Here goes . . .

I built my engine some 3 years ago with the help and advice of several friends. My engine is a pre-hydraulic block with a hydraulic roller cam and mechanical roller lifters. In the past 3 years of working on this car I have found that this is NOT an ideal set up and I seem to be doomed to having valvetrain problems.

Questions -

Has anyone swapped in a pre-hydraulic SBC into their 3rdGen and used TPI?

Yes? What kind of valvetrain are you running?

Would it be smart to simply replace the hydraulic roller cam with a solid roller cam or swap in "pre-hydraulic lifter" hydraulic roller lifters to go with the cam?

I'm just looking for some warm fuzzies and the light at the end of the tunnel here guys. I'd appreciate any advice you could give me.

 

When you say pre-hydraulic, do you mean pre-roller cam? Chevy has been using hydraulic lifters for a very long time. Roller cam blocks were introduced in 1987. For reliable performance you want hydraulic lifters. Solid/mechanical lifters require periodic valvetrain adjustment. Do you know the specs of your current cam? It may be too large for your application, or maybe not compatible with your computer if you have one.

 

There is some term confusion going on here...

Do you really mean "pre-roller" not "pre-hydraulic"? Even 1955 blocks came with hydraulic lifters.

Solid lifters on a hydraulic cam, roller or not, is a recipe for potential problems. Sometimes it works well, sometimes not so well. I've had numerous motors where people have done that. It won't generally cause parts failures or anything disastrous like that, but the cam profiles are designed differently for several reasons; sometimes the engine runs kind of funny.

TPI does not care whether the block is pre-roller or not, or whether the cam is a roller or not. All it cares is that the cam be sufficiently weenie so as not to bump the engine's peak volumetric efficiency much above 3600 RPM (its approximate "tuned" RPM), and that the VE peak be near 3600 RPM. There is no issue to be discussed there.

What cam profile do you have? What induction system are you running?

What valve train problems are you having? Maybe somebody can shed some light on it if you told about the actual malfunctions.

 

First of all - sorry about the messed up terminology - I do mean a pre-roller block. I'm just stressed over this thing.

I recently had a pushrod bend and brake.
It took a lifter out in the process.
The pushrods were stock replacements.
I bought a pair of replacement lifters and some good moly pushrods.
The cam is fine and there was no debris in the oil galley.
In the process of researching Crane and Comp for replacement parts I ran across my cam specs and realized that I had used a BIG hydraulic roller cam in a pre-roller block while using mechanical lifters.
HR cam + pre-roller block + mechanical roller lifters = ???

Original specs-
1989 IROC - Mass Air
305ci TPI - 5-speed

NOW -
1989 IROC - Mass Air
355ci
SuperRam
Edlebrock Bigmouth intake
52mm TB
1.5 roller rockers
mechanical roller lifters
nasty HR cam
AFR190 heads

*Still running the stock prom and injectors*
I've been adjusting the fuel pressure, IAC and TPS to appease the ECM as best as possible until now.
I have some 24lb injectors for the car and I'm trying to find someone to burn a chip for me.

I NEED the cam advice though while the intake is still off.
I believe that I need a new cam. I'm not sure what to look for though.
Is there any other info that I can give to help?
The car is my weekend warrior and not a daily driver. I'm looking for good power without getting 10mpg on the highway.
It's a hobby car.

COMPETITION CAMS CAMSHAFT SPECIFICATION SHEET
PART # 08-432-8
GRIND NUMBER: CS XR282HR-10
ENGINE: CHEVY SM BLK 305-350
INTAKE EXHAUST
VALVE ADJUSTMENT HYD HYD
GROSS VALVE LIFT .510 .520
.006 TAPPET LIFT 282 288
VALVE TIMING OPEN CLOSE
AT .006 INT 35 BTDC 67 ABDC
EXH 78 BBDC 30 ATDC
THESE SPECS ARE FOR CAM INSTALLED
AT 106 INTAKE CENTER LINE
INTAKE EXHAUST
DURATION AT .050 230 236
LOBE LIFT .3400 .3470
LOBE SEPARATION 110
THIS CAM SHOULD USE SPRING # 986-16

 

The mixing of terminology has me a little confused, so bear with me.

If you are using the HR cam with flat tappet hydraulic lifters, you probably already know the answer to this. A roller cam with flat tappets usually results in the destruction of both. The roller billet is not designed for sliding friction, and the profile may be exposing the edges of the lifters to the ramps.

Worse yet, the profile of a roller is designed for a single point of contact (the lifter roller fulcrum) and will operate the valve train completely differently than intended if used with a flat tappet lifter. The extremely high acceleration rates you would be producing with a flat tappet on a roller grind could explain the bent push rods, and would probably eventually lead to more valve train damage.

A HR cam with solid roller lifter would still present some mechanical problems, but not quite as severe. There is usually a pre-lash ramp on hydraulic cams that is designed to quickly actuate the lifter for a short distance (about 0.030") to close the oil check valve in the lifter and make it hydraulically lock at the desired height. This ramp could be stressing the valve train when used with solid roller lifters, since it is usually higher and steeper than the pre-lash ramps on solid roller cams. That may explain the bent push rods as well.

Either way, you have a component mismatch and need to rectify that before running again.

You would have to verify the cam lobe condition with a dial indicator. If every lobe of the cam is still servicable, the best solution may be to change to aftermarket hydraulic roller liters and the appropriate push rods to achive the correct geometry. Obviously, any failure of any of the cam lobes would require its replacement. At that point, you'll have to decide if the route will be flat or roller, hydraulic or solid, and install ALL the appropriate components.

 

Informative as always, Vader! Thanks.

So I can buy a regular set of hydraulic roller lifters and be safe?
As long as the cam is still good and I buy the appropriate pushrods, correct?

 

That XR282HR is a wicked carb cam, but highly unsuitable for fuel injection. I have one in my 400. With a 383 you could possibly run one with tha much duration if the lobe separation was wider, like 114° instead of its stock 110°.

The solid/hydraulic thing isn't what's eating pushrods. More likely you need some better valve springs. I have no idea what AFR puts on their heads but the first thing I would try is a set of Comp 986 or 987 springs. If you run that XR282 with 1.6s you should definitely go with the 987s.

Is that the cam that's there now, or what you are considering?

 

It's the existing cam.
I agree on it not getting along with my FI but it raps out SO quick!
I've run the engine up over 6000 rpm many a time in this car - the idle blows tho.

What would you recommend for a FI cam?

I think I'm just going to get the Comp hydraulic rollers I found at Summit. Do I have to worry about pushrod length if I run my hydraulic cam with hydraulic roller lifters?

I need to go to the Comp Cams site and dig around . . .

 

If you want to get another cam, and you like the way that one runs, get Comp to grind you one just like it except on 114° lobe separation.

Another possibility would be their "306" grind.

You probably need longer than stock push rods with a cam with that much lobe lift, to achieve optimum geometry. In my 400, I ended up with .150" inch long ones, which is 7.450".

The Comp lifters will work fine. Jowever, there's a shortage of hydraulic roller lifters nationwide just now; I ended up buying a set of Crane ones a couple of months ago when I was building a motor, because they were all I could find. It doesn't matter all that much whose you use.

Don't waste your time and money on a custom chip; get into PROM burning. You can get the results you want that way, not the results someone else wants; and everything you need to do it costs less than one custom chip.

 

You're right about the hydraulic roller lifters - no one has the Comp Cams ones - not even Comp Cams!
And when they do, they'll have a new version that costs over $450.
I'm not liking that noise.

Time to look at Crane . . .

 

Why are you trying to run such a big cam in a TPI motor.
The TPI runners are tuned for low and midrange power.
That is Y they call it "Tuned Port" .. Get a cam the augments
this low-- midrange tuning. Let the heads make the horsepower.
Your computer will suddenly work right too.

Pick something milder and get the right valvetrain parts with it.
Sell that cam to some one with a carbed street racer.

If you can't get the right hyd roller lifters, just
buy a flat tappet hyd cam and kit, put that in till ya can get some roller lifters and sort out the mess.

Even a budget generic cam and lifter set will do nicely

try 214/224 .442/.465" 112 From Summit. $about 100
This is the same flat tappet cam John Linkenfelter sells
for TPI on his web site.

 

Pre roller block..Roller block cam..Solid roller lifters on a hydraulic roller cam . 230 @.050.....Sounds like a conglomeration of mis matched componets.

Lonnie