roger3

I just ordered a hydraulic roller cam for my 76 vette with Bbc. Switching from my solid roller for a couple of reasons;

1. Hoping to get a wider band of power. My current setup makes good torque from about 3500rpm to 5500rpm, then runs out of umph. Running 11.6 in 1/4 mile, so I would like to maybe improve on that a little.

2. Trying to avoid the solid roller lifter failures that cross the forum from time to time.

3. Low vacuum at idle (soft brake pedal, slow head lights, etc). Not a major player, but will be beneficial.

Here's my engine/tranny details.
468 bbc
540 hp at crank with Solid Roller cam (292 duration/635 lift)
990 heads
10:1 cr
Rpm air gap
1000 Pro System Holley Carb
350 auto trans with shift kit
3500 PTC stall converter
3:36 gears
Mt ET street radials
340 composite rear spring

Cam is going is custom grind from Chris Straub.

Along with cam I will put in new valve springs and have the heads gone through, new push rods, Morel lifters.

Any ideas, tips, comments, please let me know. This is a learning curve for me.

What's the overall gut feeling about matchporting heads and intake? Worth doing, or not much gain to be had.

Roger

DRIVESHAFT

Chris seems to do a very good job of designing cams. I'm sure you'll be happy.

As far as port matching goes, unless the match is way off the best thing about port matching is that it makes you feel good.
There is very little horsepower to be had in doing it.

I would like to add my 2 cents on the cam selection though, in case the way you phrased your post confuses someone later on.
Hydraulic rollers do not inherently produce a wider power bands than solid rollers do.
Hydraulic roller cams do not inherently create a higher vacuum level than a mechanical roller for similarly speced cams.
I'm sure your new cam will give you those things. But it's becasue Chris is good at his job, not because your cam will be a hydraulic roller.

Les

Good luck with the new cam. Regarding the value of port matching, I recall seeing a couple sources over the years say that it's of little value until you reach the 500 HP level and then it starts to pay off. Since you're over that level it may be worth considering. Before I changed heads and intake, I port matched the the factory pieces but I made too many other changes to tell if it made any difference. My builder was also a friend, so he set me up so I could hog out the ports and he did the finish work. Very enjoyable and satisfying, FWIW.

rponfick

I am also anxiously awaiting a Chris Straub hyd. roller for my L-71 BBC, which he is also preparing Brodix race rites for. Mine will be strictly street, so a lot tamer than your's.

You didn't list your new cam specs, but I would assume something less than you have now?

May the force be with us.

Ralph

gkull

If you have a 292 SR cam you have something very screwed up if it runs out at 5500 rpm. My first thought is that you must have small heads and a restrictive intake.

You should be able to turn 7500 rpm if you had matching components.

a 292 also needs 11:1 compression and headers with free flowing 3 inch exhaust.

So buying a lessor duration H-roler isn't going to get you more rpm

Rebelrob

I went from a solid roller to hyd roller. The vacuum is about the same or even less, even with a lower lift/duration. I seem to have a better throttle response at lower rpm's than I did before. Engine responds better for just casual cruising. I was a statistic to your #2 concern.

cv67

Wondering if you were running out of valvespring or fuel pump?!

Let us know how the new stick works out Chris has had some real good results.

Curious to hear your impressions of the HR over the SR

I worry about it too sometimes but just cant get a hydraulic through the noggin love the way these solids want to rev

roger3

Driveshaft,

The cam I have is an older Reeds cam that was in a Chevelle and the previous owner said vacuum numbers were not a concern to him when he selected the cam. So you are right I hope to improve on things with a better cam profile not because it's a hydraulic roller, good point, I don't want to confuse anyone.

Thanks

roger

roger3

Ralph,

I just placed the order yesterday. We talked generalities about the cam so I don't have any specifics yet. Biggest improvement I hope will be a wider power band, and better low end torque. Both of which Chris thinks is attainable.

What is your engine combo? What Is your goal with cam and Brodix heads, it should be a strong motor.

Roger

roger3

Gkull,

At 5500 rpm my engine is not pulling hard. I am running stock 990 heads and Rpm Air Gap intake so I don't think they are restricting me. My valve train is older so maybe my springs are weak, I really don't know. I haven't heard them floating, but I am running Hooker side pipes with inserts that are pretty loud.

Headers are 2 3/4" tubes, but maybe the insert is too restrictive? I have not tried running the car without the inserts.

CR is 10:1.

What changes do you recommend to my engine combo?

I do think my heads are too big, but the car runs 11.6 sec 1/4 mile which is decent with 3:36 gears. I just wanted to get an optimum cam for my combo and in the process get away from solid lifters which has scared me after seeing a few failures on this forum.

Roger

roger3

Rebel rob,

Yes sir your thread documenting your lifter failure got my attention. I have checked my valves every three months or so since reading it. It's confusing to read posts saying some solid rollers go thousands of miles with no problems but others fail after only a couple thousand miles or less. My engine has about 2500 miles and 70 passes at the track. Lifter failure stays in the back of my mind.

Are you happy with your engine performance now?

Roger

roger3

Cuisinartvette,

How do I tell if my springs are weak? I Don't know what springs I should have. I don't have the actual cam specs only the numbers from the end of the cam. Reeds cam is no longer in business.

When I had the engine dynoed it showed that my stock GM mechanical fuel pump had low pressure (2.7 psi) at high RPM's. I replaced it with an Edelbrock high volume mechanical pump. Thinking of maybe switching to electric, but I want to first hook up an O2 sensor and check the air fuel ratio when I am running at the track and see if it's running out of fuel.

Chris is going to try and get the cam finished by the end of next week. If he does I'll install it by new years, otherwise it will be in January. I'm gonna dyno the engine again so I will be able to compare hp and torque, then run it at the track, lot of money so I sure hope I am going in the right direction.

Thanks

Roger

roscobbc

Which Brodix heads are you using - I am using RR Ovals - interested in your cam spec's too.

rponfick

I will be running the Race-Rite rectangular ports. I want to use my tri-power intake and it is rec. port. I also will be running the stock Corvette BB exhaust manifolds, so another reason I went with RR's with stock exhaust port location. Compression will be near 10-1, 3:55 gears, TKO 500 overdrive tranny.

I was aware that the RR exhaust port will not flow as well some other alum heads, but Chris said no problem. He will just design more exhaust duration into the hyd roller to account for same.

As I indicated, this will be strictly street engine, so Chris recommended a less aggressive cam than I had thought I wanted. He indicated that you have to take about 18 degrees out of a flat tappet cam to get to a comparable roller. He has suggested: 620/590 lift, 222/236 duration at .050, 109 lobe separation.

Ralph

I am aware of the debate that rec. ports are too large for street, and you give up some horsepower by not running headers, but this is what I will be running.

gkull

It is not right in front of me so I can't tell where the problem is. But your big retangular port 990 heads and that cam should happily rev to 7000 rpm.

Is your intake manifold a large port made to match 990 heads? Valve float is not something you hear. It is generally just a drastic drop off of power.

I have never been a side pipe man. They are not tuned length pipes like long tude headers. Then the baffelling is often very restrictive.

roger3

Gkull,

Intake is made to match the 990 heads.

Sounds like I need to make some passes without the baffles.

New cam with correct springs will let me rule out any problems I might have with my springs.

It's a long story and I got screwed when I bought my motor but I don't have much faith in the valve springs. They might have been sitting in the engine for years without the engine being turned over.

Roger

68thumper

I suggest converting to EFI. I love the Holley HP EFI on my wife's Vette. Never had fuel injection on any of my cars but after playing with the EFI system I decided to ditch the brand new Quick Fuel carb I bought with a new Edelbrock RPM air gap for my '71 Camaro BBC. I paid about $500 to have a local race shop install the EFI fuel rails on the air gap manifold.

roger3

68thumper,

I'll have to get past this cam swap first. This will cost about $2k with dyno.

Did your engine performance improve throughout your total rpm range, or mostly at idle and low RPM's? Do you race your camaro? If yes, did the EFI help yor times. Where did it help the most?

Thanks

Roger

gkull

Roger, did they give you the specs on this new mystry cam?

68thumper

I bought the Vette last year from a forum member and it came with the EFI. The car runs well from idle all the way to redline. I like being able to enter idle speed, timing, A/F ratio on the laptop and have it take effect real time. Beats changing jets and messing with distributor springs. I am putting the same EFI on the '71 Camaro which is a street car; never raced. I am also adding a crank trigger and cam sync for distributor less ignition...