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Mopar mega. Block #2818375
09/07/20 09:44 PM
09/07/20 09:44 PM
Joined: Jan 2011
Posts: 425
florida dade
C
cesar perez Offline OP
mopar
cesar perez  Offline OP
mopar
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Joined: Jan 2011
Posts: 425
florida dade
Whats the max bore size for a mega block not a Siamese block

Re: Mopar mega. Block [Re: cesar perez] #2818386
09/07/20 10:36 PM
09/07/20 10:36 PM
Joined: Jan 2003
Posts: 6,404
Minnesota
Hemi_Joel Offline
master
Hemi_Joel  Offline
master

Joined: Jan 2003
Posts: 6,404
Minnesota
Cesar, assuming you mean Hemi, a megablock means it is siamese bores. If it does not have core shift, it will go 4.500. A regular Hemi block is generally good for 4.310


[img]http://i.imgur.com/boeexFms.jpg[/img]
31 Plymouth Coupe, 392 Hemi, T56 magnum
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RS27J77
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Re: Mopar mega. Block [Re: Hemi_Joel] #2818443
09/08/20 08:10 AM
09/08/20 08:10 AM
Joined: Jun 2015
Posts: 228
Northeast Indiana
7
73DAD Offline
enthusiast
73DAD  Offline
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Joined: Jun 2015
Posts: 228
Northeast Indiana
The instruction sheets that shipped with them originally claimed they'd go to 4.600" actually, but I don't know anybody who's tried it.

Re: Mopar mega. Block [Re: 73DAD] #2818448
09/08/20 08:30 AM
09/08/20 08:30 AM
Joined: Oct 2015
Posts: 418
UK
rb446 Offline
mopar
rb446  Offline
mopar

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Posts: 418
UK
Ours is on 4.565 sonic checked ok on thrust apart from back cylinders no. 7 & 8 bulkhead side are a bit thin but no probs yet and holds temps well with street driving/racing, but the combo makes max hp @only 6000rpm.

Last edited by rb446; 09/08/20 08:34 AM.

1969 'Cuda 446ci, best 9.96@133.9 in 1990
1971 340 'Cuda, best 11.01@122.8 in 1987
Re: Mopar mega. Block [Re: 73DAD] #2818453
09/08/20 08:45 AM
09/08/20 08:45 AM
Joined: Jan 2003
Posts: 11,910
Marion, South Carolina [><]
an8sec70cuda Offline
I Live Here
an8sec70cuda  Offline
I Live Here

Joined: Jan 2003
Posts: 11,910
Marion, South Carolina [><]
Originally Posted by 73DAD
The instruction sheets that shipped with them originally claimed they'd go to 4.600" actually, but I don't know anybody who's tried it.

I thought the later MP/World "megablocks" were the only ones that claimed they'd go out to 4.600"?


CHIP
'70 hemicuda...8 sec street car
'69 road runner 440 w/ Indy SRs
'69 road runner 440-6, 4 speed...Dad's ride
'71 Demon 340 resto project
'06 GMC 2500HD LBZ Duramax...toy hauler
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Re: Mopar mega. Block [Re: an8sec70cuda] #2818467
09/08/20 09:28 AM
09/08/20 09:28 AM
Joined: Jan 2003
Posts: 6,404
Minnesota
Hemi_Joel Offline
master
Hemi_Joel  Offline
master

Joined: Jan 2003
Posts: 6,404
Minnesota
In my response above, I was referring to the pre-World Mopar Hemi blocks.


[img]http://i.imgur.com/boeexFms.jpg[/img]
31 Plymouth Coupe, 392 Hemi, T56 magnum
RS23J71
RS27J77
RP23J71
RO23J71
WM21J8A
Re: Mopar mega. Block [Re: Hemi_Joel] #2818494
09/08/20 10:47 AM
09/08/20 10:47 AM
Joined: Feb 2014
Posts: 1,151
central il.
S
second 70 Offline
super stock
second 70  Offline
super stock
S

Joined: Feb 2014
Posts: 1,151
central il.
There were 2 different mega blocks 1 was a siamese the other wasn't. The siamese has mopar cast in the block above the 2468330. As you can see 4.31 is the max recommended bore for the full water jacket block.

Mike

s-l1600 (2).jpgs-l1600.jpgHemi 1.jpgHemi 2.jpg
Re: Mopar mega. Block [Re: second 70] #2818525
09/08/20 11:48 AM
09/08/20 11:48 AM
Joined: May 2019
Posts: 183
Lake Villa Il
INTMD8 Offline
member
INTMD8  Offline
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Joined: May 2019
Posts: 183
Lake Villa Il
Fwiw I have a full water jacket block and there's a sticker on the bellhousing area that says 4.34 max bore.

Maybe best to just have it sonic checked.

Re: Mopar mega. Block [Re: INTMD8] #2818806
09/09/20 03:49 AM
09/09/20 03:49 AM
Joined: Jan 2003
Posts: 2,367
A shed in England
Tig Offline
top fuel
Tig  Offline
top fuel

Joined: Jan 2003
Posts: 2,367
A shed in England
Just for Info, we had a 4.50 bore 528, using an early # 625. The block had a crack in the external water jacket nr the starter. We got it repaired but we still always had to run it with block / rad sealer. Doing a little bit of digging I heard there was a few out there like that. Anyway, we got a replacement block sent over to the UK FOC after my wife managed to get hold of Dave Hakims email address,that one was a #624. We ran the 528 for years and it's still going with another owner but then we wanted to go 572. We dug the #624 out, it was sonic checked, there was no way it would safely go out to 4.50". We ended up with a KB block.


'74 Challenger..9.46 and 145.9 so far. 4000lb!!!# N/A, 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 4:10's and 10.5s. Marsh Performance pump gas 655ci. 9.51 @142.4 with a 580 wedge
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 14.02 @ 97.95 Best Mph 98.5






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