So the 50k mile sbc in the 78 Malibu functions but is lacking. It's a basic D/D set-up: 305/th350/7.5"/2.73 set-up. Biggest complaint would be the leaks (back china wall, rear main, front timing @ oil pan) & fuel/catalyst vapors that seem to seep into the cabin from the factory exhaust. If I'm going to pull a motor out for clean-up & re-sealing (especially a low compression/small cubed one) I want to make the most of my time & effort. With that intro, I have acquired 2qty 2-bolt 400's over the years:
Combo #1 was "rebuilt" by an unknown & was part of a package deal w/other parts obtained years ago that's been sitting bagged on an engine stand. It's .040 over, 5.7 GM rods, has Hyper/4-valve relief Flat-tops, turned OE crank, & fairly large Lunati flat tappet cam (0412: 246/[email protected]; .515/[email protected]; 108/104 LSA/ICL; 25-6500rpm range).
Combo #2 is a recent acquisition that came from a buddy that I helped swap a 427sbc into his A-body Elky. It's well used, .030 over, cast dished pistons (w/one damaged), short-rod, OE turned crank, 64cc Dart Iron Eagle 200's, & a hyd flat tappet of unknown size/ID. I know this motor has seen it's share of laughing-gas.
In 2012, a local mass rebuilder did the rebuild on my duallys 7.4l motor & for a stock D/D it's worked just fine. My thoughts were to do a similar budget D/D build-up on one of the 400's but add/change some stuff that I have just sitting around the shop already. For my 7.4l rebuild, I had them 'upgrade' it by utilizing flat-tops vs. dished pistons & upsizing the cam to an 'RV/Towing' profile from their vendors catalog. No changes to the Peanut-Port heads other that a valve job but I added 1 3/4" full length headers & Edel-B TBI intake. It's a nice, very mild combo w/excellent throttle response.
If I used one of the 400's for the 78, the flat-tops impacts compression depending on the heads used. While the 64cc Darts my buddies motor came with could be cleaned up to work w/replacement dished pistons, I have a new/old set of AFR 190's w/74cc chambers I can use as well. The AFR's definitely out-flow the Dart IE's. My problem has been trying to put together a decent combo that doesn't start getting stupid. I like the thought of using the AFR's but selecting a mild cam to get a well thought out D/D combination similar to my Dually has been delaying decisions.
I'm not worried about using a flat-tappet cam & it would definitely work better toward the budget/rebuilder agenda. The rebuilder utilizes Melling cams & they had several decent/mild choices as part of the rebuilding. I could also install/upgrade to a mild hyd roller (less break-in concern/issues & better/broader power range). I have additional supporting parts for the larger displacement choice sitting around the shop as well: 1 5/8" primary x 3" collector full length as well as 1 5/8" x 3" mid-length headers; full 2.5" H-pipe/Flowmaster exhaust, Edelbrock RPM intake; 8.5" GN/T-type 3.42 posi rear end; & a 88-94 Serpentine accessory set-up.
My wants are simple/basic: a mild, D/D, low maint, 87ish octane combo that is fun & not a PITA. What I don't want? LS swap suggestions.
It's not involved in stop-light contests of speed.
I'm open for idea's suggestions that fall inline w/my above info.....
Combo #1 was "rebuilt" by an unknown & was part of a package deal w/other parts obtained years ago that's been sitting bagged on an engine stand. It's .040 over, 5.7 GM rods, has Hyper/4-valve relief Flat-tops, turned OE crank, & fairly large Lunati flat tappet cam (0412: 246/[email protected]; .515/[email protected]; 108/104 LSA/ICL; 25-6500rpm range).
Combo #2 is a recent acquisition that came from a buddy that I helped swap a 427sbc into his A-body Elky. It's well used, .030 over, cast dished pistons (w/one damaged), short-rod, OE turned crank, 64cc Dart Iron Eagle 200's, & a hyd flat tappet of unknown size/ID. I know this motor has seen it's share of laughing-gas.
In 2012, a local mass rebuilder did the rebuild on my duallys 7.4l motor & for a stock D/D it's worked just fine. My thoughts were to do a similar budget D/D build-up on one of the 400's but add/change some stuff that I have just sitting around the shop already. For my 7.4l rebuild, I had them 'upgrade' it by utilizing flat-tops vs. dished pistons & upsizing the cam to an 'RV/Towing' profile from their vendors catalog. No changes to the Peanut-Port heads other that a valve job but I added 1 3/4" full length headers & Edel-B TBI intake. It's a nice, very mild combo w/excellent throttle response.
If I used one of the 400's for the 78, the flat-tops impacts compression depending on the heads used. While the 64cc Darts my buddies motor came with could be cleaned up to work w/replacement dished pistons, I have a new/old set of AFR 190's w/74cc chambers I can use as well. The AFR's definitely out-flow the Dart IE's. My problem has been trying to put together a decent combo that doesn't start getting stupid. I like the thought of using the AFR's but selecting a mild cam to get a well thought out D/D combination similar to my Dually has been delaying decisions.
I'm not worried about using a flat-tappet cam & it would definitely work better toward the budget/rebuilder agenda. The rebuilder utilizes Melling cams & they had several decent/mild choices as part of the rebuilding. I could also install/upgrade to a mild hyd roller (less break-in concern/issues & better/broader power range). I have additional supporting parts for the larger displacement choice sitting around the shop as well: 1 5/8" primary x 3" collector full length as well as 1 5/8" x 3" mid-length headers; full 2.5" H-pipe/Flowmaster exhaust, Edelbrock RPM intake; 8.5" GN/T-type 3.42 posi rear end; & a 88-94 Serpentine accessory set-up.
My wants are simple/basic: a mild, D/D, low maint, 87ish octane combo that is fun & not a PITA. What I don't want? LS swap suggestions.
It's not involved in stop-light contests of speed.
I'm open for idea's suggestions that fall inline w/my above info.....
Last edited: