Treblig
Well-Known Member
Not cam timing cam specs....................lobe overlap can effect compression.
Formula to shave pistons to reduce compression ??
- Thread starter Brooks James
- Start date
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Huge snafu the weisco piston 5022h6 was discontinued 5 yrs ago. . I’ve called around/internet no one has any. Even called uk and s. Africa, one guy I called said that weisco would do a special order min 4 pistons. They are
400 plus. Néw good rings 150.
I can get an eagle all forged kit balanced for 1600. I’m thinking that this is the way I’m going to go.
400 plus. Néw good rings 150.
I can get an eagle all forged kit balanced for 1600. I’m thinking that this is the way I’m going to go.
512Stroker
We are all here because we are not all there.
I am lost here, you dont have the pistons and you wanted to have them milled to create some dreamed up static CR? What did I miss?
Just remember when you do things "the cheapest way possible" when building an engine and than you hit it with a bottle the net result normally ends up to be a big steaming bag of crap.
For 4 inch stroke or 3.58 stroke
I should have said not cheap parts but rather not top shelf stuff. The piston I neede was to replace one in an engine I thought about buying.
I wanted to replace one piston but at a minimum have to buy four. Anyway it’s a moot point I’m fine with a 408 stroker kit. I’m uncomfortable with a 60 overbore even if it’s sonic checked especially as it has gouge marks in the wall.This is an engine that I was going to buy but it would have high frig factor. I’ll get the kit do it right the first time. My magnum has a stock bore and I will go 30 over.
I thought your engine was already built and ready to fire.
Is your break-in thread for a different motor ?
You are confusing the Sh.. out of me with all the directions you're going.
Is your break-in thread for a different motor ?
You are confusing the Sh.. out of me with all the directions you're going.
The piston shaving idea was for a motor I was thinking about buying. However, due to my having to buy 4 instead of just the one that is broken.They’re discontinued I am going in a different direction. I’m looking at a kit on eBay that is supposed to have Mahle pistons
That will produce 11.7 cr with a 65 cc head. My new plan is to use an .80 thousandths head gasket and take enough off the pistons to get 10.0 cr , very 93 pump gas friendly.
It still might not be a bad idea to buy 4 pistons......that would give you 3 spares to fix tuning snafu's, people who build nitrous motors buy extra pistons to replace the ones that get scorched, it's an idea
Rdrd to determine how deep it is
I wasn’t able to negotiate the price down , enough plus the guy has other guys willing to , take it as is without sonic testing. Plus there is a gouge in the wall and it’s hard to determine how deep it is , Too many unknowns, ifs, then, but, maybe etc
B3422w5
Well-Known Member
thicker head gaskets aren't going to lower compression 2 full points.
Need new slugs
dano
Evil Handy Man
Find a good block and built it right, the way you need. Someone else's damaged goods is just that.
That exactly what I’m going to do. I just don’t trust an engine that is damaged. I’m older an cantankerous , don’t want to always be worried or working on it. I need maximum durability and going with a careful build and new parts I can’t go wrong
512Stroker
We are all here because we are not all there.
Perhaps a quality built crate engine would be best for your situation.
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Everything exc crate, I want the satisfaction of doing it my self
dano
Evil Handy Man
If you plan to run it hard, you might look for one of the Mopar racing blocks.
I forgot what they are called, X or R, something like that.
At I’m guessing 3k my wife or should I say the boss I call her el jeffe Spanish for the boss in Spanish, is not going to go for it.
dano
Evil Handy Man
I got one of them too.....
Treblig
Well-Known Member
My wife will let me do anything she says!!!
Final decision, new eagle 408 stroker kit all forged. Estimated cr 10 to 1. I was thinking about having a kit with a wild *** roller included, shipped. Don’t have the parts to effectively use the cam. So I’m want to get summits kit for
1800. Thanks for all the advice.
Dustoff
1800. Thanks for all the advice.
Dustoff
B3422w5
Well-Known Member
i would make sure that kit is ALL forged. Most of the stuff in that price range is using a cast crank, not forged.
None of you will ever get this time back. I will admit, it was worth the time watching it. LOL
Yes I called two places to verify
33IMP
Well-Known Member
Cam timing, overlap, lobe speration, etc. all have an effect on cranking compression, and dynamic (running engine) compression.
But static compression ratio is determined by piston, cylinder heads and gaskets. A static compression ratio of 10 to 1, will be 10 to 1 whether its got a 210° cam, or a 320° cam.
Bret Tschacher
Well-Known Member
I'm sure by the time you read everyone's suggestions mine will have been covered, with that I'm going to say this. Milling is not going to affect valve pockets as they are dependent upon the distance from the pin center to the required spec of the distance from from the valve seat to the pin center at TDC, pockets are machined to give a set clearance with the valve opening in relation to the piston position as it moves in the bore ! You don't measure clearance with the piston at TDC and fully open, as the intake will some what follow the piston as it goes down ATC and ex, is opening as piston is going up to TDC, hence changing valve timing and lift will affect the clearance and usually only requires a small amount of material removed to insure the customary .100 " for exh. and .06 to .08 for intake. Some people like to have the same on either valve and that is probably a good thing when it comes to higher RPM. I lost a set of E valves in a BB once when index pin in the cam broke causing the cam to be SERIOUSLY RETARDED, fortunately the engine stopped running before the damage got any worse then bending the valves losing compression, however the cam failed not long after I patched the problem, I failed to see where there were a couple of tappets climbed a lobe in front of the lobe they belonged on. Anyway, AS others have said find someone that is interested in your pistons and take the lose it would be little difference when compared to the cost of having them fly cut thereby affecting the balance of the set. If you intend to balance the engine before assembly, not such an issue. I'm sure that is your plan. Long ago I built an AMC 401 for a guy from a mix and match up of parts from an earlier 390 and a 401 block. This required using crank rod and piston combination of both and having the pistons cut down .06", they were a dished piston with pockets. By the time I was finished, I had to CC the dishes in the pistons, square the block decks, CC and mill heads, (closed chamber)mock up the engine and CC the complete chamber volumes and do the math. At the starting point of the build, the pistons were above the deck so by the time the engine was ready to finalize, I had .01 deck clearance added to the compressed gskt dimension of .037. A minimum of .04 was my target and I got a little extra just for S's & G's. Point is with dished pistons the only thing at lose was a little metal above the top comp ring but I still had plenty. With flat tops it would have been a lose across the entire piston top but forged pistons are so much better than cast so there would be such little lose in strength. However, using nitrous might be an issue if you have to remove a lot. It is a big issue with the top ring ring land, especially when using power adders. It's good to have at least .200 and any extra is even better. On that note, nitrous loves higher compression as it is a cooling process. Ign. timing has to be reduced regardless, because burn rate is so much faster with all that extra O2 and the freed N2 acts as a shock absorber releasing stored energy back into the effort of pushing the piston down. Someone suggested E85 and that is truly a good idea as it loves compression just like N2O, all you have to do is recal fuel/air ratios. Now comes a truly beautiful suggestion, run away from a carbonator and set yourself up with a really nice EFI system and a flex fuel sensor, all your problems go away without having to worry about 11:1 compression. N2O will still work, remember, adding Alch to fuel will require a richer mixture regardless of how much you add so using a flex fuel sensor with EFI does it automatically. I'm currently working at building a system like this which will have just under 11:1 , not going to mention it's a Chevy though. It doesn't matter what brand it is because it was said a MOPAR SB looks like a Chevy with funny looking rockers, and late model RFI heads have stubs now so they look like SBC's and a bunch of others now. Point is what usually works for one works for the other, most of the time. If you do some research you will find that timing chains for various engines can almost if not fully interchange because they have the same number of links and pitch, the only thing that changes is the specs on the gears, tooth counts and diameters along with fitting to manufactures cams. So back to fly cutting pistons, Don't worry about pockets until you have chosen a camshaft, if you can remove enough metal to get the Comp Height you are wanting and save money even after paying someone to do the machining unless you have a lathe, measure the remaining top land keeping at least .200 along with having the top at the proper spec with the block deck + compressed gskt thickness .04 is a good place to be from any point of the head casting extending into the bore. Do a mock up and all the CCing chambers, pockets, bores can be calculated with math, and calculate volume for head gskt when torqued, some gskts will give a value for you on the listing and package like Felpro does, sometimes. Then considering a variety of cams will ultimately be the deciding factor on compression since the ratio is only a number, valve timing is what matters most since compression is a factor more important than ratio. High ratio engines will have low compression with big cams and until the engine is running in its optimum range ration has less to do than actual compression. You cannot measure actual compression on a running engine, it is always going to read way less. Next is the factor of timing in conjunction with RPM, the faster it is running the less time there is for detenation to be a real issue up to a point of how heavily the engine is loaded, and since forged pistons do so much better under these conditions, a little adjustment to timing can solve most of the problem, which leads me back to EFI, using knock sensors, the engine can be tuned to be at the optimum at all times. Then you have no issues, in a perfect world. You get the best of everything, the more you put in the more you get out applies to the whole picture, more comp, more return, more dollar more return and when you get it all right, it is so cool when you open the hood and can show off all that Super High Tech stuff. I know there are guys running turbos with high comp ratios and EFI and making it all work right so that blows off the old rule of pump gas mostly. It's all in the TUNE ! Raising comp means controlling timing, since higher comp makes more heat, you need to keep the fuel fuel until the right time to make it more heat. So keep the fuel cooler longer makes all the difference. Using methods of getting the air/fuel to its lowest possible point before it goes into the chamber is the key. Fuel needs to be warmed up for vaporization then super cool the mixture on its way to the burn chamber so it has farther to go before it ignites on its own at the wrong time. Keep the chamber as small as possible, going back to the old closed chamber verses open chamber design rules so there is no place for mixture to be compressed by flame front. This very reason is why Hemis are so awesome, no place for fuel to be ignited by compression and killing the power phase with uncontrolled ignition. MOPAR kind of dropped the ball in play with plug location on BB's and SB's were better, the old poly head 318's had a leg up and Toyota 3TC's were pretty neat with HEMI chambers, now hemi and PENT chambers are the norm with twin cams with plugs over center. I love the old engines and I love the new tech control systems, they go hand in hand together. As they say there is replacement for displacement and it doesn't simply mean bigger is better, displacement is all about how much air is being moved and we all know you can as much air in a small package as in a big package when you compress it. So compress it is as much as you can and control it more! That is the way to make real power.
Dave_J
Well-Known Member
Back around 1987 we built a Dodge Omni GLH Turbo running a true 9.5:1 CR, ported G head and a 270 Adv cam. Ran fine on 93 octane with the 'Knock Sensor' and boost set at 14 PSI. But not with spray and 20 PSI. We had added a 125-150 shot of nos. So we put a small second fuel tank with an internal electric pump. A relay would kick in the second pump for the nos and the boost bleed setup. We ran 115 Turbo Blue in the second tank. We ran the nos's fuel pill a wee bit fat due to the extra 6 PSI of boost.
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