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Skip White Heads BBC

26K views 213 replies 9 participants last post by  ericnova72 
#1 ·
I'm really tempted to ditch my BBC stock 781 heads for a pair of these.
https://www.skipwhiteperformance.co...port-aluminum-heads-assem-bbc-oval-274_89649/
This sounds crazy, but that price is for a PAIR. I could swear before that they were listed each. I know, the casting is from china, but they get nothing but good reviews.

I'm making just over 400HP now, any idea what these heads might do?
My cam has .578 lift with 230 duration, 2 degrees advanced (and with the low end it has I'm tempted to change it to straight up). Headers, Edelbrock manifold (it could be better, it's just a performer 2. Compression was estimated at 10+:1 (but somehow, I don't know how, it has 210psi cranking compression yet it runs fine on pump gas) Tried different gauges, a borrowed one from the parts store shows 205psi.

I think my valve to piston clearance is close, I can't find that number in my notes, so I'm going to check it bolted together. If I need a little more clearance, can I do anything to the pistons while in the motor?
 
#3 ·
That won't change valve-to-piston clearance one bit, so that is really poor advice.
Piston is nearly half way down the cylinder and heading away when the intake valve reaches full lift, no where near the piston at all.

Valve-to-piston collisions happen on the overlap period neat TDC, when the exhaust is just coming to fully closed, the intake is just starting to open, and the piston is just reaching TDC overlap ready to head back down drawing in mixture. All three parts are close to each other in the same small space.

Checking points are between 20° before TDC and 10° after TDC, check every 5° to find the closest point to the intake valve, then check a few degrees either side of that 5° interval to find actual clearance in the assembly.

As far as power, if your 781's are basically stock, no porting, only a 3 angle valve job.... then according to the Head's flow numbers for up to and at your cam lift it could pick up 75-100HP.

For valve to piston clearance mods I the block, you can rent a flycutting tool from Isky, you can carefully free hand it with a Dremel if it is diameter and not depth contact, or of it is just intake depth clearance you can retard the cam as this increases intake clearance and decreases exhaust.
I have also seen where guys have taken an old or spare valve and cut the face using a cut=off disc in a Dremel to resemble a milling cutter and use that like the Isky in-head tool, or solder a small piece of high speed steel or carbide cutting bit to a old valve face and carefully cut with that down in through the installed head using the valve guide as a locator.
Piston Notching Cutter Tool : ISKY Racing Cams, Do It Right

We had a member here, I haven't seen him post in a while, BobCRman, who had used several sets of those heads and never had any problems with them.
 
#4 ·
Great to hear no problem with the heads. I'm close enough to take a drive up to get them. Not to save on shipping, just be nice.

These are my pistons https://www.summitracing.com/parts/slp-l2465f30
If I do this I hope my drive train will hold up. According to weight/speed and weight/ET calculator I'm at just over 400hp now with the stock heads. TH400 and 12 bolt. I have a special bearing cap on the left side with a TA cast cover with the bolts that tighten down against the bearing caps. I should pull an axle sometime to see if there is any twist. Yes my heads are stock as stock can be. I never cc'd them but I think they have been milled quite a bit over the years. Now I'm wishing it was December.
 
#6 ·
The guy who originally built it put in some crappy axles and I twisted one after 1 day with slicks and the motor running like crap. And that was with 3.42 gears. I put in Moser axles and 4.1 gears. I should pull the left one just to see. I've heard that's most always the first one to twist, it was for me anyway. (what a ****** to get a twisted c clip axle out) No more c-clips either.
 
#32 ·
I should pull the left one just to see. I've heard that's most always the first one to twist, it was for me anyway.
There's a reason for that. Front-motor, rear-drive cars and trucks twist the chassis under acceleration in a way that the right front and left rear of the vehicle get heavy, while the left front and right rear get light. This is why you'll see Ricky Racers, when doing a "one-wheel peel", will always be peeling the right rear, because it is the light tire. The left rear is taking all the torque from the motor, so it will wear out parts quicker than the right rear. You can witness this "light left front" at the drags too, watch any of the faster cars at launch. The left front will catch air, while the right front stays planted.

The backyard way to equalize traction on an open differential is to install an air shock on the right rear only, increasing air pressure a little at a time during testing until you have two equal skid marks. This will leave the right rear of the vehicle sitting a little higher than the left when parked, but if you can get over that, it's a cheap and easy way to make a posi for yourself. Savvy racers have been doing it for years.
 
#7 ·
I believe I said it before and it's a documented vice of a BBC - you simply cannot get enough cylinder head on the engine when going for max power. So any improvement to flow that you make in the cylinder head area is going to be a win. And if you are looking for additional upgrades in the future then the stock heads are now out of the way which would be a hindrance. Besides you can probably shop the stockers locally and get some of the coin back that you spend on the new ones.


Next up would be that intake manifold - not even sure unless you simply want to compare stuff that you should put it back on with the new heads.
 
#9 ·
I thought about the intake and I'm wondering if the Performer RPM is good enough. It's one of what I call hybrid dual plane, the top of the divider isn't there for what looks like a .5" or more. Plus an open spacer like I'm running right now. Or are all the twists and turns in the runners going to slow things down?
The Q-Jet is making things tough finding a good intake. Possibly a dominator style with an adapter for a Q-jet?
 
#8 ·
Even if you had them shipped, you're still paying tax being in state. One guy I dealt with is a serious type, don't take him as rude, he's just blunt and wants to keep you out of trouble. Another guy, who has sleeve tattoos is beyond friendly and also gives good advice.

Their heads have raised exhaust ports, never got an actual measurement as to how high up their raised, so keep that in mind if it's a concern.
 
#15 ·
I will ask about the raised ports. My headers are already dented up to all heck, looks like the worst part will hit the starter, but it's stock and I have a mini sitting on the shelf.
Thanks for the heads up on the counter guys. Hopefully I'll get the tattooed guy.
 
#31 ·
The ports might need to be matched to the heads but it would be worth the effort.
Do not port match the manifold to the heads unless you are prepared to enlarge the ports all the way from beginning to end of the ports. Most fellows will cut the ports bigger for only maybe a half inch back from the transition, making a larger port diameter and thus volume at that mating point. The port ends up looking in cross section like an Anaconda that swallowed a pig. What happens then is that the slug of air/fuel mixture is travelling down the manifold at a certain speed and suddenly sees that the port volume has increased. This slows the mixture down to the point that some of the liquid fuel in the mixture falls out of suspension and lays on the floor of the port, so that the intake valve allows a lean mixture into the cylinder. Some of the mixture will be picked up in subsequent firings, so that you will have lean/rich/lean/rich mixtures entering the cylinder.

Research of fluid dynamics has proved that the lion's share of mixture goes directly down the center of the port and that mating of the intake and head exits and entries is a waste of time, unless like I said, if you start at the top of the manifold and make the ports the same diameter and the head ports the same diameter from start to finish, with no diameter change at the manifold/head intersection. This operation would take an ungodly amount of time and effort and might prove to be the biggest waste of time and effort that you ever spent on a motor build.
 
#13 ·
Going against the grain a little, this makes a great street intake if you can find one, only available used as Weiand doesn't offer them anymore since the Holley Group bought them out.

Weiand Team G Oval Port #7523, with a Q-jet adapter welded onto it and then the adapter and intake heavily hand ground blended together.

The Team G oval was a great street intake for smaller BBC (468 and smaller) that made real good torque and still powered out well on the upper end. It had smaller runner cross section than the Victor manifolds did, or any other modern single plane out there.

https://www.ebay.com/itm/NOS-Weiand...777921?hash=item364a2e3bc1:g:3mUAAOSwHGFckUUQ

A friend of mine used one on a oval port 049 head 10.5:1 compression 461 with a Nostalgia+ LS6 solid cam and it was a low and mid range monster in a '74 Nova....we were looking for ways to get rid of some of the low end as it would just bury 28" x 12.5" M/T E.T. Street bias ply cheater slicks. Tight lashed the cam, 2" open carb spacer, 950 Holley DoubleP, ...ended up using an MSD Timing Computer to drastically slow the timing advance curve below 3800 rpm then ramp it all in by 4500.

I will say, it has always seemed to me that worrying about low rpm performance when you've got a 454 is almost ridiculous....if it's built right it'll blow any normal street tire clean off the rims from either idle to even from a 30 MPH roll in second gear..
 
#14 ·
I'll, probably go with the 7164 RPM, like everything else, I wish I had bought that the first time. And back then I probably was worried about low rpm torque. Back then even with the slight dish pistons and about 140psi cranking compression it had great torque. It was a real smog motor. My first BBC, I was amazed! I recall I had a "problem" with it spinning the tires in 1st, hitting 2nd still spinning, then slowing down and into 1st again and spinning the tires. They said that was a good "problem" to have. Then I recalibrated the governor for higher shift points.



Just remembered that after the rebuild I sold the + .030 dish pistons, cam and lifters as a ".030 over kit" and someone actually bought it for about $200. I had a 2x4 with holes drilled in it numbered for the lifters. Made no guarantee on them in a different block. The guys biggest concern was if it had a lopy idle. A lope dope. Not worried about performance, just wanted to make it *sound* like it had performance. :rolleyes:
 
#17 ·
Yes they are raised a lot, I'm guessing almost an inch. I'm looking at the upper exhaust bolt hole and up to the tab part where you might bolt on an accessory. They look to be about the same distance apart, but the hole for the bolt on accessory hole is above the valve cover sealing surface where on the iron heads that hole is down what appears to be an inch. If that makes any sense at all.
I put an email into them asking how much higher they are.
I'll have to look at my headers again, I think the only problem I'll have is the header hitting the starter (a big stock one) but I have a new mini starter sitting on the shelf. Actually I'd like to get a newer style GM starter that is smaller and shorter. It's too hard to get an adjustment right on the mini ones. The newer stock ones I can just use the 1/8" drill bit measurement between the shaft and the ring gear. And believe me, my starter takes a lot of shimming. Who knows what happened on the assembly line that day when the starter holes were tapped.
 
#19 ·
Since you are not checking geometry of the valvetrain at this point, it is easier to get valve-to-piston clearances if you just go ahead and bottom out the valvetrain.
If your checking spring isn't strong enough to keep the lifter piston bottomed out in the lifter, either shim the spring tighter or use the inner spring from a dual valvespring set if you have them.

You're clearance figures are correct, but you can get by with intake clearance down to .060" as there is no chance of float holding the intake open too long to allow it to get hit as the piston is at the bottom of the bore starting to head up when the intake valve closes. Exhaust is the one that can get hit if held open during a float situation.
 
#20 ·
Lucky or Unlucky?

I was trying to check the intake clearance and it was driving me nuts. No matter how I turned the motor I had TONS of clearance. God knows how many times I turned the motor over. I started to think that I had a bad cam but couldn't picture the roller cam getting wiped out that bad. Finally I pushed down on the rod end of the rocker and it's springy. A LOT. About .128" worth of spring action. I adjusted the rocker again getting rid of the spring action minus a little for clearance. Comparing the wear marks on the rods at the guides I see this rod is down lower.


Do do I now know what a collapsed lifter can feel like? (from above anyway) I didn't even hear it last time I ran it.

Am I lucky I found it before other damage happened or unlucky that it happened?

I guess I better not start it the way it is because I don't know if it will pump up to were it should be and the valve hit the piston.

If I want the new heads, I really don't have the money for another set of lifters, I guess if I take it apart and the rest are good I can replace the one pair.
 
#21 ·
Nothing wrong with those lifters, they have just had all the oil pumped out of them from your repeated revolutions of the crank, with no oil pressure from the oil pump refilling them.

Bottom them out, make your clearance check, and readjust them back to their normal position, they are fine. Just don't forget that readjustment step ;)

A collapsed lifter is one that either the check valve is damaged or help off it's seat by dirt, or dirt has gotten between the plunger and the plunger bore in the lifter valley and stuck the piston. Will rattle and never quiet up and behave like it was a solid when trying to adjust it....it'll either run and clatter due to clearance in the valvetrain or be too tight and cause a miss due to no clearance at all, with no "hydraulic normal" spot in between.
 
#22 ·
None of the others on that head are like that. And the only reason I turned it so many times is because I didn't realize it leaked down.

But I suppose I can re-adjust the rocker and start it and see if it pumps up?
Yes, important to re-adjust first!
 
#23 ·
This pair has had all the preload removed from them when you removed the rockers to put checking springs on....that unloads the check valve.....the others, still all adjusted up will still have the check valve seated holding them full of oil.

Re-adjust and start it up and they will go back to normal.
 
#26 ·
I finally tried again to check my intake valve to piston clearance and the first time the intake got as small as .074". But I may have had it adjusted a little too tight. Two more times I got .098 and .095 just past TDC. The exhaust has me confused if I did it right because I didn't even need the dial caliper, it never got less than a good 1/4".
I found out that the piston intake valve relief is for up to a .2380" valve, so that sounds like I'm good to go.
What about that exhaust? Does that sound right?
The cam is advanced 2°, does it look like if it wasn't I'd be having intake clearance issues?
 
#28 ·
Exhaust typically misses by a mile....SBC's tend to be the same way, you clay up the piston and the exhaust valve doesn't even touch the clay to leave an impression, or leaves just a little 1/8-1/4" long ding in the clay.
That's why unless the BBC piston has a very large dome there isn't even a exhaust valve notch there.

Advancing cam tightens intake piston-to-valve clearance, retarding it opens up intake clearance.....advancing the cam does the opposite for the exhaust valve.

When you advance the cam, you're opening the intake a little sooner, so it is open a little further when that piston is making that arrival up to TDC as the intake valve is opening and the exhaust valve is closing..

I knew what you meant on the valve size, and yes you could go to a bigger exhaust if it was needed....but bigger than the Rect port head common 1.88" size is rarely needed unless this is a heavy nitrous sniffing engine with a lot of exhaust volume to deal with(600HP+ from just the Nitrous kit or kits on top of the engine power.). or an bigger cube over 580" engine.
 
#29 ·
So if I change the cam from the current 2° advanced to straight up I'd have more clearance. I wonder how much? I'm tempted to get the next size up cam but I would also like to see/feel the difference with just the head and intake change and then a bigger cam later.


You had mentioned that Weiend intake. Is that made for a standard square bore or the Dominator? I can't find any dimensions for the dominator stud spacing or the open hole size. I'd like to see just how much work it would be to adapt it. Hmm, they make wood spacers, so why couldn't I make a wooden adapter? Well again I need to know the dimensions to answer that. At least to test it before welding it.
 
#30 ·
Weiand Team G single plane for the BBC was regular Holley 4150/4160 pattern.
I don't remember ever seeing a 4500 pattern example.

You could make a wood adapter, I've got several 1/2" and 1" open spacers made of marine or cabinet grade plywood. Don't use pine, and don't use solid board, it won't stay together and splits.
If you want your homebuilt plywood versions to be more permanent, seal the inside face with a 2-part epoxy to keep fuel from seeping into the wood grain.

The example of that intake I saw was welded, a 1" spacer for a Q-Jet was TIG welded to the Holley flange, and a couple dozen beads were laid along the sides of the original plenum on the back half section of the plenum sides and across the back to make enough material to blend to the Q-Jet nicely and not add 2-3" to the manifold height.
It was a well thought out piece, car it was on really ran well, just breaking into the 8.90's 1/4 mile with a pump gas 496 in a all-steel(except hood), full interior, streetable '68 Nova.
 
#37 ·
The L31 Vortec port takes the idea of widening the short side turn to the extreme by widening the port floor for its entire length. Interesting in that common accepted practice that was also advocated by Vizard was to enlarge the port where the greatest flow was which typically is the top of the long wall on the bore wall side of the passage. The net resulting battle of concepts here is whether greater volume of port here actually makes space for the greater flow amount or whether by the gas laws it slows velocity, increasing pressure and that aids in getting more total flow into the cylinder. I'm sure in some F1, USAC, and NASCAR shop there is a math model that's more zone finite than measuring total flow on a flow bench as in Computational Fluid Dynamics. Somewhere there's a computer geek that knows more about this than all the guys with grinders breathing metal and cutting stone dust in the world and that's a sad thought.

Live and learn, the text books say a tall narrow port will out flow a square or mild rectanglular port of the same area. The LS cathedral port, however, rather disappointed those book worm believers.

Back to the grinder to ruin another head then test the results. Gotta get one of them 3D prototyping machines so I can build cheap plastic port models instead of hacking ideas on otherwise perfectly good heads only to make them contributions to the local metals recycler.

Bogie
 
#38 ·
So if I get an Edlelbrock RPM I shouldn't really touch the ports that are notoriously small at the end? I did in the Performer 2-0, but had crappy bits and never got them near the gasket size. Guess I won't be able to sell that here! ;)
 
#39 ·
If the manifold's ports at the gasket face is deliberately left smaller than both the port opening in the head, and the upstream potion of the port in the manifold, it will be okay to do some form of matching.
You just don't want to go in there and grind the opening to a big gasket hole that is already bigger than the rest of the port in the manifold....Like Techs example of a port that looks like a rattlesnake that swallowed an ostrich egg scenario.
 
#40 ·
Is there a good/easy way to install the manifold loosely with or without gaskets and some type of marking compound?


With my current Performer, I do now recall calling Edlebrock about the small ports and they said they leave them that way so port matching can be done. But to me it seems like they really go overboard making them small. Lot's of reviews I've seen claim they are made for peanut port heads.


Also, where do I buy good die grinder bits? The crap I had didn't even hold up to aluminum. Didn't get clogged up, just wore out.
 
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