I am building up a peppy little 305 for my 280zx swap (mainly because I got the motor for free, and I'm not one of the anti-305 people) and am almost done.
So far, I have some patriot alum. heads, ~10:1 comp, .040 speedpro hyper flat tops, stock powdered metal vortec rods w/ ARP bolts, freshly cut 1 piece stock CAST crankshaft, and a xr282 hydraulic roller cam w/ 1.7 rockers, pro products single plane intake, and a 600cfm edelbrock 1406 carb. It's not 100% built yet, but those are the major components.

I plugged all of the specs into desktop dyno with my head flow numbers, and I get almost 500 horsepower and about 425-ish torque. Only thing is that it looks to need some RPM to get that kind of power. here's a screen shot of the graph (http://img511.imageshack.us/img511/6524/305ti4.jpg). The peak of the power curve is about 7000rpm. Are the power and torque numbers somewhat accurate?? I know that's supposed to be flywheel power, but those numbers seem a little high to me.

Basically, what I'm wondering is if a motor with these specs can withstand 7000 rpm assuming everything is new? I would love to be able to shift this thing at maybe 7200 rpm to stay in powerband, but I'm worried that the stock cast crank and powdered metal rods are going to break.

also, I don't want to turn this into a 305 vs. 350 or anything about what I "should" do.. thanks :)

Yeah, they seem a bit high to me, too. However I'd think with a cam that big on a 305 that would be where it would peak out IN THEORY. I think the real world issues will hold it back considerably from that number.

First off, I'd like to know the specs on those heads. I wonder how you get 10:1 with flattops. Stock 58cc 305 heads with flattops will only get you about 9.5:1. If those heads have typical 64cc chambers you're even lower than that.

Also, I didn't realize Patriot made a 305 head. Most aftermarket aluminum heads will have 2.02/1.60 valves (that's what your screeen shot shows) and those might be too big to fit down the little 305's bore. Especially the large intake with the massive lift you're planning to throw at it. Some of the 305 guys here could tell you the usual limits for that kind of stuff better than I could. But .578" lift with a 2.02 valve down a little 305's gut sounds like you're way over the limit- maybe even to the point of physical contact between the valve and the bore. Almost for sure, massive shrouding issues.

Last comment about the heads.... never beleive ANYBODY'S published flow figures. They're almost always higher than actual. And when used on a small bore motor valve shrouding issues will lower them further still.

1.7 rockers with that roller cam in the 7000 RPM range doesn't seem likely. Many guys run into problems with hydraulic rollers down as low as 6000 even with lower ratio rockers unless they spent some time and money really setting up the valve train properly. I'm not a roller cam kinda guy so I'll let somebody else give you an idea how feasible it is to do what you're trying to do with that cam.

Putting the HP issues aside and answering your direct question...... you're on the ragged edge with rods and crank at 7000. You have upgraded the rod bolts and that's a good start- they're by far the weakest link. I take stock cast crank and stock rods to 6500 all the time with nothing more than what you've already done. But that's about as far as I trust the stock stuff even if it's only going to see those RPMs for brief periods of time (drag race).

Oh come on,, let's turn it into a 350 vs 305 debate,, what's the fun otherwise?? <grin>

With no questions asked about the 'why',,, I can't say anything that Damon hasn't already said. Your going to have serious issues making this all fit together and work. And just to show what you get from D-Dyno,, go in and replace the valve with a 2.10" intake, and set lift to .900 with 1.9:1 rockers. This is an obvious impossibility with the heads, rockers and bore clearance, but I bet D-Dyno happily reports another 100, 150,, maybe even 200HP more. D-Dyno assumes you have done your homework, and worked through all the issues of parts not fitting together. Be carefull what you believe there, I don't see a 305 making 500HP n/a unless it's a comp-eliminator type motor,, sheetmetal intake, splayed valve locations, 14:1 spinning 9000rpm.

You want a dynamite 305, then you should build it. Just be cautious and make SURE you research what will and what will not work, and what the results of different combinations may be. As Damon said, I think a 1.94" valve is all you can possibly use without dramatic valve shrouding. GM didn't put 2.02 or larger valves in the HO 305 for good reason.

If this is going to be a purposely built drag motor that is going to spend most of it's life above 5000, then a cast crank is not a wise choice, nor are the stock rods. To make HP with the smaller cu. in. is going to take rpm's (just as D-Dyno reported) To survive reliably in the 5000-7500rpm, 500+HP range, it's going to take quality components. Anything less may work,,,, for a while. But reliability is eventually going to be an issue.

Just my humble opinion,,,, making 1.3 to 1.4HP per cu. in. is a pretty serious motor, in that light if you make 375-400HP with a n/a 305 you've done very VERY well. (because of the valve shrouding / small bore-long stroke issue) 375-400HP at 6500-6800rpm or so is not at all out of the realm of 'fairly reliable' with a stock crank and good factory rods. You could always find a steel 350 crank and with the cost of a good Scat I-beam rod these days (compared to totally refurbishing a factory PM rod with ARP bolts),, your going to have to balance this thing anyways so the 350 steel crank is a reasonable option for reliability.

(whew, I can't believe I got all the way through that without bashing the 305 ;) )

Whether you want to hear it or not, you have already wasted time and money on the 305 build. Just because you got it for free doesn't mean it was a good deal overall. You can either cut your losses now and build a bigger cube engine, or spend even more big bucks trying to polish a turd.

It is pretty far fetched that anyone will look under your hood and be happy to see a 305. A 350 or 400 won't look any different to 95% of people out there. People will be impressed when your car goes faster than theirs. So if your are looking for the awe factor...

Marv and Damon, thanks very muchfor the advice.
The valve shrouding is what my #1 main concern was. I talked to a bunch of other machine shops in the area about the heads (they're "vortec" style w/ the heart chambers but w/ the use of a non-vortec manifold.. not specifically for a 305, its just their "small block chevy" head), and everyone said that the 2.02/1.60 valves were only .030" - .035" wider (from outside of intake across the middle to the outside of the exhaust) than 1.94/1.5 assuming the same spacing. After I bored my block, I stuck one of the bare heads on with valves and checker springs in one of the cylinders and I was able to push down on the valve about .745" before it hit the cylinder wall. With about .020"ish distance beween the exhaust and intake valves on my head, it works out to about .070" side clearance between the valve and the cylinder wall. For the 1.7 rockers, I built a pretty rad 302 ford last year that had an aggressive hydraulic roller cam with 1.7's, and the guy I built it for spun it up to 7500-ish quite a bit.. so I'm not worried about the 1.7 rockers causing problems with the lifters.

the compression ratio.. I'm at 3.776" bore, the heads have 56cc chambers after a little surfacing (they come w/ 58cc.. and yes, I've cc'd them myself to get 56), and I'm using a .035" compressed 4" bore head gasket, my speed pro hypers have -5cc of dish (valve reliefs), and I surfaced my block so the piston deck clearance is about .012". Using a calculator, it comes out to exactly 10:1. I know you shouldn't trust calculators, but I am just getting a general idea of what the comp is going to be.

In all honesty, i don't believe the numbers in D-dyno.. I mainly use it to see what the powerband from whatever mod I'm adding will be. I expect it to be about 350-ish to hopefully 400 on motor, and that's enough for me. My only concern was the rpm.

lluciano, while I respect your opinion, I also disagree with it. I work at a machine shop, and so all of this work I'm doing is in my spare time and on the weekends and costs nothing to me. It doesn't cost me anything because I do everything myself. The only things I actually had to buy for the motor are the heads and the cam.. all the other stuff I get from work. The reason I was going to build it with stock powdered rods and the stock cast crank was mainly because I don't want to sink too much money into it, yet get the best results I could from stock chevy parts that are free to me. Everyone at work has told me to ditch it and get a 350 or 400.... and I would do that if I'm going all out, but I'm not. 350-400hp in a 2700 datsun is going to scoot, and that's all I want. It's not like all this suff won't work for a 350 if I ever decide to build one... just put all my stuff on/in a 350 shortblock and bam.. If I was wanting to go all out, I would just finish my almost done propane powered, twin gm-8 turbo, venolia/oliver internal VH45DE in my 91 RX7... but since I'm a fulltime college student along with working fulltime doing machine work, my only goal right now is putting together a low-budget 305 that will make my datsun FUN to drive.....

I just got an offer for a brand new Eagle cast steel crankshaft and a set of scat I-beam rods... would the eagle cast steel crank and scat rods be able to handle 7000-ish rpm decently?

Better than stock if it is the 9000 "cast-steel" jobber imho..

Looking back at the heads again...

315hp FI 283's came stock with medium valve -461x heads and the old very low lift Duntov solid cam..

I think I have read where the old-timers used big valve heads on a 283, but then used a low lift hy-po cam so that they didn't hit the top of the cylinderwall above say .450" to .470" of actual valve lift so please consider ALL this!!

I do know that the .020" over, '66, 283 I finally got that once was my air-head Nephew's had a good set of big valve -291's on it and a TRW TP-146 hy-cam at 308/246 and only like .433" lift....

It only had like an 8.1 to 1 CR. and a DCR of like 5.2 so couldn't hardly pull me off my throne even tho it rpm'd fine!!

So please go from there..

pdq67

Actually, I DO trust compression caculators, but only when the specs being put into them are correct. Math never lies. Only bad input gives bad results.

I'd be interested in hearing how this motor runs in the real world.

Just an FYI- if this thing comes anywhere close to 500HP I think a little 600 CFM carb will be choking it. If it stays together at those RPM levels and makes good power up there I think a 750 would be more appropriate to match the combo. If you already own the 600 then by all means use it. If it looks like the motor is actually working strong in the upper RPMs then go back and try a bigger carb.

i say run it till it breaks. its only a 305 so its not a big deal if it does. i no a guy that had a 305 and he ran it all the way up 8000 and it held together, his was running about 300hp

i say run it till it breaks. its only a 305 so its not a big deal if it does. i no a guy that had a 305 and he ran it all the way up 8000 and it held together, his was running about 300hp

It is not "only a 305" anymore. Whether he got if cheap or for free, the rebuild and upgrade value is still there. Not to mention the time and money for assembly. It will still suck if it grenades.

Actually, I DO trust compression caculators, but only when the specs being put into them are correct. Math never lies. Only bad input gives bad results.



That reminds me of the morons that sit at their computer and call it "stupid" because they miss-typed something. My dad is like that. So what is it supposed to do, anticipate your mistakes? Same goes for math. Math doesn't have an opinion or state of mind. It just IS.

not my ride but i'll throw out a proven combo..this is in a 3rd gen though.

Induction\Engine:
- 113 heads. bowl blending. polished chambers. 1.94/1.5 backcut valves.
- crane powermax solid lifter cam: 238*/248*@.050 .480"/.500" lift 114lsa
-comp pro-magnum roller rockers
-holley street dominator intake
-holley 650 double pumper
-10.17:1 compression, .015 shim gasket

Drivetrain
-28" tall tire
-700r4
-4000 rpm stall
-3.73 posi rear
Chasis/Suspension:
-lca relocation brackets
-boxed factory lca's (still got rubber bushings...wouldn' hurt to replace those with some tubular ones and poly bushings)
-poly tranny mount
-poly torque arm mount
-subframe connectors (welded in)
-spohn non-adj. panhard rod w/ poly bushings
-solid motor mounts
-v6 springs
-stock front struts (to my knowledge)
-monroe replacement shocks out back
-stock torque arm
-no front sway bar
-poly endlinks on rear sway bar
-running on a 275/60/15 M/T ET Street Radial (~28x9)
Misc:
-2910lbs minus driver
-15" of vaccuum @ 850rpms in park with 18* initial.
Times:
60ft - 1.694
1/8th - 7.906@85.69
1/4 - 12.503@106.83 @5300 RPM

305 buildup's, have a good read!

pdq67

"I found the old article telling about the maxed out combo for a 305 so here goes. It was in Hot Rod Action Series Volume 2, Number 1, early 1984 booklet.

They started w/ a stock 9.5 to 1 CR. shortblock, cast pistons and all! Then added 350 rods b/c the 305's are too skinny!!

They made a 10.6 CR. 305 using -041 number heads that were reworked to 59 cc w/ 1.94"/1.5" valves. Deck height is .035" w/ a stock 305 head gasket, so is close to say the least! Intake ports were untouched w/ only bowl work done. They taped up the pistons and ground some exhaust valve clearance so the valves had enough room! Did some bowl work on the exhausts too. Manley Pro-Flo valves.

The cam was a CC magnum 292H w/ 244 duration at .050", 110 lobe centers and 501" lift. They used .100" shorter pushrods to correct the valve train geometry.

Headers were 1.75" four tube w/ 23" collectors and a pair of Supreme Super C turbo mufflers!

Carburetion was a Victor Jr. and a reworked 650cfm Holley double-pumper!

Ignition was an MSD-6A and an MSD extra duty distributor(?). A 4" K&N filter. A windage tray and crank scraper in the pan!

Here are the Engine dyno numbers!

3500rpm - 210hp -- 314t - .398 BSFC
4000 - 243 -- 319 - .394
4500 - 270 -- 320 - .411
5000 - 316 -- 331 - .417
5500 - 361 -- 344 - .419
6000 - 376 -- 335 - .444
6500 - 378 -- 305 - .451
6850 - 386 -- 296 - .461
7200 - 402 -- 287 - .479

Here it is!!

From a 1995 Chevy High Performance article.

305 Engine Build-up.

1 ’69, 041 double hump 1.94”/1.50” valve heads cut to 59 cc’s. Bowls blended and only the exhaust ports polished.
2. Manley Pro-Flo valves, PN 11560 intakes and PN 11559 exhausts.
3. CC 292 Magnum hydraulic cam, 292/244, 110/106, .501” lift.
4. 350 rods rebuilt with good bolts and nuts.
5. L-69, 9.5 to 1 CR. LU5 fuel injection short-block engine with stock head-gasket gives 10.6 to 1 CR. Or a
6. LG4, 8.6 to 1 CR. engine will give 9+ to 1 CR.
7. Deck height was .014” down with stock four valve notch cast pistons.
8. Quench was about .035”.
9. Hooker 1.75” four tube long headers with 3.0” collectors. PN 2110 for a Third Gen. car.
10. Holley 650 double pumper PN 4777 and an E-brock Victor Jr. intake.
11. 4” K&N open filter.
12. Good Electronic ignition

The little bugger made like 402hp up top!! They ran it until she spun a bearing or just came unglued!

AND

An old RHS, Memphis, TN, 305 motor build-up that makes right at 300hp. http://www.goingfaster.com/spo/290hp305.html
Chasis Dyno Test
7000rpm --- 300hp

And Hotrodding the 305!
http://www.goingfaster.com/spo/modthel03.html

And an article from mw66nova
http://www.thirdgen.org/techboard/organized-drag-racing-autocross/394788-new-bests-two-walter.html
new bests for two Walter Racecraft 305's!

well, Kody and I were able to get out to the track for one more night of racing tonight before we called it a season. i was totally stoaked at the times we got as i totally didn't think we were going to do as well as we did. remember, these cars are 100% daily driven and 100% naturally aspirated. race weight for Kody's car with him in it: 3255, race weight of my car with me in it: 3220

i'll start with Kody's car cause i haven't really told many folks about it. combo is super simple:
-305 out of ssean92's 1992 RS
-416 casting heads with backcut valves
-lt1 cam
-crane energizer aluminum roller rockers
-hedman longtubes with manderal bent y-pipe into a 2.5" dynomax catback with homemade cutout
-holley street dominator intake (the smaller of the two, basically a performer) and an edelbrock 1406
-2100 stall converter w/ 700r4 and 3.23's with a 275/50/15 mt ET Street Radial.

previous best was in the upper 15.2x range, tonight with the cool air it went 14.67@93.7mph. we went from a 28" tire to a 26" tire and rebuilt the carb and added more timing. the car needs some more gear bad. timeslip for that pass looked like this:
r/t: -.123
60': 2.205
330': 6.166
1/8: 9.441
mph: 75.20
1000': 12.276
1/4: 14.678
mph: 93.73

we were hoping for some 14.9's, so to get a high 14.6 out of the car was like walking on sunshine.

now for my car. alot of you know that the solid camshaft that was in the car was hurt and i put in a used 280H cam that my friend Eric gave me. i totally didnt' expect to even break into the 12's and i did that at the shootout we had back in the end of september with a 12.97 @ 103mph. air was SUPER nasty that weekend and i was trying to run a 13.0 index class so i wasn't looking to go blazingly fast anyhow. the previous best for my car with the solid cam in the 305 back in may was a 12.50@106.8mph. that was with hotter weather, a water pump drive kit and manual steering. this evening the car had full accessories (water pump, alt., and i put the powersteering back on) so i was going to be happy with 12.7's. i figured that would be possible because of the cool air. after screwing around on a few runs trying to get reaquanted, i clicked off a 12.42@107.49mph! the timeslip for that pass looked like this:

r/t: .088
60': 1.694
330': 5.035
1/8: 7.862
mph: 86.33
1000': 10.328
1/4: 12.425
mph: 107.49

after that pass we decided to see how fast we could actually get the car to go. i knew that the powersteering was worth atleast .1 so i snatched the ps pump belt off the car and proceeded to go 12.39, followed by a 12.34, and then finally a 12.31@108.48mph!!! that pass looked like this:

r/t: .150
60': 1.678
330': 4.994
1/8: 7.797
mph: 87.05
1000': 10.240
1/4: 12.318
mph: 108.48

as you can tell, i'm so pumped about it that im writing a thread about it at 1:18am to tell ya'll. anyhow let me know what ya think. oh, and check out a pick of Kody's ride all ready for the track wearing the mickey t's!"

I have a 305 with a 280H cam with everything else mildly built and a stock crank and low compression pistons (8.3ish).

I have driven the car hard up to 7000-7500 many times with no problems (yet). It has been revved up to 8000 numerous times as well. The only thing is my engine peaks out its power at around 6200 rpm while yours would be putting down much more power at the higher rpm. The crank has been abused pretty bad for 40,000 miles and has held up.

Knowing if a crankshaft will hold up requires way too many factors to ever be sure. I've been pretty lucky so far but it doesn't mean it will work every time. I would do your best to play it safe.

What does that thing run in the 1/4 mile? Especially if that engine has stock heads, why has it seen rpms so far past peak power so many times?

Just Get The Bottom End Balanced, Use Arp Rod Bolts And You Are Good To Rev............

What does that thing run in the 1/4 mile?

I have that cam in a 305 on the engine stand in my garage. mine had swirl port heads, pretty much the same compression and ran the stock converter. I would say I was in the high 16's or so.:cool:

I would a never thought a 280 Magnum hy-cam would do 8,000 rpm.

W/ a set of solid lifters on it and a tight .004" to .006" hot lash, YES!!!!

But why when this CHEAP little PAW solid lifter jewel will, if they still sell it.

280/246, 108/108, .498"/.498" gross lift and need's .030" lash hot on both sides!

pdq67