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Old 11-19-2017, 03:13 PM   #1
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Default So, looking for combo advice probably bad

I got Cap42's 383 and am debating pulling the heads and porting them. I suspect HP will be in the 400 range with what's there now. This is what I know about the combo as it is:

-276HR cam 224/[email protected], .502/.510 lift 110 LSA
-Holley Stealth Ram
-1 5/8 LT headers
-Going to be 2.5" full exhaust maybe no mufflers
-Stock World S/R heads with what appear to be aftermarket valves (2.02/1.60)
-1.5 ratio Comp Roller Rockers
-dish pistons, estimating around 9.6:1 CR and that's quite possibly optimistic without pulling stuff apart to measure.

I've seen flow numbers on these at 200 to 225 or so at .5 lift. I think the variance is tolerances on flow benches and possibly valves/valve jobs. I'm pretty sure I can pick up 20hp and 200 RPM pretty easily with a bowl job on these heads and some work on the exhaust, probably 15 hours or less into them plus another say 10 to put em back on, lash the valvetrain etc. I already have the tools, so that's a non-expense. All I'd be into cost wise is head gaskets. As it stands now I expect this setup to be pretty well done at 5K or less, and making peak torque near 3K.

Does TCG think port or not port the heads? I'm just trying to make my mind up and am wishy washy on it.
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Old 01-04-2018, 04:58 AM   #2
 
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SR heads dont flow that goodProbably bit lower BUT have much better flow velocity. If memory serves I would say mid 450s BUT torque would be much higher due to cam timing. And only way it would 9.6 compression would be if they were 64 cc heads and all the SR heads I saw were 72-74 average but much more consistent. Major port work might be limited success, 383 isnt rpm engine like shorter strokes. Proper tuning will net great results. And make sure fuel pressure is solid and consistent. Get it tuned with wideband if possible.
SR heads are considered stock replacement head made to give you new heads over refurbished 30-40 yr old heads or later crack prone light weight heads. But still with that cam and decent set of mufflers like Stealth Ram will give you decent torque Dynomax or Flowmaster it should sound sweet and pull like freight train. dont forget h pipe. Stealth Ram should put down good torque numbers. Being 383 its solid 6000 rpm torque engine.
As for bowl work those heads are as cast 90% better than stock. Was looking for my old catalogs from when engine building was booming. Sold a many of those heads even got set on my 355 truck engine. BUT I opened mine up for 202/160. Still not lot of overhang. I teamed mine up with GMPP LT4 HOT cam less 1.6 rockers. Depending on your gears and converter, should shred tires or toss mud. You will need at least a TCI Saturday Nite special converter but to not loose the bottom end dont get rpm greedy with super loose converter.
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Old 01-06-2018, 11:24 PM   #3
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72-74 was an option as well as 67s. The paperwork I have says they're 67 and with 2.02/1.60 valves. I've seen numbers all over the place for these heads, anywhere from 200ish to 225ish CFM. Even though they may not make all the power in the world they have all the bolt holes and are likely less crack prone which is better than working with stock heads any day.

I'm predicting peak HP at 4800ish honestly. I don't have a ton of head, and for the cam it's only a pittance more than your HOT cam. I'm planning a fuck ton of gear (4.11s or 4.30s) with a 700R4. I calculated it out to something like 110-115 in the quarter with a 1:1 ratio and where I think I'll make power, and then the OD being icing on the cake to keep the highway behavior decent. The 700R4 has a 2400 stall in it, which will likely be higher due to being a 383. Since I've got a 9 inch if the 4L80E goes in later I'll have a 25% under drive on it which will increase my overall spread and I'll drop down to 3.50s making highway use even better. That said I'll probably run my 3.23s until I figure out where I'm actually making power then gear according to that.

Did you ever test your 355, if so where'd you make power at RPM wise?
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