Ok, so I have been going through my first build. I have a stroker kit from go fast stuff with speed pro pistons pn h859cp. The kit said 9.7 to 1 compression with 64cc heads. I have 186 heads so I thought I would be good. Well I look up the part number and they have 12cc chambers and with my measurements at .030 in the hole and a .015 gasket 64 cc head chambers I get a 10.2 CR which I think is too high for 91 or 93 octane. Am I right about this? I am thinking of use either a XE 274 or a Lunati voodoo 60104LK. I would not mind running a cam where I can use a 2800 or lower stall with. But, I don't think even a bigger cam will help with the pinging enough.

I still have to cc the heads so hopefully they won't turn out to be 58 cc's or something.


Is there anything I can do short of buying new pistons or heads?

 

I just did a dynamic CR (not sure if I did it right though) for a xe284 with a SCR of 10.2 I got a dynamic of 9.8. This would not run on pump gas right?

 

measure it all out and check. If its in fact too high, remove some material from the combustion chamber on the heads. Work them all till they are equal, it could probably use this anyway to be honest. Give them a good polish. Maybe do some deshrouding if needed. Then cc all of them and get them close.

 

this is what my chamber looks like now. I am supposed to removed material from between the cylinder wall and exhaust valve right. How about the intake valve or next to the spark plug? I measured them at 60 cc's and I figure I need to be around 68 can I get that much off?

 

i think you'd be fine with a 10.2 CR on 93 octane. i've see people run their cars with a little higher CR on 93. maybe one (or more) of them will chime in.

 

Man dont mess with your cylinder heads, just buy some thicker head gaskets. Buy .051" thick head gaskets and i'm guessing if your compression is really 10.2:1 then it should drop it to 9:8:1 or 9:9:1. But you should be fine running on 93 octane anyways, ive heard of people running a 11:1 compression on pump gas.

 

Thick head gaskets will destroy quench, and then you will have pinging problems.

 

What's the reasoning behind quench -vs- ping?

 

10.2:1 CR is fine with the XE274... I used iron 601 heads (similar to your 186s), but with much smaller chambers that got my CR up around 11.25:1 and it was borderline on 91 octane (pinged a little on really hot days) and was fine on 94 octane. With a full point less compression you should be fine if you can do a decent tuning job.

 

Well, I measured the heads and they are all different. Some as small as 58cc's and some are 60cc's. So not wanting a CR near that big I went ahead and did a little deshrouding and plan to polish but wanted some feedback on what I have done so far. This head was at 60cc's and now it is at 64cc's which from what I am hearing I will be ok at 10.2 SCR with a .045 quench.

So, would the xe274 be ok? Would the XE284 be better for me with that kind of compression? Is anyone running this on a street engine? I was thinking of running this with a 2800 stall speed, a vac can, headers and upgrading the 3.23's tho 3.73's a little bit later on. What do you guys think too much for a street/strip 385?

 

Squish, quench, piston to head clearance. All the same thing.


LOw squish does wonders, alot of people over look this little detail.

Squish makes power, squish makes higher cr's safer, squish increases mpg, squish reduces detonation.

How does this so seeming simple little thing do so many feats?

Simple, better mixing of the air fuel charge. A better mixed af charge burns more in a more controlled manner, burns more completely.

study the pic below
p173572_image_large.jpg

As the piston come to tdc compression, all the air fuel charge thats on the left will be squirted or squeezed into the combustion chamber on the right. This action will cause the af charge to swirl, mixing the af charge. Now the smaller the squish clearance the faster the af charge is squirted into the combustion chamber. This will cause the af in the chamber to swirl faster, mixing it better.

 

i ran 12.6:1 on 93 octane when i had my 383 sbc with no problems and the tining set at 34* total

 

with aluminum heads you can get away with higher compression but with irons, you dont wanna be too high. I think 10.2 is a close limit on 93 octane but should be ok with conservative tuning and good quench like you have goin on

work the heads to 64 cc like your doing and you should be around 10.2 like you say

Your DCR calcs appear to be off for that 284 cam. It will be alot lower than 9.8 which is good. you want some overlap to bleed pressure off.

I'd run the 284 cam for a stroker. depending on your intake tho. Abit big but should work well with that compression and atleast 2800 stall. I'd run 3200 it will be fine. DCR works out to be around 7.93 with a 6inch rod, 7.96 with a 5.7 inch rod. So your good with that on pump gas. the other cam would raise that to 8.24 which is still good on premium 93 gas. My 383 is around 8.3 as well

But i'd run the bigger cam for more power anyway

 

Alright I am going with the 284 and I figured I was off with the DCR. I have a 5.7 rod so 7.96 DCR should be good on pump gas and maybe some octane boost just to be safe. I am a worrier mostly because I am already way over the wifes budget for this project and I don't want to f- it up