Before I get jumped on I've done a search for the last couple nights, can't find my answer. I'm putting a 53 241 Hemi in a 27 RPU project for a friend of mine. The little motor runs but it's tired. Yesterday my buddy bought a fresh rebuilt 241 Poly out of a 55 Plymouth. His intentions were to swap the heads so he'll have a fresh bottom end. I know the heads will swap but I thought Hemi pistons are different then the poly's and my search here sorta confirmed that. My buddy was quick to point out the Egge catalog shows the same piston part # for both motors. Before we take the heads off this running poly, does anyone know for sure, same piston or different?
I was told here on the HAMB that you could bolt the Hemi heads on the Poly as long as you use the proper bolts and valve train. I sold a rebuilt 259 Poly with the 241 heads with the understanding it would work. Looks like I might be buying the Poly and parts back??????????????????????? Who has the proof either way, no guessing?
yes & maybe. IF you have a high comp & high lift cam then yes the valve reliefs are across on the hemi & offset on the poly. However low comp/low lift engines are reported as having either actually installed. the 241 is nominally only 7.1 & the 241 build on www.webrodder.com had 1 measure out @ in actuall 6.19! So...you might get away with not changing pistons, a little clay will say. You have to change the complete head ***embly, push rods, ex mans for sure.
Thanks for the replies. No high lift cam so it's a maybe but doesn't sound like a perfect situation, I personally would want a lot more compression. Brigrat, I'd bet your problem is the 259. I did notice Egge list different pistons for the 259 Hemi and 259 Poly.
I think I would eyeball the pistons and apply some common sense. If they are both flat tops with out eye brows, what could happen? If the Hemi pistons have domes and eyebrows and the polly is flat, then I wouldn't;t put polly heads on the hemi short block and hemi heads on the polly may have very low compressing. Try looking at it and giving it some thought. Are they both O deck? Compare. Think.
There was no OEM 259 hemi, wonder if Egge actually has proper pistons for a 259 hemi conversion. C/R, this is where custom pistons in the 9-10 C/R area would be worth the cost. Did you check out the webrodder build yet?
"Brigrat, I'd bet your problem is the 259. I did notice Egge list different pistons for the 259 Hemi and 259 Poly." I don't have a problem "yet" just trying to avert one!
I had a 241, the pistons are flat, I would try it and see what happens. Dont run it, just put some clay on the pistons to see what kind of clearance you have. You dont have to adjust valves and rockers in a hemi so slap it on and see, it would take you 10 minutes. I wuold check at least the 4 pistons on one side to make sure.
Both pistons are 'flat', both have valve reliefs. But the reliefs on the Hemi are in a 'vertical' position whereas the Poly are offset about ½" to the side. With a stock cam there should not be an issue. But, as George suggests, put some clay in there and check it or at least put the head on and depress a valve with the piston at TDC. How far does it go? With a stock cam the net valve lift is about 0.340" (dur is about 180 @ 50). Personally, I would not not bolt-on and go. Check the clearance. No, we have never physically checked the clearance simply because we do not use the oem cast pistons and would never mix-n-match in this fashion. For a swap you will need: pistons, heads, rocker ***emblies, plug tubes, plug tube washers, plug wire set, valve covers, wire covers, exhaust manifolds and pushrods. .
This is how I would go about it, pull the heads and see what was up, most I'd lose is some time and gaskets to put the poly back together. These motors belong to my buddy and he's hoping to find out it WILL work before he tears the poly apart, he's on a short budget, don't want to buy gaskets if it won't work. I think I convinced him to pull the heads today.
i'm gonna subscribe,'cause i found 2 241 hemi's,1 car-1 truck,& i was wondering if the heads would fit anything else,i think 1 has a cracked block,
They'll fit the 241, 259 & 270, will fit the 315 & 325 but have a lot smaller ports & valves than the stock 315/325 heads & oil sealing along the top of the head is marginal.
are those dodge motors or plymouth/dodge series? could you give more info on the oil sealing issues,i read http://www.hotrodsandhemis.com/ build up of a 354,i've seen very little about 241's.is there any old 'hop up' secrets,mix-n-match parts,i know i'm not gonna squeeze a **** load of ponies out of them-140 hp from the factory.just a good relieable moteor is what i'm looking for,
They're Dodge hemis & Polys, + Plym & DeSoto Polys all use Dodge Hemi blocks. As mentioned earlier, there's a 241 build on www.webrodder.com. There's also a 315 build there using an exotic cam & crank that also uses 241 heads on it. Evedently the top of the 315/325(& maybe the 270) are wider than the top edge on the 241. There is little margin for sealing the top of the lifter holes when using 241 heads on a 315/325.
When I was 14 I wanted to rebuild an engine so my dad gave me a 1955 270 Plymouth Poly to rebuild. While at a swap meet I found a set of Dodge Red Ram baby hemi heads with rockers, push rods, head bolts, plug tubes, everything needed to intall them, the old guy said they would fit and run on a poly so my dad bought them for me as an early christmas gift. We intalled the Dodge Hemi heads on the plymouth and started the engine on the stand and ran it for about an hour. It ran just fine. I had planned on using that engine in a 53 Plymouth lead sled but before I could get started on the project we had a fire and lost everything that was in the shop. I did rescue the Hemi from the debris and stored it in the barn. I'm now in the process of rebuilding that same engine that I first rebuilt 30 years ago. I have a 31 Plymouth Rumble Seat Coupe that I'm going to run it in. The fire didn't really hurt the engine much but sitting in a damp hay barn for 30 years didn't help it at all.
The valve reliefs on a hemi are straight across from each other polys are at a little angle. Isky sells a tool for cutting reliefs in the pistons without taking the short block apart.
You might want to do your into on the "new Members" section before the forum police get ya! Good luck reviving the engine. Put "hemi tech index" in search & start reading.
You can install the hemi heads on the poly block but your going to have to modify the pushrod holes to clear the offset, also the poly cam will not work as the lobe index is different.
as George has suggested it's well worth checking out the webrodder forum, below is a link with very useful information..... http://webrodder.com/phpBB3/viewtopic.php?f=2&t=899
Surprised to see my old thread pop back up but I'm glad I did. My buddy is putting the motor together now and since the last time he's gone ahead and got a racier cam. Since this reminded me I'll tell him he better clay the pistons for sure now.
Are you sure about the index being different on the hemi and poly In know they are on the low and high deck.
There is no difference in the position of the cam lobes from poly to hemi. The pushrod may be at a different angle, but the lifters are not.
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