Will swapping 3.0 heads gain me a few HP?

[DHPMARINE]

Re: Will swapping 3.0 heads gain me a few HP?

trog,and all,<br />You've stated some facts,but somehow I missed your point.No offence intended.Just too many facts.<br />Actually,in 1992,there were a few differences between the 3.0L and the 3.0LX.The heads were not the same.The valve size was different,as the 3.0L used 2.5 valves.The carbs were not the same,they used a different carb base and venturi on the 3.0L.<br />Also the manifolds were different.Both used the same electronic ignition at one point.<br />That's about where I stopped,but it's all in the parts books.<br /><br />DHP

 

[craze1cars]

Re: Will swapping 3.0 heads gain me a few HP?

Thanks DHP. If indeed the 2 motors in 1992 had the same displacement with different heads, carbs, valve sizes, and manifolds....that would certainly reinforce the theory that the 3.0L and 3.0LX indeed had different real-life power outputs for that model year. An actual 20 HP difference? I see no reason why not, but only dyno #'s could answer that.<br /><br />And getting back to the basis of my original question, this also helps confirm that changing the head alone will likely NOT do what I had hoped. Far more likely that I'd have to change all those other parts as well in order to get the proper flow for the complete HP increase.<br /><br />That was very helpful and concise info. One of the shortest, yet THE most direct and complete answer so far...and it only took us 40 posts to get there! <br /><br />A most sincere thank you...

 

[DHPMARINE]

Re: Will swapping 3.0 heads gain me a few HP?

No Problem craze1cars.<br /><br />Sometimes it helps to remember an engine is only a pump.When you change something (bigger valves) you now have to get more air in (bigger carb).Now you have to get this all out (bigger exhaust).<br /><br />DHP

 

[trog100]

Re: Will swapping 3.0 heads gain me a few HP?

even the parts books dont seem to agree on this one DH.. the merc manual that covers both the L and the LX engines that i referenced and used to formulate my oppinon.. dont show any part differences.. except spark plugs.. and one engine was missing an oil seal on its exhaust valves<br /><br />especially the valve sizes.. all valve sizes are idential for both engines..<br /><br />at least according to the merc manual i used as a reference.. i cant speak for the one u used..<br /><br />its the fact i couldnt find any meaningfull differences that caused me to arrive at my end conclusion.. that there were wasnt any..<br /><br />there is a kinda point being made here.. DH comes up with a few simple statements of facts.. craze instantly grabs em to back up his desired belief..<br /><br />none so deaf as those that want to be..<br /><br />sooo.. we know the manifolds are different.. but aftermarket parts sellers say u can use either it wont matter and only the one is available as a replacemnt part it seems.. so are they really different in any meaningfull power affecting way.. <br /><br />carbs.. just to put me right if there is a difference (i dont think there is) cos i genuinely havnt been able to find any reference to two different carbs being fitted to the two engines in question..<br /><br />i dont doubt that sometime in the past the 2.5/120 engine had a different carb than the 3.0/140.. i just dont think the 3.0L and the 3.0LX did..<br /><br />please can someone point me to any reference at all that says these two engines used different carbs.. <br /><br />lets pretend i want to buy one for say a 3.0L circa 89 to 94.. or even the 3.0LX.. if there are two different ones it should be easy to find out..<br /><br />so far we still lack the "difference" evidence.. <br /><br />DH.. ?????.. <br /><br />trog.. <br /><br />ps.. now i cant prove a negative.. he he.. but it should be easy for someone else to prove a positive.. hows about it..

 

[DHPMARINE]

Re: Will swapping 3.0 heads gain me a few HP?

trog100,<br /><br />Perhaps you have a Seloc or Clymer Merc Parts book.(grin).I have the advantage of using the real thing,Merc's Software parts look up.But you can come close if you go to www.dougrussell.com.<br /><br />Select Mercury by part #.Then select Mercruiser.Then select 3.0L/LX GM 1990-1995.<br /><br />Next select Cylinder Head,and notice they list 2 different number 20,one for 3.0L and another for 3.0LX.Also 2 #10 Valves.<br /><br />Next select Carbs.Strange,they list 2 different carbs same thing.Also 2 #20 Venturi,and 2 #24 carb base.<br /><br />Under Exhaust Manifold you'll find the same thing. Different parts between the 3.0L and the 3.0LX<br /><br />I could go on,but you can check this one out yourself at dougrussell.com.<br /><br />DHP

 

[Silvertip]

Re: Will swapping 3.0 heads gain me a few HP?

I love this stuff. One need only review the history of the Chevy small block V8 to see the effect of several engine family design factors. The engines I'll use here will ignore the high and low end displacements but will use the 302, 305, and 307 CI versions, each of which had varying output figures. Although these engines vary by only 4 CI, various combinations of bore, stroke, cam, compression and carburetion accounted for 150 HP difference and parts from any of them would interchange. The 302 high winder was rated at 295 HP (non-emissions days) while the lowly 305 and 307 were rate as low as 145 HP (albeit in the early emissions days). All of these engines would develop very roughly the same torque, but at widely varying RPM ranges. HP was also rated at RPMs that varied significantly. GM didn't alter bore/strokes/cams/compression/carburetion because they needed something to do. It was in response to ever changing driveability, fuel economy, and performance objectives. All of these factors interrelate and so it is very likely the 3.0 head is more efficient on a 3.0 block than the 2.5 head on that same block, or vice versa. I would bet Merc early on tried the 2.5 head on the 3.0 block and determined a different head was needed as there was not a significant performance increase to justify the 500 CC displacement increase. Breathing is certainly key to power output. However, certain bore/stroke ratios resulting in the same displacement can and generally does produce different power output. By the way -- how many of you Chevy guys knew Chevy offered a V8 in 1917, 1918, and 1919. 288 CI and you got it, overhead valves. That will win you a barroom beer bet with a Ford guy every time. Cheers.

 

[DHPMARINE]

Re: Will swapping 3.0 heads gain me a few HP?

2.5/3.0 heads were always different.My take is Mercruier just had some surplus 2.5 heads to dump.<br /><br />DHP

 

[craze1cars]

Re: Will swapping 3.0 heads gain me a few HP?

https://lakesiderestorations.com/sh...ylinder Head&imageName=4chd.png&assyCode=4chd <br /><br />Here's another site I found that has Mercruiser microfiche on-line. This page gets a little more detailed in the part # listings for the head and shows the intake & exhaust valves as individual parts....with different part numbers between 3.0L and 3.0LX. It doesn't provide valve sizes other than stem sizes (which is meaningless)...but the valves were indeed different between the two motors.<br /><br />And again here's diff carbs showing for L & LX in my serial # range:<br /> https://lakesiderestorations.com/sh...ame=Carburetor&imageName=4cc.png&assyCode=4cc <br />It appears from this same site that in the earlier serial numbered motors, the carbs were indeed the same. So Trog, if you did extensive research for your 1989 motor, it appears you are correct that the L/LX carbs were the same in that model year, and maybe other parts are the same as well. I didn't bother looking because I don't own a 1989 and have no interest in it... as it has nothing to do with what I was asking about...ever since post # 1 I have been clearly inquiring about a 1992 L and swaping parts with newer LX motors.<br /><br />I really could care less about anyone proving ANYONE right or wrong (other than the fact that Trog repeatedly and specifically asks us to do so for him)...I just want to understand more about the differences between the motors. It's all become MUCH more clear to me now than it was before I asked my question. so I feel I have certainly accomplished exactly what I wanted to. It just took one HECK of a long road to get me there...thank God it's winter and I have a bit of spare time on my hands! Thanks again to all, one last time...again....I think....

 

[trog100]

Re: Will swapping 3.0 heads gain me a few HP?

i think i mentioned "merc manual".. DH forgive me i should have been more specific and said..<br /><br />Mercruiser service manual number 13 marine Engines GM 4 Cylinder<br /><br />Model 3.0L serial number OC856451 and above<br /><br />3.0L/3.0LX serial number OC868143 and above..<br /><br />printed in USA 1995 Brunswick Corporation 90-816462 2-695<br /><br />as i said the merc manuals (read above) dont seem to agree on this one..<br /><br />and craze.. 1989 was when all this crap started it continued up to 1994.. my 89 3.0L engine sits at the beginning.. your 92 one sits smack in the middle..<br /><br />still we have all learned something even if we havnt..<br /><br />trog

 

[Tail_Gunner]

Re: Will swapping 3.0 heads gain me a few HP?

Really a very informative thread, however its old yet i would like to to know if anyone has ever measured the bore and stroke of a 2.5 bottom end (labeled a 3.0 or 181 cid)<br /><br />Assuming it does diplace 181 cid then it can only a head,carb,cam,or exhasut change..... Or maybe all of the afore mentioned items.<br /><br />I do know that marine engines are cammed differntly ............Has anyone ever just had a head ported and polished and simply rejetted the carbs? That would be very cost effective assuming there are jets avaible and make perfect sense from a application stand point as ever post ive seen in props tends to point to wot and very little to midrange and bottom end tourqe.<br /><br />Also what could be intriging is the 2.3 liter quad 4, does it use the same block as the 2.5-3.0 chevy..........if so that could be a very inexpensevie upgrade.......... Kinda of reach huh.

 

[Bondo]

Re: Will swapping 3.0 heads gain me a few HP?

The 2.5l is the 153cid block,+ the 3.0l is the 181 block,+ Neither of them Even Resemble the newer Chevy 4 cylinder Blocks.........

 

[rodbolt]

Re: Will swapping 3.0 heads gain me a few HP?

cylinder head size does not play in the difference between the 181 CID and the 153 CID, thats determined by the bore and stroke, as far as the debate goes I can tell you at least 5 different intake/exhaust port configurations exist and at least 2 head gasket configurations and they dont interchange well and some not at all.<br />the 153 was used in some chevy car and at least one industrial truck application and in mail jeeps until sometime in the 70's. I dont think the 181 was ever used in US automotive production. the 151 Iron Duke was a pontiac motor and only shared corperate blue paint with anything else chevy built.<br /> its a moot point cause they are now Hechen En Mexico along with alot of the 5.0 and 5.7 stuff. so you may be able to play with the heads to gain that extra twenty ponies, you may also have to change the manifold/riser.<br />best bet is to look at that marine power EFI motor. its a sweetheart.<br /> I have installed a few.<br /> only funky thing is the return to idle dwell.<br />maybe the MPI version will solve this.<br /> man I am glad carbs are dying as EFI just works so much better.<br />over the years I have made a ton of money with carbs, however its about customer satisfaction not making money, do the first and the second follows.<br />but if you research enough part numbers you can find a combination that works. and remember that certain 4cyl chevrolet produced engines share a lot of parts with both the inline six chevy and some of the earlier V8's.<br />if your careful you can build a hotter motor for not a lot of money or save an extra year and buy the EFI version off the shelf.

 

[Tail_Gunner]

Re: Will swapping 3.0 heads gain me a few HP?

Originally posted by Bondo:<br /> The 2.5l is the 153cid block,+ the 3.0l is the 181 block,+ Neither of them Even Resemble the newer Chevy 4 cylinder Blocks.........

To the 2.5 3.0 question i assumed that the 3.0L was just a stroked 2.5, aka the 3.0 lx has a harmonic balancer on it indicating a design change.<br /><br />It would be intresting to see the heads close up.

 

[rodbolt]

Re: Will swapping 3.0 heads gain me a few HP?

the bore is different, the 153 has a balancer as well. most all american engines used it. in fact the same speedi sleeve can be used on the 2.5(153CID as the 3.0 (181 CID) engines.<br />without going and hunting my manuals I cant remember the stokes and bores. but Cubic Inch Displacement is a function of bore,stroke and number of bores. the cylinder head only comes into play for mechanical compression ratios by varying combustion chamber volumes. the design of the two balancers is very different, best I remember the 2.5 was a solid cast one and the 3.0 used a disc on a rubber hub.<br /> the two engines are very similar but can bite ya when swapping parts. the valve head sizes for the 153 and the 181 are different but most took the same main bearings for years. cams were different but the timing gears stayed the same a long time.<br /> thats why I stay away from scavenged frakenstien motors. ya spend way to much time trying to figgure out what the creator did.

 

[Tail_Gunner]

Re: Will swapping 3.0 heads gain me a few HP?

trog100: <br /><br /> Model 3.0L serial number OC856451 and above <br /> <br /> 3.0L/3.0LX serial number OC868143 and above..<br />-------------------------------------------------<br />There's the seperation point? indicating porting and waterjacketing will be compatible with the lx head?<br />-------------------------------------------------<br />rodbolt::<br /> <br />the valve head sizes for the 153 and the 181 are different but most took the same main bearings for years. <br />-------------------------------------------------<br /><br />If true (Mains that is.... no reason to doubt it) that would be comforting towards long term reliabilty.<br /><br />Does anyone know if the jet's are interchangable or is there availability?<br /><br /> Time to look up my block code and if its of the right vintage im gonna dabble in a lx head. Its been too many years to mention here since ive done this...... I guess one more shot @ it wouldn't or couldn't hurt to much.......<br /> <br /><br />There has to a lot of compatability here....christ i cant imagine GM creating all of the different above scenario's application spefic.........uhhh but then again they are almost BK......<br />

 

[lilmandavis]

Re: Will swapping 3.0 heads gain me a few HP?

man i thought my wife had alot to nag about just swap the heads with a bigger manifold and go boating, keep yer old **** and if the new is better sellit. if not sell the new **** and get different junk.

 

[rodbolt]

Re: Will swapping 3.0 heads gain me a few HP?

someplace there is a tech bulliten on how to identify the block/head compatability. best I remember it was something with the cooling passages on the stbd side of the block.<br /> the 3.0 is currently manufactured in mexico but its been used in marine and industrial applications for years.<br /><br /> I have seen it in all kinds of crazy stationary stuff and a few forklifts.

 

[Tail_Gunner]

Re: Will swapping 3.0 heads gain me a few HP?

It still lives on, I contacted the orignal owner of the boat regarding all of the work and maintance that has been done on this boat. In or part of the conversation he brought up that he ordered a high preformance head with the engine and a electronic dist.<br /><br />Now the dist is quite obvious, but i cannot find any part number's on the head. I'm just to lazy to take off the valve cover and all of the parts attached, unless someone can verify the part number is indeed under the valve cover's or just where are they @.....?