Build options for Mk IV BBC

J

joeblow55

Member
Thanks for that ... I plan on port matching the performer intake to the oval ports on the 1966 heads. I cant believe that the "performance" manifold has ports that are that much smaller than the heads. Either way, I lose about 30 ish lbs from the cast iron intake. I think the shorty headers have
1-7/8 tubes. I am still trying to educate myself on the sniper F I but most of all, this is a tuff machine and it has to sound like one. My choosing the hydraulic roller was basically "insurance", as I have read ALOT about garbage steel from you know where finding its way into our cams and lifters...
Rollers (high quality) have a higher probability of making it through the break in process... and as long as we're going roller, lets get the right lopey sound ... still haven't found the right pistons yet ...
 
J

joeblow55

Member
found these... https://uempistons.com/product/10346/ICON-Premium-Set-IC776.STD Looks like a 9.7 CR forged piston using a stock rod. There will be questions about quench coming up fella's. My understanding is that these pistons are spec'd at "zero deck" and alot of BBC engines usually come in with the piston down in the hole ... typically .010 or more ? Only way to know is to measure it... AFTER I already bought the pistons?
...is the only way to control the quench distance to Mill the head surfaces and select proper head gasket thickness ?... I think a 9.7 CR would be ok to run on todays gas...
then there's these https://uempistons.com/product/8361/ICON-Premium-Kit-IC777KTD.030 online catalog says 10.9 but when you look up the actual specs for the part # comes up 11.9 for the compression ratio.
That one might be iffy on pump gas ...

Heads (as mentioned earlier) have the hardened seats... with proper valve springs for hydraulic roller valvetrain... Good to know I don't need to port match the intake to the oval ports ... alot of material to remove for very little gain.

Whadya think ?

Thanks fella's
 
J

joeblow55

Member
Also had an interesting conversation with one of the "tech" dudes at UEM ( Icon ) pistons. So I will pose this question to the guys that build alot of engines here ... piston to wall clearance ... and do I understand it wrong ?
Example :
1" bore
.990" piston diameter
so, is it .010" ... or .005"

there is .010" clearance overall, but for 360 degrees around the circumference of the piston would have .005"

For sure engine builder will know it, but I wanna make sure I haven't misunderstood it ...
Dumb question ?
 
D

Don Jacks

Well Seasoned Member
Supporting Member 3
The first piston that you listed for a street driven,n/a combination would be the one to use here.Most of the replacement pistons that you buy will be down in the hole because the piston don't have anyway to know if nor how much your blocks decks have been machined.For what you're doing,don't be as concerened as much about an absolute zero deck,but how much the quench distance actually is.You want a to achieve from about .035-.050 here.The only ''dumb''questions are the ones that aren't asked.
 
Murphdog

Murphdog

Well Known Member
Supporting Member 2
Both pistons you mentioned are technically .017 below a "stock" 9.800 deck. I would be tempted to find a GM steel shim head gasket (.015/.017) and put it together.
Piston clearance, follow UEM's spec. If they say .005, that is total, NOT, per side.
If your block has provisions for a front thrust plate, (some blocks are drilled, some have the boss that can be drilled) I think you can get a late model roller type snout on the cam and the appropriate timing set and not have to dink with a cam button.
Jeff
 
dakota tom

dakota tom

Well Known Member
Supporting Member 2
Manifold wise I would be looking for a C-396 Edelbrock. Would be period correct and flow better than the performer.
 
J

joeblow55

Member
Thanks for pointing me in the right direction guys... Not sure how you would know that those pistons would be .017 below the deck without actually measuring them, unless we assume that the deck surface is exactly 9.800... I haven't built enough engines to know, but I am guessing that the deck surface of your average BBC would come in close to the 9.800" ... +/- a couple thousandths given manufacturing tolerances...? If I am understanding this correctly, a piston that is spec'd at 9.7 : 1 CR (at zero deck) would be slightly less if it is "down" in the bore. Essentially the distance that the piston is "down" would effectively "add" volume to the combustion chamber. Working from there, a 4.280" bore (427 + .030) that is .017 down in the cylinder would give you roughly 4cc's , making the 98cc combustion chamber "look" like 102cc's ???
I know I am overthinking this, but I'm learning a few things along the way...and lessons learned here will be put to good use when building the 409.
I have also read elsewhere that .040" - .045" is a good target for the quench distance so that lands right in the neighborhood that Don mentioned.
Thanks again for sharing your knowledge and experience guys...

Joe S.
(a.k.a. "JoeBlow55")
 
dakota tom

dakota tom

Well Known Member
Supporting Member 2
Joeblow55 isn't decided on this build. If he was th400 stock converter, 3.08, 4000 lb car. 200 degree cam the performer 2-0 would be good. But we know 4sd, 3.73s, and he wants a lope at idle so a 230s cam should work.
A performer rpm is 40 some year newer technology so it should be better than a C-396 but the C-396 Is good and near the age of the car.

409/409ER you mention you peanut port engine, what is you car and weight?? My brother threw a car together from my parts pile. 425/427 short block, flat tappet solid cam about 250 degree that was done over 6200. Unported 215 closed chamber heads, C-396 intake, 3310 780 Holley, 68 all steel Camaro about 3400 lbs. Ran 11.40s at 1500 ft on an uphill track.
 
425/409ER

425/409ER

Well Known Member
dakota tom said:
Joeblow55 isn't decided on this build. If he was th400 stock converter, 3.08, 4000 lb car. 200 degree cam the performer 2-0 would be good. But we know 4sd, 3.73s, and he wants a lope at idle so a 230s cam should work.
A performer rpm is 40 some year newer technology so it should be better than a C-396 but the C-396 Is good and near the age of the car.

409/409ER you mention you peanut port engine, what is you car and weight?? My brother threw a car together from my parts pile. 425/427 short block, flat tappet solid cam about 250 degree that was done over 6200. Unported 215 closed chamber heads, C-396 intake, 3310 780 Holley, 68 all steel Camaro about 3400 lbs. Ran 11.40s at 1500 ft on an uphill track.
Click to expand...
Car is a 1980 Camaro, 3450 with a BBC in it, 8:1 compression at that time. I was surprised by the poor performance of the 215's I had but then again in the past all my closed chambered heads were kind of slow. When I stumbled on to running the 781's I had then put the heads on my old 396 my street car flew. I should have know back then the open chambers made more power, I was just to dumb to realize that. Here is some food for thought, my buddy with his 505 BBC had a sq. port (no porting) and that engine made 802hp with the RPM intake, so I guess it's ok for most street cars IMO.
 
region rat

region rat

Well Known Member
Supporting Member 3
joeblow55 said:
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
Click to expand...
If you pulled the threads out of that 396 block, I would recycle it. That isn't normal at all. Not worth the gamble.
 
SSpev

SSpev

Well Known Member
Supporting Member 3
1675522191936.jpeg

I built this with mostly shop parts on hand. 396 +60 063 heads hypereutectic pistons. 268 extreme compcam. weiand dual plane intake.
10.2 ish CR on 87 obtain. daily driver. 4 speed 4:10 100mph 13.8sec with a $hitty 60ft 2.3.

Your problem will be piston to fit those old heads. The dome HAS TO fit in it. BBC heads / piston are fit to the chambers. If you are 0 deck. flat top to 15 cc dome max. (9.2 - 10.4) that with a MEASURED chamber of 98 cc. you are like likely bigger maybe 100. Chamber will need polished to run 10:1 CR.

For those heads you need something like this
https://www.summitracing.com/search...l/biscayne/piston-head-volume-cc/minus-8-00cc
 
SSpev

SSpev

Well Known Member
Supporting Member 3
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J

joeblow55

Member
Been on a bit of a break for awhile with this build for a few reasons…(family drama) Then, when the engine block and crank were ready to go to the machine shop, I realized that the rear main cap was missing / misplaced. I knew I had it, but could not find it to save my soul. It got separated from the other ones as I was using it for making modifications to an oil pan for another project I was in the middle of. Now that I have found it I am getting ready to move forward with this build, however, I am now wondering if this particular engine block would benefit someone else. What I have is a block with casting # 3963512 and date code D 2 70. I believe it is a 454 block from a 70 corvette… stampings on the even cylinder bank are T0507CZU and 70S409877. I read somewhere that the CZU is an indication that this block was originally mated to a Muncie 4 speed, but I don’t really know how that can be verified, or if it even matters. What I do know is that if it IS a 1970 corvette block, there might be a corvette guy out there who may want or need this block more than I do. My needs are not for a numbers matching engine, but to someone who might looking for a April 1970 date coded block, it could be worth something. I thought I would put it out there in case there were any interest… BEFORE I start spending some cash to build it.
 
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