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13.1 compression Chev 355?

25K views 23 replies 10 participants last post by  Choctaw Bob 
#1 ·
I bought a complete running Chev 355 that was built for drag racing and raced for 1 year. I want to use it for a 69 Camaro im going to buy. The motor is 13.1 compression. Are there octane modifires or boostres that can be added to 93 oct fuel that my motor can run on. I plan to buy a good set of aluminum heads. Im dont want to buy $8.00 per gallon gas for 110. I know I can swap to E-85 but I want to do that as a lats resort. Are there other options? I dont plan to race the car. Just street drive. Thanks in advance.
 
#2 ·
Sorry dude, but nope....all the octane boost in the world isn't going to stop that from eating itself on pump. Which pistons are in it? If the compression is there by tiny CC heads, then maybe you will be OK when you switch to alum heads. That's going to be what you need to know.
 
#4 ·
The only place that sells E-85 where I live in a metropolitan area of over 1-million drivers, is one Kroger Food store. There are some turbocharged ricers that use Kroger Food Store's E85. None of the race shops sells the stuff. If you think your fuel system is prepared correctly and can successfully use alcohol based fuel, use VP M1 or M3 Methanol racing fuel that contain lubrication and combustion additives. M3 is easier on the eyes and nose.

Speed shops in my area sell VP M1, M3 and M5 Methanol racing fuels. VP M5 is what the top alcohol race cars use. My cousin, Mark Talliaferro, uses VP M5 Methanol exclusively in his MARKCO Top Alcohol Dragster.
 
#6 ·
There's 13 to 1 and there's 13 to 1; which is to say you've got to get at the Dynamic Compression Ratio. 13 to 1 as a static is used in race enignes as a means of improving off idle to torque peak performance that is otherwise lost when very long duration which brings a late to close intake valve. This usually needs to also be combined with a lot of gear ratio to essentially prevent the engine from lugging on the bottom end and going into detonation as a result. The lugging period of a drag enging runninng through the gears as it transits the lights may be momentary but it is significant this is where probably half the engines blow up Typically mid strip in the upshifts not form over revving but form detonation either blowing the piston or rod, or wiping the oil film from the rod bearing to journal spinning the bearing with explosive result. So one of the first things you need to know is in crankshaft degrees when does this cam put the intake valve on the seat in the compression cycle. Later begets more SCR to drive an operational DCR range of 8 thru 9 to 1. 8 being street gearing and pump octane friendly and 9 being race gears and gas. You also need the connecting rod length for this calculation, DCR calculators are all over the web when GOOGLED.

Off the top of my head I'd say you'll have to give on compression for the street and maybe even have to calm the cam. A 13:1 the pistons are probably pop-up so figure on their replacement as well.

Bogie
 
#7 ·
That a good point.... I dont know if the high compression is from the pistone or smaller cc heads. I dont know. I assume from the pistons but I didnt build it. I have a build sheet but not with me now. I think it eagle rods and Wiesco pistons. I think iron 2.02 ported heads. If the rise is from heads cc maybe new edelbrocks will lower it... Where I live E-85 is everywhere. I dont care about to 30% more fuel comsumption. I thought E-85 is 105 octane? Based on what I've read it sounds like it might be the best for me to sell it to a racer. Someone said ger a 350 from a junk yard and?? No. I may build anther but not something cheap....
 

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#11 ·
My somewhat limited experience with E85 indicates that an octane rating of 105 is much higher than the performance I’ve seen from it, not withstanding that vehicle weight and gearing play pretty big on compression ratio performance.

That said; if you look at the numbers and the process of determining octane for unleaded pump and leaded race fuel which is taking the fuel and testing it two way one the Research Octane Number (RON) method which always drives a higher number than does the Motor Octane Number method (MON).
When one goes to the tables you find that fuel grade ethanol is rated at 109 octane RON but only tests to 90 octane in the MON test. Since to make a comparison to gasoline octane ratings the 109 and 90 need to be added together and divided by 2 which nets out 99.5. Better than pump unleaded but not the same as high octane leaded race gas.

Then E85’s ethanol is diluted with 15 percent gasoline. If one assumes that the gasoline is a pure petrol premium 92 octane base and that the octane rating of either ethanol nor the gasoline reduces when mixed (the kind of thing that often happens with fuel mixtures) you get ethanol at 99.5 times .85which nets 84.6 as its contribution and gasoline at 92 octane times .15 which gives 13.8 the sum of which only makes 98.4 total octane. Scientific data of the octane rating of blended fuels that makes any sense to my simple mind is hard to find. Everybody’s trying to sell something and distorts the truth with the most favorable numbers they can find and certainly ethanol’s high RON number is quoted against gasoline’s ROM+MON/2 average a lot and everywhere. Problem where I live is pump gas already has 10% ethanol in it. When I read the blend data from the manufacturers and the scientific communities it looks to me like one of the first things they do with 10% alcohol is use it to raise a lower grade petrol feed stock to the needed octane of sale at the pump. It does appear that this is a situation where more is not better, it looks form the data like 10 to 15 percent alcohol is in an octane sense the biggest bang for the buck. So it’s not a clean exercise to figure out what a pure petrol feedstock that would make 92-93 octane without any alcohol and how it would behave when mixed with 85 percent ethanol would really be like. Then consider that 100% fuel grade ethanol can actually be 95% alcohol and 5% water. And if I know the fuel companies at all; you can be sure that looks more like 93 to 7 maybe even 90 to 10 because when mixed with 15 to 90 percent petrol the stuff will burn even with that much water in it. So the other question is how much octane behavior is due to the unknown amount of water injection that comes along for the ride.

My limited experience with E85 roughly tells me that its actual performance in a competition engine when compared to VP’s C12 which is rated 108 RON+MON/2 for example is not equivalent to E85’s oft stated 105, 107, 109 octane depending upon the reference source.

Bogie
 
#9 ·
If you can't find the build sheet, at least pull a valve cover and get a casting number. Acc holes mean they likely aernt camel's but who knows, 0 decked, flat tops and 49cc chambers gets you real close to 13:1 depending on hg thickness. Which means a set of 64cc (most after market) heads gives you a real easy pump gas 10:3 comp. Be a shame to dump the motor if its full of good parts. Especially if u planned on buying heads anyway.
 
#10 ·
Is there a way thru compression testing I can calculate the the actual compression ratio? I dont have a true build sheet. I have a word document typed by the owner outlining the items in the motor. Im sure it makes no reference to the decking of the heads if any. Like I said the plan would be to go to Edelbrock heads anyways. Not if my only option would be 110 gas. I live in a large metro area (Minneaplois) so E85 is everywhere but I dont want to regulate my trips around town based on where I can buy 110. If E85 is not an option, which I hear mixed reviews about, and I would need to change pistons and heads then its not worth doing anything to it. Id sell it and build another. ??????
 

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#14 ·
The best suggestion has already been stated. Pull one of the heads to see what type piston you have. If it is a 13.1 compression engine most likely you will have domed pistons. The part number of the piston is usually stamped on a pad on the bottom of the piston. You would have to pull the oil pan to see that number. If you don't want to buy racing fuel sell the engine. IMO more would have to be changed than just pistons to make it useable for the street.
 
#16 ·
I wouldnt need an engine that is good for traffic or cold weather. This would be a cruiser/street racer. I dont think I want to take apart this combo. The only thing I wanted to do was replace heads to help with detonation. I didnt know if these heads were any good. I wouldnt want to trade anyone for a stock type of motor. 500 hp would be perfect for what I want to do. In fact if what I use is 500 hp is would be the least powerful of the muscle cars I have (2 SuperBees and Shelby GT500). I was just not in love with needing 110 gas.

What do you think this engine combo carb to pan is worth complete?
 

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#19 ·
?????? Who said anything about "a stock Super Bee and stock GT500" ???????? 1969 1/2 A12 six pack Super Bee Hemi orange restored 6/2012. 543" ci stroker, Edelbrock heads, 3.5" hookers, 3 worked holley 500 cfm carbs, hydraulic rollers cam, lifters, rockers+++ Dyno done 4/2012 715 ft lb torque. Thats the orange Bee in the pic earlier in this post.

Oh ya "stock GT500" Ford racing 2.3L TVS supercharger, Kooks 3" race headers and exhaust, high flow elbow + twin TBI. VMP performance underdrive supercharger pulley kit 2.59" boosts 18 PSI (double OE). Eibach lowered suspension. +++ too much to list here. Above are the highlights. Yes I have the engine and chassis dyno with many pulls. Videos too. All 3 cars are in previous pics in this post.

Most of my performance experience is in Mopar and Ford. Thats why I was asking you guys what you think the 355 Chevy as I posted the specs prior is worth. ?????? Any other ideas of value?

But I agree, 500 hp is much more than "STOCK" Super Bees and Shelbys...
 

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#21 ·
The info is helpful. I think based on what I've read it sounds like the set up I have is a good engine. I dont think I want to mess with it. I think that I may try it in a car and have a careful tune and mix some 110 with the pump 93. Worst case it pings and I pull it and sell it. Or I may sell it as it is and buy/build another. I knew the compression may be a factor when I bought it. I bought it @ Iola old car show the last day of the swap meet. He did not want to bring it back home. I may not be a Cheve expert like some who have responeded but im not new to muscle cars amd HP motors. I wouldnt have bought it if it didnt sound/run right. Its solid.

You made mention of if the guys were idiots they woudnt have used those quality Bow Tie heads 2.02. Whats different from these to any other chevy small block 2.02 head?
 
#23 ·
Not trying to "market an engine". Marketing it would include including my contact info, which I wont do. Ive never bought or sold a used engine. Im also not familar with GM or high compression race gas engines. I bought it based on the idea I would modify it to run on 93. Based on responses from people like yourself it sounds like its not a good idea to take it apart. Thats why Ive used this forum for advise from others with more experience like every other person who has posted a question looking for help here. Chill out.
 
#24 ·
Sounds like you already buy race gas by the drum. What's one more? Me, I hate to admit I've made a serious uncorrectable blunder. Now, with that said, it doesn't sound like you have the skills or the inclination to fix this problem yourself. If you did, you would pull it apart on the stand where it sits and see what you got. Most folks I know would never buy a used race engine from anything less than a reputable engine builder. So...that leaves you with the option of breaking it down and selling for salvage the parts you don't use. Use the block, the rods and crank and buy new parts that fit what you intend to do with the car. 500 HP on pump gas is not difficult with a 355 if you use a set of AFR or comprable heads and a hydraulic roller cam. It's at the upper range of what you can expect without power adders.
Maybe the guy you bought it from will buy it back at a discount you can live with.
 
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