305 build ?
hello, my name is robert
I had some ? on a sbc build im been wanting to do. this is what i was thinking so far. and yes i know that I would be better off with a lot of other engines but I'm just wanting to build a 305
bore/stroke - 3.766/3.75 in
rod length - 5.7 in
combustion chamber vol - 68 cc
deck clearance - 0.010
Piston Head Volume cc - +10.00 cc
compressed head gasket vol - 0.030
4 bolt conversion with a girdle
high vol/high presser oil pump
195 cc intake runners/ 80 cc exhaust runners
dose what i have sound about right?
thanks for you time :cool:
The compression ratio is very very agressive for 92 pump gas, for street use.
Marginally a bit too high for that. May be fine for strictly 1/4 mile drag.
98 to 102 octane is fine for street use.
9 1/2 on the compression sound about right to you? would you know what cam would match up well with that or how I would go about doing the math to find the correct cam?
Well with the parts you have posted the cr will be 11.36:1
The 10cc dome on the piston is a mistake for building for pump gas.
If you mean to say it is a -10cc dished piston then the cr will be
a bit on the low side 8.95:1
A better match for the -10cc dished piston for that motor would be to combine with a 58 to 60cc head.
This get the cr to a 92 octane pump gas happy 9.8:1 to 10:1.
Is this what you are wanting to build.?
Camshaft selection: need more info on the car and how you will be using it.
light duty 78 c10 and ill be running 105 in it all on the strip maybe on the street now and then just to show it off the trans will bee a th350 from monster i haven't pick gears for it yet and the rear is a gm 12 bolt 3.73:1 locker not sure on the trucks wight yet but ill let you know when i'm done with the rear end
I was also think of maybe going with a low compression build with a set of turbos?
thanks for the help man.
Instead of spending all the money on the stroker crank and block girdle huge heads etc.
That will need a ton of RPM parts and need to rev to the moon.
Why not use the stock block and crank and supercharge it. You need raw torque and power to get that heavy truck going. low cr 305 with a weiand 142 blower+750 holley/edelbrock. 400+++HP on pump gas.
stock low compression 305 short block.
ported stock heads, ported vortec heads, .....ported 083 head
ported camel back head) (1.94x 1.50)
ported 113 corvette l-98 aluminum or equal or a better aluminum head.
big power at moderate boost on pump gas. bigger power on race gasor water injection wiith agressive 10-14psi boost from a weiand 142 blown 305. Big visuals on your truck.
twice the power and torque gain for the money spent.
1/4 the complexity and hassle.
305 blown with a larger 177 weiand is another path. Even more power and visuals.
Nothing grabs the eye like a Roots Supercharger. Turns as small CID motor into a much larger motor.
i was thinking of putting a 142 on my 305. Is it just a bolt on, tune and go sort of deal or do i need to go inside and do some work
a 305 with a 3.75 stroke? 335? are you looking for high torque with moderate HP? what heads are you using with 195 cc runners that fit a 305/335?
what is the performance target ?
I suggest you hold off a rear end gear ratios until you have firmed up your game plan.
FYI: The blower option is neither cheap or easy. A simple quick search shows some pricing for it and when looking at that remember you need to buy all the parts to make it a turn key.
weiand superchargers | Price comparison and reviews at best-price.com
Oh and you don't just increase the boost at will on them without a consideration for the internal parts of the engine.
Of all the power adders,the turbos are the easiest on a engine.
Boost is boost 7psi boost is the same on a roots blower or a turbo.
12psi of manifold boost is the same 12psi wether created by a blower or a turbo.
Boost does not excessivly stress engine parts. But detonation does. Its the difference between pushing on something and smacking it with a hammer. Big difference.
You can bolt on a 142 on a stock block 305 and make 450+ hp at high boost with high octane gas
without fear of hurting a stock short block as long as detonation is avoided.
A turbo motor that detonates will self destruct just as quick as a supercharged motor will.
The basic weiand 142 SBC Kit retails for $2000 .. Get a 750 jet it and a blower friendly camshaft and home port the stock 416 heads. Bolt onto a stock dished piston 305. Get a timing retard control for high boost.
The car/truck will need a upgraded high flow fuel system (flow volume), reguardless.
7psi and easy timing on pump gas, 12psi for race gas. Its just that simple.
Keep it simple basic, affordable and fun.
To get a turbo system right for the motor so it is responsive and powerfill is a lot more technically involved than a roots blower, especially the 142 lil blowers. Its about as simple as it gets.
The only way you will hut a stock short block is by detonation. A blower and a turbo that are incorrectly tuned will cause engine destroying detonation equally. There is no difference to the engine. Detonation is detonation.
for the boost you will be using on the street.
Detonation is avoided by correct tuning. by not getting greddy n boost, on pump gas.
jetting, tming under boost, good 92+ octane pump gas.
7psi boost is plenty and will add +++100hp+++ to a 305.
A blower friendly cam is nice to add.
The Summit SBC hyd's make a great blower cam
Dual pattern wide LSA. eg summit cam #1102 1103 1105
Some of the factory SBC cams make great blower cams EG: 350HO 330hp vortec crate motor cam 212-222 .430 .460 112
EG 327 350hp "151" cam 221-221 .447 -.447 114
EG the 350 LT4 hot cam hyd roller cam 218-228-.525-.525 112
EG the ZZ4 crate motor roller cam 208-221- -471 .510 112 .
Crane cams has many many off the shelf hyd solid and roller cams that are great as blower cams.
a 750carb works great. a few mods and rejetting is needed to dial it in. A spark retard box "BTM" is great.
blowers love improved cylinder head flow just like any motor does.
Port the stock heads to get some flow on.
or port some stock large chamber 350 heads (1.94 valve)
to drop the cr even lower (7.5:1) for high boost on pump gas.
5 to 7psi and 8.5:1cr works real good on the street.
Your 305 will make the power and torque of a 400 to 425cid engine
Its not rocket science and is very cost effective.
There are Millions of good used 305 SBC engines in old rusted out impallas, Monte's. Camaros. trucks,
in peoples yards. So if say you do happen to get a carried wawy on boost or fubar the tune (jetting/timing) and smoke the
305. it (the basic 305 short block) can be replaced for as little as FREE+ gaskets and time.
You will never run out of a good source of perfectly good used 305's to try and kill.
You will find that boost will not kill the motor. But detonation will.
Be prepared to go very fast for very reasonable cost. If thats too much for you, stay on the porch.
If you check out the supplied links:
MSD 6-BTM CD Ignitions 6462 - SummitRacing.com
From $2600 to 2900 for the kit with more parts yet to buy
A easy $500 for a MSD and ignition parts
And we haven't even bought a 750 Holley or mod'ed for a blower
Still haven't bought a cam and kit
Still haven't bought headers and exhaust
Still haven't bought acceptable heads and done the machine work
A easy $5000 to $6000 that as you said is trail and error that if a mistake is made you then have $6000 invested setting in the shop in pcs.
That pixs with a blurred head shot...........................well
I think if I have to hand hold these blower advises given so a more accurate cost factor is posted,maybe it is you that should spent more time on the porch.
The turbo's can be had for next to nothing.And do not cost anything in the loss of power to drive them as a belt driven blowers do.
ya,someone do a turbo board for comparison.Im reading up on boosted engines and I would love to rob the parts yards for power adders
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