Build options for Mk IV BBC

[joeblow55]

Apologies in advance for the long post. I’m in the process of dusting off and upgrading an old build from the 80’s, and have a dilemma. Engine is / was a
396 engine from a 66 Caprice ... My issue is that the original 396 block must have had some kind of “block rot” as when I torqued down the cylinder heads, the threads were pulling out from the block. I eventually ended up with HeliCoils in every single hole for both heads … not ideal, but it’s what I could do at the time with the resources I had. Engine seemed to run really well, and after crashing the car in the early 80’s, the fresh motor sat on engine stand for 30+ years. Now, after having freshened up the heads, (3872702 / 65-66 oval port closed chamber 98cc … the original heads from that motor) I am thinking the smart move is to use a 427 / 454 block which I already have. Basically, I think the chances of success with the 454 block is higher than going through all the build steps with the original block only to have more problems torquing down head bolts. The 427 internals were from a 425 HP motor (forged crank, rectangle port heads) … I would need to get a fresh set of pistons to use with the 396 oval port heads mentioned above. I have already gone thru the heads and they are ready to bolt on… new guides, hardened exhaust valve seats, 3 angle valve job, and new springs and hardware for use with hydraulic roller cam. Time to select the right set of pistons and roller cam for this combo. Since I plan to use the later block, I can use a roller cam that does NOT require the grooved rear journal. (The 65-66 big blocks required a grooved rear journal to get oil up to the cylinder heads and rockers… ask me how I know) There seems to be a lot more wisdom regarding engine building here than on a couple of other forums I sometimes read. I don’t usually post a lot here, but I do read quite a bit. Hoping to get some solid suggestions and feedback regarding this build, as I plan to start ordering parts. I am assuming that there would not be any issues using the oval port heads with the larger cylinder bore … Oh yeah, and it will need to run on todays unleaded pump gas without knocking. Once short block is assembled, I will look at the budget, but most likely planning on replacing Holley carb with Sniper EFI for drivibility and reliability. Engine will be mated to a Muncie 4 speed, and 3.73 rear gears. Suggestions and/or comments would be helpful...
Again, sorry for the long post...
Joe Blow 55

 

[Murphdog]

Are you building this 454 block as a 454 or 427. A stock 454 flat top piston may make plenty of compression with the closed chamber head. You will need to do the math. Just watch compression heights of when shopping for pistons. You want something that will make zero deck height without totally whacking the deck to get there. Otherwise you will be dealing with manifold fitment.
Jeff

 

[425/409ER]

I hate to tell you this but I would just get a 454 out of the truck, rebuild it with forged slugs and use a set of oval port or peanut port heads (they work great) and have a better engine to start with. The closed chamber heads belong in a museum someplace as power wise the open chamber stuff blows them away. Use a nice hyd roller cam with an RPM Performer intake. I have a flat top forged piston .030 454 with ported peanut port heads that runs in the low 11's and car run on 87 octane if a wanted it to. I would not hesitate to run this on the street any day.

 

[joeblow55]

Thank you both for your feedback. I would be building this block as a 427. I am trying to use the block, heads, and forged crank that I already have
as opposed to acquiring more "stuff". The parts that I already have are in good shape, and the heads mentioned above are literally ready to bolt on and run. The "rotten" 396 block with all of the HeliCoils makes me nervous enough to not put any cash into it, and besides, it would require the roller cam to have the grooved rear journal... making it unable to be used in any newer block. I agree that open chamber heads and more cubic inches are a better combo in the long run, but I am not trying to build an 11 second car. Regardless of the combo, a roller valve train would be used so the cost of those components would be a wash. I am trying to do the best I can with what I have. I think with the right compression ratio, and the right roller cam, (coupled with a Performer intake and headers which I also already have) this engine would run plenty strong enough for a street car. Doing this on somewhat of a budget will allow me to start on my 409 build for my other car. I hope this makes sense.

 

[1958 delivery]

The problem with using the 427 crank is they didn't make flat tops for 427 so you either have high compression or buy custom type pistons, maybe off the shelf blower pistons to get the comp down. Otherwise nothing wrong with a 427
I just saw ICON makes a forged flat top

 

[Don Jacks]

Joe,What makes you think that your cam that has the required rear cam oiling groove won't work in a later block. Yes the modefication must be made for the early blocks,but it shouldn't hurt the later blocks.Using the crank and rods is a good idea.To go with those parts and a 4.250 bore block,use a piston for a 385 -390 horse 427 witch used a very small dome for a cr of 10.25 with your heads.

 

[1958 delivery]

You can use a grooved cam in any block.

 

[1958 delivery]

10+ ain't making it on pump gas. I think it's easier just to get a 454 crank then there is an off the shelf flat top for 9-1 comp with his combo

 

[427John]

The remark about closed chamber heads being museum pieces only applies if you are upgrading to larger valves,that was the reasoning behind switching to the open chamber,when they switched to the larger 1.84 then 1.88 exhaust valves the closed chamber became an issue with valve shrouding hindering flow.The flip side of the open chamber was the required high dome for high CR which could cause its own hinderance to flow. Depending on the piston, domes can be milled off,for example the TRW low dome 427 pistons have plenty of thicknesss to mill off the small dome to make a flattop.But as 1958 Delivery said switching to a 454 crank gains commonly available flattops,I run a flattop piston 454 with close chamber heads and have no trouble running pump gas,my heads still have the 2.06/1.72 valves and make plenty of power for my needs.

 

[joeblow55]

Maybe I misunderstood, but I thought the grooved rear cam journal was specific to the early 65-66 blocks only. My thinking was that by using the "better"/ newer block, completely eliminates the need to worry about the grooved rear cam journal. All things considered, going this route is a potential winner in a number of ways.
1. I gain about 30+ cubic inches
2. Block in better condition, and by using head studs instead of bolts, less of a chance to strip the threads out of the block
3. 427 crankshaft is forged ... 396 crank is a cast piece
4. Only needing new pistons, I can select (almost) any compression ratio which would complement the roller cam specs and the 3.73 gears

Blower "flat top" pistons mentioned above certainly seems like something to consider. Those who responded, thank you. I appreciate your feedback. This site / forum is awesome.

JoeBlow55

 

[1958 delivery]

Maybe I misunderstood, but I thought the grooved rear cam journal was specific to the early 65-66 blocks only. My thinking was that by using the "better"/ newer block, completely eliminates the need to worry about the grooved rear cam journal. All things considered, going this route is a potential winner in a number of ways.
1. I gain about 30+ cubic inches
2. Block in better condition, and by using head studs instead of bolts, less of a chance to strip the threads out of the block
3. 427 crankshaft is forged ... 396 crank is a cast piece
4. Only needing new pistons, I can select (almost) any compression ratio which would complement the roller cam specs and the 3.73 gears

Blower "flat top" pistons mentioned above certainly seems like something to consider. Those who responded, thank you. I appreciate your feedback. This site / forum is awesome.

JoeBlow55

The groove is specific to 65/66 only but using a CAM with the groove on any year is ok, you just can't use a non groove cam in the 65/66 block

 

[oldskydog]

396 crank should be forged same as 427.

 

[MRHP]

10+ ain't making it on pump gas. I think it's easier just to get a 454 crank then there is an off the shelf flat top for 9-1 comp with his combo

I run 11.70’s on pump gas on the street and at the track, and mine is 11.97 compression.

 

[La Hot Rods]

They did make a cast 396 crank.

 

[oldskydog]

They did make a cast 396 crank.

For the 402 as I recall, maybe 69 non SHP 396.

 

[joeblow55]

Not that it matters if I'm gonna use the 427 crankshaft, but if it will clear up some confusion or provide useful info for the community I'm glad to find the casting numbers and date codes off that 396 shaft... I'm 99% certain that's the original shaft out of that 396 motor from the 66 Caprice... and it is definitely a cast crankshaft. After all, I and many others come here seeking info and knowledge, and I'm happy to provide same if I can. From some other things I have read, I think you can safely run about 10:1 on pump gas if you pay attention to quench distance. Perhaps "Sniper" injection system helps in that regard ? It certainly cannot hurt, and for drivability and reliability, I am certainly leaning in that direction. I will see if
I can find that ICON piston Mike "58 delivery" mentioned, or the one Don J. mentioned. I was on JEGS site last nite and got nowhere ...

 

[Don Jacks]

Look at the Icon's website directly,you'll find a lot more info on what is made for your combibnation.Yes,quench distance is essential on these closed chamber heads for detonation supression.Another tip would be unilize the availeable electronic ign.control for tunning.What are the spec's on the cam that you're going to run,nd which transmission?

 

[La Hot Rods]

The quench is controlled by the piston to head surface including head gasket that you use. This is very important to control detonation running pump gas. It also makes it a snappy engine.

 

[joeblow55]

Hydraulic roller cam, no cam specs yet ... big/heavy car (66 impala) running muncie 4 speed and 3.73 rear gears. I assume the final selection of the piston used in this engine would affect the choice of cam as far as lift, duration, and overlap, etc...

 

[Don Jacks]

For a good all around cruiser I'd suggest something in the 230 in. -236 ex.at 050,a good dual plane intake and headers ,your Sniper injection and holley's duraspark ignition.