Thread: SBC 350 build

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Originally Posted by Bowtiepickups

Haha. That sounds like a solid way of thinking. I read little article and the boys at Hot Rod magazine used vortec heads and used a set of COMP Cam's beehive springs and ran .490 lift. (they say they are good for .560) If i understand correctly, I can put on the beehive springs and retainers and be good for a .560 lift cam. I was thinking I would do this since the heads are already on the motor it would be a decent way to make power and save some serious scratch. Of course, I would check the casting numbers on the heads before I did it.
Link to the article:
http://www.hotrod.com/techarticles/e...ild/index.html
Check page 2
Link to springs:
http://www.summitracing.com/parts/CCA-26915-16/
Link to retainers:
http://www.summitracing.com/parts/CCA-787-16/

That could be a plan. Parallel springs such as the Cranes I linked really need a spiral-wound damper spring to cancel harmonics in my opinion, whereas beehive springs do not, so my choice in what you have presented here would be the Comp springs.

Notice that the builders used a cam ground on a 108 degree lobe separation angle and had some horribly low intake manifold vacuum because of it. Generally speaking, the motor will make more power the tighter you go with the LSA, but vacuum stinks for operating power brakes and other vacuum-operated accessories. You'll also note that they mentioned a reserve vacuum can or an electric vacuum pump. If you need additional vacuum, don't waste your money on a reserve can. Either pop for the pump or install a hydroboost system like was used on some Cadillacs, trucks and such. Works great with the wildest cam because the brakes are not dependent on vacuum to operate. I don't care what anyone else says, you need a minimum of 16 in hg to operate power brakes.

You can still make good power for street/strip and make a little more vacuum by choosing a cam ground on a 112 degree LSA and keeping the duration reasonable. You keep the duration reasonable by using a reasonable static compression ratio. Understand this: YOU CANNOT INTELLIGENTLY CHOOSE ANY CAMSHAFT FOR ANY MOTOR UNTIL YOU ABSOLUTELY, POSITIVELY KNOW THE STATIC COMPRESSION RATIO BY MEASURING COMPONENTS YOURSELF OR HAVING SOMEONE ELSE MEASURE THEM FOR YOU.
You need 5 values:
1. Cylinder volume in cc's
2. Combustion chamber volume in cc's
3. Piston deck height volume in cc's (the volume between the piston crown and the deck of the block with the piston at top dead center)
4. Piston crown volume in cc's (a true flat top piston will have about 6-7 cc's in the eyebrows that are cut into the crown for valve clearance. Otherwise, for a dished or domed piston, the mfg will usually publish the volume). Most of the stock-type 350 pistons have a recess that isn't actually called a dish, but it is a depression across the crown, with a very thin ring of material sitting up a little higher around the bore. That little thin ring of material is insufficient for generating a good squish and you should be very careful with compression ratio and cam if you use that type of piston. The very best type to use in a street/strip build in my opinion is a D-cup dished piston. These provide a generous shelf of material that comes up against the underside of the cylinder head to generate a very good squish. If you build any kind of reasonable static compression ratio into the motor without using a good squish, there is a good possibility that the motor will detonate on pump gas.
5. Head gasket volume in cc's
If you want me to go through the entire routine and teach you how to find the exact SCR, just ask.
The camshaft will normally be the last component chosen, after everything else is nailed down for the build.

If you do end up using L31 heads, don't let anyone talk you into increasing the valve sizes. Stock, they are 1.94"/1.50" and will do a fine job on a 350. Any cutting done on an already thin-wall casting is just asking for trouble.

Thanks for that post. It cleared up a few things for me. I will definitely get you to help me go through calculating everything when I have it tore apart and it's closer to re-build time. Which is greatly appreciated. I have no desire to increase the size of the valves. So would you recommend I get some new pistons instead of the stock ones? Would they have to be something with a D-Cup dish? Or would flat tops due alright too? Also, what would your input be on rockers? Would roller rockers be worth it for me? Thanks again for your input, it seems to be helping my understanding a lot.

You got a LOT of great opinions already. Tech is correct on many things and he is one I would listen to and trust and not have to think twice if he knows what he is talking about or not. The RHS heads he mentioned are supposed to be awesome heads for a street motor along with the Weiand Stealth intake manifold (I have one of these on a 351W and it's awesome)! As for the cam the roller cam is your best bet of course but some of us cannot afford a roller cam and can only opt for a flat tappet which is fine but like Tech said, you need to watch your spring choice and use the additives and just hope for the best after that because even with additives and a mild cam I have seen them go bad about 3 times in the past 2 years.

If this is going to be a daily driver truck, I would stick with a good highway gear (nothing above a 3.50). I know in my 66 F100 I have a 3.70 and it screams on the freeway so I have a 3.25 that should be much better for city and highway driving. Your gearing and transmission choice will play a HUGE role here. I would figure this out before choosing a cam and engine components. Stay away from those Thumper cams and high lift stuff and go with a nice low-mid torque street/towing cam. That will help with gas mileage, low end and economy, especially for a daily driver.
Do what is mentioned here followed up by nice flowing exhaust and a good set of tires and you will have a nice reliable daily driver that can still get up and go when you want. Later when you have the money you can build a motor, swap over the parts and heads after they are freshened up and keep going.

Oh as for pistons and freshening up, do the compression check, pull the heads and check cylinder walls. If they are decent you can probably do a basic hone job, new rings and bearings and let it go. If it's in bad shape you will need to take to a machine shop, rebuild, etc. As for pistons I am not an expert here but what I have in my 355 and what a lot of people seem to use are Speed Pro TRW flat tops. With 64cc Vortec heads and the correct head gasket thickness you will push about 9.6:1- 10:1 compression ratio and still be able to run on pump gas. I probably wouldn't run over 10:1 compression and wouldn't go under 9:1 for sure. Raising the compression some will help in gaining some power as well.
I am not an engine expert like some of the guys here so this is all I will say and this is all based on my opinion and what I have learned personally and from the guys here.
Good luck on the build!

Yep, I think the vortec heads with the COMP springs will be my best option. I will be sure to pull my rear-end cover and see what I have for gears. I'll be putting in new bearings all around in the bottom end of things and likely put in new pistons if the cylinder walls seem all good. You said not to run too much lift on my cam, what would you recommend for max lift I should run for a daily driver?
I was looking at the COMP XE274H
In lift-.490 lift
Ex. Lift-.490
In @.50-230
Ex. @.50-236
LS-110 degrees

Originally Posted by Bowtiepickups

Thanks for that post. It cleared up a few things for me. I will definitely get you to help me go through calculating everything when I have it tore apart and it's closer to re-build time. Which is greatly appreciated. I have no desire to increase the size of the valves. So would you recommend I get some new pistons instead of the stock ones? Something with a D-Cup dish? Also, what would your input be on rockers? Would roller rockers be worth it for me? Thanks again for your input, it seems to be helping my understanding a lot.

Let's find out what pistons are in the motor first. Another thing that I didn't mention about pistons, the compression height is the distance from the centerline of the wrist pin to the top of the crown. On a 350, this dimension, stock, is 1.560", so that when you add the 1.560" to the rod length of 5.703" and add to that the stroke radius of 1.740" (half the 3.480" stroke), you get a total "stack" height of 9.003". Since the block is normally ~9.025" give or take a few thousandths, you can see that with the piston at top dead center, the piston deck height (distance from the piston crown to the block deck) is 0.022" in this case. Now, when these motors were put together at the factory, they used an embossed steel shim head gasket. It has been a long time since I measured the thickness of one, but I seem to remember somewhere around 0.020"/0.022". OK, so if the piston is 0.022" down in the bore and the gasket is ~0.022" thick, you can see that there will be 0.044" of clearance between the piston crown and the underside of the cylinder head with the piston at top dead center. This is the squish dimension in this case, 0.044". Since most builders will agree that 0.035" to 0.045" is ideal on a small block, we are right there for this example.

Now, that was using a piston with a stock compression height of 1.560". There are also pistons made for a 350 with a 1.540" compression height. These are usually, but not always, cheapo cast pistons with an ultra-cheap price. They're called "Rebuilder Specials". The reason these are made is so that the rebuilder of the motor can take a 0.020" cut on the block decks to clean them up and still have the same crown to deck dimension (piston deck height) as the motor had stock. The problems begin when Henry Hotrod is looking for pistons and sees these really inexpensive pistons for sale. He has no idea about squish and how it affects his motor and is totally unaware that there is any such thing as piston deck height and squish. All he sees is the cheap price of a new set of pistons, so he springs for them. He also has no plans to deck the block. So, he ends up with the piston sitting 0.020" deeper in the bore at top dead center and has eliminated any possibility of generating a good squish. He bolts the motor together and is dismayed when it will not run on his regular grade of pump gas without pinging (detonation). Desparate to stop the detonation, he pulls all the ignition advance out of the motor and now it won't pull the hat off his head. Or maybe he just lives with the detonation and the motor finally throws in the towel with several cracked pistons.

I have seen this scenario come to life time after time after time in the years I have been on these forums.

The very best combination you can put together is a motor that uses absolutely flat-top pistons with just some shallow eyebrows for valve head clearance. Problem with this is that you have to use a cylinder head that has chamber volumes that will produce the proper static compression ratio for the fuel you plan to use. For instance, if you have L31 heads, the chambers are ~64 cc's. If you used flat-top pistons with those heads, your static compression ratio would be around 10.3:1, which would be over the line for using pump gas with iron heads. With aluminum heads and a very tight squish of 0.035" and the proper cam that would close the intake valve at the proper time, you might get away with it. But with iron heads, you'd have to run so much camshaft that the motor wouldn't be any pleasure to drive on the street and I don't think that's what you're looking for.

So, the answer is dished pistons to lower the static compression ratio so that you can use less cam and run pump gas. Using a 12cc dish with 64cc heads would result in a 9.6:1 static compression ratio. Here is an example of such a D-cup piston from Keith Black. Notice in the photo on the left side, that there is a generous flat area on the crown. This is the flat area that comes up to the underside of the cylinder head to generate squish across the chamber. When the fuel/air mixture is squished or "jetted" across the chamber, the turbulence homogenizes the mixture and eliminates any over-rich or over-lean conditions in the chamber, making a more complete burn that will result in maximum power and minimum chance of detonation. The tighter you run the squish, the less octane you can run in the motor.
http://www.kb-silvolite.com/kb_car/p...tails&P_id=155
With such a 9.6:1 combination, I might use a camshaft like this one, or something close to it...
http://www.summitracing.com/parts/CCA-12-420-8/

Now, if a fellow moved to an 18cc D-cup instead of a 12cc,
http://www.kb-silvolite.com/kb_car/p...tails&P_id=154
then the static compression ratio would be somewhere around 9.1:1 and you might use a camshaft such as this one....
http://www.summitracing.com/parts/CCA-12-410-8/

It's all about the combination. You have to choose pieces that will like each other and make max power for the combination.

Tech, on my TRW flat tops .030 over with 4 valve reliefs, it says 9.6:1 compression ratio with 64cc heads. Are you saying that is not true? I know that sometimes the specs on the directions or Summit are not correct and I have always thought this to be true with 64cc heads and also that would also assume that my deck has NOT been cut down any.

Originally Posted by FMXhellraiser

Tech, on my TRW flat tops .030 over with 4 valve reliefs, it says 9.6:1 compression ratio with 64cc heads. Are you saying that is not true? I know that sometimes the specs on the directions or Summit are not correct and I have always thought this to be true with 64cc heads and also that would also assume that my deck has NOT been cut down any.

the speed pro book shows were its parts number will be at given deck height. many pistons makers will move the C.H on a flat top if the cr needs to be some what close as the bigger bore gets the more swep volume more CR .with domes they adjust the CR by moving the dome .many do this so you need to deck to O or 010 to be were you want . I do it all the time

as for a flat lifter cam solid or hyd i used many over the years and to say its oil or to much spring its alot more then that .so spin the wheel lay your bets down. as some one that send s engines out all over the USA and Canada .i have no controll over the oil or how many times will the guy dry crank a engine( I CAN NOT BE THERE) so if the guy can spend the $350 more for a retro fit roller... bare bones kit... i will do that.. if not. i take the time to get them understand just how critical break in on a new cam is with the right oil and thing still could go sideways . i never lost a cam on a SBC or potiacs fords amc and others over the years i done many flat cams over the years 32 years .two jobs still stick in my mind . did a magnum mopar roller engine. guy told me he crank it till the battery was dead and used a full can of starting fluid. he did not check the dist not plug in .i do not think a flat cam would of lived thru that guy? .i did tell him is was not happy with him. them i started up a 454 mark 5 engine for a guy i made sure it fired right up. a good friend built it very mild flat lifter cam engine he has been building engines and machining for 35 years less then a 100 miles cam was gone . i did the next rebuilt it with a rollercam. i built 6 engines for the guy over the years with the mark 5bbc. all his engines he wanted roller cams all but one bbc with a hyd flat lifter cam engine . i have rebuilds with flat cams with 100000. miles on them and rollers with over 200000. if i can get a guy to spend 350. more for a roller i will try .if i am building the engine and i getting the core i will get a block that came machined for a roller or can be set up with stock roller lifters they are less for a roller block. alot of warranty jobs in engine rebuilding comes from flat lifter cams that fail .customer have came to me after there flat lifter cams have failed .they looking for a job that will last so i lean to roller cams and after paying for another rebuild its not a hard sell . ones that do not i still build 6 or so engine a year with flat lifter cam s if i can not be there for break in .i talk with them abit i get to know if there getting over there head i try to line up someone that can help them fire up there new engine

Pat, what brand roller cam kits do you usually use? You have helped me in the past choose some cam styles and look at some head combos but I cannot remember if you use or prefer a certain brand or not?

Originally Posted by FMXhellraiser

Tech, on my TRW flat tops .030 over with 4 valve reliefs, it says 9.6:1 compression ratio with 64cc heads. Are you saying that is not true? I know that sometimes the specs on the directions or Summit are not correct and I have always thought this to be true with 64cc heads and also that would also assume that my deck has NOT been cut down any.

If each of the reliefs is 3 cc's, then 4 of them would be 12 cc's, which would yield 9.6:1 with 64cc chambers on a 355.

Pat what would be your Cost for a Re-Man Short Block 355 with Hyper Cast Flat Tops rebuilt Rods Zero Decked HV oil Pump with retro Roller Camshaft and Lifters Roller Timing Set With Button and HD Cover ?

Originally Posted by Bowtiepickups

Yep, I think the vortec heads with the COMP springs will be my best option. I will be sure to pull my rear-end cover and see what I have for gears. I'll be putting in new bearings all around in the bottom end of things and likely put in new pistons if the cylinder walls seem all good. You said not to run too much lift on my cam, what would you recommend for max lift I should run for a daily driver?
I was looking at the COMP XE274H
In lift-.490 lift
Ex. Lift-.490
In @.50-230
Ex. @.50-236
LS-110 degrees

Well, max lift will be determined by your valve springs and piston to valve clearance. I'm going to say it again. The camshaft is the LAST piece you buy for your build, after you have everything else lined out to work together.

One thing that I would not do, even if I were to use a flat tappet camshaft, is to use an extreme energy grind on a street motor build. The lift off the base circle of the cam on these grinds is the maximum rate of velocity that can be achieved with a flat tappet before the edge of the lifter digs into the side of the cam lobe. This is just stupid for a street motor. If you are in competition and an extreme energy grind will get you half a tenth, then the gamble might be worth it. Otherwise, use a cam with nice, easy ramps and let the valvetrain live in a kinder environment.

The following is my own approach to figuring out the relative work that a lobe is asked to do compared cam to cam. I don't know how scientific it is, but it makes sense to me in the context of how I use it. Math is black and white. There are no gray areas.
You can determine the relative tappet velocity of a grind by subtracting the 0.050" tappet lift duration from the advertised duration. I remember for years that Crane used a 56 degree difference on most of their cams. If you had a cam with 270 degrees advertised duration, then the 0.050" duration would be 214, for instance. Now, if we assume a symmetrical opening and closing lobe configuration for the sake of argument, that would mean that there would be 28 crankshaft degrees of tappet rise from the advertised point (usually about 0.006" up off the base circle of the lobe) to the 0.050" tappet lift point. So, we are lifting the tappet 0.044" in 28 crankshaft degrees. This would work out to a lift rate of 0.00157" per crankshaft degree.

Now, let's look at a cam with 270 advertised and 228 @0.050", a difference of 42 degrees. This would be a much more agressive camshaft lobe design. If we are using up the same 0.044" lift in only 21 degrees of crankshaft rotation, you can see that the rate of lift would be 0.00209" per crankshaft degree.

If you'll just think about it for a moment, you'll see that the cam lobe has to endure quite a lot more pressure to do more work in the same amount of time. If you plan to run one of these extreme energy grinds, then have the cam nitrided at the factory before they ship it and use the best lifters the grinder can offer. This is no job for "white box, no name lifters". Also, I would suggest backing up to the post where I listed all the things that can frag a flat tappet cam and pay attention there.

One other thing that I meant to address for you is the roller rocker. The value of a roller rocker is in the trunnion where it swivels on the rocker stud, not at the tip where is engages the valve stem tip. High speed filming of the valve action by a famous cam grinder, Racer Brown, showed that the roller tip is too small in diameter to generate a mechanical couple with the tip of the valve and that the roller just skids across the valve tip instead of rolling. As I said, the main advantage in a roller rocker is at the trunnion, not the tip. Do not be tempted to buy those fosdick Magnum rockers from Comp that use a conventional ball and socket at the trunnion and a roller tip. Comp got it bass-ackwards and those things should be against the law. They should have made a roller trunnion and a conventional tip if they really wanted to improve things. The other thing is, don't waste your money on 1.6 rockers for a small block Chevy. Use stock ratio 1.5's. In my opinion, the best value on the planet for roller rockers is the Scorpion units. You can get them in narrow body models to fit inside the L31 valve covers and they are made with the rail tip feature as well.

One other point. I made reference to using either the Edelbrock Performer RPM or the Weiand Stealth as the best manifolds for a street/strip motor. Tango has brought it to my attention that the Holley 300-36 is at least as good and after doing a little research on other forums, I understand it may even be better than the RPM or Stealth. Thanks Tango for the heads-up.

Originally Posted by FMXhellraiser

Pat, what brand roller cam kits do you usually use? You have helped me in the past choose some cam styles and look at some head combos but I cannot remember if you use or prefer a certain brand or not?

on rollers i look at the numbers i do abit with ERSON they make me cams if i can not get a shelf grind i have used .howards. comps . isky .lunati .crane.crowers .but on the last ford i used a howards Big Nos cam numbers were wanted to see them and they had a core to grind the numbers on

a much more critical rate of camshaft effects are the DECELERATION rates as the tappet nears the full open and also the closed area---one to elininate the valve from flying off rocker/pushrod/lifter combined diminsions and the other to eliminate bounce as the valve seats.