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310cid sbc

11K views 94 replies 9 participants last post by  Oldsm 
#1 ·
Hello!

I recently bought olds with chevy 305.

Now i know more about the engine.

10,3:1 comp
xe-268h
601 heads
0.030 oversize
Some kind of high comp pistons
Quench 0,02 inch
Pistons 0,0157 inch over deck
Holley 650cfm
Edelbrock rpm
Flowtech headers


Wrost thing is that man who did that engine is died and when i readed his messages on forum before death, engine have little problems.


Pinging, idle and 10-12hg vacuum etc...


Is that basic compination in this engine okay or is thicker head gaskest must?
 
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#5 ·
Is that basic compination in this engine okay or is thicker head gaskest must?
DO NOT USE A THICKER HEAD GASKET TO LOWER STATIC COMPRESSION RATIO. The resultant wider squish will make the motor more detonation-prone than if you'd have left the thinner gasket in place with the slightly higher static compression ratio. So says John Erb, chief engineer for KB Pistons.

You alter static compression ratio with the piston crown configuration and the volume of the combustion chamber. You alter squish with the piston deck height and the thickness of the head gasket.
 
#6 ·
Normally I would agree, but right now according to his info he is at .020" quench height, which is way too tight.

He's giving info as piston sticking out of block .0157" at TDC. If that is correct, he needs about .050-.055" thick head gasket to get quench to a reasonable figure near .035-.040"

Oldsm, you need to confirm these numbers you posted, as it won't survive long with only .020" piston to head clearance, at upper rpm you risk bouncing the piston off the head. It won't be good(nor pretty) after that happens.
 
#8 · (Edited)
Sorry guys!

Im from Finland so my english is bad. Youre right, measures was metrics which i converted to inches.


Quench 0,6mm and pistons goes 0,4mm up to deck or how i can tell it for clear.


That problem was in 2012 and he died 2013 so i dont know what he did before that.


Is there something that i can check without removing heads, no?



And surpise surpise the original forum messages are in finnish language too.


"Bolt on" building is what i just understand but quenches and weird compinations is somethng new for me. I mean that if i build engine i just but 70's block and good heads for that era and some aftermarket cam + headers etc...


But now when somebody has oversized 305, tight compressions and so...


That engine gives nice power on 80's cutlass, wheel spins and burns. I've heard that car is 14,X on 1/4mile. Rear is 3.73.
 
#9 · (Edited)
Huh! Thanks!

I need some time to solve all things :D


Engine builder was told that comp is that what i tell.

Now it has th200 and guru has worked it to work over 400hv+, torque converter is stock.


"In a street strip cutlass needs 4.56's" <-- you mean rear end? I dont need tight strip car because i drive highway too, now it revs about 3000rpm @ 60mph.



Do you have anything horsepower quess worst and best at my parts if specs are what i have heard?


With 750cfm holley engine revs 7000rpm and 6500rpm with 650cfm when builder tries to adjust it. Crank and bottom of engine is pretty original i think so it wont last high rev?
 
#11 ·
If i measure compression with just compression test gauge, what psi i should have if i got +10: comp?


225 sounds low with my experience :D


I had 79 and 81 cutlasses too, olds 350 '71 with best orig heads and intake, quadrajet, howards 510011 cam and headers. Didnt burn tires or go that fast than that 310sbc one.


Another was 69 year olds 350cid, burned tire okay but werent that fast too...
 
#14 ·
I doubt it but 270 on crank.
If your engine produces 1 horse power per cubic inch,its a very good street able engine.It takes more than a camshaft to make any engine.Most important is the cylinder head flow and design,good intake and fuel management,free flowing exhaust,strong and well managed ignition system.
Are your parts well matched and good quality? What transmission are you using? How much drag does it cause? Example; a turbo 4oo is a very strong transmission,but it may take as much as 40 horse power to operate. By the time your put the power through a couple universal joints,change direction through the diff and spin some heavy/wide tire wheel combination and make it quiet the rest is available to get you where you want to go?
 
#16 ·
I have 601 heads from 305, 58cc. I have heard that those wont flow like the best but chamber is good? Because smog heads are 76cc or something?

If i switch heads about 70's era heads with better flow (which are from 350 with some kind of horsepower example) but chamber is bigger 70-76cc, can i get more horsepower or does my compression loss determine horsepower?


Sorry my language, very hard especially technic words...



I have hei-distribrutor and edelbrock performance rpm intake, holley 650?cfm carb. Flowtech headers whit somekind of diy-tuning.

Trans is th200 which is pretty good for improve horsepower? It takes 400horsepower so its not stock.


Rear tires are 235 width and rubber burns good :thumbup:



We have couple 1/4 races on here so maybe i some day go there and check what i get.

Flat 15s isnt that bad too... beats many street cars.
 
#17 ·
3 things need to match well,
The total head flow will determine the horse power available
The cam and valve timing need to extract the power with enough valve lift and duration
The compression ratio has to be high enough(or low enough) to use what ever fuel you use without detonation and give proper dynamic compression ratio

fuel air intake and exhaust must meet same requirements
 
#19 ·
Forget about any of the 70's smogger heads, they won't be any better port-wise and will just kill your compression ratio and you'll lose power for that reason.

You could look into either having the heads you have ported, or possibly a set of the aluminum L98 engines "113" castings as they are also 58cc chamber (might be hard for you to find those in your country though??).

I would say 270 hp right now is a decent estimate.
 
#20 · (Edited)
Yeah heads are pretty rare think. Any heads of chevrolet arent too common here (which is most common engine in here ).



So, is camshaft too big or too small from 10:+ comp?

0.6mm quench too small? Stock engine is 9,5:1.


And crank and engine bottom or what it is, is original. So how fast i broke it if i rev engine 6000rpm?
 
#21 ·
I checked timing today and compression test.


Timing with distributor hose off was in idle about first mark on left when you look at front of car.

With hose on it was about 5mm left of first mark.

This have 350 balancer and marks i think because they are in clock 2 position not 12 like 305 original? I mean that you cant look timing marks straigt up.

Timing mark is like that:



I Dont have pro type timing lamp so i didnt check how much degrees it was.


Compression test gived about 200psi so compression is 10+?
 
#23 ·
I read some articles but does it work like that:

Example: if balancers "lenght" is 150mm (i mean if i take tape measure and but it over balancer)

Round item is 360 degrees so if i take 150mm and split it to 50, then i get 3mm.

3mm = 7 degrees on balancer? 6mm = 14deg etc...


Is that right? So if i take 0 BTCD and go counter clockwise, 3mm and i have 7deg and 6mm 14deg etc...
 
#30 ·
take the EXACT diameter, multiply by 3.14159 then divide that by 360 and you have youre arc distance per degree on your balancer.

to find 0 on your balancer you need to set your #1 piston at EXACTLY TDC, your balancer should be correct but sometimes they aren't and this needs to be checked. you can then mark out each degree beyond that on your balancer, or every 2 degrees to make the lines easier to mark/read.

you can also create a degree wheel in a similar manner to degree in a cam. I made one a long time ago out of a sheet of really heavy weight card stock and it works better than any that i've seen in a catalog, make the diameter as big as you can and it becomes super easy to read. I just use a magnetic base with a locker dial indicator as the timing tab when using the wheel.
 
#31 ·
Balancer is 7"



I had issue with too high intake/carb/air filter.

I have now fly eye type filter which stucks on hood metal frames. There is no room for air or anything.


Carb had 1 inch spacer. I taked it off and now i think idle is more rought and light acceleration is little bit stumple too...


Are those spacers worth of anything? Or will i adjust carb without it?


With spacer nothing normal type filter solution doesnt fit.
 
#35 · (Edited)
Okay! Which "steps" i should try them? 5 smaller?

Dont hear knock anymore...

Today i take some 0-100km/h times which are little more than 0-60mph.


Flat 8sek with my fault, second gear and i switched to neutral and engine revs 6500 one and one and then i got D. My shifter is too tight, all "gears" are in couple inches movement.

So i claim that 6.Xs 0-100 time is true.

Didnt tell too much about 1/4 but good start i think?


And stock converter is bad because stall is low, needs little brake when you take off but if you press liiiiitle bit too much brake it will burn tyre whole first gear
 
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