stroked small blocks in the race cars?

[PDUB]

I know that life is a tradeoff, and that aluminum has its advantages, but is there any truth to cast iron as a material providing a power advantage over aluminum, holding all other things equal?

[MAStuart]

Jim if starting with a new block how come you are going to 30 over right away? Is it because you are going to reuse your 30 over pistons. I would have thought you would start a standard bore and get e few more bore jobs out of the block. Most of the time you bore because the bore is bad not because of the few extra inches you get. Even if your engine makes 2 Hp per inch its only going to gain 8 hp at the most from the over bore. In reality it will not be that much more.

[1795]

The engine builder wants to go .030 over as the block comes requiring final honing and going over gives him more room to adjust for discrepancies in the block bore that may be there. Since the pistons will be custom, they cannot be returned and if a cylinder requires over boring then, we would have to buy another set. Since we are getting custom pistons, he suggested that we order 10 instead of 8 just in case something happens to a piston, we will have a spare as it is not easy to get someone to build just one piston and it gets really expensive to have a small number built.

Not going to reuse the old pistons as we are dropping the compression ratio and they are popups. Also, pistons show some evidence of going lean at times with some heat spots that did not burn through. I am adjusting the fuel pressure and jetting and when it is all done we will be finalizing the air/fuel ratio on a chassis dyno so that we get more accurate information pertaining to actual use on the track as opposed to an engine dyno.

Jim

[blykins]

Originally Posted by 1795

The engine builder wants to go .030 over as the block comes requiring final honing and going over gives him more room to adjust for discrepancies in the block bore that may be there. Since the pistons will be custom, they cannot be returned and if a cylinder requires over boring then, we would have to buy another set. Since we are getting custom pistons, he suggested that we order 10 instead of 8 just in case something happens to a piston, we will have a spare as it is not easy to get someone to build just one piston and it gets really expensive to have a small number built.

Not going to reuse the old pistons as we are dropping the compression ratio and they are popups. Also, pistons show some evidence of going lean at times with some heat spots that did not burn through. I am adjusting the fuel pressure and jetting and when it is all done we will be finalizing the air/fuel ratio on a chassis dyno so that we get more accurate information pertaining to actual use on the track as opposed to an engine dyno.

Jim

I think that's pretty typical for older shops. A couple decades ago, piston diameters varied by so much that you had to sometimes custom tailor each cylinder to the piston. These days, pistons don't vary by more than a couple tenths (.0001") and there's no need for that.

Per MAStuart's point, it is a little beneficial to have the meat there for future rebuilds. The Dart blocks come in .005" undersize, which is exactly the amount needed to hone. Even if something were to happen (and things do happen), custom pistons can be made in .001" increments. If a piston had to be made for a 4.001" bore size, it could be done. Also, with most custom piston manufacturers, they give you a job number and getting a single is really easy these days.

If you haven't ordered pistons yet, you may discuss this with your builder.

[blykins]

Cast iron will usually make more horsepower, whether it's a cast iron head or a cast iron block.

[PDUB]

Originally Posted by blykins

Cast iron will usually make more horsepower, whether it's a cast iron head or a cast iron block.

Thanks, Brent!

[MAStuart]

Yes most of the time when custom pistons are ordered guys get 10 . The extra 2 are there to make sure you never need them. To me if the new block cant be honed to standard bore it should be sent back because to me it would be defective . Jim there is mothing wrong with what your doing . I just a lot of whys. That how I learn.

[1795]

Originally Posted by MAStuart

Yes most of the time when custom pistons are ordered guys get 10 . The extra 2 are there to make sure you never need them. To me if the new block cant be honed to standard bore it should be sent back because to me it would be defective . Jim there is mothing wrong with what your doing . I just a lot of whys. That how I learn.

I have no complaints. I like to get differing opinions and then sort through them to make a decision. The last thing I want is a bunch of people who say, "That's perfect" or in some other way agree with everything I say. Eventually that leads to some very faulty thinking. I know that I do not know everything, and the only way that I will learn is to ask questions, some of them being stupid at times

You know that if you do not order those two extra pistons, you will need them

I am a hard person to offend.

Jim

[CompClassics]

Blykins,

What is your thought on running a hydraulic cam profile using mechanical roller lifters? Longevity?

[blykins]

Originally Posted by CompClassics

Blykins,

What is your thought on running a hydraulic cam profile using mechanical roller lifters? Longevity?

Same deal.

Any solid lifter will need lash and more spring pressure to keep the valvetrain happy. When you introduce lash into the system, then the lifter is not in contact with the cam lobe all the time. Add spring pressure to that and you get a hammering effect on the lifter's roller bearings. Over time, it hammers them down. Even the most expensive lifters made for "street use" will not last a long time.

With the amount of research that I've done on hydraulic roller cams in the past several years, there's no need to run a solid roller unless it's a race application where aggressive cam lobes are necessary. I've had my FE engines at 7500 rpm with a hydraulic roller camshaft.

[1795]

Thanks for al of the input guys. My engine builder is going to be sorry he ever agreed to do the build I will have a lot to discuss with him. He reminds me of Brent, he lives in farm country, his shop started out as his garage and has slowly expanded over time. There is a local drag strip, so he does a lot of drag racers, also does some street stuff, an occasional road race car, and in addition to a variety of small block and big block Ford engines in his shop, there is a tractor engine on the bench.

I sent an email to Dan Case and asked if he knew the specs on what the 289 race cars were using for a cam and he said that in his 289 with Webers he is running the C7FE cam, which is what Ford sold off the shelf for race applications. He thought that it had a lobe separation of 107. I looked up on the web and this is what I found:
http://nebula.wsimg.com/8590605db382...&alloworigin=1

Another site said that the duration of that cam was 250, with an intake lift of .528@.050" and a lobe separation of 108.

Does this sound similar to what you guys are thinking?

Jim

[Mark IV]

Originally Posted by 1795

Thanks for al of the input guys.

Will Rick be pi$$ed that I sent you there?

[1795]

He probably is having nightmares already. He actually is enjoying the build and every time I talk to him he starts off by saying he did some more research last night.

I will be doing a balancing act between what I would like to see, what you guys suggest, and trying not to step on his toes too much, as he is the engine builder and knows more about it than I do. He has a good reputation, so I do need to heed his advice, as he is the one that will be building the engine.

Jim

[blykins]

Originally Posted by 1795

Thanks for al of the input guys. My engine builder is going to be sorry he ever agreed to do the build I will have a lot to discuss with him. He reminds me of Brent, he lives in farm country, his shop started out as his garage and has slowly expanded over time. There is a local drag strip, so he does a lot of drag racers, also does some street stuff, an occasional road race car, and in addition to a variety of small block and big block Ford engines in his shop, there is a tractor engine on the bench.

I sent an email to Dan Case and asked if he knew the specs on what the 289 race cars were using for a cam and he said that in his 289 with Webers he is running the C7FE cam, which is what Ford sold off the shelf for race applications. He thought that it had a lobe separation of 107. I looked up on the web and this is what I found:
http://nebula.wsimg.com/8590605db382...&alloworigin=1

Another site said that the duration of that cam was 250, with an intake lift of .528@.050" and a lobe separation of 108.

Does this sound similar to what you guys are thinking?

Jim

The factory cam would have been picked for factory heads and factory part combinations. Today's parts, including Dart heads, would change the specs. It could be that you would need a 106, or maybe even a 109-110, but I would have to get the head stats in front of me along with all the other parts.

I wasn't suggesting that you go back to 60's cam specs, I was only suggesting that you get away from the normal "internet spec'd" camshafts, with long LSA's.

[olddog]

Originally Posted by blykins

Same deal.

Any solid lifter will need lash and more spring pressure to keep the valvetrain happy. When you introduce lash into the system, then the lifter is not in contact with the cam lobe all the time. Add spring pressure to that and you get a hammering effect on the lifter's roller bearings. Over time, it hammers them down. Even the most expensive lifters made for "street use" will not last a long time.

With the amount of research that I've done on hydraulic roller cams in the past several years, there's no need to run a hydraulic solid roller unless it's a race application where aggressive cam lobes are necessary. I've had my FE engines at 7500 rpm with a hydraulic roller camshaft.

I believe I fixed a typo. Delete to word hydraulic (in red) and insert the word solid in bold. I couldn't find a way to strike through a word.
Excuse me if I am wrong.

I might add a hydraulic lifter acts as a dampener to reduce the shockwave of metal hitting metal. I think the oil pressure in the hydraulic lifter holds the lifter in contact with the cam, but I'm not certain of that.

[blykins]

Originally Posted by olddog

I believe I fixed a typo. Delete to word hydraulic (in red) and insert the word solid in bold. I couldn't find a way to strike through a word.
Excuse me if I am wrong.

I might add a hydraulic lifter acts as a dampener to reduce the shockwave of metal hitting metal. I think the oil pressure in the hydraulic lifter holds the lifter in contact with the cam, but I'm not certain of that.

You are correct. Should have been solid instead of hydraulic.

[Anthony]

Originally Posted by olddog

I might add a hydraulic lifter acts as a dampener to reduce the shockwave of metal hitting metal. I think the oil pressure in the hydraulic lifter holds the lifter in contact with the cam, but I'm not certain of that.

Yes, that is because the lifter is in constant contact with the lobe of the cam, and lash is always at zero. I think the contour of the cam, after the lobe, is different between solid and hydraulic cams. Hydraulic lifters have spring loaded plungers with the added effect of the oil pressure to keep the lifter in constant contact with the camshaft.

[CompClassics]

“I think the contour of the cam, after the lobe, is different between solid and hydraulic cams.”

This was what my question was mostly regarding, would the less aggressive profile of the camshaft allow for longevity of the valve train?

[eschaider]

Originally Posted by CompClassics

Blykins,

What is your thought on running a hydraulic cam profile using mechanical roller lifters? Longevity?

Camshafts are ground with a lobe rising off a camshaft base circle. The amount or rise the lobe exhibits above the base circle multiplied by the rocker ratio is the lift observed at the valve less any mechanical distortions in the mechanism while operating.

As the cam grinder transitions from base circe to the opening ramp on the cam he builds in something called a clearance ramp. For solid lifter cams this is a gradual take up of the valve lash designed to minimize the hammering effect each time the lifter experiences moving from the cam base circle to the actual opening ramp of the cam.

Cam designers sometimes will speak of 0.006" lift durations and also 0.050" lift dutrations. The 0.006" lift duration is essentially the beginning of the actual opening ramp after the clearance ramp and represents the beginning of actual valve movement. This number is helpful in backing into some things like ramp acceleration rates. The intake port will not begin to flow significant air volume until the 0.050" lift point. This is the Harvey Crane originated duration measurement point for guys like us to compare cams.

This is a pic of a cam lobe from CompCams identifying the nomenclature associated with the various points on the cam lobe. Notice the clearance ramp notation on the lower right of the picture.



When you cut a cam for solid lifters (roller or flat) you need to provide clearance ramps to take up the valve lash gently without hammering the operating components to death. The Hydraulic lifter cam (roller or flat face) has no valve lash to take up because of the hydraulic lifter's 100% in contact with the lobe design.

As a result the clearance ramp used on a solid lifter cam to soften the impact on valvetrain components at each valve opening event is not present on a hydraulic lifter version cam. If you put a solid lifter tappet (roller or flat face) onto a hydraulic grind camshaft it would have a much foreshortened service life because of the hammering effect the valvetrain would experience without the clearance ramps.

Because a hydraulic lifter (roller or flat face) always operates at zero lash, hydraulic lifters can be safely placed on solid lifter grind cams but that begs the question why would you do this, other than to get away from lashing the valves — there is no performance advantage.

If the cam was ground as a solid lifter cam use solid lifters (lashed correctly), If it was ground as a hydraulic lifter cam use hydraulic;ic lifters. Don't mess with the primal forces of nature.


Ed

[eschaider]

Jim,

+1 on what Brent said about modern pistons and suppliers. My engine is supercharged and my pistons have very small compression heights which means it beats up the piston skirts. Add to that the fact even with the stock stroke more piston that I would prefer comes out the bottom of my cylinder bores at BDC.

When I used the typical aftermarket pistons from all the usual suspects they consistently had thinner skirts than I preferred and would collapse within the first year of use. I ended up going to a predominately race piston manufacturer that builds their pistons from a pure billet of 2618 aluminum stock.

We initially built the pistons in Solidworks, using a finite element analysis software tool to reinforce the highly stressed areas and remove material from the lower stress areas. There was a fair amount of effort involved because of the blower. Naturally aspirated pistons operated below 7000 rpm are a much easier puzzle to solve. BTW although my case was a special (don't we all think our cases are special ) no one but Gibtec would build the piston in Solidworks and noodle out the design for me or with me.

When we were done my pistons, H-13 heavy wall tool steel pins, and TotalSeal rings came in equal to or less expensive than a "custom piston" from any of the highly rated usual suspects. Like Brent suggested good practice for most firms dictates they use and preserve a job card for every set they make.

They will produce the pistons in 0.001" increments (which really saves expensive blocks) and if you need a replacement (you should of ordered ten but ...) they can turn around a single piston that will exactly match the old piston right down to the gram weight — which in the bigger picture is not that surprising because each piston is a CNC machined original.

The company typically builds for the NHRA pro classes (T/F, F/C and P/S along with the Pro-Mods). If you are interested in investigating what is possible, the company is Gibtec Pistons and if you want, I will introduce you to the design engineer who built the blower pistons for me. BTW those pistons were about 10 or 15% lighter than any aftermarket blower pistons form any of the usual suspects. More important to me they have easily survived four plus years for me and guys I have built blown engines for.

N/A will not work the pistons as hard and you might say why do I need to go to a piston at that level. The answer is simple reliability, consistency, strength, quality and they are the same price or less than pistons from the usual suspects.

If you want an intro let me know by PM and I will help. BTW full disclosure I have no financial interest in them and receive no form of any type of compensation from them. Like Brent, they are just real good guys with a real good product that are easy to work with and helped me when no one else could.


Ed