81Chero Posted January 3, 2015 Share Posted January 3, 2015 I'd like to get around 9.5-10:1 and was wondering if pistons might be able to swap from other models/makes to raise comp besides having custom pistons made. I'm picking up a '88 comanche 5spd for my son, but it's got 230K on it. So, I'm going to be either looking for another 2.5 or start storing up parts. It runs OK from what I've witnessed but couldn't drive it due to a e-brake cable 'pull' breaking and couldn't release it, since it was on a hill.. Sounds like its in need of a tune up and probably vacuum line replacement. OH, I've been 'wrenchin' for decades and always want an extra engine to have as a safety. But having a little more comp is always good thing. Just joined to get insight on the 4cyl that's in the little Pioneer. (well, that and some other little stuff..) had a few 'other' Jeeps too. thanks E Link to comment Share on other sites More sharing options...
81Chero Posted January 3, 2015 Author Share Posted January 3, 2015 Don't know if these will work or not with that huge dish. http://www.ebay.com/itm/Silv-O-Lite-Hyper-Coated-Pistons-1979-93-Pontiac-AMC-151-L4-2-5L-040-Set-Of-4-/390960047587?pt=Motors_Car_Truck_Parts_Accessories&hash=item5b0708e5e3&vxp=mtr Or these.. http://www.summitracing.com/parts/slp-h822cp20?seid=srese1&gclid=CKP_5K7R-MICFafyMgodrHAAKw E Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 3, 2015 Share Posted January 3, 2015 Don't know if these will work or not with that huge dish. http://www.ebay.com/itm/Silv-O-Lite-Hyper-Coated-Pistons-1979-93-Pontiac-AMC-151-L4-2-5L-040-Set-Of-4-/390960047587?pt=Motors_Car_Truck_Parts_Accessories&hash=item5b0708e5e3&vxp=mtr E The ones you listed are not for the AMC 2.5 that you have.....these are for the GM version of the 2.5, not the 84 up AMC/Chrysler. Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 3, 2015 Share Posted January 3, 2015 Go here- http://comancheclub.com/topic/44902-po-boys-88/ No, I do not agree, simply increasing compression alone will do anything but cause you to increase your fuel costs by going to higher octane. Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 3, 2015 Share Posted January 3, 2015 http://www.summitracing.com/parts/slp-h823cp30/applications/make/jeep?prefilter=1 Stick to the ASE and not the Metric, better oil control. You can likely pick up some compression by shaving the decks, talk to your machinist, this will also cost you about $100 in custom length push rods. Also discuss with him, air flow, cam and valve timing. Link to comment Share on other sites More sharing options...
randomguy310 Posted January 3, 2015 Share Posted January 3, 2015 the stock 2.5 is already 9.2 iihr. not sure 1/2 a point would help much Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 3, 2015 Share Posted January 3, 2015 Go to www.4bangerjp.com there are several threads there on performance upgrades for the AMC 2.5. Including different pistons to use and decking the block for proper quench or whatever. To join there you need to friend them on their Facebook page and request a username and password. Link to comment Share on other sites More sharing options...
81Chero Posted January 4, 2015 Author Share Posted January 4, 2015 I've been raising compression on many different engines for a long time, and they all ran tons better. THanks for the help E Link to comment Share on other sites More sharing options...
81Chero Posted January 4, 2015 Author Share Posted January 4, 2015 Don't know if these will work or not with that huge dish. http://www.ebay.com/itm/Silv-O-Lite-Hyper-Coated-Pistons-1979-93-Pontiac-AMC-151-L4-2-5L-040-Set-Of-4-/390960047587?pt=Motors_Car_Truck_Parts_Accessories&hash=item5b0708e5e3&vxp=mtr E The ones you listed are not for the AMC 2.5 that you have.....these are for the GM version of the 2.5, not the 84 up AMC/Chrysler. ...? They BOTH show that they are for the AMC 2.5 that's why I asked. Or, is it that amc just grabbed some other makes pistons for these motors? And the comp ratio, I thought that I read somewhere that the 88's had comp in the 8's. Must have missed that one. Also, I don't "facebook" and probably never will if I can help it. Pretty much a waste of time if ya ask me E Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 4, 2015 Share Posted January 4, 2015 I've been raising compression on many different engines for a long time, and they all ran tons better. THanks for the help E I'll take a chance and read sarcasm into the "thanks for the help" since you dismissed my comment. I did not piss $3000 down the drain on my own 2.5 before gathering as much information as I can about the 2.5 over the last couple of years. Very few of us put any time, effort, money, into the 2.5, as a result, there is scarce information and performance parts. Most guys will tell you that the 2.5 is a 4.0 with the middle two cylinders removed, not true, the 2.5 came first and the 4.0 was designed after and out of the 2.5, look it up. Besides the obvious differences, the 2.5 and 4.0 share many of the same parts- water pump, oil pump, water necks, timing cover, timing set, head bolts, push rods, valves, lifters, springs, pistons, rods............etc........ On the later MPI 2.5s, it shared much of the same....injectors, throttle body, sensors such as CPS and TPS........etc...... If raising the compression to 10:1 were the answer to the 4.0 performance, then every MJ and XJ owner here would be off to the races. There are several Stroker guys here and many more elsewhere, balancing performance and reliability seems to the common issue among them. I have yet to see anyone successfully supercharge or turbo charge a 2.5 and brag about their success. Apparently a few 4.0 guys have but I have yet to read anything about reliability as a daily driver....bear in mind that you will be in the $6000 neighborhood going supercharged. The most common failure of the 4.0 is head gasket failure, just based on what I have read over over the last 3 years, ads for XJs and MJs for sale....common thread........head gasket, maybe 80% or more. The biggest hurdle you will experience is electrical, getting a Renix 2.5 or 4.0 to run well...electrical, and you need to go through every bit of it. Money and TIME, hope you got both. The greatest hurdle you will have to 2.5 performance.....air flow.........>NOT compression. You have entered the world of Jeep, and you've got a lot to learn yet. Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 4, 2015 Share Posted January 4, 2015 Don't know if these will work or not with that huge dish. http://www.ebay.com/itm/Silv-O-Lite-Hyper-Coated-Pistons-1979-93-Pontiac-AMC-151-L4-2-5L-040-Set-Of-4-/390960047587?pt=Motors_Car_Truck_Parts_Accessories&hash=item5b0708e5e3&vxp=mtr E The ones you listed are not for the AMC 2.5 that you have.....these are for the GM version of the 2.5, not the 84 up AMC/Chrysler. ...? They BOTH show that they are for the AMC 2.5 that's why I asked. Or, is it that amc just grabbed some other makes pistons for these motors? And the comp ratio, I thought that I read somewhere that the 88's had comp in the 8's. Must have missed that one. Also, I don't "facebook" and probably never will if I can help it. Pretty much a waste of time if ya ask me E No, Jeep used the GM Iron Duke in the 70s/80s CJs......completely different animal. There are multiple versions of what seems to be the same engine.......Pontiac and S10 share many of the same parts.....look to the Fiero sites for info.....GM versions. AMC/Jeep version you have is not part interchangeable. Facebook is the gateway to the site he directed you to.....you want in......you want to learn........that's how you get there. Link to comment Share on other sites More sharing options...
MuddFoot Posted January 4, 2015 Share Posted January 4, 2015 i shaved the head on my 90 2.5 with port matching polish ect and will say it made a big seat of the pants difference orly thing that sucked was i had to run 91 octane it was 50-60cents more back then but if i drove easy i always got over 20mpg. Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 4, 2015 Share Posted January 4, 2015 Little something to drool over- Link to comment Share on other sites More sharing options...
Wesleypipesyo Posted January 4, 2015 Share Posted January 4, 2015 Please forgive my ignorance on this particular subject. But if you are going to put $3,000 into a motor that will require you to run a higher octane gas and make it less reliable as a DD, why not just put a mild v8 in the truck? Keep in mind I am not into the jeep world for speed and power. I just like driving in the woods. But a motor swap seems like a more effiecent use of money. Link to comment Share on other sites More sharing options...
Eagle Posted January 4, 2015 Share Posted January 4, 2015 No, Jeep used the GM Iron Duke in the 70s/80s CJs......completely different animal. I believe AMC also used the Iron Duke in the 4-banger Eagle SX/4, which was in production at the same time that AMC was using the engine in the CJ. Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 4, 2015 Share Posted January 4, 2015 Please forgive my ignorance on this particular subject. But if you are going to put $3,000 into a motor that will require you to run a higher octane gas and make it less reliable as a DD, why not just put a mild v8 in the truck? Keep in mind I am not into the jeep world for speed and power. I just like driving in the woods. But a motor swap seems like a more effiecent use of money. http://comancheclub.com/topic/45526-before-and-after/ See above. I did not change the compression ratio in my engine and I expect to run 87 octane as I am now. Torque is what I'm after, not necessarily horse power. I have every expectation that my engine will fall away above 4K rpm as I retained the TBI. My truck is a daily driver, I cannot afford for it to sit idle in front of my garage while I mock-up and wait on parts...etc. Going V8 has it's own challenges and costs. For example- the thread posted above, the builder is building a 2WD street driven truck, if for off-road he'll need a stand-alone injection system from a GM engine or aftermarket. If you already have a lift.....now you have to balance spring hight and rate to accommodate the additional weight of the V8 and maintain the desired hight. Now you have transmission selection and adapters.........ask the builder what he spent at Novak? Cooling is another matter....and so forth..... My guess is that the builder above will have an easy $4K in his before it's over with. Link to comment Share on other sites More sharing options...
mvusse Posted January 4, 2015 Share Posted January 4, 2015 i shaved the head on my 90 2.5 with port matching polish ect and will say it made a big seat of the pants difference orly thing that sucked was i had to run 91 octane it was 50-60cents more back then but if i drove easy i always got over 20mpg. I have a stock 87 2.5 as a daily driver. No mods to the engine, consistent 20-21 mpg mixed driving on cheap 87 octane. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 5, 2015 Share Posted January 5, 2015 On 4bangerjp they talk about installing a certain piston from a 4.0 that has a higher crown than the 2.5 thus increasing compression or conversely decking the block for the same result. That site also has multiple write-ups concerning every other aspect of the 2.5 for better performance. Maybe you can have a friend message them on Facebook for a username and password to access the full site. Link to comment Share on other sites More sharing options...
benjy_26 Posted January 5, 2015 Share Posted January 5, 2015 Little something to drool over- Gads!! Is that a blower for the TBI 2.5? Link to comment Share on other sites More sharing options...
CobraMarty Posted January 5, 2015 Share Posted January 5, 2015 Who's 2.5L supercharger kit is that? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 9, 2015 Share Posted January 9, 2015 I've been raising compression on many different engines for a long time, and they all ran tons better. THanks for the help E I'll take a chance and read sarcasm into the "thanks for the help" since you dismissed my comment. I did not piss $3000 down the drain on my own 2.5 before gathering as much information as I can about the 2.5 over the last couple of years. Very few of us put any time, effort, money, into the 2.5, as a result, there is scarce information and performance parts. Most guys will tell you that the 2.5 is a 4.0 with the middle two cylinders removed, not true, the 2.5 came first and the 4.0 was designed after and out of the 2.5, look it up. Besides the obvious differences, the 2.5 and 4.0 share many of the same parts- water pump, oil pump, water necks, timing cover, timing set, head bolts, push rods, valves, lifters, springs, pistons, rods............etc........ On the later MPI 2.5s, it shared much of the same....injectors, throttle body, sensors such as CPS and TPS........etc...... If raising the compression to 10:1 were the answer to the 4.0 performance, then every MJ and XJ owner here would be off to the races. There are several Stroker guys here and many more elsewhere, balancing performance and reliability seems to the common issue among them. I have yet to see anyone successfully supercharge or turbo charge a 2.5 and brag about their success. Apparently a few 4.0 guys have but I have yet to read anything about reliability as a daily driver....bear in mind that you will be in the $6000 neighborhood going supercharged. The most common failure of the 4.0 is head gasket failure, just based on what I have read over over the last 3 years, ads for XJs and MJs for sale....common thread........head gasket, maybe 80% or more. The biggest hurdle you will experience is electrical, getting a Renix 2.5 or 4.0 to run well...electrical, and you need to go through every bit of it. Money and TIME, hope you got both. The greatest hurdle you will have to 2.5 performance.....air flow.........>NOT compression. You have entered the world of Jeep, and you've got a lot to learn yet. Actually, the 4.0 DID come first in development but not in production. I know this for a fact as I was told how it was done by a friend at JeepTech who was involved in the development of both engines. Link to comment Share on other sites More sharing options...
johnj92131 Posted January 10, 2015 Share Posted January 10, 2015 I'd like to get around 9.5-10:1 and was wondering if pistons might be able to swap from other models/makes to raise comp besides having custom pistons made. I'm picking up a '88 comanche 5spd for my son, but it's got 230K on it. So, I'm going to be either looking for another 2.5 or start storing up parts. It runs OK from what I've witnessed but couldn't drive it due to a e-brake cable 'pull' breaking and couldn't release it, since it was on a hill.. Sounds like its in need of a tune up and probably vacuum line replacement. OH, I've been 'wrenchin' for decades and always want an extra engine to have as a safety. But having a little more comp is always good thing. Just joined to get insight on the 4cyl that's in the little Pioneer. (well, that and some other little stuff..) had a few 'other' Jeeps too. thanks E Why not order a set of forged pistons from www.Bulltear.com? They will sell you any compression you want. They are a small AMC supplier who deserves support of the jeep community. Another option is to look for a stroker crank. Archer brothers used one if I recall correctly. Or do an offset grind of your current crank and custom pistons (from BullTear). Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 10, 2015 Share Posted January 10, 2015 I read a story somewhere once (saved link on another computer), about a guy who's brother was a machinist and had his 2.5 block bored out to 4 inches and used Chevy small block flat top pistons. It is an unconfirmed story but after some initial research it does seem possible with minor mods. That and the pistons are cheap. The stock 2.5 bore I think is 3.850". The article talked like there was plenty of meat there for a .150" overbore. I think they said that would bump it up to 2.7L. I plan to do more research on this when I get to build my spare engine. I know 505 performance probably has all this info already but I don't really expect them to just hand it all over, especially after the email questions I had about their 2.5 cams were poorly responded to. Link to comment Share on other sites More sharing options...
Jeep Driver Posted January 10, 2015 Share Posted January 10, 2015 I've been raising compression on many different engines for a long time, and they all ran tons better. THanks for the help E I'll take a chance and read sarcasm into the "thanks for the help" since you dismissed my comment. I did not piss $3000 down the drain on my own 2.5 before gathering as much information as I can about the 2.5 over the last couple of years. Very few of us put any time, effort, money, into the 2.5, as a result, there is scarce information and performance parts. Most guys will tell you that the 2.5 is a 4.0 with the middle two cylinders removed, not true, the 2.5 came first and the 4.0 was designed after and out of the 2.5, look it up. Besides the obvious differences, the 2.5 and 4.0 share many of the same parts- water pump, oil pump, water necks, timing cover, timing set, head bolts, push rods, valves, lifters, springs, pistons, rods............etc........ On the later MPI 2.5s, it shared much of the same....injectors, throttle body, sensors such as CPS and TPS........etc...... If raising the compression to 10:1 were the answer to the 4.0 performance, then every MJ and XJ owner here would be off to the races. There are several Stroker guys here and many more elsewhere, balancing performance and reliability seems to the common issue among them. I have yet to see anyone successfully supercharge or turbo charge a 2.5 and brag about their success. Apparently a few 4.0 guys have but I have yet to read anything about reliability as a daily driver....bear in mind that you will be in the $6000 neighborhood going supercharged. The most common failure of the 4.0 is head gasket failure, just based on what I have read over over the last 3 years, ads for XJs and MJs for sale....common thread........head gasket, maybe 80% or more. The biggest hurdle you will experience is electrical, getting a Renix 2.5 or 4.0 to run well...electrical, and you need to go through every bit of it. Money and TIME, hope you got both. The greatest hurdle you will have to 2.5 performance.....air flow.........>NOT compression. You have entered the world of Jeep, and you've got a lot to learn yet. Actually, the 4.0 DID come first in development but not in production. I know this for a fact as I was told how it was done by a friend at JeepTech who was involved in the development of both engines. I read an article over a year ago regarding the 2.5 and 4.0 engines, Hemmings or Allpar, can't remember but it was a legitimate source. I cannot find the article now.........2.5 ran 3 years in production before the 4.0 came out, the claims made perfect sense to me. So, explain, why did AMC wait so long to release the 4.0? Link to comment Share on other sites More sharing options...
cruiser54 Posted January 10, 2015 Share Posted January 10, 2015 More than likely a contract to buy the 2.8s from GM and passing emissions. Perhaps adaptation and development of transmissions from different suppliers. A lot goes on behind the scenes. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now