RB83L69

This came from a 305 yesterday...

It is in emissions trim so it could probably be a whole lot better with minor tweaking. It had the stock air cleaner, intake, chip, and carb, and all emissions devices installed and operating including the EGR, AIR, & cat. The A/F ratio was between 12.5 and 13.0 all the way through the run, so the carb (stock computer-controlled Q-Jet) is set about right. Total timing at WOT was 41° from 3300 on up, with no knocking. The red curve is actual RW HP, the green curve is calculated engine HP using 20% drivetrain loss. The blue curve of course is torque, the actual rear-wheel value that the others are derived from. Outside air temp was about 76° and this is at sea level, or about 20' above sea level anyway... the Pacific Ocean is visible from the dyno. Some of you guys in the So Cal area might know the shop, it's Scott's Automotive in Leucadia on the north side of Encinitas, on the PCH.

And yes, it is definitely a 305 (well, 310 or whatever, it's .030" over).

Opinions? Comments?



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"So many Mustangs, so little time..."
ICON Motorsports

[This message has been edited by RB83L69 (edited August 18, 2001).]

rezinn

According to the main page, an automatic 83 z28 with carb put out 150hp@4000rpm and 240ft/lb@2400rpm.(Im guessing auto from 20% loss) You're getting 213hp@4475rpm and 282ft/lb@3350rpm and at higher rpms.. I would say the extra 5 cubic inches are negligible, so you were able to put out 63 more horsepower and 43ft/lb more torque than stock, just by advancing the timing?

RB83L69

Ummm.... no. That would be preposterous to say the least. There are a few other minor differences.

Also BTW the ratings you quoted was for the LG4 at the crank. This is a L69, which was rated at 190 HP from the factory at the crank. So it's actually something more like a 45-50% increase over stock. It's not far from double the crank output of a stock LG4.

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"So many Mustangs, so little time..."
ICON Motorsports

[This message has been edited by RB83L69 (edited August 18, 2001).]

jcb999

sounds like a stout 305. I thought your 400 also made about 280rwhp. Was there a big difference in the torque?

ede

ok i'm impressed, but it doesn't take much to impress me. what heads and cam?

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Vader

RB is pleased, Ede is impressed, and I'm just confused. I understand that the "crank horsepower" number is interpolated from measured data and some presumtions, but the preogrammer of that dyno eveidently didn't attend the same physics/engineering lectures I did. Horsepower and torque must (by definition) become one in the same at the divisor RPM number (5,250). What's wrong with this picture? I've seen some graphs that touch at that point and HP and torque continue on the same plot for a period (on high RPM engines) but eventually HP must exceed torque on the upper end.

See why I'm confused?

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rezinn

Since you said 20% loss I presumed it was an LG4 engine. I believe 15% is the acceptable loss for a manual, which the main page shows is the only way the L69 came stock. What has been done to this engine?

RB83L69

The HP and torque curves do in fact intersect at 5250 RPM. The red curve is RWHP, the blue one is RW torque. And, as it should be also by definition, the HP curve is above the torque curve above that RPM. Of course the motor had pretty much cratered by then so it doesn't really matter all that much.

It has a pair of 186 heads (69-70 double-humps) with a gentle bowl port job, enough polishing to remove hot spots, and not much else. The cam is a Comp XM264HR-12 (got it cheap), with Comp 1416 1.6 roller-tip ball-fulcrum rockers. It has Edelbrock TES. Most everything else is stock, with all the sensors and other crap installed and working.

The 400 that used to be in this car did 284 HP and 373 torque at the rear wheels, with the L69 air cleaner, a Performer not RPM intake, and the same exhaust. At that time it had a Comp XE274H cam and a Holley 6211. So that's about right... these numbers are about ¾ of what that 400 did.

The guy at the dyno shop has a friend with an engine dyno; he says he has taken a number of engines, run them over there, then put them in cars, and run them on his chassis dyno. He says the lowest driveline loss he's ever seen when measured that way is 16%, and that was on a circle-track car with a Powerglide with a metallic drive instead of a torque converter; he says he usually sees a difference close to 25% between those 2 particular dynos. This car is a 5-speed, but due to some limitation of his dyno, he checked it in 3rd gear rather than 4th; so the loss might be a little higher that way than one might otherwise see. So I chose the 20% figure for calculating crank HP merely as an approximation, not as any kind of proven reality. Take that guess with a grain of salt or feel free to use your own preferred loss factor, it's all just a guess anyway. The rear wheel numbers however don't lie.

I wan't particularly impressed or pleased, or disappointed or surprised for that matter, as I had no particular expectations for what it would do. I kind of halfway expected from the way the car drives that the numbers wouldn't be quite that high but the peaks would occur at a higher RPM, since that's how it feels to me. But all in all it's OK I guess, for a car that passes CA emissions. Dyno man couldn't remember ever running a N/A 305 that did any better.

I was kind of hoping to show what a 305 can do in the right circumstances, both good and bad. This engine has close to 50% more output than stock, with alot of the stock stuff still on it. This does a fairly good job of illustrating where the bottlenecks of the carb motors are as they come from the factory: exhaust, cam, heads. Apparently those 3 things took this one from 190 HP and 240 ft-lbs to somewhere around 265 HP and 350 ft-lbs, and it still passes smog. Intakes, cabrs, etc. aren't all that necessary at this level. Of course to get it much farther, that stock intake would have to go. I believe that's the next bottleneck.

I'll have to run it at the track and see what kind of times it puts up. I suspect it might beat alot of L98s.

Now imagine that it had 45 more cubic inches.... and you can see why it makes more sense to do this to a 350. I should have taken my own advice.

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"So many Mustangs, so little time..."
ICON Motorsports