250 "Freshen Up"

[Econoline]

Safest way is to use a 100ml graduated cylinder filled to 100, then draw from that with the syringe and shoot back in any left over and do the math. I tried mine with just a syringe, later I did it as above and there was a 3 cc discrepancy from the syringe only numbers.

 

[drag-200stang]

Cobra being a rebilt engine you could have a dog log head on it. can you post pics of intake and chamber.

 

[powerband]

I would believe that the head has been milled. My measurements may be off a little off due to where I put the syringe plunger on the 10ml line and small bubbles in the syringe but not a whole lot. I can always recheck.

Take your time and check your methods,. The syringe, spark plug and a few small variables are taken for granted to add to measuring fun. Lately I measure using a medicinal type plastic shot glass, with CC or OZ 's already marked out, Marvel Mystery oil (red and smells nice when spilled) eyedrop'd into the plastic cover over head. Thinkin' @ 1 ounce (shot glass) = @ 30CC's(29.573 CC), measuring the typical 48 to 62CC log head is simpler, I empty one- 1oz/30cc's shot cup, then see/measure what's left of second1oz/30cc cup.

> what is correct Spark Plug range or recommend's for Compression Chamber measurement ?

have fun

 

[cobraguy]

Oh crap I know why I'm getting such a small number. I tossed the old plugs already so I used my compression gauge to plug the spark plug hole. I'll pull a plug from the engine in the car and recheck. Still I have a clue as to what I'm doing and can talk to the machine shop and not feel like a total tard. Any body had any experience with Titan Engines in Ocala Fla. They advertise a Master rebuild kit on Amzon for $430ish but don't give specific brand names for the parts. I know I can get what I need at CI but I'd go over budget.

 

[bubba22349]

I ysed a 10ml syringe and got 47ml/cc for the chamber and 7ml/cc for the dish in the stock piston. Deck height .145 Head gasket .045. Bore 3.700 at .020 over and 3.910 stroke equals 8.87:1 if all I do is bore .020 over and new pistons are just .020 bigger. Decking .020 gets me to 9.2:1 as long as new pistons....... So it looks like I get my rebuild kit first and measure the dish and piston height and recalculate. Thanks for the help In the past I've always just threw the parts together and hoped for the best. This time I feel like I will know exactly what I want the machine shop to do. I would like to get the CR close to the upper limit for 87 octane. Where would that be?

The quick and safe way is to just put a desmal point in the middle so 87 Fuel = an 8.7 C.R. the upper limit though all depends on your tuning skills 9.2 to maybe as much as 9.5. But because of the 250's excessive deck height, you will need everything to be just right to push it to the high end of the limit including getting the distributor's (you need to at least use a DS II) advance curve set up correctly there are a couple of site members that are good with that if you need help. If your on a real tight budget and your stock cam is still in good useable condition then you could advance it to 4 degrees. That would help low end power some at the slight expense of some lost top end but with your light weight car it could work out very good, this is what I will be doing on my 250. On your engine kit if you could get them to customize it by including 255 V8 pistons in place of the 250 stock type that would help get the compression up without the need to deck the block beyond a light cleanup cut if it even needs to be trued. Other items I ask or look for in Master Kits are Felpro gaskets, Clevite bearings, Melling oil pump, and Molly Rings. One other way to get the pistons up higher in the bore is to use the 300 rods with a set of custom pistons if your budget allows. Your are getting lots of good suggestions from everyone for your build. Good luck

 

[cobraguy]

OK so I re measured my chambers and got 59cc. According to the calcularor shaving the block to a .075 deck height I will have an 8.9:1 static CR. Wich sounds good for 87 octane. I think I'll stay with the stock cam because I'm not doing anything to the head at this point. I found an affordable kit with name brand parts and a trusted local machine shop to do the dirty work. All in I'm at $750 for this build.

 

[Econoline]

I ysed a 10ml syringe and got 47ml/cc for the chamber and 7ml/cc for the dish in the stock piston. Deck height .145 Head gasket .045. Bore 3.700 at .020 over and 3.910 stroke equals 8.87:1 if all I do is bore .020 over and new pistons are just .020 bigger. Decking .020 gets me to 9.2:1 as long as new pistons....... So it looks like I get my rebuild kit first and measure the dish and piston height and recalculate. Thanks for the help In the past I've always just threw the parts together and hoped for the best. This time I feel like I will know exactly what I want the machine shop to do. I would like to get the CR close to the upper limit for 87 octane. Where would that be?

The quick and safe way is to just put a desmal point in the middle so 87 Fuel = an 8.7 C.R. the upper limit though all depends on your tuning skills 9.2 to maybe as much as 9.5. But because of the 250's excessive deck height, you will need everything to be just right to push it to the high end of the limit including getting the distributor's (you need to at least use a DS II) advance curve set up correctly there are a couple of site members that are good with that if you need help. If your on a real tight budget and your stock cam is still in good useable condition then you could advance it to 4 degrees. That would help low end power some at the slight expense of some lost top end but with your light weight car it could work out very good, this is what I will be doing on my 250. On your engine kit if you could get them to customize it by including 255 V8 pistons in place of the 250 stock type that would help get the compression up without the need to deck the block beyond a light cleanup cut if it even needs to be trued. Other items I ask or look for in Master Kits are Felpro gaskets, Clevite bearings, Melling oil pump, and Molly Rings. One other way to get the pistons up higher in the bore is to use the 300 rods with a set of custom pistons if your budget allows. Your are getting lots of good suggestions from everyone for your build. Good luck

I'm not nearly as experienced as you bubba, but I'm always wanting to learn and hear from those that may know. And I don't want to hijack the thread. But from what I've gathered during my build, isn't the "safe way" to calculate the DCR and shoot for 7.7 for 87 w/ a 250? I see that decimal rule of thumb thrown around all the time but it seems so out to lunch when what you really need to know is the effective C/R. I saw after my cam selection how my effective C/R ie DCR was pretty low even though I'm looking at 9.5:1 C/R. I'm at 7.4 or 5 and going to shave the head to bring it up to 7.7 or more DCR which iirc puts me somewhere around 9.6 or 7 C/R with my config. Isn't 7.7 a pretty safe dcr #, even in the 250?

 

[bubba22349]

OK so I re measured my chambers and got 59cc. According to the calcularor shaving the block to a .075 deck height I will have an 8.9:1 static CR. Wich sounds good for 87 octane. I think I'll stay with the stock cam because I'm not doing anything to the head at this point. I found an affordable kit with name brand parts and a trusted local machine shop to do the dirty work. All in I'm at $750 for this build.

Your headed in the right direction leaving the head alone (keeping the Comb. Chamber bigger) and instead working on the deck height is the best way to go with a 250's excessive deck height. This is why I suggested using the 255 V8 piston swap they would raise deck height .085 higher then the stock pistons and the C.R. Would also be raised to about 9.0 to 1 before any decking. Good luck

 

[bubba22349]

I ysed a 10ml syringe and got 47ml/cc for the chamber and 7ml/cc for the dish in the stock piston. Deck height .145 Head gasket .045. Bore 3.700 at .020 over and 3.910 stroke equals 8.87:1 if all I do is bore .020 over and new pistons are just .020 bigger. Decking .020 gets me to 9.2:1 as long as new pistons....... So it looks like I get my rebuild kit first and measure the dish and piston height and recalculate. Thanks for the help In the past I've always just threw the parts together and hoped for the best. This time I feel like I will know exactly what I want the machine shop to do. I would like to get the CR close to the upper limit for 87 octane. Where would that be?

The quick and safe way is to just put a desmal point in the middle so 87 Fuel = an 8.7 C.R. the upper limit though all depends on your tuning skills 9.2 to maybe as much as 9.5. But because of the 250's excessive deck height, you will need everything to be just right to push it to the high end of the limit including getting the distributor's (you need to at least use a DS II) advance curve set up correctly there are a couple of site members that are good with that if you need help. If your on a real tight budget and your stock cam is still in good useable condition then you could advance it to 4 degrees. That would help low end power some at the slight expense of some lost top end but with your light weight car it could work out very good, this is what I will be doing on my 250. On your engine kit if you could get them to customize it by including 255 V8 pistons in place of the 250 stock type that would help get the compression up without the need to deck the block beyond a light cleanup cut if it even needs to be trued. Other items I ask or look for in Master Kits are Felpro gaskets, Clevite bearings, Melling oil pump, and Molly Rings. One other way to get the pistons up higher in the bore is to use the 300 rods with a set of custom pistons if your budget allows. Your are getting lots of good suggestions from everyone for your build. Good luck

I'm not nearly as experienced as you bubba, but I'm always wanting to learn and hear from those that may know. And I don't want to hijack the thread. But from what I've gathered during my build, isn't the "safe way" to calculate the DCR and shoot for 7.7 for 87 w/ a 250? I see that decimal rule of thumb thrown around all the time but it seems so out to lunch when what you really need to know is the effective C/R. I saw after my cam selection how my effective C/R ie DCR was pretty low even though I'm looking at 9.5:1 C/R. I'm at 7.4 or 5 and going to shave the head to bring it up to 7.7 or more DCR which iirc puts me somewhere around 9.6 or 7 C/R with my config. Isn't 7.7 a pretty safe dcr #, even in the 250?

Yes your right about DCR its the better way to calculate it especially when building a combo that's no longer stock I. E. Using a performance cam and other performance parts. The major problem with a 250 though is that the piston is so far down the bore (.140 and sometimes even more) this causes detonation much sooner. The other problem is that the cam is retarded in all but the early model 250's. To be able to answer your question as to if it's pretty safe in a 250 I would need to know more details of your engine combo like what methods you used to raise your DCR to 7.4 or 5? In my opinion milling / or cutting the cylinder head down though it's the easy way it' not always the best way to raise CR or DCR in a 250.

 

[cobraguy]

Thanks Bubba. I looked at the 255 pistons for a minute. The problem is then I'm buying the rebuild parts individually. That drove the price up more than the cost of shaving the block. My deck hieght was .145". Was there a difference in cams from 69-72 to 73 on. I ordered the engine kit last night and ordered 69-72 parts.

 

[Econoline]

I've read here somewhere you should only deck the 250 .040" max. So I would look into that before you take too much off the deck. When I did mine I decked it .032" and used 2.5 HSC pistons, silvo-lite 1192. I did this b/c the 255's are really hard to find and they are really expensive at this point, got 2 set's of 2.5's for $80. Had 8cc D dishes milled into them for another $100 which I would have had to do with the 255 pistons as well. Still not zero'd though, .015" in the hole iirc. The 2.5's raise comp height .056" iirc. If I had it to do over again I would have decked .040" b/c with my cam I still would have been fine, now I'm looking at shaving the head a bit to bring up DCR.

 

[bubba22349]

You picked the best of the stock short block parts for cam timing (1969 to 71). The cams were all the same, Ford then used the timing chain set to retard the cam timing on the later model 250's (from about 1972 and up). Good luck

 

[cobraguy]

My kit does not include the timing set. I am getting that from another source. There also ordering for a 69-72. Econoline raises a red flag. Can I deck my block .070" without worry?

 

[Econoline]

Someone will chime in on that. If you search you can find some info. Some say not to deck it at all and either use 2.5 hsc or 255 pistons and early 300 rods. iirc I've seen at least 1 build were they did deck it like 70 or 80 thou. but from what I understand it's not recommended b/c they can crack at the bolt holes.

.145" is really high! I'd dbl check that when you get your new pistons before it get's machined. I just checked my final numbers and mine was originally .108"(virgin block) assuming the machinist actually took off the .032" I asked for b/c I originally measured .103" but I may(read: probably was) have been in error. My final deck height measurement was/is .020", not .015" I was shooting for. So with the Victor gasket I have, I should end up @ .064". Not ideal, but certainly much better than the .152" it would have been if not for the decking and piston swap. If I could find a good oem steel gasket I'd be in like Flynn.

Good luck cobraguy!

 

[powerband]

a few more grains of sand:

Can I deck my block .070" without worry?

Your stated deck height of .145" is more a than few OEM 250's I've measured. CI tech lists 250 OEM deck height at .123" or just a little more than 1/8". Your decking of .070' is a little more than 1/16" (.0625) so you should be safe. Simple to measure deck height with drill bit on top of piston and straight edge.

The final build should make you glad you took the effort to make it all work together.

Do the research, do the math, then do what you can afford ... .
have fun

 

[cobraguy]

Well I can't determine the final cut until I measure the new pistons. If the new pistons are same I will cut .060 for a new deck hieght of .085 which calcs out to 8.74. Looking at some other threads .060 can be done safely. I have adjustable rockers on the engine in the car now so I'll swap that over. I'll get the timing set from Classic Inlines.

 

[bubba22349]

I've read here somewhere you should only deck the 250 .040" max. So I would look into that before you take too much off the deck. When I did mine I decked it .032" and used 2.5 HSC pistons, silvo-lite 1192. I did this b/c the 255's are really hard to find and they are really expensive at this point, got 2 set's of 2.5's for $80. Had 8cc D dishes milled into them for another $100 which I would have had to do with the 255 pistons as well. Still not zero'd though, .015" in the hole iirc. The 2.5's raise comp height .056" iirc. If I had it to do over again I would have decked .040" b/c with my cam I still would have been fine, now I'm looking at shaving the head a bit to bring up DCR.

Econoline, you did your 250 right! If you could score an original steel shim or a custom copper head gasket you would be golden.

 

[powerband]

... RELATED TO DISCUSSION :

If you could score an original steel shim or a custom copper head gasket you would be golden

The original and re-issued steel shim gaskets for later 200/250's are very hard to find, BUTthe listings for the older 144/170 3.5 vs 3.68 bore steel shims are listed together and will not work.
.

The small Ford "Metal Shim" head gaskets application sometimes cites fitting both 144/170 and 200 . Without a verified part number I would assume it's the fairly common 7916 144/170 gasket. The 200 cyl bore application gasket is harder to find:

Truthy archive:

Ford STEEL SHIM GSKTS:
> 144-170 CID CODE-6051A CODE-6051C
>Ford 200 CID C3OZ-6051A or C5AZ-6051B
> Ford 250 CID C9DZ-6051B
The last 200 metal shim gasket I got on Ebay was NOS but had been folded and creased - reluctantly I returned it - still wonder if it would work ...

Currently run a steel shim 6051 OEM gasket on C8' 170 (MAverick) with milled worked D7 head/2bbl/headers. - At @9.5:1 cr 170 runs strong . Deck and head prep and careful 'torqueing is encouraged.

more:
viewtopic.php?f=1&t=65150&p=499087&hilit=steel+shim#p499087

have fun

 

[bubba22349]

I been looking at the newer tech MLS head gaskets lately too. These would also be an excellent choice for a Hi Performance build, if they don't cost an arm and a leg to have them made!

 

[cobraguy]

Well I got all the pieces and the block and head are at the macine shop. The pistons new are Silvolites and are .020 shorter with a 6cc dish. I measured using a new wrist pin holding a new and old piston next to each other head down on the block and feeler gauged it. So the block is getting .060 shaved. Plugging in the #s I end up with an 8.53-1. Maybe a smidge higher after the head is cleaned up with a lite pass. Machinist says .060" is safe but anymore is pushing my luck. He's done a few 250s for Bonneville and says after about .070" it turns into a crap shoot. He also said .145" was unusually high but not unheard of. I did remeasure using a dial indicator .145"