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Topic Review (Newest First)
10-14-2012 08:36 PM
cobalt327 Who said they were "the same"? I did say
Quote:
Your 148 heads are more like the c/n 215 heads as far as the chamber volume goes.
. As in smaller chamber, not the bigger chamber seen on the 049/781, etc. heads.
10-14-2012 07:12 PM
OMARS67 Thanks fellas very informative.That's exactly what I need to know. I think I'll invest some $$$ into the 049 heads.
10-14-2012 12:29 PM
F-BIRD'88 The #215 396 head is not the same it has small 98 to 101cc closed chambers and full size oval ports.
it was used on the hi perf 396-350HP chevelle motors.. also used on the 360hp and 390HP 427
its a good high perf closed chamber oval port head. (gets real good with porting)

The 148 head is a low compression low rpm 2 barrel carb truck head.
10-14-2012 12:14 PM
cobalt327
Quote:
Originally Posted by OMARS67 View Post
so is it safe to say that if the 049 and my 148 were cc close and both had 2.19 vavles they would produce close to the same power. thank for the response guys.
Mortec has the following info on the c/n 148 BBC head:

3933148....'69-'84; oval port; 112cc open chamber; '69 396/265hp, 366T, 427T

Your 148 heads are more like the c/n 215 heads as far as the chamber volume goes. They're sometimes called "semi-open" chambers and should be about 110-112cc.

If the CR was the same there wouldn't be much difference in performance between the two heads. Getting compression is easier w/the smaller chambers especially if building a small BBC (396/402). In a 454 engine, watch that the compression isn't too high.

Fitting larger exhaust valves in the semi open chamber requires some finesse to minimize shrouding.

BTW, if you look at the info at the nastyz28 site, it shows:

3933148- 1969; 366/396; 122.1cc open chamber; 2V/427 265HP car & truck

The nastyz28 chamber volume is a typo.
10-13-2012 02:50 PM
OMARS67 come on man.. is that response needed??? you answer my question by saying my 148 may have a different runner. just that would have been fine. cobalt327 answer by agreeing my compression would go up after saying theres different variable effecting compression . then i ask if the difference between my 148 and the 049 is the runner volume/design assuming the valve size is the same and the cc volume and all other variables between the two heads. that shouldnt be a broad assumption.
10-13-2012 02:18 PM
F-BIRD'88 Why don't you post what you really are trying to achieve, instead of trying to find someone to buy into your broad based assumption.. the 148 truck casting may/probabily has a much different port.
10-13-2012 12:57 PM
OMARS67 so is it safe to say that if the 049 and my 148 were cc close and both had 2.19 vavles they would produce close to the same power. thank for the response guys.
10-13-2012 11:17 AM
F-BIRD'88
Quote:
Originally Posted by OMARS67 View Post
yeah i figured it wouldnt be worth the time. the reason i ask is because i have a set of 049 heads. and i read there the best hi perf head for oval BBC. what so special?? 049 have advertise smaller cc chamber. maybe the intake runner volume?? i understand about things that can affect the compression but lets assume both heads are virgin cast. i know my existing 148 heads are and these 049 head are as cast.
the 049 and 781 are:
Good when ported and big 2.19-1.88 valves are installed.
Some of these heads have a 116chamber.
Like posted you have to CC your heads to know the chamber volume.

The small chamber closed chamber oval ported heads work very well too.
063, 290 215 etc 1970 and back.
again best with porting and larger valves.
The closed chamber gets reworked a bit.
10-13-2012 10:28 AM
OMARS67 yeah i figured it wouldnt be worth the time. the reason i ask is because i have a set of 049 heads. and i read there the best hi perf head for oval BBC. what so special?? 049 have advertise smaller cc chamber. maybe the intake runner volume?? i understand about things that can affect the compression but lets assume both heads are virgin cast. i know my existing 148 heads are and these 049 head are as cast.
10-13-2012 10:07 AM
F-BIRD'88 You would need to replace your 122cc had with a 110cc cylinder head to increase the compression ratio by 1.
10-13-2012 02:37 AM
cobalt327
Quote:
Originally Posted by OMARS67 View Post
do i guess right to think a 119cc head would raise the compression on my 454 BBC. currently i run 148 heads with 122cc but i have pretty tall dome piston. given i use the same gasket for both heads.
First, the advertised volumes are almost never right, the real volume of an unmolested head tends to be a bit more.

That said, the chambers have to be CC'd in order to know exactly what you have. If the heads have been milled, they can be radically different (smaller) than advertised and this can affect the piston to valve clearance. More things to check here. Changing valve sizes, unshrouding or polishing the chamber, valve jobs, etc. can all change the chamber volume.

You are right that a 119cc head will raise the CR over a 122 cc head. But you're only looking at about a 0.2:1 change- so if you're doing this only for the rise in CR, don't bother.
10-13-2012 12:08 AM
OMARS67
hi or low compression??

do i guess right to think a 119cc head would raise the compression on my 454 BBC. currently i run 148 heads with 122cc but i have pretty tall dome piston. given i use the same gasket for both heads.

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