Once upon a time, some body made 1.6 and 1.9 valves in the std Windsor length with out braking the bank.
Any body still do these ?
When I rebuilt the 351 2V in my car I used dished pistons to match the original compression ratio, added a Comp 268H cam (slightly lumpy idle) and a Edelbrock performer manifold with a Holley 1850 600cfm carb.
This combination with a set of shorty headers/2200 stall converter and 3.50 gears performs very well.
After experimenting with the jetting on the Holley (went from a 65 to a 71 main) the drivability and response is excellent as long as all of the air bleeds in the carb are kept clean.
I have considered swapping to fuel injection but I can’t see spending the 2-2500 bucks to do this when it is working as well as it is.
Do you use a wire to clean the air bleeds?
I have a stock 69 351w 2v in my 68 that I put an Edelbrock performer intake, Edelbrock 600 cfm and tri y headers. Real happy with it as a driver- runs in traffic or on the interstate without fussing with it. My Shelby and Mustang buddies recommended the Edelbrock over the Holley as a “set it and forget it” carb and that has been my experience so far. My wife says I drive it too fast so that tells me I have setup pretty good.
The first time I had an issue with the air bleeds I took the carb apart, let it soak overnight in carb cleaner then sprayed the living crap out of all of the passages with aerosol carb cleaner and put it together with a new kit.
After that I have made it a point to spray aerosol cleaner in the air bleeds about once a month with the carb on the car and I haven’t had an issue since.
A bit of old school here, but an old trick was to use 327 Chevy valves, the intakes are 1.940 in and the exhausts are 1.600 in. They have the same stem diameter as the Windsor 289/302 (not sure about 351). The valve stems are longer, so you will need to check spring height and rocker geometry. If need be, may need longer push rods which you can get for the Windsor’s.
When I did my (2V) 289 heads I used a 351 Windsor inlet valves and a Chevy stainless steel exhaust valves, I had to cut down the stem on the Chevy valve so it matched the 351 Windsor inlet valve stem height, this caused the spring retainers to be too close to the rocker, but roller rockers solved that problem. The valve springs had to be shimmed on both the Chevy valve and the 351 Windsor valve to get correct seat height.
To get the correct valve geometry I changed the length of the push rods, but this was no big deal to me as I needed to purchase hardened push rods to suit the guide plates.
I used the Chevy stainless steel exhaust valve because it was the only one I could get with the undercut stem, They where a high flow valve and the Windsor’s need all the exhaust flow they can get, especially for fuel economy.
From memory I cut down the diameter of the Chevy valve heads because I also went to hardened valve seats and was concerned about clearance between the inlet and exhaust valves?
Also ported the heads to suit the camshaft profile.
Smilodon, I either did not convey the concept here or you have miss read what I was trying to say. Dished pistons actually increase power and fuel economy. Careful, I did not mention anything about lowering the compression ratio. Putting a dished piston into an engine and running a 10:1 compression ration is not the same as putting in a dished piston to lower the compression ratio to say 9.5:1. That is why I hinted at using a 289 head with it’s low combustion chamber size and then using a dished piston, I don’t know of any aftermarket heads that have small enough chamber to work correctly in this concept.
Dished pistons improve the flame propagation and reduce the surface area of the combustion chamber. To build an engine one needs to build it with the least combustion surface area, this allows the engine to run leaner under max power and cruise mode without damage. Lean fuel mixtures release more energy into the combustion increasing pressure on the piston, and inturn increases power out put.
On an engine with a lot of quench area there is a lot of unburnt fuel mass in the burn which results in lower combustion temperatures, this then allows the engine builder to use a higher compression ratio.
But this unburnt mass then enters the exhaust stroke where it now burns producing a force downwards on the upward moving piston. To reduce the downward force on the upward moving piston on it’s exhaust stroke the engine builder/designer has to lower the energy level of the fuel, this is done by running a rich fuel mixture. (Engine builders run the engine rich under maximum power mode.) The rich fuel mixture with it’s lower energy rating again lowers the combustion temperature even more, which allows the engine builder/designer to raise the compression ratio more again. It is a case of two steps backwards and one big step forward, the net result is a gain in power. But at rich fuel mixtures. The problem arises when the engine goes into cruise mode (lean fuel mixtures) it becomes inefficient and is only partly compensated by the higher compression ratio.
As Bluestuff say’s “Its going to be a driver that i can just get in and go somewhere with out fighting with it.
smooth and quiet, idle sweetly at the lights, and not pass every thing but a petrol pump”
So he does not want an engine with a lot of quench. He needs a small amount of quench and a dished piston for a street engine. With a dished piston less unburnt fuel mass enters the exhaust stroke and such there is less fuel burning when the exhaust valve opens, and thus the exhaust is quieter without the need for an excessive silencer.
What you are saying about the Cleveland’s is correct, and quench is important, but it is only productive when the piston is close to TBC. But when the piston is close to BDC, a different approach is needed to solve engine efficiency. That is where a dished piston comes in.
Even on a Cleveland a dish pistons shows gains, but the problem is how do you build a Cleveland with a dished piston and still build it with a high compression ratio?
Yearby, a dished piston provides a pocket in which a combustion event can occur in the combustion chamber. Unfortunately, the primary combustion event in a gasoline engine should always be started at the spark from the spark plug.
In an engine with tight clearances and a good amount of quench, secondary ignition events caused by hot spots, compression, and even remnants of former combustion events all get ‘squished’ into the combustion chamber of the head, which favors the primary combustion event. Effectively, the secondary events are stomped out, while greatly encouraging the spark event. Further, the act of violently ‘squishing’ the full charge into the combustion chamber creates a wonderful amount of turbulence, homogenizing the air and fuel, and promoting a rapid explosion of great ferocity instead of the long slow burn allowed in a larger chamber.
In other words, a flat piston with a well-designed quench-head combustion chamber can get better efficiency, not worse, because the fuel is more completely burned in the chamber early in the cycle instead of ejected into the exhaust later.
For any given compression ratio, there is a given amount of room in the chamber in which the fuel and air charge can be burned. However, creating a heart-shaped chamber that promotes the swirling motion of the charge, directing it through the chamber towards the exhaust is very effective for a ‘wedge’ in-line valve chamber. Reducing the size of that chamber in favor of a large open dish in the piston to create the same compression ratio reduces the velocity of the mix, and helps it move around the combustion chamber in a nonproductive manner.
And while I can honestly say that I don’t know if you’re right or wrong about the dish being more efficient near Bottom Dead Center, I do know that the most important part of the combustion process happens before, at, and after peak pressure, which should be just after TDC, because it is this part of the combustion event that actually pushes down on the piston.
Using a piston that is sculpted to mate with the head and utilizes the quench area, forming part of the combustion chamber with its own features can be very effective. A true dish however, only allows the edges of the head to come into close proximity with the piston. With a flattop, running tolerances as close as effectively possible has another effect: at very close proximity to the head, there is actually a transfer of heat from the surface of the piston into the head itself, preventing hot spots in the combustion chamber. David Vizard suggests that running as close as .030 is probably the limit of practicality for a street motor, but in experimental engines, they’ve been able to run it much closer to very good effect.
Believe it or not, they’ve run plain old ordinary pump gas at compression ratios like 17:1 and even higher with flattop pistons and good quench. Most of the science behind quench and even turbulence was not very well understood until the mid 80s, at which point research and computer modeling helped to explain why some engines seemed to be much more octane-tolerant than others. Quench effectively adds octane to your fuel, preventing detonation and improving power output by allowing higher compression and better fuel burn.
With its disregard for combustion chamber topography, a typical dished piston greatly reduces the effectiveness of a well-designed chamber. Despite increasing the chamber size, reducing compression, I would not recommend their use.
Im very much in the camp supporting small chamber, flat top piston and 10:1
The heads will be C90e or Dooe with 60cc chambers to keep pressure and subsequent torque up.
What length are chev valves?
Im thinking they are shorter than the Windsor’s there for not ideal geometry.
The last 351w i did i used Rollar rockers , adjustable studs etc etc
and a port job.
I didn’t want to go to that expense this time around for street driver.
The Chevy valve stems are longer than the Windsor’s so as to clear rail rocker tips. From what I have read the keeper groves are in the same position as 289/302. I also read that when using the Chevy valves in the 289/302 Windsor the valve geometry is correct in most cases. But I have also come across a 302 (Windsor style engine) built at the Cleveland plant and it had longer valve stems and longer push rods than the normal 289/302. Just saying don’t presume anything. All I can really say is I used a cut down Chevy valve in the exhaust port of a 289 and a 351 Windsor valve in the inlet port of the 289/302 I built years ago.
Smilodon,
Obviously we have two totally different ideas on how the internal combustion takes place, therefore I suggest that you start another topic regarding engines design or something like that and then invite me to respond. That way we can leave Bluestuff to his engine build, he seems to have his mind set on flat top pistons regardless of what I would say. That is his discretion, it’s his car and engine.
As to what you have said above, I understand, and yes this is 1980’s theory but still I am finding holes in it. To me the theory has gone off on a tangent and needs to step back a bit, because that theory is not working, If it was, manufacturers would not be investing in electric cars.
As for David Vizard, I think I may have spoken to him on the internet before. The guy (also called David) I spoke to was full of knowledge, seemed to pick numbers out of his head regarding building engines, resided in the South east of the USA, got into drag racing with a 283 in the 50’s, Raced a white Mustang with Cleveland power. Sometimes we talked about Smokey Yunick, the guy I knew as David seems to know Smokey as if he was a long time associate. Then one day the guy I knew as David just disappeared, I sent him a email to see if he was okay but never got a reply. I often wonder if the David I knew was the David Vizard of engine building fame. What has happened to David Vizard?
Im happy to let the thread stay alive guys …lol
I might learn something …lol
BTW Yearby,
Windsor valves are 5.070 length i think
and chev is 4.88.
that leaves me .200 short.
lash caps are a bit archaic, and i was going to try the roller tipped rockers that have built in rails .
The cam i would use is only 204/214 duration and 448/472 lift so it has a reasonable margin ?
Always open to more imput?
That’s weird, when I did it the Chevy valves where longer than the 351 Windsor??? Does not seem right.
Iv settled on Pistons, KB151-030 flat tops with two valve reliefs.
But i want to increase the valve sizes with out spending the bank ?
Windsor valves for the 351 Windsor can come in sizes from 4.900" to 5.540" in length.
The Chevy 327 valves can come in sizes from 4.030" to 5.50" in length.
Each has their own unique applications and it is the engine builders discretion as to what suits the application.
I think 0.200 maybe a bit much, I would have liked to see valve stems of similar length. But it is like asking how long is a piece of string, you will not know until you measure it. In this case I mean check the valve geometry with the engine assembled. There are just too many variables, have you fitted valve seat inserts or have you just reground the seat. Has the block or head been decked? Is it a tall block or the short block, what thickness head gasket are you using, even the camshaft lobe lift will have some bearing on the valve train geometry. You need to check it .
Is this the piston you wish to use?
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The main way to get torque is to have the highest intake manifold vacuum as possible & highest possible fuel air charge velocity.
The camshaft you choose is critical & there are many out there to optimize different power bands including max torque. It’s also helpful to get an adjustable timing chain and run your camshaft timing 3 degrees advanced.
An Edelbrock carb works much more like a motorcycle carb then the typical automotive carb does. If a particular carb is recommended with your camshaft together with an intake, do that. Such combinations take the guesswork out of the picture and the results are much more predictable. Such combinations may well even recommend what types of pistons or compression ratios to use.
Obviously, if you can do a stroker motor the results will be dramatic and no one will be able to tell from looking at the outside of your engine, ultimate sleeper.
Re Yearby: that general design is correct.
the KB piston is a genuine flat top with just two valve reliefs per piston.
This will maintain compression/quench flame travel etc …
I have a double row, tru roller timing chain set, with multiple key positioning.
Im planning to run it at 4degrees advance
Iv run this combination befor and was very impressed with the torque and drivability with just a hint of “cam” idle.
The difference between this job and my previous version is that last time was with Try-Ys headers, and it was a manual.
This will have OE manifolds and an Auto.
Re: Whitelight,
Regarding your comments on velocity etc,
I tend to agree that a very conservative choice of CFM is a key to torque and drivability.
My previous engine used a Holley 490cfm,(?) vac sec, and was super responsive and ran well.
I think we often over carb our engines chasing the HP numbers rather than Torque numbers because big HP numbers sound more impressive.
It become more of a pissing contest than rational thinking.
We forget that the OE spent millions $ on making a car drivable and powerful, and we come along 40-50 years later and pretend we can do it better than the manufacturer did it the first time.
We need to keep the real word in mind as we go along.
In fact, if i cant find a small Holley again, i may try the 4V OE carb, altho im not sure if it would like having a small RV cam under it ?