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NintendoKD 04-24-2013 11:51 PM

Wtb sbc 305 high rev low comp
 
Sounds nuts I know, but it's not for me. The customer wants a 305 to be built with as low static compression as possible with the ability to reach 6500 plus without damaging anything. I tried to guess that he wanted to go forced induction, he just smiled and asked if I could do it. I told him yeah but to be honest I usually just offer a 350 or other bigger sbc to guys who want. Ore power. I have a pile of old 305's lying around because of just this. So what do I do? How do I build a high revving low compression 305 for. Cheap, and don't try the just use a 350 gig, I already tried that, kid won't listen to reason. He wants arp head studs in the build so I know he plans to make some power, but for now he just wants me to start with teardown and inspection of his 305. I have some ideas, but how much power can you make on stock 305 internals? Kid won't listen, he's a paying customer so I won't complain but I need help to do this.

Thanks,
Kevin

gearheadslife 04-25-2013 04:08 AM

not knowing where you are located..
maybe the kid wants a 305.. because of the EPA laws.. that change state to state.. if he goes into the armed forces.. he might have to deal with many different rules/laws/etc..
I know my 86 SS would fail if the 305 wasn't there.. up untill a few years ago here.. and why the 305 is still in it..
maybe he just wants to be different.. who knows..
I know here they kept going back and forth on the rules.. for 5 years and part of the reason my 355 sat in a corner of the garage..
and there is that fear that as soon as I drop the 355 in it they'll change the rules yet again..
these things might not even be on the table.. but you never .

why would a 305 that needs lower compression and buzz to 6-7k be any different than a 350 build.. other than cam..
shouldn't be that hard to find some 350 smogger 70's heads with 76 cc chambers and small valves to dump on it.. as the newer heads with 58cc might be hard to find on shelf pistons to get low compresion.. how low he want 8 to 1 or lower?

F-BIRD'88 04-25-2013 04:42 AM

Build it exactly as you would if it was a 350, except only use a 1.94x 1.50" valve set.
use a 76cc 350 head. such as the #920 casting. Or a Dart/WP 72+cc S/R head with 1.94x 1.50's Fully hand port the heads. These heads will easly flow 230++cfm when fully ported
Do not use 2.02 valves. felpro 1205 gasket size is plenty big.
Use a solid lifter cam and valvetrain. EG : Crane F278-2 or F280-2 (roots or centrifugal blower)
Use crane 1.44" double springs or a good stock diameter spring like the Isky 235D
Drill and roll pin the rocker studs or replace with screw in type. 1.5 rockers are fine
Bore it + .030 use a flat top or dished hyper 305 piston.
If it is going to be getting a power adder ope up the ring end gap.
If the customer insists on using head studs, double the price and void the warranty.
(they often seep coolant up the threads on stock SBC blocks) They are not nessessary anyway.
The cr will be a low 7.85:1 with a flat top piston
and 7.37:1 with a typical -12cc 305 dished piston.
use the stock 305 crank, stock 305 or 350 rods resized w new ARP rod bolts.

It will rev well beyond 6500 and make very good power with a blower on it.
If the customer is going to turbocharge it you will want a custom turbo cam for it.

Since you have no control on how this engine will be used, write on the bill/work order "NO guarantee or warranty/ race use only"
Get him to sign off on that before you start. You have no obligation to warranty this motor but must make that clear in writing.

This engine will need a very high 8" 9" 4000+ stall and lots of gear. It will really like to rev up.
If the customer whats to use a hyd cam tell him to go somewhere else.

this engine will rev up higher than required. Will be lame without a blower. But will GLH with one. You can hit it with quite a bit of boost on 92+ octane.

gearheadslife 04-25-2013 05:50 AM

why would studs seep coolant up the threads any more or less than a bolt..

vinniekq2 04-25-2013 06:38 AM

" So what do I do? How do I build a high revving low compression 305 for. Cheap,"

just toss out reliable and powerful,,,,

This is the time to instead of dazzling them with brilliance,its better to baffle them,,
explain piston speed to the last detail,
valve train harmonics,
torsional stress and dynamics in the crank shaft,
after a few minutes of this,give them some math to come up with their best formula,then add in everything you know about oiling a high revving sbc and again let them formulate a formula for you to follow

I doubt it goes that far and they will call off the build,or share info as to the purpose of the engine and reason for the secrets.You use all these questions to put them straight

F-BIRD'88 04-25-2013 06:59 AM

Quote:

Originally Posted by gearheadslife (Post 1670120)
why would studs seep coolant up the threads any more or less than a bolt..

Because of the way the threads are formed.. Same pitch but a slightly different shape.
Most aftermarket blocks have all blind head bolt holes that won't leak.
Studs add nothing to this build except cost and likely hood they will leak coolant.

F-BIRD'88 04-25-2013 07:00 AM

This engine will be plenty strong and will likely out last the owner unless he does something really dumb.
You have no control over that. If you want to buy into having to warranty this motor just triple the price quote.

RPM and boost will not be a problem. Stupid excessive rpm and boost, will.

gearheadslife 04-25-2013 07:33 AM

Quote:

Originally Posted by F-BIRD'88 (Post 1670134)
Because of the way the threads are formed.. Same pitch but a slightly different shape.
Most aftermarket blocks have all blind head bolt holes that won't leak.
Studs add nothing to this build except cost and likely hood they will leak coolant.

I've always used arp studs,
are you telling me that arp studs threads are formed differently than their bolts , ???

NintendoKD 04-25-2013 07:51 AM

No backing down
 
Kids a Marine, usually not tough customers, but I think this one is particularly thick skulled. Just got back from afghan, single, no family. He is putting this into a 69 camaro he lready had with a ford 9" he also insisted on using a 700r4 for driveAbility, which he also has. **** I can build it, just never did anything quite like this. Thanks for all of the help so far. I guess for track guys this is fairly common? Good advice, after my "yes I know it's cheap" 55$ clean and inspection I'll roll a paper quote outgo him and maybe scare him off. This is California, and he is from. Cali, but it's a 69' so it doesn't have to smog.

gearheadslife 04-25-2013 08:04 AM

Quote:

Originally Posted by NintendoKD (Post 1670142)
Kids a Marine, usually not tough customers, but I think this one is particularly thick skulled. Just got back from afghan, single, no family. He is putting this into a 69 camaro he lready had with a ford 9" he also insisted on using a 700r4 for driveAbility, which he also has. **** I can build it, just never did anything quite like this. Thanks for all of the help so far. I guess for track guys this is fairly common? Good advice, after my "yes I know it's cheap" 55$ clean and inspection I'll roll a paper quote outgo him and maybe scare him off. This is California, and he is from. Cali, but it's a 69' so it doesn't have to smog.

ever think i's a street racing thing,
a guy sees the g.m. cid/ltr markings on the block and will think easy pickings..
the guy might not be all that dumb
low 1st gear, high rpm to make up for the 7004r wide gear spilts..
sounds like a racer to me..

NintendoKD 04-25-2013 08:25 AM

interesting
 
well it will definitely be a build to remember. I do not know what amount of pressure bar/psig this will handle safely reliably, or what the stock internals will handle, or how much power he will make. Any estimates? the more I can tell him the better. I always assumed that stock internals were 450-500~ all day but I was never too sure on this. I want to tell him 15psi is safe for this setup but once again, where in the power range is that going to get him with 92 octane? We still need to talk gear ratios and tires so I can get the right cam, and torque converter combo. For the record, he did mention something about twin turbo setup, I have to admit, I am a bit curious now, never seen one like this up close. Thanks again for all of the advice.

gearheadslife 04-25-2013 09:07 AM

around 1988 I helped with a buick (monza clone) with a 267 v8 and 2 mopar 2.2 turbos running through a pontiac turbo t/a carb..
it had no low end but the midrange was sweeeeeeeeeeeeeeeeeeeeeeeet
keeping head gaskets in it was a whole other story..

vinniekq2 04-25-2013 08:02 PM

69 Camaros came with 6s to 427 rats,putting a 305 in that car is just silly,unless he is thinking its a 302?

the bore on the 305 is very small and does not allow much head flow,I would rather see him build a 307

Brandon H. 04-25-2013 08:30 PM

You won't be able to tell him X amount of boost will be safe or not, 10 psi from a big turbo vs for a small turbo vs twin turbo will get you very different results.

He needs a tuner, someone who has the knowledge of good tuning on turbos, because there is a whole hell of a lot more then just throwing new parts in the bottom end. Nothing against you, build the long block like f-bird 88 said and refer him to a good tuner, boost can get messy quick if its not tuned just right.

tresi 04-25-2013 08:36 PM

Sounds like he doesn't need you. He already knows everything. You'd be money ahead to stuff a list of other shops in the area in his shirt pocket and send him down the road.


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