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#1
06-22-2012, 04:35 PM
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What block to use
I'm building a new engine for my 1970 Firebird. The plan is to drive it to the track run mid sixes (1/8 mile) ande hopefully drive home. The heads are HP's by SD Performance with a 64 cc chamber. They flow 370 at .750". Victor intake and solid roller cam.
My question is what block to run. I have a 72 400 drilled for 2 bolt mains that I would put studs in. With that bock I have a 455 N crank that's turned down to 3" mains that I would run with Dude's spacer (I already have the kit) or buy a forged crank. I also have BRC .30 over pistons with 23cc dish. My second option is a 455 block with steel 4 bolt mains. I would use a N crank with this and turn the rod journals down. I have both of these blocks ready to go. I know best option is splayed 4 bolt on the 400, but I don't know anyone in my area that can do the conversion. Which should I use? |
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#2
06-22-2012, 05:30 PM
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Which one has thicker liners?
Everything equal, i'd use the 72 400 with 455 crk. As far as forged crank and 4 bolt caps. What rpm range? Any power adders? With the rods and pistons availible now, you can get away with lot more reliable power then back in the day.
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If you cant drive from gas pump to gas pump across the map, its not a street car. http://s207.photobucket.com/albums/b...hop/?start=100 |
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#3
06-22-2012, 05:39 PM
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Quote:
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#4
06-22-2012, 05:46 PM
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No power adder. Eagle rods with L19 bolts. Probably up to 6500.
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#5
06-22-2012, 07:35 PM
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CNS/S
At that power level , I would use a after market block. With the money you "will spend" on upgradeing a stock block, you can have the real deal without all the modifications to the stock block.
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505 KRE HP head 2x4 HP 1000s 60' 1.33, 5.78 @ 120.88MPH in 1/8 9.11@149.8MPH in 1/4 |
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#6
06-22-2012, 07:47 PM
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Shop in your area..
Quote:
Clements Racing Engines in Spartanburg, S.C. can align bore and align hone your block. Hell they can even align bore and hone the cam tunnel for roller bearings if you'd like. If you want to stay with a stock block, then go with the two bolt 400 and install splayed main caps. I usually install a steel main cap on the #1 location because I've found that the #1 cap can, and does, crack at the dowel pin location at times. My  Have a good one, Larry S. http://www.precisionautomotivespecialists.com |
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#7
06-22-2012, 08:22 PM
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I don't know the weight of your car, but mid 6s with a stock block is not going to hurt it, if prepped properly. The 400 would be stronger with the splayed caps, but the 455 with the steel caps should be trouble free at that et level. You might want to get them sonic checked before you proceed any further.
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 1963 Cat SD Clone (old school) streeter 1964 GTO post coupe, tripower, 4speed (build) 1965 GTO 389 tripower, 4 speed, driver 1966 GTO dragcar 1966 GTO Ragtop 1969 Tempest ET clone street/strip 1969 GTO Judge RA lll, auto 1969 GTO limelight Conv. 4speed go and show (sold) 1970 GP SSJ 1970 GTO barn find..TLB…390 horse?….yeh, 390 1972 GTO 455 HO, 4 speed, (build) 1973 Grand Safari wagon, 700hp stoplight sleeper 525ci DCI & 609ci LM V head builds |
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#8
06-22-2012, 08:39 PM
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I am sorry if I missed what the compression is going to be but I busted a 400 with 14 to 1,so I am going to agree with going with an aftermarket block.Buy it and be done with it
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#9
06-22-2012, 08:50 PM
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I have an IA II block in my racecar. Compression ratio in this car about 10.5:1. This will just be a car to have a little fun with. I have 10 or 12 stock blocks and want to get some use out of them.
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#10
06-22-2012, 09:58 PM
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Need a lot more info to make a good comparison of your choices.
Rough Wallace calculator says at 3700 lbs you would need about 720 HP to run 6.50s. So what is the real weight of this street car? Please post up more accurate info. Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#11
06-22-2012, 10:32 PM
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I haven't weighed the car. Pontiac lists a 1970 esprit at 3450 lbs. The air conditioning is out and cast heads and intake changed to aluminum. Add a roll cage,and probably around 3500 lbs.
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#12
06-22-2012, 11:21 PM
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Back in the 80's I ran a 1970 trans am. 455 with RA IV heads roller cam old wenzler intake with 2 650's. It would go 6.80's-7.00's. Broke several SD rods but never had a problem with a block(unless a rod went through it). This engine should be more powerful than that one. I always ran 455 bocks with 4 bolt mains then. A 400 with a cut down crank wasn't an option. So though I have the 4 bolt main block, I Wondered if the 400 was better.
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