Set up- 1970 350 (currently at machine shop) .030 over, new cast pistons, performer rpm intake, HEI set up, 1406 edlebrock carb. Motor was a history unknown purchase and has a comp xtreme energy part number (42-222-4). New valve springs had been added.

Trans- 2004r-oz with shift kit (replaced under 30k ago)
Rear- stock 2400 converter with eaton hd 3.73 (replaced 15k ago)
Exhaust- Headman header to x-pipe to 40 series FM (full welded 2.25)
Going to be 9.5-9.75:1 compression. I am looking for a somewhat aggressive sound with good throttle response and 300hp+. The current cam looks kind of whimpy but this is a first build for me so all suggestions welcome.

Thank you,
-Adam

 

Erson Viking 100h. 222/222@.050, on a 108. Lift is in the .480 range.
Great throttle response and you'll hear it.

 

Sir. I see in your signature you deal in Erson cams. I'd like to get some spec numbers to my engine builder to make sure everything will run tight. Can I buy direct from you?

 

I guess I should also ask about the Carb. I have a Ebrock 1406 on the 307 with #43 squirt and upgraded accell pump. My 307 is bogging when you stomp on it and I havn't figured that out yet but is that enough carb for this new motor. Assuming I stay with the comp xe262 or move to the xe268?

 

Yes. And no need to call me sir. My name is Mark and happy to help.
Thanks!

 

Thanks Mark. When I was looking at this build I was sort of using a w-31 motor as my guide. I don't want to go over 10:1 so the listed range sounds good. The cam spec I found on that motor had .474/.474 lift (the duration confused me a bit but thats another conversation). Anyway, the motor has a xe262 cam in it already (which achieves a lift very close to the w-31) but I'd like something with some more sound and overall performance. Is the xe268 worth the extra money? The motor builder was very "ok, you have this cam and thats great on to the next question" which makes me think I'm trying to over cam this motor but this is a first build for me and I want something bad *** dammit! I did a lot of searching for the cam you mentioned originally and I can't find one for sale and I'd like all the numbers on it so when I talk to the machinist tomorrow I can give him a concrete answer.

Thanks again

 

How are you getting 9.5 to 1 with cast pistons? Most cast pistons are 24cc dish, means it is tough to hit 8 to 1 compression. Other than Egge, no one makes small dish cast pistons. The Speed Pro forged with the 5.8 dish would work and cost the same as or cheaper than the Egge cast pistons.

 

He gave me a ring this morning letting me know it was going to need to go .030 over and asked if I wanted Cast or Forged. No n20 so no need for forged. I know he will be milling the deck when the block is gone through but I didn't get into that with him. I guess I just assumed the original pistons were cast and the original CR was 9:0:1+ (though I have never seen a conclusive factory figure sans a w31 motor) so a replacement must be available. Perhaps I assumed wrong

 

It would be very wise of you to ask for all measurements and specs so you know for sure you're going to get the compression ratio you want. Do not trust anyone who just throws out a claimed CR number without being able to show you exactly how they got that.

After you know exactly what your CR is, then decide on a cam.

 

x2. A '70 should have approx. 9.0:1 but it is best to check and verify with your machinist.

 

Supercarsunlimited has .030 over 9:1 350 pistons in stock on the website. This has been rather eye opening and I'll be verifying today.

Thanks for the help. Still curious about carb suggestions as well.

 

Quick Fuel Slayer 750.

 

Never knew what that really meant. What is an "x to 1" piston supposed to mean when lots of other factors determine what your actual CR is? There are probably tons of disappointed hotrodders out there wondering why their engines run like crap and many times it's because they overestimate their CR then over cam it.

 

This is correct for the 2bbl low compression motor, but the 4bbl motor, which was standard on the Supreme and optional on the all but the W31, was 10.25:1.

 

I agree. You need to know the volume of the dish and also the piston's compression height - this is VERY IMPORTANT! Most cast pistons are shorter than the factory pistons, some by as much as .030", and that will cause the CR to be much less than you expect.

Factory CH = 1.615"
Speed Pro forged = 1.612"
most cast aftermarket = 1.595"

 

Here is a link to that piston, I could not find any specs; dish, p/h, etc.
http://www.supercarsunlimited.com/350-Piston-d982.aspx
Kinda pricey at $320/set, get some Speed-Pros for that price.

 

Based on the application (68-70 9:1 350) they appear to be 14cc dish pistons, but who knows what the compression height is? So the theoretical MAX you would get is 9.0:1 with everything being at factory specs; larger combustion chambers, thicker head gaskets, shorter piston, larger piston-to-deck clearance and it goes downhill from there.

I would get pistons with a smaller dish, such as the "10.25:1" pistons (the Speed Pros mentioned above with 5.8cc dishes). They have a smaller dish and are the correct compression height so your machinist won't have to mill the block deck as he would with the too-short cast pistons.

 

Thank You Kenneth. I spoke to the machinist yesterday and I'll summarize where we ended. The motor is getting new slugs as established and Jim (the machinist) is taking care of selection as I must defer to his expertise and he gets factory direct pricing.
The block- .030 over deck/head will be milled down .0010 until we are at the desired compression ratio (9.75:1) with a .040 gasket.

Internals- Comp xe268 cam has been selected along with new lifters/rockers and steel spring retainers (currently has alm) and valves. The crank will be cut and balanced along with replacement/machine service of all bearings to ensure proper operation.

Replace: Timing chain, all gaskets, oil pump, brass freeze plugs

Desired outcome- 300hp+
Current Price Tag: $2,500 (parts, labor and delivery back to my house)

Goodies I already have. Performer RPM intake, HEI Set up, New water pump, new alter, no 800 cca batt, hayden hd fan clutch.

Not yet purchased: Carb. Both Mark and Jim mentioned the quick fuel 750 and I'm leaning that way. The car currently has a 2-core radiator that was a non-brass replacement and is small. Not engine heating issues with the hayden HD clutch but I'm going to assume a beefier radiator will be needed. Any suggestions? Olds 307, What are you running Sir?

Thank you for all the information all.

 

What do your head chambers measure out to be? What about the piston dish size?

Xe cams are known to be very noisey so be aware of that. The Voodoo line of cams were designed to be better than the Xe line of cams in all respects including noise level. Take it for what it's worth.

I wouldn't worry about the radiator for now.

 

What is he cutting, the deck, the head or both? If he's cutting the deck find out how much and how it will be done, i.e. mocked up and measured from there or an educated guess.

This is ultimately for your benefit.

 

We havn't gotten into final product or full measurements, I sent in payment to start the machine work.

 

Based on our conversation yesterday Jim will be cutting the deck. I'll get details about the procedures. When I posed the question yesterday about achieving the desired CR and the way we would get there Jim informed me after the piston installation he would determine the size of combustion chamber and shave the deck down to get to our # of 9.75

 

What? So let me get this right. If he needs to cut say .030 off the deck to get the compression needed, even though the piston may stick out of the top, he's going to cut it anyway? Jmo but you need to find another machinist.

 

How's that go? Measure once, cut twice!!!


I agree. All of this should be calculated before purchasing the pistons. But maybe that's too much work ....

 

Nothing has been purchased at present. The motor has been disassembled and we've gone over some broad strokes and I sent in a deposit for the machine work. The man is 44 years in the business, comes recommended from the family mechanic and has been very cool with me about everything. I'm gonna trust him because he is older and wiser. I'm an on going learner fellas; I'm not in a position to tell this man his business. We had a quick chat yesterday on the phone and I'm going to call him for some measurements and potential component configurations on Tuesday because it sounds like my irresponsible speculation is digging me in a hole.
Thanks for the advice.

 

That's fine, but make sure you're on the same page. It's your money and you're paying him for his expertise. Make sure he has the knowledge needed for YOUR build, not anyone else's.

 

Just an update. I went to the shop today to get some information and here is where I stand:

The block is .030 over and the crank has been cut "10/10" is what the machienist told me (I am assuming that meant .010 has been shaved from the crank for fresh metal?).
-The heads have new valves, steel bridges have been installed to replace the current alm. ones. The rocker arms are new and are stock ratio (not sure what that is?).
-The pistons are a stock replacement. How it was explained to me was 64cc combustion chamber+ stock piston replacement (p.n p1531) will yield a compression ratio of 9.67:1 but this will all be satisfied once we see how the pistons sit.

I'm still listing between a QuickFuel 750 of eddy 750 for cab choice and if anybody out there reading this has brackets I want new P.S pump bracket.

Thanks for reading and the help.

 

Problem with your calculation is that your stock number 6 heads do NOT have 64 cc chambers. They are 68-69 cc. This will change your compression ratio.

 

You will not be anywhere near 9:1, let alone 9.67:1 with that piston. The shop you are using is incompetent when it comes to Oldsmobiles and how to get compression. Don't take this as me being a jerk, but I have built many Oldsmobiles (I'm a small block guy) and know how to make compression in an Olds motor. It appears to me they do not have access to a simple online compression ratio calculator. If they did, they could tell you exactly what your compression ratio would be.

Those pistons lack on compression height. I will break it down for you:

Bore: 4.087
Stroke: 3.385
head gasket thickness: .039
head gasket bore: 4.250
Piston to deck: .050
Combustion chamber volume: 69cc
Piston dish: 24cc
COMPRESSION: 7.45:1

Now, you can deck the block (those pistons are cheap and will have compression heights all over the place) to probably .010". Mill the heads .060" and you got 8.72:1.

You would spend a lot of money by machining various components when it would be cheaper to just buy the Speed Pro forged flat top piston. Or better yet, the Probe piston.

 

You're right. I couldn't find the info on that piston but I suspected it was the short one with a big dish.
And your statement about his machine shop is spot on. I tell people all the time I'd rather have a smart "Chevy" machinist than a dumb "Olds" one. However it seems he has neither.

Thanks.

 

So that part number is the "stock replacement piston" for the low compression 71-72 350 engines, and even then it is short on compression height compared to factory, so as stated it will yield a lower compression ratio than the factory 71-72 engines.

 

What do you figure for cam duration on a 7.45:1 350 cubed engine........190*..............seat to seat

Really, at the end of the day, compression is a very important piece of the puzzle when it comes down to making streetable power on pump gas. Being able to achieve maximum compression to the octane going to be utilized is well worth the investment.

I wouldn't fret over .3 worth of compression as long as you are over 9:1. But, if you are under that number, you have some work to do to get there, and it comes down to a cost analysis. The gains that are made going from 8:1-9:1 are substantial.

 

I think they call them "stock replacement" because they are cast......just like stock. And they fit an Oldsmobile.

Plus, since they are inadequate to yield much compression, it limits the maximum horsepower output.......which means they won't have any issues with them pistons being destroyed in the field since the engines they are put in to have a hard time making an honest 160-180hp at the flywheel.

 

Hey all above!
My block is almost done and I have been researching for 2 months on this subject, anyway I've chosen SP 2320 flat top pistons....Comp cam's xe268....and Comp's 1441 roller tips.......It sounds like I've made some good choices based on the posts above....Anyway Adam, it sound's like we're building the same motor I would love to here what your final decisions are with your machinist? Mine is 70 block..30 over...#6 heads being recut to W31 valves...no deck or head milling (don't cut unless you have to)...using stock stile shim head gaskets...double roller...HV oil pump...OEM exhaust and intake w/ dual exhaust...3.42 posi....650 Q carb....I'm hoping for a nice street driver on mid grade w 10.1 CR and 325HP w/o too much steering wheel shake Also Mark, interesting about the comp cam? noisy? my machinist is stuck on comp? I might consider an Erson? This is my 1st build in 30 yrs and a good cam is no need w/o good heads?
Well thank you all for your input
Eric M

 

In my opinion your cam is too small (xe268) as your actual compression ratio is around 10.3:1 assuming 68cc combustion chambers and a .017 head gasket. You are in dangerous territory for detonation even with premium gas.

 

Alright, well let me get some more clarity here and pardon me because I may sound stupid in the process.
1- I have not seen anything stating these heads are larger that 64cc?
2- Whats the solution here- Thinner gasket? Flat top piston?
3- How it was explained to me (and to be clear this whole experience is a first to me) was the block would be assembled and measurement taken to find out how deep the piston sits in the block and the deck would be milled down to create a higher compression ratio. Where I am getting confused is this: The stock motor wasn't 7.45:1 so why would a collaboration of stock sized pieces yield that ratio? When I inquired about flat top pistons the engine builder said the car would run like **** with flat tops because of the poor quality of the gasoline today.

 

1. Joe Mondello years ago did a study of combustion chamber sizes a=on all heads years ago and compiled them in his tech manual. 64cc is the factory stated cc, but with stock up of tolerances and casting quality, they usually came out to more. Around 69ccs to be exact. Many others, myself included, have checked and verified this to be accurate.

2. Yes, a flat top piston would get you 9.61:1 compression assuming 69cc heads, .030 deck height and a .039 head gasket. If a Speed Pro piston is used, you need to make sure they set the piston to wall clearance looser than what the instruction say on the box. They need at least .004" clearance. Also, if he decks the block to .010, you really can't use a thinner gasket because you don't need the piston to head clearance too tight. Especially with a cheap piston like that.

3. The reason why it comes out to 7.45:1 is the factory shim gasket is thinner than the aftermarket replacement composite head gaskets. Also, the factory uses 64ccs in their equation to get the advertised compression ratio. Factory motors were never really what they were advertised for the most part.

I know the machine shop thinks they can deck the block to get the compression ratio up there, but what they fail to realize that even after doing so, you will not reach 9:1 compression.

I put an example in my first reply to you, and it will only yield around 8.7:1 compression by decking. Plus, decking a block excessively will cost more $$ in the long run then the extra money you dish out for the right piston in the first place.

If your builder's reply is that the car would run like **** with a flat top piston, he obviously knows nothing about flame characteristics of a burn. I really find it hard to believe that was his response (not calling you a liar, I believe you).......he could be a great machinist, but he should just stick to that and not pretend to know how to build an engine. The world needs competent machinists, and good builders. They aren't always wrapped up into one.

Also, if your builder had a free downloadable compression ratio calculator, he would already know he is blowing smoke up your *** about 9.67:1 compression with those pistons.

Look, I know I am sounding harsh, and I am not intending too......but some of the things your machinist has said has me floored. Especially the flat top piston thing. Just so you know, I am not some blow hard internet jockey. I have lost count of how many performance Olds motors I have built. I also used to work for a well known Oldsmobile machine shop with the initials RR.

 

Hey Adam,
I'm with you on the heads, everything I've found on the net list our heads as 64cc? But I've read on several threads here on CO that they are 68 - 69cc.....I guess we both should have them cked to be sure? On the pistons, I decided to go with the flat tops (cheaper$) and no milling$$$...now after what 80 rocket says....I'll prob go with the Felpro 040 gaskets...once again cheaper$$$....I'm all about the bottom dollar LOL! Also our stock pistons were a shallow 6cc dish, not available in cast (that I can find?) once again more$$$ so anyway my machinists has not said one thing about assembling to ck piston height? Can all be figured out from the stock dimensions....of coarse I'm going to have him double ck all math before I buy anything? Here are some of my 1st calcs on CR...of coarse I need to redo after we ck the true cc's of the heads. Thanks for the calcs 80 Rock.....what do you come with? with the Felpro gaskets 9.8-1 ? I don't want a bigger cam...to much rattle of the bones....not building a race car...just a nice street machine that I plan to drive and enjoy and really would love to run on mid grade (figured stay in the middle and I can always put hightest in if need be?) Sure don't want to have to add booster every tank Anyway I hope this helps Adam?
Thanks for every ones input on our builds
Eric M

 

Good info Don, but to expound on that for all in the last few posts especially.

The stock crank is seldom really 3.385 stroke, typically they're a little shorter than that.
Stock rods, especially after reconditioning will be shorter than 6.00".
Most 350 deck heights are around 9.325-9.330 from the factory.
(3.385/2=1.6925+6.00(rod length)+1.612(piston height)=9.3045, and that's a best case scenario.

So unless you use a BHJ fixture or similar http://www.bhjproducts.com/bhj_conte.../bt1_intro.php it'll be tough to check for a square deck, even if you use the same rod and piston combo in every hole. You'll still have stroke differences in the crank unless it's ground and "blueprinted" by the crank grinder.

Why anyone wouldn't use the Probe .030 over or CP .008 piston in place of the L2320F is beyond me. Yes they're both taller than the SP piston but that also allows you to adjust squish with gaskets, not by having to deck X amount off the block.

I agree with Don, get yourself another machinist if possible wherever applicable. And too many "machinists" are blinded by the amount of advertising Comp does. Just because they advertise the most doesn't necessarily mean they're automatically the best. There are lots of other good companies out there.

 

Speed Pro piston compression calculation.

SpeedProCR_zps0bdee62a.png