stroked 409 RPM limitation

[61 Bubble]

I'm trying to get some info why the W engines seem to be a bit on the low rev'ing side as far as engines go? Most seem to say around 6500/7000 and I'm wondering why this is? In a bit of a dilemma with my 476"/409 and doing my research before delving into this head first like the other projects.

My 476"/409 I got of Jim seems to want to rev and I know Jim has vastly more knowledge on these then I do, so I respect and welcome his insight. He didn't run this motor to high and just wonder WHY these engine seem to be low rev'ing? and when you consider that there either short strokes, or stroked like mine with a 4.00" stroke and BBc rods.

Are there any guys out there that run these a bit higher in the RPM range? Like 7500/8000? IF these short block can hold that without beating themselves apart, I would like to have about 75/7800 RPM deal. Is that asking too much out of the old girl?

 

[models916]

Piston weight is higher than most. Longer rod helps move the pin up and allow a shorter lighter skirt. In the old days the heads were holding revs down in the useable range. Now days things are different.

 

[63 dream'n]

I believe BSL 409 Was shifting his Four bolt main stock block at 7400 rpm. He has a great video here somewhere on the site Showing 1 of his passes

Edit...........checked Brian's post ......he was shifting at 7700 rpm.

 

[63 dream'n]

Look up, YouTube. 61 409 at Epping

 

[jim_ss409]

For some reason the 409 has the reputation of being a low revving high torque engine. Probably because many people think it's a truck engine.
The stock 409 stroke is 3.50" which is almost the same as a 350 ci smallblock and the hi performance 409's had a factory redline of 6,200 rpm which was really spinning by 1962 standards.

There factory intake had 90 degree turns that limited the high rpm potential. I think a better manifold would have helped a lot. The hard turn just before the valve in the intake port also had to limit the rpm potential, although we've seen race engines with ported factory heads that rev pretty high.

I think the relatively heavy pistons and two bolt mains can give you problems at high rpm with a stroker crank. I had a rod bolt let go on a stroker engine that I was pushing to about 7,300 rpm. It had pretty good Eagle H beam rods with the standard cap screws. I think I'd at least upgrade to ARP 2000 series bolts if I was aiming to go much past 6,500 with a 4" stroker. I also think four bolt mains might start to look like a good idea at about 6,500 rpm, although many guys are revving that high or higher with two bolt mains. I think detonation is harder on the main bearings than rpm is.

Jim's aluminum 409 crosses the finish line at 8,200 rpm. (511 ci with a 4.25" stroke) but it has raised port heads which has to help. I'm not sure what rpm Dave Mills was turning but I think it would be in about the same range, and that was with his ported 690 heads. I'm guessing he'll be able to spin it even higher with the new raised port heads he's got on there now. I can't wait to see that car run at Bowling Green.

 

[Ishiftem]

I think it's just a numbers game. There are VERY few people building these engines to such a level that they would need to spin them to 7500. Most are street/strip cars. I think that's the only reason you are getting the info you have. No reason you can't spin one to 7500+ if that's the kind of power you are looking for.

 

[MRHP]

I would regularly spin my 474 to 7500 on the street. Did it for years. After finding out these heads are the limiting factor most times, and peak power is usually around 6500, I now shift 6200 or so.

 

[61 Bubble]

Thanks guys. Keep them replys coming. Just looking at a few things to do once these other couple jobs gets done. I don't want to try and put my BBc "mindset" onto one of these and end up busting everything for no reson at all. Once I get into this motor later this year, I can see what Jim did, and go from there. Sounds like bolts and a resizing job in order. Check the pistons and maybe a lightening program, and concentrate on the cam and induction.

Now don't get me wrong. This 476" motor MAKES power, and seems to have plenty of it. But when I bought it off Jim, it's been around and a good "going-thru" is in order. So while in there, just going to do some digging. Will get right into the 690 heads and see where that takes us.

Reason why? We did a 468 BBc last fall, HIGH pump gas, solid roller that looks 100% stock even with the OEM dual-plane intake and steel LS-6 heads. But the thing make TONS of power. 709Hp @ 6100 and 714Tq @ 4800. and that's not the big # dyno sheet. Customer was keeping that to himself. Were running out of carb, 4150. So with the 2 x 4's on these, might be able to run it up the RPM range and maybe pass this with a very respectfully manned, runs on pump gas, 409 based motor????

Time will tell.

Thank you all, John

 

[jim_ss409]

700 plus horsepower out of a stock looking engine is pretty cool.
It would be neat if you could rent a time machine and go back to 1969 with an engine like that.

If I remember right your 409 was either 9.42 or 9.48 to 1 compression. If you end up changing pistons, it sure would help to get the compression up a little.
The cam was 250/258 @ .050 .714 gross lift with a 110 LSA. I remember that I was going to order the cam with a 108 LSA which I think would have been better with the relatively low compression but I wasn't sure if the valve notches were deep enough for that.

I'm sure there's some power left in those heads if you install bigger intake valves and do a bit of porting.
The guys that do our engines got 625 hp out of a 476 with 690 heads using pretty much the same cam as you've got. I'm sure there's more power available with a bigger cam but it is pretty good just as it is.
Here's a link to a post about that engine...
http://www.348-409.com/forum/threads/flow-numbers-690-heads.28471/page-2#post-264237

 

[303Radar]

700 plus horsepower out of a stock looking engine is pretty cool.
It would be neat if you could rent a time machine and go back to 1969 with an engine like that.

If I remember right your 409 was either 9.42 or 9.48 to 1 compression. If you end up changing pistons, it sure would help to get the compression up a little.
The cam was 250/258 @ .050 .714 gross lift with a 110 LSA. I remember that I was going to order the cam with a 108 LSA which I think would have been better with the relatively low compression but I wasn't sure if the valve notches were deep enough for that.

I'm sure there's some power left in those heads if you install bigger intake valves and do a bit of porting.
The guys that do our engines got 625 hp out of a 476 with 690 heads using pretty much the same cam as you've got. I'm sure there's more power available with a bigger cam but it is pretty good just as it is.
Here's a link to a post about that engine...
http://www.348-409.com/forum/threads/flow-numbers-690-heads.28471/page-2#post-264237

Better take some modern tires with you in that time machine!

 

[61 Bubble]

Thanks Jim. If I had a time machine, it would be strange with guys like Grumpy asking me for help!!! 700+ with the OEM 163 intake AND 4150 carb!LOL And when MY ZL-1 gets dyno'ed in March, it should be more than this 468 had!

I think we can settle on 9.3 to 1 comp ratio in my 409 I got from you guys. With the solid, I seem to think it's in the 550Hp range, as we discussed when I was buying this. BUt was looking at the cam cards for both (another why I was asking about RPM as the cam wants 3000-7500 and you were mostly around 6000) and I believe that this cam is actually .735 I, E, lifts but with 1.73 rocker.

THEN this will get us to induction. BOTH my engine and the other one Jim listed, use the Edelbrock intakes. Now where would we be with the Speedport, or the NEW McQuillen 2X4???

Can a hyd roller, 690 headed, 9.3 to 1 comp stroked 409/476 with the NEW McQuillen intake and EFI make 625+Hp??

 

[Ishiftem]

I'm sure you could. I have 690 heads, Edelbrock intake, 260/254 cam with 660 lift, and 13.5 compression. I shift it at 6500 and it pushes my 3850 barge to 10.50s in good air. The intake and cam are the big choke points right now. Even with lower compression, a good intake will make up the difference to getting to 625 hp..

 

[Skip FIx]

"After finding out these heads are the limiting factor most times, and peak power is usually around 6500, I now shift 6200 or so."

If you do the math/formulas on airflow and CI of at least a stroker motor we are head restricted using standard 690/Edelbrock/Walla heads for high rpms. There are aftermarket SBC heads that flow more. BBC heads do flow better and the dyno results above on the 468 show a 6100 rpm HP peak.

My 600ish HP 470ci with ported E heads and ported intake flowing 304cfm @28" through the intake and head (got to look at both not just raw heads unless a real free flowing intake like the new one out)was not a high rpm motor. It is 10.25:1 pump gas solid roller 251/251@ 0.050

Yes the heavy pistons do not help but that is more ability to rev quicker and stress on rods.Neither does 3/8 stem valves for vale train stability

 

[61 Bubble]

Skip, looking over some of my research. I noticed that your flow number, 304CFM @28" THRU intake. Does this Edelbrock intake really choke off that much? I know for a fact what a GM "198" intake costs me on my ZL-1, and figured with this low number these heads actually flow, it wouldn't be as bad as the "198"? But must be wrong on that. Seems that the 690 heads are good for about 330 @ .700 in most cases (some more and some less). So I'm figuring that your Eddy heads should be in the 330 range as well, maybe more! So this intake KILLS that much flow????

If so, and the new McQuillen intake can get that back, hell that could be as much as 80-100Hp in the swap alone IF you can utilize these flow and RPM's? Umm

 

[dm62409]

The Edelbrock intake is a dual plane with turns in the runners. The McQuillan is a straight runner single plane which should help flow . That being said, I have never tested any intake, on any head design, that didn't drop flow a little bit.

 

[Skip FIx]

Intake kills it but the 881 did worse, and the single 4 aluminum did way more!. There is a definite different in the "short runner" not choking it as much as "long runner" that makes the turn. I want to think the "long runner" port was in the high 290s. And yep any intake will drop the flow although a=occasionally at one lift point it may pick it up s little as it smooths entry.

I think to get 330 out of a 690 head you either need a really good 409 porter that has done lots of these heads or a "generous" flow bench. I want to think the old 690s I've had for years that had some pocket clean up and port matching only go about 260 on the same bench as the aluminum Eddy heads.

Funny thing on flowing one of my Pontiac ported Edelbrock heads my old M/T crossram really killed flow and runners were about the size of the port entrance.

Try throwing a carb on the intake on the head, and even a aircleaner base and different filters and you really get things dropping! Although a paper filter only lost about 5 cfm on s 320 cfm bare head flow head. Heck my machine shop's brother has a new COPO stocker Camaro they have been flowing the cold air intake to tweak it even!

 

[Ishiftem]

330 cfm at .700 with a 690 head is very difficult to do. I think I am at 312 or so at .700 and 318 at .800 with a 2.275 intake valve and a LOT of porting. The pinch area is as thin as I can get it and a lot of bowl work. I have a 3/8 valve stem so that hurts a little. Unless you are stuck on using the iron heads (like me), you would be time and money ahead to get the edelbrock or BWR heads with one of the cnc programs out there to get 330 cfm. 330 out of a 690 would likely require brazing, welding, or epoxy to fill in certain areas and patch the holes in the port you are bound to make.

 

[BSL409]

You really do not want to be spinning these iron 409 blocks much past 7200 rpm even with the block being partially filled with hard block these cast cylinder walls cannot take the rpm for too long

 

[Carmine]

WOW. Some very serious RPM's there. I get nervous approaching 4800 LOL, Carmine.

 

[61 Bubble]

You really do not want to be spinning these iron 409 blocks much past 7200 rpm even with the block being partially filled with hard block these cast cylinder walls cannot take the rpm for too long

Brian, can you expand on this? I know we sucked a cylinder wall in on our Cleveland powered record setting B/D back in the day at 9800. So seen the carnage first hand in that respect.

You seem to be pretty knowledgable on these '09's. So what would be a safe over bore on say a '68 truck block, then RPM threshold?? And do you think an auto be better suited than a Nash 4+1? I have the Nash just sleeping on a creeper so thinking of replacing the BW T10, which would then work pretty well with the 3.36's throughout the powerband.

John