

Thanks for all the insight and suggestions

[Ron Sutton]

I have stock gears In the rear but looking at 3.83 gears in the near future

"Stock" doesn't narrow it down, as cars have come stock with gears ranging from 2.56 to 4.11. Figure out what you have. You can make 3.08-3.42 "work", but 3.55-3.73 would be better.

and with the converter I have a 2500 stall I'm going to throw in.

Good.

Now wouldn't this cam theoretically give less sound/power since the lift and duration are different? ( I don't now much about cam specs and info)

Which cam are you referring to ? ... the XE268H or the XE270HR?

what is the benefit of having the intake/exhaust different?

Decades ago, camshaft builders made many cams with all the lobes the same, because it was simpler & cheaper. But it was always a compromise. Anytime you're slapping a lobe on the exhaust side of the engine, just because it was what worked well on the intake side, that's a shortcut, and does not optimize performance of that engine.

Dual pattern cams are not new. Cam designers have been using them for decades. It just takes time & testing to work out what lobe profiles work best on the intake ... and what profiles work best on the exhaust ... and they are not the same. When you buy a dual pattern cam, in most cases, the intake flow & exhaust flow are each optimized to create more power & a better, wider, more usable powerband.

What is new-ish (been around 20+ years, but on the down low) are 4 pattern cams, meaning the opening ramp on the intake is different (faster, steeper, sometimes even reverse flank) than the closing ramp (softer, gentler, to reduce valve bounce) on the intake lobe. And, the opening ramp on the exhaust is different (fast, but not as fast as the intake) than the closing ramp (quicker, to achieve longer valve openings) on the exhaust lobe. They are optimizing the opening ramp & closing ramps on each lobe ... not just opening & closing it at the same rate.

I have been looking into vortex heads but if I was to upgrade heads it would be too aluminum so I'm kind of skeptical on spending the money now when I really want aluminum.

I understand.

Thanks for all the insight and suggestions

You're welcome. All the guys on this Forum have different strengths & experience that makes it fun & helpful for all of us.

[cornfedbill]

Your block may be roller ready.

Does it have the bosses in the valley like this one?



If so, you can use the less expensive OEM roller lifters, the anti-rotation plates and "spider" from a junkyard donor. You will also need to thrust plate from the front of the block behind the timing chain.

Check before you buy a cam. A hydraulic roller cam from Howards Cams is about $250. The conversion parts vary depending on if you can find used ones.

I am running a split duration Summit cam in my 377. The split duration cams are much better than the old style cams. I ran out of money to by the Lunati Voodoo cam that would have been my first choice.

I would recommend looking into converting to Vortec heads. I did and they beat my old camelhumps all to peices from idle to redline. They can be had for as little as $200 a set if you watch Craigslist.

[Ron Sutton]

Thanks for sharing your experience Bill.

I'd like to hear more about your 377" Vortec engine combination.

What cam? Compression? What intake manifold?

Did you dyno your old combination & new combo?

Thanks for sharing.

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

Dylan, one thing to consider if you switch to the Vortecs, is with performance valves springs that simply replace the stock Vortec springs, you are limited to valve lift of around .470" ... so you would want to pick a dual pattern cam that has .470" lift or less, which eliminates the suggestions above. (The XE268H might work. It will be close. Your engine builder would need to measure closed & open heights before buying the cam.)

Or ... you could change the spring & retainer style to a special trick piece Comp Cams offers, which lets you run valve lifts up to .540" on these Vortec heads. But this costs more money.

Not trying to talk you into anything ... just want you to be informed ... to make the decision that works best your goals & budget.

[Mr_Roboto]

As mentioned checking for roller vs non roller should be your first priority. These blocks came 4 ways:
-Roller gear installed
-Roller cam bosses tapped and drilled
-Roller cam bosses present but untapped. Can tap your self if you're careful.
-No roller bosses. Never really had much luck on these all the 350 TBIs I ever got were like this.

Secondly those should be 193 "swirl port" heads. Considered by most not to be a good performance head. If you keep within their lmits they're not bad. Look up Fast305/Fast355 on thirdgen and Full Size Chevy he has done a ton with these. I would cam before I would do heads though unless you want to go high lift. They have a very good intake to exhuast flow ratio so you may want to consider a single pattern cam. I would do back cut valves and a good valve job at the very least. They will pick up considerable flow at low lifts where it will do you the most good.

Thirdly valve train is important. If you're set up for positive seals on your retainers you may need to look into changes to increase lift such as retainers or removal of the positive seals from the intake side and going to old school umbrella seals. I wouldn't want to run any aftermarket cam hardly without springs. On a lot of older engines the springs can wear out and should be changed. It's definitely on the slate for my Pontiac. I would Definitely want to do break in of any non-roller cam with the old springs though just to prevent wiping a lobe.

Lastly I will say that you should take this advice with a HUGE grain of salt. Any engine that's been around nearly 20 years takes the risk of having changes made, and you know yours has had changes made. I would verify the head castings before thinking about head and cam work.

[cornfedbill]

Thanks for sharing your experience Bill.

I'd like to hear more about your 377" Vortec engine combination.

What cam? Compression? What intake manifold?

Did you dyno your old combination & new combo?

Thanks for sharing.

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

Dylan, one thing to consider if you switch to the Vortecs, is with performance valves springs that simply replace the stock Vortec springs, you are limited to valve lift of around .470" ... so you would want to pick a dual pattern cam that has .470" lift or less, which eliminates the suggestions above. (The XE268H might work. It will be close. Your engine builder would need to measure closed & open heights before buying the cam.)

Or ... you could change the spring & retainer style to a special trick piece Comp Cams offers, which lets you run valve lifts up to .540" on these Vortec heads. But this costs more money.

Not trying to talk you into anything ... just want you to be informed ... to make the decision that works best your goals & budget.

Sorry for the late reply.

Camshaft - Summit Racing SUM-1105

Pistons - Silvolite hypereutectic flat top claimer pistons with high compression height so the pistons are flush with the deck

10.6: compression

Comp cams 1.6:1 full roller steel rockers

400 block bored 0.030"

Scat 350 steel cast crank

Ported Vortec heads with stainless 1.94"/1.60" valves. I also re-cut the spring pockets.

K-motion K-700 valve springs

Edelbrock Super Victor Vortec intake with a Holley 3310 vacuum secondary 750 CFM carb. Will be changing to EFI.

No dyno pulls. I just ran dyno2000 to check it out. It should be about 400 HP and 425 lb/ft torque. All I know is that it pulls hard right off idle, idles reasonably and makes great tire melting power.

[Ron Sutton]

Hey Bill,

Thanks for sharing. A few questions ...

1. What does your timing curve look like? ... and did you have to tweak it to avoid detonation?

2. What top end rpm does it "pull to" & still make power without nosing over?

* Side Note: You're one of the few I see running a Super Victor instead of a Victor Jr. We run Super Victor's on our 408" engines that rev 7500rpm.

[cornfedbill]

Hey Bill,

Thanks for sharing. A few questions ...

1. What does your timing curve look like? ... and did you have to tweak it to avoid detonation?

2. What top end rpm does it "pull to" & still make power without nosing over?

* Side Note: You're one of the few I see running a Super Victor instead of a Victor Jr. We run Super Victor's on our 408" engines that rev 7500rpm.

The timing curve is not right yet. Vortex heads burn fast and like about 30 degrees total advance. I have too much mechanical advance and had to back off timing at idle more than I wanted. In will recurve the distributor when I get it back in the car.

In theory, it will pull to 6500. But I did not have it on the road enough to really work it hard. The mule I used did not have a tach, so I took it easy at the top end.

It seems to like the Super Victor. I was worried at first. But I was pleased at the throttle response and low RPM torque. I think it likes the mild can and ported heads. I used a Super flow bench to make sure my porting worked.

[Ron Sutton]

That's good to hear about the Super Victor.

Thanks for sharing your info. Take care!

[Ron Sutton]

Hey Guys,

I'm on the Forum today for a few more hours ... then I'll be gone for a week.


I'm meeting up with my friend Neil Porter at Sears Point where he's running 2 formula cars in SCCA racing.





Then I'm camping with my girls the rest of the week.





I'll be back online late Thursday (7/11) or Friday morning (7/18).