stroked small blocks in the race cars?

[PDUB]

Originally Posted by blykins

I was referencing an AFR 185cc head on a 347.

OK, thanks!

[1795]

Ed,

Thanks for the chart. The cam I have is from the prior build and is still in good condition. It was designed for the Webers. I probably will need to only do some minor porting to smooth out air flow. According to my cam card, with the 112 degrees of lobe separation, the intake valve opens at 20 BTDC and closes at 56 ABDC. So, taking that into account and looking at the graph you supplied, given that I have rollers lifters, there will be a lot of time for air/fuel flow into the combustion chamber.

Well, now I have to wait until Monday to find out which head I have and if it was ported at all.

Keep the education coming.

Jim

[blykins]

A 112 LSA is a big no-no for Webers in a road race car. That would be more suitable for a street car, where you need to watch overlap, but in a road race car when you're on the gas hard all the time, it will cost you power and throttle response coming out of the turns.

[MAStuart]

Ok with all this head and stroker talk I thought you all would enjoy watching some of these


vids by Richard Holderer. It is about head flow and dnyo testing about 30 or more heads . Some of the testing is old and some of the heads are not on the market anymore. A lot of the heads are aluminum so may not be of use to some of the guys here. It is a 4 part series but only 3 parts have been released. Hope some will learn from them. Wanted to add the there is no testing of early 289 heads .

https://www.youtube.com/watch?v=EWSlYvstFIU

[1795]

Brent,

What lobe separation would you suggest? You have my email address, send me a quote for a roller cam, 11:1-11.3:1 compression ratio, 110-112 octane fuel depending on what's available at the track (some only have 110), the Iron Eagle heads, close ratio top loader, 3:54 gears, the Webers, engine will be bored .030 over, light weight pistons, rods and light weight forged steel crank.

Let me know if there is anything else you need. Planning on running in the 3500-7,000 rpm range.

Jim

[blykins]

I'd need to know what the heads flow, their port volume, etc.

LSA is based on what overlap the engine needs. Most guys want to go 112-114-116 because there's a lot of people on the internet that say the Webers need that.....and I wouldn't necessarily disagree on a street car.....but a road race car is completely different. Depending on the duration, you could end up on a 106, like a lot of the Shelby cars ran.

If you're wanting to save money by keeping the same valve springs, then I'd need to know how they're set up as well.

[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?

[blykins]

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

[1795]

Originally Posted by blykins

I'd need to know what the heads flow, their port volume, etc.

LSA is based on what overlap the engine needs. Most guys want to go 112-114-116 because there's a lot of people on the internet that say the Webers need that.....and I wouldn't necessarily disagree on a street car.....but a road race car is completely different. Depending on the duration, you could end up on a 106, like a lot of the Shelby cars ran.

If you're wanting to save money by keeping the same valve springs, then I'd need to know how they're set up as well.

I will let you know about the heads when I verify which ones that I have on Monday. I will need new springs, as the ones that I have need to be replaced.

If the heads have not been ported, the flows will be what Dart Iron Eagle heads show on the website, as I have no way to measure. The engine builder has a full machine shop, but he does not do head porting from what I recall and he would send them out.

Jim

[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!

[PDUB]

Originally Posted by eschaider

With Hydraulic roller tappets we can have access to the same breathing enhancements without the danger of premature tappet failure that plagues solid roller tappets when they are placed into day to day service as opposed to weekend race duty.

Ed

Does a solid roller have a lower life span due to some inherent design issue in the lifter itself, or is this due to other factors like higher spring pressures for running at increased rpm levels? I would not think that the solid roller would fail any quicker given an identical set up. What am I missing?

[blykins]

Solid roller lifters fail earlier because of a combination of higher spring pressure and lash. Lash causes the lifter to bounce off the lobe.

[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.

[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?

[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

[xb-60]

Ed, how did you simulate the areas on the pistons that are stressed differently in your situation by the forced induction ? That must have been a challenge?
Cheers
Glen