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1955 270 Hemi rod noise, backfiring
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'55-3Hemi
Posted 2018-09-21 5:57 PM (#570527)
Subject: 1955 270 Hemi rod noise, backfiring



Member

Posts: 20

Location: VIrginia
My 1955 Dodge Custom Royal Lancer has been making rod bearing noise on startup and under load. I have also noticed the oil pressure has dropped from it's normal position at idle when it's fully warmed up. (not good) It' has slowly been burning oil (blue smoke), lost a lot of power and now starting to miss and backfire through the carb. The car is also running hotter than normal. Not wanting to make it worse, I took it off the road to check out the engine. I ran a compression check and soon found out bad the engine is. The compression test was not good and was performed when warm as follows: When purchased last year, all of the cylinders were around +- 140 with 62,000 miles

#1 60 PSI, #2 90 psi,

#3 48 PSI, #4 92 PSI,

#5 68 PSI, #6 90 PSI

#7 20 PSI; #8 92 PSI

I added a couple of squirts of oil in the cylinders and tested again

#1 90 PSI; #2 110 psi

#3 48 psi; #4 110 psi

#5 85 psi #6 90 psi

#7 20 psi #8 115 psi


I am surprised the motor ran at all with these low numbers. Am I correct to assume the cylinders that increased in psi after adding oil indicate possible ring wear and where no change in PSI after adding oil suggests valve or gasket problems?

I do not have at the moment the funds (guessing round $5,000) for a turn key rebuild if I take out the motor and drop it off. The only thing I can think of is to start the teardown and at least check the crankshaft rod and main bearings, pull the heads and check the valves, head gasket ect. I can also measure the cylinders to see how worn they are for out of round, taper, etc. Any suggestions that I can do myself to help save funds on this rebuild would help. I would even consider a rebuilt short block if available

I plan on starting the teardown tonight. Since this has to be rebuilt anyway, I would like to possibly change the CR from 7.6 to 9.5 if pistons are needed. Has anyone done this on a 241/270? The only pistons I could find were forged units by Ross via Hot Heads for $$$$. Hopefully there are more affordable options out there. teardown pictures soon to come....




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Mopar1
Posted 2018-09-21 8:20 PM (#570544 - in reply to #570527)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Posts: 2683
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Location: N.W. Fla.
besides Hot Heads, check with Gary (Quality Engineered Components), "Wayfarer" on the Board. To get the C/R up to modern levels you'll need forged pistons. A 241 with advertised C/R of 7.0/7.1:1 measured out at only 6.19. I recently redid my 331 Hemi. got parts from Gary, HH, Kanter & Rock Auto. The more you can do the cheaper it'll be.
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'55-3Hemi
Posted 2018-09-23 6:10 AM (#570605 - in reply to #570544)
Subject: Re: 1955 270 Hemi rod noise, backfiring



Member

Posts: 20

Location: VIrginia
Thanks for the info. I'll check with Gary.
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'55-3Hemi
Posted 2018-09-23 8:26 AM (#570609 - in reply to #570527)
Subject: RE: 1955 270 Hemi rod noise, backfiring



Member

Posts: 20

Location: VIrginia
I worked on the teardown till after midnight. The shop manual stated to remove the oil pan all that was required was to loosen the idler Arm and lower the linkage. I ended up having to drop the entire steering linkage (I have PS) from both outer tie rods and from the pitman arm just to have enough clearance to remove the pan. After draining the oil & antifreeze I finally dropped the pan and found about an inch of sludge at the bottom and no signs of water. Took forever to clean the pan and bolts, but at least that is one less thing to do. Started to pull the rod bearings they looked fairly good until I came to #6 rod. it was loose with a fair amount of slop. Upon removal it was badly grooved and so was the crankshaft. The factory rod journal size is 1.9365 +- .001. with .0025 max clearance. I measured the diameter along 5 different points which ranged from 1.920 to 1.933 which gives a clearance range of .0165 to .0035. If I have done the math correct this journal at it's worst point is .0165 " over the factory. What surprised me was the adjoining #5 rod journal was in fairly good shape measuring at 5 different points from 1.932 to 1.933 or +-.0045> Rod journals #1 - #8 clearance ranged from .004 to .008. If the crankshaft is not cracked, it looks as if can be salvaged and turned down .020"on the rod journals. Rod bearings are available .020" oversize on E-Bay. If for some reason the crank is cracked or cannot be turned, does anyone have a crankshaft?

Spent most of the day on Saturday removing the heads which were stuck to the block. Thank heavens the exhaust pipe flange bolts came off. After finally getting one head off it was easy to see why the motor was running hot and why #7 compression was so low. The water passages were almost completely full of gunk in both the head and block. (When I opened the block water pet**** nothing came out. Had to insert a small pick to clean out the opening). The intake valve pushrod was bent on #7 cylinder to a point where it hardly opened the valve at all. There was no apparent damage to the valve other than it being very pitted. The valve seat was also pitted. My guess is this cylinder was the main cause of back firing through the carb. The head gasket was torn up trying to get it off the head but looks like it leaked between all of the cylinders and numerous water passages. Pictures of gasket soon to follow

The bearing on the right is #6. The bearing on the left is a new one - Need to find a better picture editor - the one I have reduces file quality & size too much.

Edited by '55-3Hemi 2018-09-23 9:45 AM




(IMG_3060.JPG)



Attachments
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Attachments IMG_3060.JPG (25KB - 15 downloads)
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wayfarer
Posted 2018-09-29 11:17 AM (#570897 - in reply to #570527)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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...looks like it is time to pull the engine out. Regardless of your next move it will start with removing the 270.
Your initial guess of $5k for a rebuild may actually be on the light side unless you can source the parts and
do the re-assembly leaving the machine shop to do only machine work. Alot of shop guys will not like this approach
and the labour rates may take a bump. Obviously, the shop will not warranty the parts and if something 'happens'
the finger pointing will start.

....please minimize the oversize on the bore to only the minimum required. Core shift is a constant problem with the EarlyHemi.
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56D500boy
Posted 2018-09-29 12:16 PM (#570900 - in reply to #570897)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Location: Lower Mainland BC
wayfarer - 2018-09-29 11:17 AM
....please minimize the oversize on the bore to only the minimum required. Core shift is a constant problem with the EarlyHemi.


Gary: Based on an anecdotal story from my local NOS guy, Ron W., who had a 55 Custom Royal with a 270 hemi back that he street raced when they were new(ish) (Ron's in his late 70's), I *THINK* I know what "Core shift" means.

However, could you please elaborate.

Thanks


Edited by 56D500boy 2018-09-29 12:17 PM
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Mopar1
Posted 2018-09-29 5:40 PM (#570915 - in reply to #570900)
Subject: Re: 1955 270 Hemi rod noise, backfiring



Expert

Posts: 2683
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Location: N.W. Fla.
56D500boy - 2018-09-29 11:16 AM

wayfarer - 2018-09-29 11:17 AM
....please minimize the oversize on the bore to only the minimum required. Core shift is a constant problem with the EarlyHemi.


Gary: Based on an anecdotal story from my local NOS guy, Ron W., who had a 55 Custom Royal with a 270 hemi back that he street raced when they were new(ish) (Ron's in his late 70's), I *THINK* I know what "Core shift" means.

However, could you please elaborate.

Thanks
:)
instead of equal thickness on the walls on all sides, one side will be thinner than it supposed to be & thicker than it supposed to be on the other, basically off center.
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56D500boy
Posted 2018-09-29 7:07 PM (#570921 - in reply to #570915)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Posts: 3685
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Location: Lower Mainland BC
Mopar1 - 2018-09-29 5:40 PM
56D500boy - 2018-09-29 11:16 AM

wayfarer - 2018-09-29 11:17 AM....please minimize the oversize on the bore to only the minimum required. Core shift is a constant problem with the EarlyHemi.

Gary: Based on an anecdotal story from my local NOS guy, Ron W., who had a 55 Custom Royal with a 270 hemi back that he street raced when they were new(ish) (Ron's in his late 70's), I *THINK* I know what "Core shift" means.
However, could you please elaborate? Thanks
:)


instead of equal thickness on the walls on all sides, one side will be thinner than it supposed to be & thicker than it supposed to be on the other, basically off center.


Okay. Thanks. That makes sense based on the terminology. My NOS guy's story was different. It was based on block shrinkage.



Edited by 56D500boy 2018-09-29 7:08 PM
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'55-3Hemi
Posted 2018-09-30 1:09 PM (#570965 - in reply to #570897)
Subject: Re: 1955 270 Hemi rod noise, backfiring



Member

Posts: 20

Location: VIrginia
Wayfarer, You are correct that is time to pull the engine on this. I have spoken to a local machine shop mechanic who has done several Desoto's over the years and knows first hand that these motors are expensive to obtain parts and may take a little more time than the typical Ford or Chevy. They are fairly booked up and are willing to work with me if I allow them "time when available" to work on this motor.

I checked the bores with a dial bore gauge and the "worst cylinder" taper was .019. (The machine shop of course will confirm). The least amount of boring the better for I was not aware of core shift in these early hemis. If funds permit and I go with forged 9.5 cr pistons, would keeping the stock rods, wrist pin diameter be sufficient or is there a better alternative? Would chrome rings help with less cylinder friction as compared with cast iron rings? The shop also talked about having the block "decked" should I go with custom pistons. This is the first time i have looked into custom pistons and not sure what questions are needed to see what is required. I need to do some research on decking for I am not sure exactly what it is.

Does anyone know about how much additional horsepower/torque can be gained just by raising the CR to 9.5 Would hate to spend all of this extra money if only 5hp & 25 ft lbs torque is the best I could hope to obtain.

Could not find hardly any information on camshafts other than possibly regrinding a existing old cam. Are there any alternatives?
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Powerflite
Posted 2018-09-30 11:48 PM (#570992 - in reply to #570527)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Location: So. California
If this is a hemi motor, I would go up to 10:1 compression. Hemi motors don't suffer as much from timing issues because of the centrally located spark plug. With the additional compression, you can get away with a little hotter cam without the idle vacuum issues. Do this, and you will notice a nice difference.
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'55-3Hemi
Posted 2018-10-04 10:59 AM (#571133 - in reply to #570992)
Subject: Re: 1955 270 Hemi rod noise, backfiring



Member

Posts: 20

Location: VIrginia
Thanks for the information about the CR. I have a just come across a 270 hemi block that has been bored .060" over, hot tanked, decks milled square, new cam bearings installed etc. No pistons but has crankshaft and rods that need to be serviced. The guy was going to put it in a hot rod project but lost interest Asking $450.00

I have reservations about being bored 0.60" but otherwise looks like a great deal. Any thoughts?
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Mopar1
Posted 2018-10-04 11:59 AM (#571134 - in reply to #571133)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Location: N.W. Fla.
'55-3Hemi - 2018-10-04 9:59 AM

Thanks for the information about the CR. I have a just come across a 270 hemi block that has been bored .060" over, hot tanked, decks milled square, new cam bearings installed etc. No pistons but has crankshaft and rods that need to be serviced. The guy was going to put it in a hot rod project but lost interest Asking $450.00

I have reservations about being bored 0.60" but otherwise looks like a great deal. Any thoughts?
As a rebuildable core that's a great price. With a sonic check the rule of thumb is low deck blocks "can" go out to .125. Emhasis on the core check. less is best.
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'55-3Hemi
Posted 2018-10-04 12:11 PM (#571135 - in reply to #571134)
Subject: Re: 1955 270 Hemi rod noise, backfiring



Member

Posts: 20

Location: VIrginia
Thanks Mopar1, I just got some quotes to do my engine (hot tank, bore, milling decks square, installing cam bearings, ect.) It was a lot more than $450.00. I just was not sure about the .060" overbore but if the low deck can go possibly to .125 it sound like the .060" overbore is ok
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jboymechanic
Posted 2018-10-04 1:41 PM (#571145 - in reply to #570527)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Location: Muskego, WI
I went 0.0625" over bore in my 354 Chrysler hemi, that brought the bore out to stock 392 Hemi bore. I've heard of people building 318 Polys with 0.125 over bore as well, so I would think 0.060" is fine in a Dodge hemi.
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Mopar1
Posted 2018-10-05 11:32 AM (#571172 - in reply to #571145)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Location: N.W. Fla.
jboymechanic - 2018-10-04 12:41 PM

I went 0.0625" over bore in my 354 Chrysler hemi, that brought the bore out to stock 392 Hemi bore..
That's .125, so you're maxed out.
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Powerflite
Posted 2018-10-05 1:36 PM (#571174 - in reply to #570527)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Location: So. California
He's talking about .063" diameter. The stock bore of a 354 is 3.9375, and he took it up to the 4" bore of a 392.
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jboymechanic
Posted 2018-10-05 3:40 PM (#571179 - in reply to #570527)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Location: Muskego, WI
You're exactly right Nathan, I was referring to total diameter increase.
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'55-3Hemi
Posted 2018-10-05 9:11 PM (#571188 - in reply to #571179)
Subject: Re: 1955 270 Hemi rod noise, backfiring



Member

Posts: 20

Location: VIrginia
Thanks for all the input on this, This might be a dumb question, but if I go with custom pistons with 10.1 CR and this 0.060" overbore will there be any issues using the stock style head gaskets. I m just thinking that with the 0.060" overbore, the head gasket may stick out little bit in the chamber causing all sorts of issues.
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56D500boy
Posted 2018-10-05 9:28 PM (#571190 - in reply to #571174)
Subject: Re: 1955 270 Hemi rod noise, backfiring



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Location: Lower Mainland BC
Powerflite - 2018-10-05 1:36 PM

He's talking about .063" diameter. The stock bore of a 354 is 3.9375, and he took it up to the 4" bore of a 392.


Yeah, let's be clear, overbore = diameter, not radius.

Not the best example but one that I found on the net:

"we see that on a Chevy 454 V-8 (4.25-inch bore x 4.0-inch stroke), a 0.060-in overbore (4.31-inch final bore size) yields a 466.9ci engine, but keeping the stock 4.25-inch bore size and increasing the stroke by 1/4 inch to 4.25 inches results in 482.3 ci. (If the engine was both bored 0.060 and stroked by 1/4 inch you’d get 496 ci).

Insert better, i.e. Mopar, example here:



Edited by 56D500boy 2018-10-05 10:54 PM
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