Cam you dig it?

[CopperNick]

So, for Project Regress, one thing that has been on the back burner for its engine is the cam. At present, the resident cam and associated components are factory stock, and the plan was to get the engine running well before tinkering with its innards. That said, I do happen to have an Isky 256H flat tappet cam and related geometry sitting on Indian work bench #2 and the plan had been to do a cam swap. The 256H is not a high lift cam, if fact it falls into the RV category, it is about torque for low end acceleration and the one currently resident in my Van works and works well. It does like to sneak up on you around 35-40 and surprise you by coming on at that point. Around town you have to be careful as it will easily put you over the speed limit without too much rpm needed to do so.

The problem here is that lifters for flat tappet cams have been getting a very bad rap for some time in the quality control department. The lifters that I have came as part of the package that I ordered and they predate the chinesium versions that do so love to fail, but...........

What I am now considering is a roller version of the 256H. I have paid a visit to the Isky site but did not see anything that seemed to match what the 256 has for specs. This is not a race cam I am looking for here and it seems that Isky equates rollers with racing, understandably I suppose. The biggest benefit to the 256 was that it could be slipped into place without worrying about valve springs or shims or valves hitting piston tops. This cam is about duration, not lift. And that would be one of the primary requirements for any roller cam that I would elect to acquire. Think of what I want as being a highway cam with ability to step out and readily deal with the Susie slowpokes that seem to pop up out of nowhere on the Interstates.

Any thoughts, ah , oh yeah, American Made and never to see the asphalt of a drag strip.


Nick

 

[carnutjw]

Not sure what vintage your engine is, but assuming factory hydraulic roller, something like this?

https://www.summitracing.com/parts/sum-8800/make/chevrolet

They have larger ones too.

 

[Bonnewagon]

I am all Pontiac, but BOP engines are all torque monsters. I used a Crane H-260-2 cam in a 350 and a 400 Pontiac. [260/272- .427/.454] As you said, that short duration placed all the power at low RPM's. The 350 loved it, and really woke it up. The 400, with it's larger displacement, not as much as the 350. But both engines could climb trees with all that bottom end grunt. Both were out of breath at around 4500 RPM. But from idle to there they just flew. My cruise RPM was around 2000 RPM and very economical. Pontiac engines like dual pattern cams, biased towards the exhaust side, and the stock heads flow well up to .500", so you can see how that cam worked perfectly with a Pontiac engine.

 

[565bbchevy]

I would look at Howard's cams.
I have their hydraulic roller with retro fit lifters, works well in my 355 SBC.

 

[CopperNick]

Carnutjw, the motor is an 85, 305, same as my Monte. The year makes it a flat tappet cam as rollers didn't start showing up in SBC's from the factoy until the introduction of the Vortec block with the one piece rear seal, among other changes.

To go roller in a flat tappet block, the roller lifters have to be paired together using attachment straps because there is no way to use the vortec cam valley "frog" or roller retainer, the bosses for the attachment bolts aren't there for one thing.

For another, roller cams in a high torque medium HP application, like exists when you are towing or rolling heavy, seems to be something of an oxymoron. Say roller, think High Perf/high winding mill; think RV, think Low/Med Perf work mill with Torques out the wazoo.

As for alternatives, i did give some thought to the Howards cams but they seem to come with a high buy in and a complete kit would be 1500 or more in CAD.

For those who would immediately point out the limitations of the 305, and yes , they are legion, the option to go bigger in terms of cubic inches is there, but it would mean building that 400 block that I have which would entail $$$$$$$$$ since it is just that, a bare block. Plus which one of my build parameters was to stay fairly close to what the factory installed for a drive train while "upgradiing" a couple of the less durable components that got used, and adding a surprise or two to dismay the earthworms; the guys that like to hit the ground and peek beneath the vehicle to see what's what.

And I don't think it is possible to match roller lifters to a flat tappet camshaft. but if anyone on the board has done it successfully, I would sure like to hear about it at the nitty-gritty level.



Nick

 

[78Delta88]

What's the block number on your 305?

256H at .006...(advertised) ? Should put you about 212 at .050. The 212 cam ok for basic street and lift much better than stock, but for The 305 I like closer to 220, but just my preference that's all.

I have a test engine just never finished due to covid silliness so still in storage. I was building two test engines, just for curiosity sake. Hydraulic flat cam with roller lifters and the other long duration roller cam with moderate lift using solid lifters. So basically a flip flop of what it should be.

I figured it will either work or blow up.

The issue with the flat cam is the lobe profile. With using the rollers and should work, max lift comes on and leaves very quickly. A good SBC doesn't have a filling issue, mainly a scavenging problem and I think this is where the limits will come into play.

One thing I think you will have to do is when built, crank by hand and watch the rocker geometry. I was going to use roller tip rockers so I could watch the path of the tip on the valve, film it and watch on the lap top. This would also allow me to measure the angles as the rocker moves through its travel.

Unfortunate at this point never finished or had it running. Theoretic is should work, but then again as Mad Max put it..., "A-pocky-clips, and full of pain!!

 

[Yav8]

You could look for a stock running 305 or 350 vortec form 96-2001 and it would be better then your stock 305 with a cam. only thing needed would be a electric fuel pump and a intake. Everything bolts right up. These are all roller cam motors. The 350 stock vortec would be the best choice. There are 305 out there but not a big seller so they can be had for CHEAP. Any marine motor would be a good choice if you could find one in the vortec years 96-2001. 880 casting for the 350 not sure for the 305.

 

[Bonnewagon]

Nick does that 305 have pressed-in or screwed-in rocker studs? A buddy had an '85 or so Camaro and he had a pressed-in stud get pressed OUT by the cam. It wasn't even a high lift cam, just an RV type but with a bit more lift than stock.

 

[CopperNick]

What's the block number on your 305?

256H at .006...(advertised) ? Should put you about 212 at .050. The 212 cam ok for basic street and lift much better than stock, but for The 305 I like closer to 220, but just my preference that's all.

I have a test engine just never finished due to covid silliness so still in storage. I was building two test engines, just for curiosity sake. Hydraulic flat cam with roller lifters and the other long duration roller cam with moderate lift using solid lifters. So basically a flip flop of what it should be.

I figured it will either work or blow up.

The issue with the flat cam is the lobe profile. With using the rollers and should work, max lift comes on and leaves very quickly. A good SBC doesn't have a filling issue, mainly a scavenging problem and I think this is where the limits will come into play.

One thing I think you will have to do is when built, crank by hand and watch the rocker geometry. I was going to use roller tip rockers so I could watch the path of the tip on the valve, film it and watch on the lap top. This would also allow me to measure the angles as the rocker moves through its travel.

Unfortunate at this point never finished or had it running. Theoretic is should work, but then again as Mad Max put it..., "A-pocky-clips, and full of pain!!

Block casting number?? Hadda ask, dintcha? Being as how i plan to be in the shop this pm for a minute or two in order to test fit the bits for the support frame for the winch that is getting installed on the press to help with lifting and dropped the press deck, i can add a few more minutes to see if I can candle the block beside the time and try to see the numbers.

All I know for sure about this engine is that it came out of an 85 C-10 pickup and I drove the vehicle home from the seller's home without any problems. Would have been nice to keep intact but too much to safetly and no where to park it. Besides which, I needed a mill and the transmission; dude up the block wanted the truck box, (still has it on a trailer in his back yard (LOL)) and the rest went for scrap.

Funny thing you should mention Vortec 305 because that is what came out of this car, along with a 200R4. Never could get that motor to run right. Still have the long block sitting on an engine stand. The "Vortec" is not guaranteed right because it had a mechanical fuel pump so, if correct, it must have been pre 90. Think the biggest issue was that whoever dropped the mill tried to mix and match the ignition components in order to decommission the CCC unit and made a botch of the task. The CCC was dead; made sure of that myself, but the carb was probably still a "controlled" variant of the Q-jet that needed the various inputs to respond correctly and ran either rich or lean without them. Ignorance truly is bliss in some cases. Throwing a Holley spread bore base carb and HEI at the problem was a stop-gap that sort of worked.

All of which is why I went back to the year correct engine for the car. Back in an hour or so.


Ah, Bonnewagon, pressed. Same/same for my van engine. That was another reason for going with the 256H back at the time when I did the van. The lift is virtually unchanged from stock, it is the duration of the cam that is longer so it can allow more air/fuel in and generate more torque and greater efficiency of sorts. That cam in that motor has gone down both I-35 and I-90 on a regular basis and easily kept up with the squirrels and idiots. it is even happy in commuter traffic although I have to be extremely careful as to how much waa/waa pedal I use because it WILL come on faster than you'd think.




Nick

 

[78Delta88]

85 C10 should be the 305 HO. Last I heard was GM put the HO in vans and trucks. Over the years pulled several from vans that were

As far as the 305 Vortec those were the best heads for the 305 even though GM did not cast the runners like the 350 Vortec. I was thinking 527. But just checked list. 305 Vortec should be 058, the 350 was 880. TBI is 627

The 85 HO should be ... Last 4 = 4766. If it is (last 3) = 201, 202, 203, you can add The conversion caps and make 4 bolt main. And I have seen L69 HO with the 202 block from factory. So, not everything set in stone.

The best head for 305 was the Vortec head, next was the 416 and 601 HO heads, next to that the HP 283 will raise SCR, so good for dished but don't use on flats with today's fuel, even with 91 octane may detonate.

On the CCC, open loop (or disconnected) will run rich.