Well,
Here is an update on the rebuild. The shop just finished disassembling my engine. It turns out that I will need to get a new crank and 2 new connecting rods. The connecting rods were bent. I have no idea how that happened, but I don't think that getting stuck in the snow would do it.
The shop is going to bore the engine 20 over, and use OEM replacement pistons. Thus, the compression ratio should not change.
I am also going with a cam shaft upgrade. I am not going to be using the comp cam 08-501-8. There have been numerous speculations about that cam shaft working with the stock speed density computer program. Since I don't have the means, or know how to reprogram the computer now, I was recommended that I use a different cam. It is the comp cam 08-500-8. This cam is what comp cam recommends for speed density computers and they say that it would work with the stock computer program. Comp cams says that I will be looking at about 25hp gain over the stock setup.
Hopefully by the end of next week I will have my car back. I will let you know how it is. Although, I will need to break in the engine properly prior to testing its performance.

 

I wouldn't count on that. "OEM replacement" pistons are exactly the type that'd be another .020" down the hole.

 

What are the specifications as far as pistons are concerned, that I need to look at and compare to make sure that the compression distance of the new pistons is not different from the stock pistons?
Thanks

 

They are boring all 8 cylinders...right? So you need 8 new pistons. The machine shop should carge the same money if you bore the block 30 over. The reason I bring this up is there may be a difference in the piston pricing. Speaking of piston....Look at KB Claimers or Speed Pro. By up grading the piston you should select ones that will get you to 9-9.5 CR. The Hyperuetectic will allow for a more efficient motor. More power. less gas, less oil use,... ect. You should have the motor rebalanced, so that cost will added reguardless.

 

the 501 cam works fine on the stock tune .. im currently running it with bigger heads, edelbrocks hi flow intake, flowmaster exhaust (not cat), hooker headers ..

and i have no problems .. it runs and drives fine .. but after 900 miles i can notice it needs some small tweeks ..

but i'd imagine that if everything is "stock" on your motor .. and all your doing is cam / exhuast than i would go with the 501 .. i wouldnt go smaller b/c that wouldnt be much over the stock cam ..

unless you going to race it off every stop light .. stick with the 501 without a tune .. then later you can upgrade other stuff and maybe even get into tuning

 

The 08-501-8 camshaft produces 15.5" of Mercury of vacuum at 800 rpm. This might be ok, but I was told by the shop that is rebuilding my car and also by comp cams that it might require computer adjustments in order for it to run right. I don't know if the installation of your heads and intake may have improved engine vacuum ever so slightly. I have not heard so far of anyone that has installed that cam and running it successfully on the stock TPI with the speed density computer control. I am certain, and so are the people at comp cams, that this cam causes no problems in MAF equipped stock TPI motors.
I initially was considering the crane compu cam 104221, which has an LSA of 116 degrees to make up for the slight increase in duration. This cam has been installed and ran successfully in speed density TPI motors with the addition of an adjustable fuel pressure regulator.
The shop however that is working on my car recommended that I go with the comp cam 08-500-8. It is slightly less aggressive than the 501, but produces 17" of mercury at 800 rpm. This value is on the lower end of the stock 17"-22" of hg. I am sure that even with this setup, my car is going to need some tunning, but at least I will be able to drive it until I can afford to dyno tune it. I have had to choose to go with something that is going to give me slightly less power, but is not going to be as big of a pain in the behind to make it work properly. Thanks for your suggestions and advice. I will let you know how it turns out.

 

The machine shop is going to bore all 8 cylinders, replace all 8 pistons, the crank, 2 con rods, recondition the rest of the rods, and balance the engine.
They told me that the pistons that they were going to use were not going to change the compression on my motor. They said that they don't put cheep parts in and don't cut any corners, but I need to know what the wrist pin to piston top distance is on the stock pistons. If it is the same as the distance on the new pistons, I should not have to worry about compression loss, correct? In fact I would think that the compression ratio might be a little higher since of the slight increase in bore. I did not ask if the pistons they were putting in were hypereutectic, or cast, and what company they are from.
I suppose that this is something I will ask in the morning. I just hope that they have not ordered them yet.
Quite frankly, the replacement of the crank, clutch, and connecting rods has increased my expense with this rebuild a bit, and at this point I am just looking for a good stock replacement piston that is not going to lower my compression.
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Do you know what the stock piston wrist pin to piston top distance is? I guess that would be the only way I can verify that what they are putting in is not going to lower compression.
Thanks

 

As far as I know, reconditioning the stock rods is false economy when compared to the benefits of buying new units.

 

1.560"

 

i agree, get new rods, they are about the same price as reconditioned factory rods and are stronger to boot. If you upgrade to good rod bolts, they will hold alot of power

 

Especially if you shell out the extra coin and get some H beams instead of I beams.

 

for what he's doin, a good i beam will work just fine.

 

It's one of those, "While you're there" purchases. Like, when you put in your SFC's, you might as well box your LCA's/buy aftermarket LCA's because they come out anyway. :P

I can only count how much money I've spent on, "Well, while I'm there..."

 

For what he's doing a stock rod will do fine, too.

 

Well, you are right. These rebuild pistons that they want to put in have a compression distance of 1.540 inches. They are seal power hypereutectic aluminum pistons.
How much less compression do you think they will produce with this kind of a 0.020" compression difference? How much difference in power will that make?
The guy at the shop told me that he has built many of these engines before and he guarantees me that I will not be able to tell any difference. He said that for my applications it would not be worth the extra money.
Do you think that this is a significant loss?
Thanks for your suggestions.

 

It'll add about 3.5cc to the combustion space.

 

Is this a significant change as far as compression is concerned? How much power loss would that result in? Also, would the increase in bore diameter by 0.020" compensate for that?
Thanks

 

You'd have to do the math to find out how much it'll change your compression ratio. It'll also increase your quench height so you won't be getting the benefits of "squish".

 

How would you calculate what the compression ratio is going to be? Also how much horsepower do you think my engine will loose as a result? If it is just a couple of horsepower, than that's OK. I don't know if I should insist that the stock compression distance is maintained. Do you think that the guy rebuilding my engine is right in telling me that I would not be able to tell a difference?
Thanks

 

You might consider just using a thinner head gasket, or milling the heads a bit as well.

 

sorry to spoil your long post .. but look right above it ..

I AM RUNNING THE 501 CAM .. with a speed density, bigger (trick flow vortec) heads, hi flow tpi intake, and hooker 2055 headers..

the car runs perfectly fine on the stock tune .. but b/c of all my other stuff i do need some slight tweeking ..ive driven 950 miles so far on with this cam and it runs just fine with GREAT street manners in bumper to bumper traffic ...

im pretty sure that the 501 cam will do you fine even if you do all the other bolt on's i did .. the power brakes work perfectly on mine .. and it idles down to 700 on its own and rumbles ..

that cam has enough torque to cruise in top gear as low as 35 mph (1000 rpm w/ 3.08 gears) .. and it pulls like a motherf&ck#@ from 3500 to 4800

right now im getting 20mpg going easy on it .. and lowest ive got yet is 16 stompin on it at every light .. my fuel pressure is 46 psi .. and timing is at 8* .. im sure when i tune it, i should be getting 20 +

hope that helps

 

you use a compression ratio calculator to figure that out. You need to know bore diameter, stroke, gasket thickness and gasket bore diameter, piston to deck clearance, piston valve relief dish cc, and combustion chamber volume

3cc difference of combustion chamber will make a big difference. .020" more in the whole makes it even worse

 

Dude, c'mon man, you're spending A LOT of $ here. Throw in the towel on this 305. Take the money you were gonna spend on the crank and rods AND GET A 350 CORE!

 

I do have to agree with GMgod. This is a lot of bank to drop on rebuilding a 305 to stock specs. Either get a little wild with the build (it WON'T cost that much more) or build a stock spec 350. Heck, you might even find a 350 that's in running condition. Pull it, yank off the intake, pull your 305, swap intakes & sensors and call it a weekend well spent.

 

i built my 305 for just under $3200

that included all the machining, new vortec heads, flat top pistons, complete rebuild kit, comp 501 cam, hooker 2055 headers, all new sensors, edelbrock hi flow intake, taylor 8 mm wires, accell shorty plugs, and there is more ...

if i could do it again / had a little more money at the time .. i would of built a 350 .. just b/c then when you twin turbo it one day when your bored .. ... you can get a little more out of it .. hahah ..

but i must say my little 305 puts up a good fight ... if only they sold a turbo kit for our cars .. damn supercharger is $5000

 

I bet that you did most of the work yourself right? I am sure the machining was left to a machine shop correct?
I on the other hand, don't have the time, tooling, experience, or space to do this kind of work, at least at this point in my life. So, I have had to spend the money for someone else to do the work. The whole thing with crank and camshaft and everything is coming up to be about 4K, and that includes the removal and installation of the engine. I just need to figure out what to do with these pistons. The guys at the shop seem quite partial to the pistons that they are using in saying that 1.54" vs 1.56" compression hight is not going to make much of a difference. I don't want them to deck the block, because I want this to be a numbers matching block. This is one of the major reasons as to why I am keeping the car with the engine it came with.

 

Can you ask them what head gasket they're using?

 

yes .. i did all the work except the machining ..

heck if i wasnt able to do it myself .. go pick yourself up a crate motor for less than 4K and bolt on your tpi intake .. and pay a few hundred to get them to drop it in the car ..

EDIT: that .020" on the pistons .. go get the thinnest head gasket summit sells .. i put it on mine and they work just fine .. and they take 6cc's off your combustion chamber compared to a conventional "rebuild gasket".. so you will be -3cc which will raise the compression a little which will give you a few more horses ..

if you go for the thin metal gasket .. make sure to pick up some copper gasket sealer that is in the spray can .. its kinda like a glue to seal the gaskets since there metal ..

 

I don't think I'd trust a steel shim gasket on an undecked block.

 

I agree...

Get a thin one, but not a steel shim.

 

felpro 1094 is a rubber coated steel shim .015 thick. its what i'd run on that motor and should seal well if you make sure both surfaces are clean.

else GM and MR gasket make .028 gaskets. IF you are actually .040-.045 in the hole, the .028 will make your quench .068-.073. that sucks but can work with stock heads/mild cam, low compression. I'd love to see more like .055-.060 with the steel shim. Will raise power with better quench and compression

the difference in compression heights of only .020" is about a half point of compression so its a big deal. the gasket difference of .028 vs .015 is about .3 points of compression

 

i am running the felpro 1094 gasket on my 305 tpi ..

didnt deck the block .. just made sure it was real clean .. and the heads were clean .. then spray the copper gasket "glue" on each side of the gasket and let it tack up .. then assemble it ..

i was a bit hesitant about using the gasket b/c it is EXTREMELY thin .. i mean it took 20 minutes just to cut the package open and remove the gasket without bending it

it is a "rubber coated" steel shim .. which is a nice bit of insurance .. but use the "glue" i was talking about and the gasket works like a charm ..

havent had any problems with mine ..

 

Wow,
0.5 in compression loss is quite a bit. I am definitely not happy about this. That means that my compression ratio will go from 9.3:1 stock to 8.8:1. If I use the 0.015 felfpro gasket, I will be down to 9.1:1. I suppose I could handle a loss of compression that would net around 9.25:1, but that is a significant loss. I am going down to the shop tomorrow and am going to fully express my dissatisfaction in this. I wonder how cheep those pistons are that they are putting in. I would not mind spending a little bit more money to get something that is going to bring me up to at least stock compression ratio.
If anyone has a formula for computing compression ratios, would you please let me know what it is. This way I can go in there tomorrow with my calculator. The way I see it is that I am spending a lot of money just to get something that I am not happy with. It would really suck to have to put this much money into this, and end up with something that puts out less power than stock, or right about the same amount of power as stock.
Like I have said before, I am not interested in making a ton of power, but waking the motor up with 20 extra ponies should not be an unreasonable expectation.
I don't think that I am going to deck the block. If I were going to do that in the first place, I would have bought a new engine (would have been cheaper). I want to keep the numbers on this thing matching.
Thanks for all of your suggestions. I am very grateful for the time that You have put into answering my questions.
I will post the details of what is happening after I speak to the people at the shop tomorrow.

 

i would just make sure you get replacement pistons that keep the stock compression height at around 1.56", I know federal mogul ones are 1.54. Keith black and speed pro are advertised at 1.56 Keep a flat top if possible. Measure the ones that they are gonna put in to verify their dimensions.

I just use online calculators for compression as hand calculations would be much more extensive. I dont know the formulas off hand

 

They're probably using H534 pistons at about $18/slug. You could upgrade to a set of Keith Black KB143s for about $23/slug. That's only $40 more for the whole set. With the pistons down the hole a nominal .025" and still using the Fel-Pro 1094 you'll be around 9.2:1, but you'd have a much better .040"ish quench height.
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Not much of a formula, just geometry. CR = swept volume / combustion space volume.

 

yeah lol but you still have to add the volumes up of the circled cylinder shapes and convert cc's to inches or vice versa for the chamber volume, i didnt feel like typing that out

 

I looked at the pistons the 1st ones KB153 have the narrow top rings 1/16th.
used more for racing....less weight/friction/tension. Also more chance of blow by. But does have the flat tops.

The 2nd KB229 (I think) has the more common 5/64 top rings. But the 4 valve reliefs. I would use the KB229's due to the top ring size, for a street car everyday useage.

The gas octane you use is based on a few things, compression, altittude, load, head velocity, heads material iron vs aluminum, temp, timing. just to name a few...

 

KB229s are almost $30 each, and aside from the small rings the KB153s are almost $40 each.

The KB143s are the same as the KB153s with standard rings, but cost much less.

 

Conversions and simple math formulas are not a problem for me. What is the swept volume? Is that the volume that is displaced by the piston's stroke from BDC to TDC?

 

Actually it's (swept volume + combustion volume) / combustion volume.

The swept volume is the displacement of the cylinder, stroke*pi*(bore/2)^2.

The combustion volume is the sum of the volumes of all the empty spaces above the piston. Chamber volume, head gasket volume, down-hole volume, valve reliefs, etc.

 

KB143's then would be the ones I would use then also.

 

Thanks for your suggestions. What do you think about these pistons from speed pro:
http://store.summitracing.com/partde...&autoview=sku#

 

looks good. Press fit wrist pin so the shop will have to use press fit style rods

 

im pretty sure those are the pistons that came with my rebuild kit from summit ..

they are REALLY nice to look at when they come out off the box ..

got the machine shop to push them onto the rods ..

but other than that there the same compression hieght as stock .. but i think they are more flat ..

anyone know the cc's for the stock pistons .. b/c these are 5cc .. im running them right now in my motor .. machine shop guy said they should raise my compression a litlle

 

i think stock are either 12cc or 7 cc. I'm not sure. I know L98 earlier years were 12 cc dish, while 90+ and corvettes had 7cc flat tops

 

im pretty sure mine were 7cc then b/c they were almost as flat as the new ones ..

the only difference i could see were the edges were rounded on the old ones .. the new ones are flat corners

 

Just got my baby back, and she runs great!!!
First off,
The cylinder compression is 160 PSI after the rebuild. The shop that I had my motor rebuilt at even repainted and cleaned up my engine compartment, valve covers and timing cover. The engine looks great.
The first 50 miles of driving were a bit questionable. I was not sure if I was happy with what was going on. The car was idling about 1000 - 1200 RPM and seemed to lack low end torque. It was also running a bit hot, about 220 to 230 degrees. However, as I kept driving her, while taking it easy and not exceeding 3200 rpm, she started getting better and better. The torque started coming back, the idle started coming down to about 700 - 800 rpm, and she started running cooler.
I never took the car much past 3K rpm, but she seems to be hauling a$$. Power comes in right about 2K rpm. The comp cam 08-500-8 sounds great. The car sounds a little lopy at idle, however, as soon as she gets right about 2K rpm, she smoothens out and sound great. I just took her on an easy 120 mile drive, and just love how she runs.
I have an appointment on Monday to get an alignment, from where I went off the road in the snow storm, and also to have a couple of minor exhaust leaks repaired. I can't wait until the motor is properly run in and I can get her dyno tunned.
Thanks alot to all of your suggestions. I will keep you all informed about how things are turning out.

 

i just got all my stuff to tune my 91 305 tpi .. was tweaking a stock .bin file last night, so today i might have a new beast on my hands ..

as for the running hot .. go get a 185* thermostat (jet or hypertech) and the matching fan switch (goes in passenger side head) .. my motor never gets over 215 now .. and is allways in the 190 range, even in traffic

so you went with the comp 500 .. probably a good choice since you got stock components, i went with the 501 since i could flow a bit better with the new heads / intake ..

mine does the same thing, start to get power around 2K .. once you get her broken in .. take her to redline and youll have a real treat ..

just about to roll over 1500 miles on my motor .. and lovin every miles of it ..

and about the dyno tuning .. do what many have told me .. spend the $229 (equipment / shipping from moates.net) and do it yourself .. they dont tune everything on a dyno, just WOT at most shops ..

i can say from the last couple days of tuning .. everything you need to know is on this website, and theres multiple highly knowledgable people that will help you through any problems

plus its a TON more fun tuning your own car .. and youll know exactly what is going on under the hood ..

 

I intend to learn how to do the computer programming myself. The guy that runs the dyno charges $40 per pull. I am a bit cautious about screwing something up. But will make sure to consult the members of this board prior to plugging in a new chip.

Yes, I decided to err on the side of caution and got the slightly smaller cam.
By the way, what equipment did you get for your tunning?

 

i got the g1 adapter (comes with two blank chips), a burn 1 chip programmer/burner, and the cable to datalog

got it all on moates.net .. came to $220 plus $9 shipping ..

then there are a couple different programs you can use to burn / datalog..

im using tunerpro rt and the program that came with the chip burner ..