Thread: 355 build HP and Torque?

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Richard/Techinspector,

Good to hear the latest from you and Pat as well. Just how "bad" are those roller tip rockers? I just got finished (yesterday) replacing a potentially troublesome 1.6 set with the 1.5 set from Speedway. Pat, do I understand you to say that up to about 0.045" off the block surface will still match up the intake ports in a non-smoke way, I have an Edelbrock Performer RPM on heads that have been resurfaced by 0.020".

Don Shillady
Retired Scientist/teen rodder

Originally Posted by rollie715

Thanks for the reply. Where do I find the 29 deg ABDC number?
The CompCam link says 56 deg. Am I reading it wrong?
Here's the link:
08-410-8 - Magnum

If it was 56 deg, would the 18cc dishes still be ok? I hope to be verifying the cc's on the heads in the next couple days and can calculate the actual SCR and DCR before I order the pistons and have the block bored.

I purchased and am studying the following two books by David Vizard. Thanks for the suggestion.
How to Rebuild Your Small-Block Chevy
How to Build Max Perf Chevy Small-Blocks on a Budget

Glad to see that you have taken the initiative on buying and reading books relative to your project. Good job!

There are several different ways to measure the opening and closing points of the intake and exhaust valves. The 56 degree figure is measured at a tappet lift off the base circle of the lobe of 0.006", (six thousandths of an inch). That's pretty much standard for a hydraulic tappet camshaft and is used by most of the cam grinders, shown as "advertised" duration. For some reason, Comp does not publish the tappet lift at 0.050" in their specs like some of the other grinders do, so you have to figure the 0.050" lift for yourself. You need the 0.050" lift figure to use the Dynamic Compression Ratio calculator on the Keith Black Piston site. It asks for you to add 15 degrees to the 0.050" figure in order to calculate the DCR.

Take a piece of paper and draw a circle like the circle seen on the 08-410-8 timing diagram, the one where the 106 degree intake valve centerline is shown. Make a pencil mark at about 7:30 O'Clock as is shown in the diagram. That is the centerline of the intake valve, in other words, that's the max valve lift position. On either side of that 106 mark, the valve lift is decreasing. Somewhere inside the circle, write the 0.050" duration, shown in the diagram as 206 degrees. Draw a line under that and write 103 below the line. This is just to help you keep track of the numbers you need to use. 103 is half the 0.050" duration of the intake valve.

Now, if we assume that the action is going counter-clockwise on the circle, we can begin at the 106 degree intake valve centerline and go clockwise toward top dead center to find the point where the intake valve is beginning to open. If we move 103 degrees (half the 0.050" duration) from the centerline of 106 degrees, we find that the intake valve opens at -3 (minus 3) degrees BTDC. The intake valve opening is always expressed as opening before top dead center, so on a short cam like this one, we have to show the open as minus 3 BTDC, because it actually occurs at ATDC going counter clockwise. But since we must always show the intake open as some value BEFORE top dead center, we will use the minus sign to show the opening point properly. I may be spending too much time on this, but I want to make sure you understand what you're doing.

Now, we have the intake opening at -3 BTDC. If we go counter-clockwise from that point down to bottom dead center, we have travelled 177 degrees (180, or half a circle, less 3). Now we have to figure how many degrees past BDC the intake valve closes. If we know the 0.050" duration of this grind is 206, then we can subtract 177 from 206 and find that the intake valve closes at 29 degrees ABDC @0.050" tappet lift. How cool is that?

You can do the same thing with the exhaust valve if you want to, just do it in reverse, where the exhaust centerline would be at about 4:30 PM and you would go counter-clockwise back to TDC. Of course you will need the exhaust centerline number. You can figure that from the lobe separation angle. We know that the LSA is a mathematical function, whereby the intake centerline and the exhaust centerline are added together and divided by two to find the LSA. On the cam card, the intake centerline is shown as 106 and the LSA is shown as 110 degrees. If we subtract the IC from the LSA, we find a difference of 4 degrees. If we double that to 8 degrees and add it to the IC, we find an exhaust centerline of 112 degrees BTDC. Both EC and IC are expressed at some value BEFORE TOP DEAD CENTER.

If anything in this tutorial is unclear, please ask questions. I want everyone to understand how to do this procedure.

Other grinders, such as Lunati, will give you all the 0.050" info right up front. Here's an example....
Cam Spec Card :: Lunati Power

One other thing while I'm on camshaft timing.....the difference between advertised duration and 0.050" tappet lift duration will be an indication of the agressiveness of the lobe lift. Some of the younguns on here and other forums seem to think that the quicker you get the valves open, the better for performance. While that is basically true, there has to be some consideration for how mechanical things work together. You can YANK the valves off their seat and SLAM them back onto the seat only so many times before things begin to fail. Using a softer valve open and close can extend the life of all the valvetrain components and this seems like a good thing on a street motor. If you want more flow past the valve, use more duration and more SCR to match it.

If you subtract the 0.050" duration from the advertised duration, you will begin to get an idea of how radical the grind is, from an opening and closing standpoint. In other words, let's say we have a cam with 280 degrees advertised duration and 220 degrees 0.050" duration. The difference is 60 degrees, or 30 degrees on each flank of the lobe from 0.006" valve lift to 0.050" valve lift. Now, let's look at a cam with 230/280. The difference between advertised and 0.050" tappet lift is 50 degrees, or 25 degrees on each flank of the lobe from 0.006" lift to 0.050" lift. Can you see that there is more effort on the tappet face/cam lobe? You're doing the same amount of work in 25 degrees, that the easier cam is doing in 30 degrees, and you're extending the force over a longer period of time, which makes the cam live longer, theoretically. Again, if you want more 0.050" duration, then use a hotter cam with the same difference between the events, such as a 230/290 cam. Roller tappet cams will eliminate most of the problems associated with flat tappet cams in my opinion.

You can get away with snappy valve action on a roller cam because there is no way for the lifter to scuff the lobe, but on a flat tappet cam, you'd better do your homework. Crane Cams used a 62 degree difference (for instance, 230/292) on their flat tappet cams for years and years. I haven't looked at them lately, so I'm not sure what they use.

To throw a monkey wrench into the works, most grinders show mechanical (as opposed to hydraulic) lobe duration at advertised valve lift and 0.020" valve lift.

A couple more thoughts.....
When the motor is all together and after you have done the initial cam break-in and have the valves adjusted properly, place a piece of thin glasses lens cleaning paper (or doobie paper) between the rocker tip and the valve tip, then roll the motor over by hand through 2 complete revolutions. Remove the paper and inspect. It should be compressed, but not torn. If it's torn, then the rocker geometry is off and there's more work to do. This assumes you have adjusted the sweep of the rocker tip across the valve tip and minimized travel from closed to open and vice versa with different length pushrods or whatever.

Originally Posted by Don Shillady

Richard/Techinspector,

Good to hear the latest from you and Pat as well. Just how "bad" are those roller tip rockers? I just got finished (yesterday) replacing a potentially troublesome 1.6 set with the 1.5 set from Speedway. Pat, do I understand you to say that up to about 0.045" off the block surface will still match up the intake ports in a non-smoke way, I have an Edelbrock Performer RPM on heads that have been resurfaced by 0.020".

Don Shillady
Retired Scientist/teen rodder

Hello Don, good to hear from you.
Don, I don't have all the expensive equipment to test different products, so I have to lean on the fellows who do. One of the most trusted cam grinders on the planet was Racer Brown and I have read his writings extensively. He's the guy who designed and ground the muscle car cams for Chrysler Corporation back when the factory hp wars were in full swing. His take on roller rockers was that the benefit was in the roller trunnion, not the roller tip. He said that the rollers on the roller tip rockers were of insufficient size to make a mechanical couple with the valve stem tip. That leads me to believe that if a fellow had a roller trunnion with a conventional tip, he'd have the katzenjammer setup. Unfortunately, nobody makes such an animal.

As far as the difference between 1.5 and 1.6 rockers on a SBC, I have found only single digit improvements. The added stress introduced by a quicker valve action isn't worth it to me. If I want more hp, I'll change to a nastier cam with more static compression ratio and still use 1.5 rockers. My attitude reflects an appreciation for the metal in the pieces used. Yes, iron and steel are tough, but they are not indestructable.

Concerning the cuts on your heads/block/intake. Except for the intake, being new, you have no idea what procedures were done to the pieces by previous owners, so you really have no point of reference. In my opinion, a couple of sacrificial intake gaskets are a cheap price to pay for witnessing a good seal all the way around each and every port.

Thank you so much Richard. I continue to feel humbled by your willingness to continue to teach me. I think I followed most of what you described regarding valve timing. Here is a CAD drawing I made to try to show it:

Here's a screen shot from the CompCam Software I'm using. I notice it does show the IVO etc. at the .050", but I am still grateful for your descriptions.

Your CAD drawing knocks me out. Excellent homework. A+

Originally Posted by techinspector1

Your CAD drawing knocks me out. Excellent homework. A+

Yup - I think I like this guy!! Listens and interacts on a very intelligent level.

Originally Posted by glennsexton

Yup - I think I like this guy!! Listens and interacts on a very intelligent level.

If you were talking about me, I was just thinking the same about you guys.
I do have some automotive mechanical experience, but this is the first time I have dived into the engine details this far. Without good quality guidance from people who have been down the road and know what they are talking about, I would not attempt to go through this on my own. I appreciate you adapting your advice to my particular situation.

None other my friend!

It's refreshing to work along side people who want to learn and bring a open mind to the table. The folks here continue to teach and amaze me - Tech, Pat, Jerry, Don, and the list goes on and on.. I've built my share of engines and in the early days used a lot of "brute force" to make cars go faster. The school of hard knocks is a wicked teacher - but we've all learned a few lessons there that will not soon be forgotten. I've come to understand over the years that patience and gentle "persuasion" work a lot better most of the time when dealing with an engine.. (I still have the big ol' knocker - but it's reserved for very special / difficult occasions!!)

The minds here have the deepest collective knowledge anywhere on the web and I appreciate the, "let's work smarter-not harder" approach. You Sir, have quickly assimilated into this mind set and it's obvious that you're sincere in your quest for knowledge and "doing things the right way" rather than having to do them over.

I think I can safely say several of here have take a shine to you and are looking forward to the results of your build!

Regards,
Glenn

Update:

After cleaning off all the carbon deposits, of which there was hardly any, and with the valves still held in by the original springs, I cc'd the Vortec heads tonight.
6 chambers measured 66cc's
2 chambers measured 65cc's.
I didn't have the correct sparkplugs, so I used the old set out of the 89 350. They are shorter and hang back in the threads. The sparkplug hole inside the chamber held about 1/2 cc to fill it up flush with the chamber, so deducting the 1/2cc from the above measurements would give 64-1/2 and 65-1/2.
So now what do I do to balance them if needed?, or is that close enough?
Do I match the larger ones and remove 1cc material from the 2 smaller chambers? I read about "sinking a valve" on another racing site. Should I have my machinest grind the exhaust seats a little on those 2 chambers to make them even?

Actually I'm wondering if my measurements could have been off just enough, to not worry about it and assume they are all pretty close as they stand.

At this point I am assuming the heads don't need a valve job, although I do plan to do a simple fine lap job on the seats, after they check out on the magnaflux and then pin the studs and install the beehive springs.

Using 65.5cc and 18cc dish pistons, and a .040 quench, I calculate an 8.90 SCR and 8.08 DCR with my new cam calc of 29 IVC at 0.050.

Wow!, Look at all those numbers I'm throwing around, that I had no clue about a few months ago.

I think my next step is to finish stripping the block, taking it to the machinest, verify the bore size and order the pistons.

Thanks again for all your input.
Together we are going to build a very nice engine.

Originally Posted by rollie715

So now what do I do to balance them if needed?, or is that close enough?
Do I match the larger ones and remove 1cc material from the 2 smaller chambers? I read about "sinking a valve" on another racing site. Should I have my machinest grind the exhaust seats a little on those 2 chambers to make them even? Actually I'm wondering if my measurements could have been off just enough, to not worry about it and assume they are all pretty close as they stand.

For a street driver motor, I wouldn't worry about the 1cc difference. The only reason I'm expanding on this is because of your eagerness to learn.

What I would do is to sit the heads on a flat and level surface with the chambers down and stand up the edge of a straightedge on the top of the valve stems to make sure that none of the valves are installed shorter or taller than the other ones. If the valves are reasonably the same height from the deck, then measure from the bottom of the straightedge to the surface where the heads are sitting to see if they run downhill or uphill from one end of the head to the other. This will require that you use a buddy to hold the straightedge while you place a standard under the straightedge at each end of the head, right up against the head and measure the difference between the top of your standard and the bottom of the straightedge with feeler gauges. I'm trying to explain this so that most anyone reading it can do it without the use of precision tools which they may not have. The standard can be anything that is flat on the bottom and offers an area on the top where you can insert a gauge blade between the standard and the bottom of the straightedge. When I was a young man with few tools, I used an upside-down drinking glass from the kitchen. Use the same glass on each end of the rule of course and measure at the same place on the glass bottom. You might mark a spot where you will measure with a Magic Marker or Sharpie. Of course, to do this properly, you should measure all valve lengths with a 6" dial caliper or other suitable tool. If you don't have one and can't buy one, have a buddy measure them or go down to the machine shop and pay 'em their shop fee to measure them for you. You will want to measure the margins also and see that you have a matched set of valves. As good as it could get is that the two small chambers could have the valves closer to the deck than the other valves in the other chambers. Then you could cut the seats a little to equalize the distance from the deck to the seats on all valves. Then you'd equalize valve stem heights and you'd have a set of blueprinted heads.

I've read that the L31 design was reached only after GM engineers tweaked for six months on their best Corvette LT1 chamber design. THEREFORE; RESIST ANY NOTION YOU MAY DEVELOP THAT INVOLVES GRINDING IN THE CHAMBERS BY YOU OR ANYONE WHO DOES NOT HAVE A DOCTORATE IN FLUID DYNAMICS.

Originally Posted by rollie715

At this point I am assuming the heads don't need a valve job, although I do plan to do a simple fine lap job on the seats, after they check out on the magnaflux and then pin the studs and install the beehive springs.

Check carefully what the angles and the dimensions are on the seats and valves. I've read from more than one source that the valve job from the Chevrolet assembly line is about as good as it gets and contributes greatly to the flow of the heads, so, you don't want to fix it if it ain't broke. If they held the fluid for you to do the cc procedure and didn't leak into the port, then leave 'em alone, assuming they're low-mileage heads. Number the valve faces upon removal so you can keep everything in order upon reassembly.

Originally Posted by rollie715

Using 65.5cc and 18cc dish pistons, and a .040 quench, I calculate an 8.90 SCR and 8.08 DCR with my new cam calc of 29 IVC at 0.050.

Wow!, Look at all those numbers I'm throwing around, that I had no clue about a few months ago.

LOL, funny stuff. Reminds me again that I should have been a teacher. Not all is lost though, I'm able to contribute in my own way.

Originally Posted by rollie715

I think my next step is to finish stripping the block, taking it to the machinest, verify the bore size and order the pistons.

Sounds ok to me.
In my opinion, you'll be better off in the long run if you can save the cam bearings by not using a caustic cleaner on the block. The shop will want to replace them because that's how they make their money. You, on the other hand, should be making your decisions by what you can afford to do that will still offer a good service life. I got tired of all that expense of changing cam bearings on street motors and the fact that usually, the replacements were slightly small or slightly large or slightly narrow or whatever. The ones that the factory put in will work fine for a long time and I would only replace them if there was excessive play between the cam journals and the bearings. There are more than likely fellows on here and other places who will tell you to change the cam bearings every time. If they make more sense to you, then follow their advice. I just know what works for cheap for me.

Thanks for the advice on the valves. Just for fun I may put a straight edge accross the valve stems and see how even they are, but if 1cc difference accross the chambers is acceptable, I probably won't spend too much more time on this set.

I appreciate your willingness to fill in extra details, as I am interested in finding out more of what it would take to create a finely tuned or blueprinted engine. Maybe someday on a future build, I will spend more time buiding one with more precision. I've still got a ways to go on this build and haven't even got to the transmission, headers exhaust system, or rear end. Or for that matter, my entire 67 Camaro has a lot of tweaking needed throughout. Just yesterday, when my wife went to fasten her seatbelt, the belt pulled out completely where the original belting stitches failed. Now I'm looking for a new original replacement in blue. I digress. My vision at this time is to badge the car as an SS350 and paint and accessorize this new engine to appear as close to original as possible.

Originally Posted by techinspector1

In my opinion, you'll be better off in the long run if you can save the cam bearings .....usually, the replacements were slightly small or slightly large or slightly narrow or whatever.

I have already removed the original cam bearings. I bought an sbc cam bearing tool and did it myself after my machinest advised me to do it before I brought the block in to be hot tanked.

On the subject of replacement cam bearings, can you recommend a brand or part number that would be of good quality that could avoid getting out of spec bearings as you suggest happens sometimes?

As for the crank bearings, the 350 crank kit I purchased per your suggestion from Mabbco in Texas came with a set of bearings, looks like 10/10, the rod bearings are Clevite made in USA, the mains are EngineTech made in Israel. If I check the endplay with a feeler gauge and the clearances with Plastigage, I assume they will work just fine. I didn't realize bearings were made out of aluminum.

Originally Posted by rollie715

On the subject of replacement cam bearings, can you recommend a brand or part number that would be of good quality that could avoid getting out of spec bearings as you suggest happens sometimes?

Let your machine shop guy supply the bearings, he knows what is currently the best choice to use.

Ok, I'm ready for my next lesson.

I've been thinking about valve rocker geometry and push rod lengths.
I was under the impression that the rocker pivot point was located a little lower then the endpoint contact points of the valve stem, so that as the valve approaches it's maximum openings and when the pressure against the valve stem is at it's greatest, the pivot angle in relation to the valve stem is crosses over the 90 degree point, which would result in the least amount of sideways travel and the least amount of side pressure on the stem as well as the least amount of sideways rubbing between the contact surfaces,

I would like to make a scale cad drawing of these relationships so I can better understand the variables and more easily communicate these principles to others. And to apply it directly to my project and cam lift.

Where can I go to find the exact geometry and dimensions of my setup? GM 906 Vortec with stock rockers.

And please feel free to present a detailed discussion on this subject, and to fill me in on what I don't know yet.

Thank you.

on cam bearing s there is guys that do this every day on here .i like to take out cam bearings on all blocks not just small blocks as the housing bore is fully grooved and there is no way to clean that out and the bearings can kill the caustic in most hot tanks they have to come out first thing that must be done if you forget $$$$ the cost of HAZ wast is over $500 a fifty gallon drum and 5 of caustic $125 so it could cost $1250.+ most guys do not forget to take them out yep machines shop s have hot tanks and you want it clean cam bearings are coming out.... another thing i may add the cost of putting cam bearings in is not much at a shop .buy the tool and drive them in it is not hard ? well there more to it then that . a hell of alot more to it .any one thinking any thing else has never done any machine work. ROCKER ARMS you can lay it out like you want on paper ? and get close . but every make rockers are not the same roller tip s are bigger and some makes are smaller roller tips . push rod cup can be bit off .that why i check push rods at mild lift i do them this way on every engine with roller rocker arms

Thanks Pat and all,
I just dialogged with Brent, the owner of this site, and he changed the IMG status for these threads to Allow Image Inserts, so now our pictures will show up inside the thread instead of only being links. I like that as I would like to post a lot of pictures of things as I progress through this build. I plan to turn this thread into documentation of my engine build.
Here's a test:
The following posts include some of the pictures and the beginning of my story.
This is going to be fun !