Looking For Advice

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Old Muscle

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I am building a 70 SBC 350. .040 over and stock stroke. Comp cam 12-366-4 w/1.5 ra. 113 ls, 487 In 483 Ex, 63 IVC. I'm using the original 186 CI heads w/ 202 150 valves. I opened up the bowls, blended the runners and polished the cc and runners. Shaved the heads about .028 and ended up with an average of 58.25 cc overall, lowest being 57.6. Using Speed pro H631cp40 pistons and Scat rods. The deck is at .017. My intention was to use a 26-30 head gasket and end up with mid 40's quench and around 11:1 SCR. When I purchased the cam I was told with the late IVC 11:1 would be no problem with 93 pump gas. After doing some research I don't think this will work. I plugged my numbers into the Wallace DCR calculator and confirmed my thinking. My delema now is to decide on what head gasket to use. A .041 head gasket would give me about 10.7:1 SCR, 8.64 DCR and .058 of quench or a .051 would give me 10.4:1 SCR, 8.4 DCR and 68 quench.
 
welcome too the web site!
got to ask , what are your intentions as to the fuel youll be using?
if its E85 youll be looking at being far less likely to run into detonation damage,
if its typically pump octane gas,
your much more likely to eventually see detonation related issues
obviously drive train gearing and the weight of the car will effect results and if your using
efi rather than a carb, that allows you other options .
factory engines are rather notorious for not having tight and effective quench, measurements,
so obviously you could go with the less effective larger quench,
but keep in mind most factory engines are not designed to maximize power,
they are designed for durability and as such they are rarely concerned with,
getting the fine details as finely tuned as the typical knowledgeable engine builder may be.
personally Id be inclined to install the cam at split over lap or strait up
(4 degrees retarded from the dot-to-dot location)
and use the tighter head gasket and run the ignition advance slightly slower,
and see how that works for you,
Id also make an effort to keep coolant temps under 200F if I could and add a decent oil cooler and 7-8 quart baffled oil pan.

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=121&sb=2
 
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I'm using Edlebrocks Pro flo 4. I intend on 180-190 thermostat and a good cooling system. I have a 6 quart pan and a Melling sharktooth. The car is an 85 Elcamino 3400 lbs. Not going to much on the gearing. Want to drive it on the highway. 4 speed st10 342 first. I have been looking at octane boosters to get it up a point or two. I have a chemist at my disposal and is looking at Boostane.
 
please keep us up too date on your choices and results,
this should be an interesting build and project.
it sounds like it should be a strong running car.
especially if you go the e85 route,
let us know how that "shark tooth oil pump" works out,
Ive heard few people were pleased with theirs,
hopefully they worked out the initial bugs
 
yes a very valid question, its hard to give good advice ,
if you don,t have all the current facts and know the options available,
thats a good question.
 
Welcome Old Muscle. I know Rick's DCR calculator is accurate. But I am shocked that by just retarding that cam by 4 degrees, the cranking pressure goes from 197 all the way down to 165. I see this is with the -12cc pistons, not the -5cc you have now. I realize that you put a lot of work and time into those 186 heads (I like them too and I also had a set), but if it were me, now is the perfect time to upgrade to better heads WITH 64cc chambers. That will get your numbers back in line. The rest of your combination is good. Your heads still have the bottleneck at the pushrod pinch area where the cross-sectional area MIGHT calculate to 1.7 sq in, if you are lucky. That will limit your RPM to 5200. Your cam already has a range of 2000-6000 rpm. http://wallaceracing.com/chokepoint.php
Don't spend more money to downgrade your parts trying to make all this work while being stubborn! Been there - done that.
 
Thanks all for the input. I am looking at heads. I think the important thing is to get the quench in line (mid 40's) with the DRC in the low 8's. On the subject of octane boosters does anyone have any input.
 
Old Muscle said:
On the subject of octane boosters does anyone have any input.
Click to expand...
You might be better finding a local supplier of racing fuel, I have one about 5 miles from me. But
if you are going to buy octane booster, then you might as well buy it in a 5 gallon can. Otherwise
it's going to be very expensive.

https://www.amazon.com/Best-Octane-Booster-Torco-Accelerator/dp/B0077C0GF8/ref=sr_1_92?crid=1NFMQSLAWGHB1&keywords=octane+booster+for+gasoline&qid=1564336906&s=gateway&sprefix=octa,aps,179&sr=8-92

Octane Calculator
http://garage.grumpysperformance.com/index.php?threads/toluene-octane-calculator.11278/
.
 
Old Muscle said:
Thanks all for the input. I am looking at heads. I think the important thing is to get the quench in line (mid 40's) with the DRC in the low 8's. On the subject of octane boosters does anyone have any input.
Click to expand...

Like you said, get the DCR in the low 8's and you shouldn't need an octane booster.
And like Grumpy said, proper oil and coolant temperatures will have a HUGE effect on detonation.
 
Looking back at what Grumpy said about using E85 I live in the midwest and it is readily available. I read the article by Jeff Smith and he is saying you can run higher compression if your using E85. Is this an option if I went back to my original idea of a .030 head gasket, with a SCR of 11:1, DCR of 8.89:1 and a final quench of .047?
 
Welcome.
E-85 loves compression! Your quench is fine... (my E-85 motor is at .042) Like grumpy stated, you will have to make sure your fuel system Including carb, and fuel pump
are E-85 compatable. You will need to supply about 40% more fuel to the motor so your lines may need to be larger.
 
Old Muscle said:
Well gang a lot of water under the
Click to expand...
OOPS. Bridge. Had some health issues but I'm back. Made some changes using your advise. Bought a set of AFR Enforcer heads, 1.6 rockers getting the lift to 520. Got the Quench to .047. DRC is at 8.29. AFR is telling me I should be fine with 93 octane. Would love to hear all of your thoughts.
 
Will you go out of town with this car ? The higher 93 octane is not available everywhere, I can only get 91 octane in Oklahoma.
 
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