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11:88:1 Pistons...I need help

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jfrye1911

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Discussion starter · #1 ·
Here is my situation. A buddy of mine sold me a new set of Speed Pro forged pistons, minus one piston for only $80.00. Like many here, I was seduced by the idea of paying so little for a brand new set of pistons. Any way, the part number listed in Jegs is L2252AF. According to what is listed, these are 60 over 350 pistons with a 11:88:1 compression ratio with a 64cc head. In my conversations with friends, we are speculating that with a 76cc head, the compression ratio figures to be more in the range of 10:1.

Now for my questions.....#1) Is it reasonable to think that I can get the compression ratio down enough so that I am able to use pump gas. #2) With these pistons, what recommendations can you offer as it relates to building as stout a street motor as possible. In other words, what cam/head/intake combinations would you recommend that would afford me the most power potential. I dont need anything too radical....just your basic 400hp thumper for the streets. #3)Is there anyone out there that wants to make a complete build recommendation.....perhaps sharing your engine specs as a guide for me to suggest to my builder. I do believe that there is plenty of value in following the path of others....so please, feel free to share what you would put into this motor if it were you. This time around, I want to stay below the 5 grand mark and perhaps get a budget build for around 2-3 grand.

Thanks a lot..............
 
#2 ·
I won't go into specific recommendations for a complete build. There are too many options and opinions and what is right for me probably won't be right for you.

When piston manufactures give compression specs, they are assuming you have a zero deck height (meaning the piston is flush with the deck of the block at TDC). Unless you are going ot have your block decked, you won;t be at zero deck, this will drop the compression some, with your deck height measurement and gasket thickness calculated, you can figure out your ball park compression ratio. Since you mentioned a 76cc heads that leads me to assume an iron head, if that is the case 10:1 would be pushing it since you said you didn't want anything to wild. This would mean a mild cam and in order to get by with 10:1 with iron heads, on pump gas you will need a healthy cam.

You may want to figure out your compression with 72cc heads, then you will have more options for heads. The thing is, a set of pistons is a lot cheaper than a set of heads. You may be better off selling the pistons and getting a set of true flat tops for your build.
 
#3 · (Edited)
I got into this same issue and had a set of 12:1 pistons and all I had was el cheapo smog 76 cc heads. Deck height was already down to about .030, I used the steel shim .017 gasket. If i recall correctly, With that big head volume I managed to get compression down to about 10.3 or so and ran a old Sig Erson 270 * cam with about 480 lift. Motor ran well , did not have any issues. I sold this motor and the last I heard, it was put in a 76 vette on the street that out ran a 428 Ford Mustang. So I know it can be done.
L2252AF-60 5.7" Rod 360 - - 11.89 11.28 10.74 10.25 1.560 .200 dome $67
Little link refreshes my memory , select your piston.
http://www.flatlanderracing.com/trwchevy350.html
 
#4 ·
actually all of trws old piston numbers are rated at 64 ccs with pistons 020-025 in the hole. with composition head gasket and open chamber head, 10to1-10.25-1 will be a generous figure.but you will have terrible quench and probably rattle worse that way .id run it at 11-1 and maybe run more cam with tighter lobe centers to bleed off some cyl pressure.depends on your gear and converter though:thumbsup:
 
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Discussion starter · #5 ·
Wow....I never thought that jumping on what appeared to be such a good deal would turn into such a complex scenario. But at least I have some options. As for cylinder heads, I will probably opt for a set of Worlds. Looks like my best option will probably be the S/R Torquers. From there, I will rely on my builder to pick the best cam that he thinks will compliment what I have. From the responses I have read, looks like I may be in for a build that may end up on the high, cost wise...that's if I dont bail out and just buy a new set of pistons.
 
#6 ·
jfrye1911 said:
Wow....I never thought that jumping on what appeared to be such a good deal would turn into such a complex scenario. But at least I have some options. As for cylinder heads, I will probably opt for a set of Worlds. Looks like my best option will probably be the S/R Torquers. From there, I will rely on my builder to pick the best cam that he thinks will compliment what I have. From the responses I have read, looks like I may be in for a build that may end up on the high, cost wise...that's if I dont bail out and just buy a new set of pistons.
Click to expand...

You are changing rules now if you purchase new heads and I dont think you would want to buy new heads with large chambers? So might as well get your new pistons to match your new heads and Ebay the others.
 
Discussion starter · #7 ·
Ok, you got me a little confused now. I thought going with a 76cc head would allow me to run this higher compression piston. I have a set of 400 sbc heads (Casting Number 3973493) but thought for the money that goes into these heads, I would simply by aftermarket.
 
#8 · (Edited)
jfrye1911 said:
Ok, you got me a little confused now. I thought going with a 76cc head would allow me to run this higher compression piston. I have a set of 400 sbc heads (Casting Number 3973493) but thought for the money that goes into these heads, I would simply by aftermarket.
Click to expand...
Thats correct, but what I was getting at , why let $88 stand in the way of getting a better combo. You will prolly spend what $800 to get a good flowing set of head and use these pistons? Just bringing this up, if you had your mind on using these pistons. gofer it but just beaware there are better choices. Does not cost any more on the head side but you will have to spend some $300 for pistons to match. I guess it would really not make much differance in what piston you use in terms of street use, but definately the head chamber will make a diff in an aftermarket head. My thought is that if you changed short blocks to one with smaller pistons, you can't very well use the 76 cc on anything with smaller pistons. Understand?

I guess I could add that I just used what I had and it worked so guess you can too.
 
#9 ·
Hi ! Sorry but I couldn't let this one slide by. You call him a buddy ? It's more of an aquaintance I'd bet. I'm sure he ran into some of the same issues as you are. Never buy anything from a friend ! Warning flag # 1: Why only seven and not eight ? Warning sign # 2 Why are they .060 over ? I have only had 1 experience with an .060 350 - could not keep it cool. Some say a street motor would be OK. I don't think I'll try it. .060 overbore is usually the 3rd and last time a 350 can be built. Don't waste your money on anything .060 overbore unless you can go larger like with a 283. If you are going to build a motor, start with a stock bore, so you can use some of the parts again and again ! Not just once and you are done.
 
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#12 ·
TJS69,
Not sure what the issue was with your .060 over 350 block but, there are a lot of them running around with no issues. If a block will clean up with .010 over then there is no need to go any more but, if the block has already seen .030 and .040, chances are .060 will be what it needs and will be it's last go around. With that said, my blown engine is .060 over, it's a GM 350 block (now displacing 388ci) with 12lbs of boost it runs just fine on the street even in 100+ degree weather. Sure I would rather have it at .000 but, these days you don't find many virgin factory blocks. My point is don't let an .060 over bore scare you, just make sure the block is sonic tested.
 
#13 ·
jfrye1911 said:
Here is my situation. A buddy of mine sold me a new set of Speed Pro forged pistons, minus one piston for only $80.00. Like many here, I was seduced by the idea of paying so little for a brand new set of pistons. Any way, the part number listed in Jegs is L2252AF. According to what is listed, these are 60 over 350 pistons with a 11:88:1 compression ratio with a 64cc head. In my conversations with friends, we are speculating that with a 76cc head, the compression ratio figures to be more in the range of 10:1.

Now for my questions.....#1) Is it reasonable to think that I can get the compression ratio down enough so that I am able to use pump gas. #2) With these pistons, what recommendations can you offer as it relates to building as stout a street motor as possible. In other words, what cam/head/intake combinations would you recommend that would afford me the most power potential. I dont need anything too radical....just your basic 400hp thumper for the streets. #3)Is there anyone out there that wants to make a complete build recommendation.....perhaps sharing your engine specs as a guide for me to suggest to my builder. I do believe that there is plenty of value in following the path of others....so please, feel free to share what you would put into this motor if it were you. This time around, I want to stay below the 5 grand mark and perhaps get a budget build for around 2-3 grand.

Thanks a lot..............
Click to expand...
Here's my take...

I wouldn't start a build up just because a got a good deal on some pistons. You should have more in mind of what you want and what you already have.
These have a .200 dome on them, and according to summit with a 76cc head you'll have 10.25-1. should be ok for pump gas. You will need to becareful with cam selection for valve clearance.



1) yes, a head gasket, cylinder heads and cam duration contributes to compression. ( it might be the cam overlap)
2) you already have some 400 heads, next you'll need to find out how much lift the 400 springs can handle, and make sure you have enough clearance between the piston and valve. (heads-cam-intake)
ZZ4 cam - i think it's .501-.510
3) I don't have any combination recommendations, your builder should know what you want.

Do you already have a block?
 
#14 ·
Are they solid domed pistons??

if they are, just have a machinist cut some of the dome off so that you end up with the CR. you want running the heads you want to run.

Can't do this if they are hollow domed pistons..

pdq67
 
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