'55 270 Hemi top end on a '57 325 Poly ?
Moderators: scottm, TrWaters, 392heminut
'55 270 Hemi top end on a '57 325 Poly ?
this is another one of my projects and I'd like to get some opinions on this:
I have a 1957 Dodge 325 Super Red Ram poly engine
I have access to a complete 1955 Dodge 270 Hemi top end
Hemi top end will bolt onto the 325, but valve sizes are smaller on the '55 Hemi heads, than what a "real" 1957 Hemi 325 would have
is the only difference the valve sizes, or did the 1957 D-500 Dodge hemi 325's also have larger PORTS
in other words, is this swap worth doing, or should I just hold out for 1957 Dodge heads with the bigger valves ?
I have a 1957 Dodge 325 Super Red Ram poly engine
I have access to a complete 1955 Dodge 270 Hemi top end
Hemi top end will bolt onto the 325, but valve sizes are smaller on the '55 Hemi heads, than what a "real" 1957 Hemi 325 would have
is the only difference the valve sizes, or did the 1957 D-500 Dodge hemi 325's also have larger PORTS
in other words, is this swap worth doing, or should I just hold out for 1957 Dodge heads with the bigger valves ?
You'd be best useing 315/325 heads, but check out Doc Fromader's 315 build on www.webrodder.com
George wrote:You'd be best useing 315/325 heads, but check out Doc Fromader's 315 build on www.webrodder.com
where exactly is that buildup ?
Click on this...
http://www.webrodder.com/index.php?sear ... ies&CID=15
Wow, what a wealth of information!
http://www.webrodder.com/index.php?sear ... ies&CID=15
Wow, what a wealth of information!
Scott Moseman
http://www.TheHEMI.com/
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Yeah! But I'd hate to think of what he spent on that cam/crank/rod set up!scottm wrote:Click on this...
http://www.webrodder.com/index.php?sear ... ies&CID=15
Wow, what a wealth of information!
yeh, I'm starting to think spending big bucks on a Dodge 325 hemi may not be worth it- I always had the opinion that the only early hemi worth messing with would be a 392- but could never find one for good price- so I never did a 392- now I'm trying to low-buck it with a Dodge 325 poly with hemi top end, or a 331 Chrysler poly with early 331 hemi top end- it seems like it may very well be a waste of time power-wise, I'm sure I could get the engine assembled and running, but the HP level would be 250-280 HP at best with those stock small port/small valve heads, if that even
those Dodge hemi ports look mighty restricted to me
is there a PORT SIZE difference between 270 Red Ram and 315/325 Red Ram hemi heads ? That's what I really need to know before I proceed.
those Dodge hemi ports look mighty restricted to me
is there a PORT SIZE difference between 270 Red Ram and 315/325 Red Ram hemi heads ? That's what I really need to know before I proceed.
I dont believe there is a significant difference in port size. The slight problem with using 270 heads on a 315-325 block is that due to a casting difference, the heads do not quite cover the keyhole shaped pushrod holes in the 315/325 block. You will need to either add some weld or epoxy onto the heads to completely cover these holes.
Early hemi to late sb Mopar trans adapters. Precision billet parts for early hemis.
TrWaters wrote:I dont believe there is a significant difference in port size. The slight problem with using 270 heads on a 315-325 block is that due to a casting difference, the heads do not quite cover the keyhole shaped pushrod holes in the 315/325 block. You will need to either add some weld or epoxy onto the heads to completely cover these holes.
why would you want to cover excess pushrod keyhole space ? it only is dead air space between rocker box area and lifter valley area- both areas are open to crankcase pressure- what's the purpose of adding expoxy to make it smaller ? I don't get it, please explain
ok, looking at picture of bare block in Tex Smith book, I see the row of keyhole pushrod holes across top of block for pushrods to go into heads- if the 241/270 heads have less surface area towards top of head, that area would become a thinner sealing surface- this is similar the problem some Pontiac valley covers have, when bolted down.
the fix is, bolt the heads on, then wipe a layer of black permatex across the top of that area, from front to back- between head and block- then it won't leak oil there
the 270 hemi ports look pretty dismal from a performance standpoint, in that one webrodder thread- it kind of took the wind out of my sails for that project- I'm starting to think the only way to go, is the 315/325 heads on the 315/325 hemi
what grabbed me was they ported them considerably, and they only flowed around 209 cfm, which is only what a wedge head flows out of box, and many like Buick, Olds, Pontiac actually flow more than that- but with the 270 heads, you have to work to get it
a labor of love, for sure
but I'm still attracted to the 325 for a few very good reasons- #1 it has comparable displacement to the most affordable big hemi, the 331 Chrysler- #2 the Dodge is lighter and smaller #3, it's still a Hemi !
the fix is, bolt the heads on, then wipe a layer of black permatex across the top of that area, from front to back- between head and block- then it won't leak oil there
the 270 hemi ports look pretty dismal from a performance standpoint, in that one webrodder thread- it kind of took the wind out of my sails for that project- I'm starting to think the only way to go, is the 315/325 heads on the 315/325 hemi
what grabbed me was they ported them considerably, and they only flowed around 209 cfm, which is only what a wedge head flows out of box, and many like Buick, Olds, Pontiac actually flow more than that- but with the 270 heads, you have to work to get it
a labor of love, for sure
but I'm still attracted to the 325 for a few very good reasons- #1 it has comparable displacement to the most affordable big hemi, the 331 Chrysler- #2 the Dodge is lighter and smaller #3, it's still a Hemi !
Actually, thats not a fix. Its an oil leak waiting to happen. But to each their own. Good luck with your build.
the fix is, bolt the heads on, then wipe a layer of black permatex across the top of that area, from front to back- between head and block- then it won't leak oil there
Early hemi to late sb Mopar trans adapters. Precision billet parts for early hemis.
TrWaters wrote:Actually, thats not a fix. Its an oil leak waiting to happen. But to each their own. Good luck with your build.
the fix is, bolt the heads on, then wipe a layer of black permatex across the top of that area, from front to back- between head and block- then it won't leak oil there
I totally disagree with you there, because the new liquid sealants are better than gaskets ! Many new OEM engines don't even use gaskets anymore, you get a gasket kit and there's a head gasket, thermostat o-ring, and intake gasket- the rest is sealed- with sealer.
If that head/block interface is wiped and ends up leaking, it can only be due to excessive blowly causing pressure blowing the gasket out- because modern black permatex is good stuff.