250 build

Yep...rope seals are way old school and the pin was there to prevent the rope seal from moving. The majority of the seals today are neoprene and fit in their nice and tight and the pin needs to go. I used a nice bead of ultra grey silicone on mine and they don't leak at all.
 
Ok, that make since. Thinking about it now, I notice people over lap the rear seals 1/4 of an inch to keep it from leaking.

So here is a question for ya.

Should there be any issue with pump gas if the CR is between 10-10.2?

Did some math and I think I'm gone get the machine shop to shave .030 off the block and gonna go for 52cc chambers on the AL head.
 
Another question. Who do you guys use to rebuild your dampers? Mine is shot to hell! A lot of the elastomer or whatever rubber they used s disbanding and coming out.
 
Here is an idea I have, but not sure if my thinking is right. So the lower the quinch area( deck height ) the less likely detonation? With 255 Pistons and AL head, compression is way too high due to the deck height of my engine being .110.
Now if I zero deck the block and use the 13cc dish Pistons, would this help eliminate detonation/pre ignition? My thought is if you zero deck, there will be very little if any of an iron lip present during combustion. Since aluminum disparate so heat better, would just using a dish piston make an AL inline work with a 10-10.5 compression ratio on pump gas better than just using flat top Pistons and decking the block accordingly? Am I thinking correctly? Or am I missing something?
 
Yes in theory the ideal quench area ranges from .035 to .050 (some brave souls even go down to .030) this includes the head gasket thickness plus the deck height i.e. The head gasket thickness plus distance from the top of the piston to top of the block. A flat top or dished piston are two of the best designs to use, the best dished pistion design would also be shaped to mirror the heads combustion chamber. Good luck :nod:
 
rOLLER TIP ONLY ROCKERS dont realy do much except make it more difficult to set proper valve tip contact. Just off idle the friction they reduce is the same as a slipper tip. However a full roller rocker does reduce friction throughout the rpm range reducing oil temps as much as 25* around the fulcrum.
 
Bubba: so what I am trying to weight out right now is if the lighter weight 2.3 piston with a higher deck height is a better choice than the heavier 13 cc 200 piston with a lower deck height. Using the 13cc piston allows for getting the quench area between that .060-.035(including the .050 crush of the head gasket) and keep compression around 10.2:1 with 52 cc chambers on the AL head. Is this a better rout? Or does the lower weight of the 2.3 HSC piston make up for that higher deck height? Let's say the CR is the same for both set ups.

Turbo: I kinda figure that the full roller is better throughout. Based off what you have said; is the roller tip rocker worth getting? Or would I just be better of getting the full rollers now?

Anyone feel free to chime I need.
 
Yes in most cases using a lighter weight piston along with lightening of the rotating assembly is better, including lighter pistons, polishing the rods, knife edging the crank etc. That said there have been some problems with those HSC pistons being used in 200's and 250's for Hi Performace use. X wrote a great deal about this problem in a number of posts, one of those is this (see below post) and it also has what to look for in a good cast type pistion well worth the read. It's near the bottom of the phost, in the link below. Hope that's of some help.

viewtopic.php?f=1&t=72474&hilit=Why+do+we+keep
 
I read that thread this morning while looking around on the net.
And from the stuff I have read along with looking at the piston designs of most engines made now days with CR of 10.0 and up. I am thinking the dished Pistons make more since to use. Now my question is if anyone know what company makes the 13 cc dished Pistons? I know that was a later design in the 70s for the 200, but when looking at them all online, the ones I see on the net do not spec the dish cc.
 
You will need to go direct to the pistion companies sites to be able to find their specs listed. I also rembered that Powerband has used an AMC pistion in his 250. A std pistion is .070 over for a 250 and it has about 21 cc dish. Good luck :nod:
 
If you use the 13cc 200 pistons you'll be back down in the hole... Are you going to use different rods to bring them back up?

On my 250 build, my oem pistons were .108" down not including the gasket. Previous owner had replaced the head gsket w/ a felpro and didn't mill the head. Static compression was @ a whopping 8:1 :banghead: I used Silvolite 2.5 HSC pistons which brought me up .056", decked the block .032" and ended up with a deck height of .020". Ended up with .040" overbore to clean up the block. This left me with .064" in the hole using a Victor gasket and a SCR of 10.7:1 and a DCR of ~8.5:1 with the cam I'm using and assumed 60cc chambers. To help with that I had the pistons dished 8cc's in a D shaped dish the matches the combustion chambers. This brought me to 9.7:1 SCR and 7.7:1 DCR. My head is getting done now, C9 head, having later intake valves and 144 intakes installed for the exhaust, valve guides and cleanup of the exhaust flange and a minimum clean up of the mating flange. The head has 62 cc chambers. So I'm hoping for no more than 1-2 cc's lost.

I mis-measured the original deck height by 5 thou, I was shooting for a quench distance under 60 thou. Either that or the machinist didn't take the right cut on the deck, unlikely. I did it this way b/c I was on a tight budget and just trying to optimize the engine a little better. Low end power and torq, not high RPM. Saved alot of money over custom pistons and rods or even 255 pistons which are about as rare as hens teeth or very expensive and would also need dished more than the 2.5cc's worth of valve relief in them. I think it worked out OK, I can still use an aluminum head with 54cc chambers w/ a corteco gasket and be @ 10.2 SCR and 8.1 DCR. One thing I did not do and hopefully won't regret is have the rods reconditioned and upgraded.

Anyway, just thought I'd share my experience with you. Sounds like you want to build a higher revving engine though than what I built for the Econoline. Cheap cast pistons milled may not be adequate for your needs/goals.
 
What I am trying to do, or the idea I have, is to bring th quench to .06-.065. I measured my deck height from the lip of the dish to the block surface. It measured .110. From researching and asking questions or seams to me that bringing that lip up closer to the head and directing the combustion to the dished area, this will help to prevent detonation on pump gas at the 10-10.2 CR range. At least this is how I am understanding it from my research.

The 13cc Pistons will help with the cc of the combustion chamber, assuming they are 52cc's.
If my thought process is wrong please l t me know.

Econo: thanks for sharing your experience
 
iF YOU can find them light weight wrist pins reduce the reciprocating mass more than a light weight piston does.
 
depending on spring installed ht would look around to see if beehive springs would fit. I do have some dual springs never used and retainers. They were for a solid lifter cam not sure of the specks
 
As for timing chains the leaf chain will strech in about 5000 miles beyond what I would like. They will last maybe 3 years or so at best before economy and performance take a real dump. That was on a daily driver I had around 200 hp.
 
The head that is on the way is coming with duel springs. I think that is the best choice with the 274/274 cam.
I'm looking around to see how much the full roller rockers are gonna cost right now.

on the timing chain. Who makes a good one? The one I pulled off had 3/8 inch of deflection while it was on the engine.
 
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