76 L82 Corvette 355 engine build questions

[grumpyvette]

Right, so what all does the machine shop usually need to shave a block to a certain height?

most shops line hone the mains then

indexing off the trued mains deck the block square and parallel too the crank center line axis


Just the block or do they need the crank and pistons as well?

NO
And does it matter that the cam bearings are already installed?

no not really but it would be best if you removed them, cleaned the block and all internal passages then replaced them, during that process to prevent machine debris crap being trapped in the block

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[76GrayVette]

I decided to have the block fixed and have already checked each of the four corners, they are all the same.
So I've finalized my compression ratio calculations and believe the Crane 266 to be the cam I will use but I wanted to hear opinions.

So, my static compression ratio would be 9.5:1 and my DCR would be 7.7:1 with the cranes intake closing angle of 62 degrees. I think the 210/210 duration at 0.050" lift and 62 degrees will fit my goals well.

What do you think? I haven't heard from Indy in a while but he offered to run my combinations through dynosim or something so that would be interesting to see.

 

[Indycars]

Hayden, I asked a few questions back in January to make sure I had the right info
for the simulation and I apologize if I missed your answers. I also realize that you
went thru a rough time there with your dad and all, so if you can provide the
answers, I would be delighted to run the DynoSim program with your best info. I
still have all the files that I produced so far, so it should be easy to add the additional
info and provide the data and graphs.

I'm running a engine simulation using my DynoSim5 program and will post graphs
if it will help. To confirm, let me know what heads you are most likely to use and
if you know the flow numbers that will help. I might already have them, so let me
know what heads you are thinking about first.

 

[76GrayVette]

Thanks so much Indy! I'm glad you're still around. You and Grumpy and the others have been a huge help to me through this build and I really appreciate it.

So the heads I'm most likely to use would be the Brodix IK180 70cc chamber heads (part#1021002)
And my two most likely cams are the Crane 266 (part#10004) mentioned above with the following specs:

And I'm also considering the Comp Cams High Energy 268 (part#12-210-2). It has slightly more duration than the Crane but a 2 degree sooner intake closing angle.

Let me know if you need any other info Indy.
Like I said before I think the Crane 266 would be alright, but I'm worried it might be a bit small. I'm not sure, that's why I'm asking you guys.

 

[grumpyvette]

if you want a bit more cam, duration , crane makes those, and Ive seen FAR LESS problems with CRANE cams, and yes theres no doubt youll pick up more mid range and peak power, and a bit more resistance to detonation,with low quality fuel, octane, at the cost of a bit of lower rpm torque, doing that, and since you have a manual transmission thats not a bad idea.

 

[Indycars]

I had time during lunch to compare the two Crane cams 10004 and 10005. I can get the ComCams later.

 

[76GrayVette]

Thanks Indy, that graph is really interesting. I guess I didn't expect the HP curves to be so close together.
Also, I wonder if the difference in torque would really be noticeable?

Grumpy, I've definitively considered the Crane 272, it's my third most likely cam.
I would like to stick with Crane if possible as I've heard good things about them, but I was curious to see how the Comp compared and didn't know how much the later intake valve closing point would effect the engine.

 

[grumpyvette]

keep in mind software dyno's are RARELY completely accurate, especially concerning lower rpm torque predictions, in fact I have found the peak power is usually fairly close to that predicted, by the better soft ware dyno programs IF you input the data correctly and don,t put in bogus info, but most of the lower torque curve is usually wild conjecture at best, and while they are both interesting and a useful tool I would hardly put a great deal of trust in the predicted torque curve being an exact match to that the software shows, especially when comparing two similar cams from different manufacturers simply because the ramp acceleration rates tend to differ a great deal.
I,ve always suggested looking at maximizing durability ,rather than looking for peak power, and understand that correctly installed parts with the correct clearances tend to last far longer,and as its rather expensive to have to keep buying replacement parts that you just bought recently because they don,t wear well or break.

keep in mind that different manufacturers have a different way of looking at a problem,now this is just my impression from years of dealing with some companys, but especially CRANE , and to some extent CROWER, LUNATI,ERSON,tend to emphasize, long term durability and the idea of maintaining complete valve train stability , and if that might cost a couple peak hp to achieve thats fine, you have to finish to win!
from what I see, a few others are more likely to push for maximum peak power numbers, as its good for advertizing , and if you engine durability suffered,using thoose parts as a result,.... well,thats not the main concern as long as you made good power while those parts lasted, its a race car engine,and they sell race parts and they don,t especially warrant or expect you to be running those parts several years from now, its expected to be in need of constant maintenance and parts replacement.


RELATED INFO
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[76GrayVette]

Yes, I would much rather have more durability over higher peak power any day.
My only concern with the Crane 272 is would I be loosing to much cylinder pressure with the later intake closing?
DCR would be 7.77:1 with the Crane 266 and like 7.59:1 with the Crane 272.

 

[grumpyvette]

Yes, I would much rather have more durability over higher peak power any day.
My only concern with the Crane 272 is would I be loosing to much cylinder pressure with the later intake closing?
DCR would be 7.77:1 with the Crane 266 and like 7.59:1 with the Crane 272.

thats a valid concern but keep in mind you generally loose about 3% of your torque percentage point in compression lost, if you mad 400 ft lbs at 7.77 compression, at 7.59 thats .18 percent of 3%, so in theory you could expect to see a 2.16 ft lb reduction in torque, which is meaningless because the engines extra duiration easily allows the engine to pull a bit higher in the rpm band ,potentially more than compensating.

horsepower=torque x RPM/5252
thus looking at this chart you see the result, a minor dip in low rpm torque compensated for with noticeably more upper rpm hp, which BTW you can improve on with 1.6:1 roller rockers if you don,t currently have those

RELATED THREAD AND SUB LINKED INFO
viewtopic.php?f=52&t=126&p=156#p156

 

[76GrayVette]

So your recommendation is the 272 over the 266 keeping in mind that my utmost max desired rpm is 5500, while almost entirely staying under 5000 all the time?
It doesn't really matter if the 272 pulls more HP or torque over 5000 as I don't plan to spin any more than that hardly ever, right?

 

[grumpyvette]

obviously its your choice to make, why not call and talk to the tech guys at crane before you make a choice, personally Id select the larger duration simply because you have a manual transmission that allows the cars engine, power curve to easily be matched to power demands

 

[Indycars]

I added the CompCams 12-210-2[268H] to the mix. DynoSim5's opinion is
it's nearly identical to the Crane 10004.

I'm not sure where you are at with the quench distance. You might be able
to gain a little compression with a thinner head gasket.



I just discovered a mistake I made entering the valve timing for the Crane
10005. The above graph has the corrected numbers. Although it doesn't seem
to have made much difference. But I invite you to look over the number to
make sure there is not another mistake.

Each file is an 8 page report done in a PDF file. It takes Adobe Reader to open
which is free and most people already have on their computers.

 

[76GrayVette]

Thanks again Indy. That is a ton of information. My quench is 0.045''
Thanks Grumpy. I think I'll do that.

 

[76GrayVette]

I talked to Crane and the tech there recommended the 272 as well. So I went ahead and ordered that.
I was checking my cam bearing oil hole alignment and was unsure if they were correct or not as I didn't look at them before the machine shop replaced them.
Here's what they look like right now.
This is looking at the front of the block with the crank facing up. The lines in the circles represent where the holes are.

As you can see, 2, 3, and 4 aren't lined up with the hole in the crank bearing seat in the block and number 1 has two holes in the bearing. Is this correct or no?
(I know, more questions, I promise I'll finish this build one of these days.)
Thanks guys.

 

[grumpyvette]

yes that looks like it will work, you may want to read thru this thread

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[76GrayVette]

Hey guys, I have a question about my rings. The oil expander ring that came with my Speed Pro forged piston set has little red a black things on the ends where the ring meets that look like plastic. Am I supposed to leave them on or no? The limited instructions that came with the pistons don't mention them at all.

Oh, by the way, I finally got my heads and intake. They are wicked cool!

I was happy the Weiand 8125 had the correct bolt holes.

 

[grumpyvette]

if you have oil ring expanders with the plastic bits,they are there to prevent you from over lapping the ends of the oil ring expander, theres some oil ring expander s that are vertical ,some horizontal, but all have the ends butt , none over-lap

 

[Indycars]

Oh, by the way, I finally got my heads and intake. They are wicked cool!

We do love engine porn around here !!! Better than Christmas, since it's exactly what you want!!!

I don't remember which heads you were leaning towards, although it looks like I can see Brodix on one of them.
IK180 or IK200 ???

 

[76GrayVette]

Thanks Grumpy, so I guess they are supposed to be left on then. It seems like they would melt.

Yep, those are Brodix Indy, the IK180