Interesting engine combo in an old MM+FF mag

[85_SS_302_Coupe]

I'm flipping through the August '02 MM+FF and they have an article about different engine build ups. There is one in particular that has my interest peaked. They list it as a 306, but they also list the pistons as being stock forged pistons. So my first question before i get into the specs is, is that even possible? I didn't think you could go .030 over without new pistons...do you use fatter rings or something?


As for the specs, they go like this:

306ci
Stock short block (production crank/rods/pistons) with notched pistons
AFR 185 heads, unmilled, CNC ported
9.2:1 compression
Edelbrock Victor Jr. intake w/ Wilson open spacer (1 inch)
750 Speed Demon carb
MSD ignition
1 3/4 long tubes
Comp Cams XE266HR cam (.544/.555 lift, 216/224 dur, 112LSA)
1.6 RR's
3'' exhaust w/mufflers

417 hp/ 372 lbs/ft


Now, of course this is on an engine dyno, probably with an electric water pump and no accessories, but this engine should still make high 300s at the wheels. Does this sound typical? They also did the same combo only with the heads milled for 10.2:1 compression and made an amazing 454hp/398ft/lb with no other changes. That combo should still make close to 400hp at the wheels....hell my buddy's 347 with 11.5:1 compression is barely making that.

 

[vristang]

They probably meant stock style replacements....


Does this show that a 750 carb is TOO BIG for a 306?
Does this show that 1 3/4 Long Tube headers are too big for a 306?

 

[85_SS_302_Coupe]

They probably meant stock style replacements....


Does this show that a 750 carb is TOO BIG for a 306?
Does this show that 1 3/4 Long Tube headers are too big for a 306?

I dunno...good questions. They said in the picture caption that they're notched stock pistons, i don't think they would have to notch aftermarket pistons. I guess you can make up the difference with rings but i've never heard of doing it that way.


As for the carb i would've bet a 650 would've been fine but maybe they were looking for peak numbers. The same combo would probably make a lot more torque with a 650 and 1 5/8 headers. They did say that a duel plane intake would make a good 20lb/ft more and sacrifice less than 10 peak hp, but the torque numbers were still impressive for a single plane intake.

The thing that gets me is that it's a 454hp 306....it should still make a good 385hp at the wheels. There are guys with strokers making that kind of power, so why aren't more people making that kind of power with unstroked engines? Why can't i use a production 302 with notched pistons and make at least 350hp at the wheels??

 

[vristang]

Well.... NO you can't make up the .030" difference with rings....
The piston would flop around inside the bore and fail quickly.


The answer to your question...
It's all about the combo. That cam coupled with the Vic Jr, large long tubes, and good heads is what makes the power.

Heck, I've seen posts where guys claimed an AFR 185 was too big for a 306!

 

[85_SS_302_Coupe]

Well.... NO you can't make up the .030" difference with rings....
The piston would flop around inside the bore and fail quickly.


The answer to your question...
It's all about the combo. That cam coupled with the Vic Jr, large long tubes, and good heads is what makes the power.

Heck, I've seen posts where guys claimed an AFR 185 was too big for a 306!

Yeah, the whole thing is big parts on a small engine. What really kills me is the 454hp with the milled heads. That's damn impressive for an unstroked engine.

I forget to mention, peak hp came in at just 6300rpm...so it's not like they have high dollar high rpm parts on it.

 

[irish]

Of course, that is if you believe everything you read, my mustang runs 9s NA with a 9:1 compression ratio and a stock lower end and stock suspension. I just wrote that line of BS and if it was in a mustang magazine I could probably make a bazillion dollars selling whatever parts I put together for my miracle motor. Get my drift? Dyno numbers don't mean near as much to me as time slips.....

Matt

 

[85_SS_302_Coupe]

Of course, that is if you believe everything you read, my mustang runs 9s NA with a 9:1 compression ratio and a stock lower end and stock suspension. I just wrote that line of BS and if it was in a mustang magazine I could probably make a bazillion dollars selling whatever parts I put together for my miracle motor. Get my drift? Dyno numbers don't mean near as much to me as time slips.....

Matt

Well, dyno numbers and timeslips are truly apples to oranges. I'm running 12s with far less than 300hp at the wheels. Imagine what i could do if i had 454hp at the flywheel to play with.

Yeah, you can't believe everything you read...that's why i'm posting about it

 

[Duncan McDougal]

Does that article have an expanded dynograph or just peak numbers? I would like to see the area under the curve if you know what I mean.

 

[NIKwoaC]

If you can make torque at a high enough RPM, any HP number is possible. The issue is, most typical 5.0 combos you see on the road use heads and a cam that stop making torque after about 5500 rpm. That's not to say they don't perform well below that. That engine, with the 185s and the 750 carb, I'm sure was not out of breath at 6300.

Did you see October's issue of Car Craft? They built a 331 that made 500HP. It also had to scream to 7000+ rpm to do it, and obviously, it had a soft low end.

 

[85_SS_302_Coupe]

Does that article have an expanded dynograph or just peak numbers? I would like to see the area under the curve if you know what I mean.

Yeah, i'll try to take a pic of it or something and post it. They're pretty small but you get the idea. The curve isn't really as soft as you would expect, but it's not broad by any stretch. They comment about swapping to a duel plane and say "if it was anything but a dedicated drag strip combo" so i don't think low end is the point with it.

 

[HaynStang]

Those parts making that kind of power on a 306 isn't that hard to believe; but that the motor made those numbers at that RPM and with that compression is a little surprising.

A 306 may be fairly small for a V8 but it's still a lot of displacement in a much more general sense... enough to make plenty of power if the airflow is there, and with that combination of parts the motor is definately capable. But 6300 RPM seems a litttle low... I'd like to see what that same combo would do at higher revs, I would assume it would keep making power...

 

[85_SS_302_Coupe]

Well, don't get mixed up...there's 2 combos i'm speaking of. The 454hp was with a milled version of the heads that made 10.2:1 compression, the 9.2:1 only made 417hp, but that's still pretty damn good.

The thing i'm curious about is MY setup. I have the same intake and a similar cam, but my heads don't breath quite as well and i have a 650. I'm just wondering how close i could get to those numbers, or if it's all just magazine miracles at work.

 

[Stopsign32v]

Don't believe everything you read.

 

[NIKwoaC]

Well, don't get mixed up...there's 2 combos i'm speaking of. The 454hp was with a milled version of the heads that made 10.2:1 compression, the 9.2:1 only made 417hp, but that's still pretty damn good.

The thing i'm curious about is MY setup. I have the same intake and a similar cam, but my heads don't breath quite as well and i have a 650. I'm just wondering how close i could get to those numbers, or if it's all just magazine miracles at work.

You won't know until you try it yourself...