6T5RUSH

Thought I should post here...did all my questions & followed the many topics covering the conversion of hydraulics to solids (70 LT1 cam & lifters) like Allcouped up and others have done in the C1-C2 section. SWDuke is a big fan and I was encouraged by that fat torque band width achieved way down low.

So, long story short I'm done with the conversion (ended up rebuilding my 327 (.040 over) in the process. Visually the 327/300 block looks like a 327/365 version (factory 350/365 intake & carb (list 2818 Holley 600 cfm, vacuum secondary), water pump, idler pulley to name a few obvious changes.

Just came from the dyno shop Saturday. This shop dyno'd my '5 4 years ago. I had the luxury of seeing the best run from 4 years ago compared to my best run from this Saturday.

Frankly, I'm happy to say from my initial drive-in first pull, the shop was able to adjust the carb and timing to pick up 34 horses and 23 ft lbs of torque at the rear wheels. Good driveablity and snappiness are what my goals are. That's been achieved.

Now for the disappointment:

The car did not improve from 4 years ago...both horse and torque. The one key improvement though is the horse and torque carry on beyond 5,500, no drop.

The owner, Chris, of AP Engineering thinks my exhaust is acting like a restrictor plate....possibly a bigger carb would help too but he thinks definetely exhaust. Reason: I swapped out the stock heads and purchased a set of Dart Iron Eagle 180 runners, 64 cc's (2.02 exhausts). These heads were professionally ported.

4years ago:

327/300 converted to, what I think approximates the 350 horse. Original '461 1.94 heads ported, Federal Mogul cam CS186R (230/230, .480 lift with an LSA of 109), using 1.6 Crane Gold Roller Rockers, coupled with factory 2 1/2 rams horns and factory chambered side exhausts

Best Run: 216.6 Horse @ the rear wheels @ 5,000 r's with 266.7 ft lbs of torque @ 3,000 r's

Saturday 9/11/04:

327/300 converted to, visually, a 365 horse. Dart Iron Eagle 180 runners, 64 cc's ported heads, Federal Mogul (dual pattern cam CS1145 (242/254, with intake lift of .459 and exhaust lift of .485 with an LSA of 116). This is the LT1 factory replacement cam for the 70-72 solid lifter LT1 Corvette (and I believe the Camaro Z28). The heads were professionally ported. As a comparison, the shop flowed my '461 heads and compared this to the Dart heads after porting. The smallest improvement in flow on the intake side was 15% (all the way up to 20% at .500). On the exhaust side, the improvement in flow was a minimum of 21% to a high of 36% @ .400. Carb, intake and exhaust identical to 4 years ago.

As part of the tweaking done with an O2 sensor, the factory jet settings of 65 fronts and 76 rears were bumped 3 #s both front and rear. Doing this picked up 25 horse and 18 ft lbs of torque from my initial base drive-in run Saturday. Additionally my timing was set at 9 intial, all in @ 3,500. This was adjusted through dynoing in increments of 2 degree bumps to 13 initial, all in @ 3,000.

Best Run Saturday after tweaking: 225 Horse and 260 Ft lbs of Torque.

I have to believe these aftermarket heads, ported are scavenging the exhaust to a point this "air pump" can't push it out, therefore a restriction results. The shop indicated that a good of headers would free up 30 to 40 horses. I know this improvement would be there but I was hoping to keep the "stock look" and, frankly achieve #s close to 280/290, both horse and torque.

Your thoughts/suggestions on this setup are appreciated.

PS If my website was working I'd post these dyno sheets there. The curve is nice and long and sweeping accross. I've got the sheets in a .pdf file if anyone would like to host 'em...let me know.

PPS. My best run at the track under hydraulic setup was 14.2 @ 98mph with a lot of tire spin on street radials. I am going to the track this weekend and will post my real world experience Sunday.

Thanks!

Jim

skid

Check out www.castheads.com and see how they enlarge the ports on the ram horns using an exhaust gasket as a template. I've done this my ram horns and noticed a difference by seat of pants. You can pickup significant flow doing that. I would also go with a dual 2.5" mandrel bent exhaust with an H pipe or an X pipe. Make sure you have mufflers that can flow enough for your hp. Dynomax publishes flow figures for their mufflers. You need 2.2cfm/hp divided by 2 for dual exhaust for your flow. Best of all, it all looks stock

Also check out their stealth intakes; look stock but flow like an rpm airgap!

6T5RUSH

skid,

Thanks for the tip on the rams horns. That's a cool site. I've always felt that the rams horns function better than some people think. This outfit does make 'em flow better.

Well, the real world awaits and we'll see how she performs at the track this weekend. Participating in a muscle car fun event. I had posted this thread on the C1-C2 forum as well and the one thing I do need to check is: are my secondaries opening fully at WOT. I would have thought the dyno shop would have checked for that...I know they did 4 years ago...different owner today.

Skid, if I didn't already have factory chambered side exhausts, I'd do that X pipe. But, to convert over to an undercar exhaust now would be $$ when you consider all the incidental things. Rear valance panel, priming and painting to match, rocker molding, all the metal tabs that ain't there now + the complete exhaust system. Realize I'd get good money for the existing side pipe system to offset this...but, I REALLY like the look and sound. I'm thinking maybe I can improve on the existing side pipe flow system. I know the 2 1/2 inch pipes actually taper down to 2" once they curve around to the frame rail. Maybe just maybe a true 2 1/2 inch systme to the tips would help flow.

Here's a link to my actual runs + a comparison of my original '461 heads to the Dart Iron Eagles (180 runners, 64 cc), professionally ported.

http://nonethewiser.net/temp/6t5rush.pdf

Thanks again for a fix on flow.

Jim

comp

try new pipe first

gkull

I can't remember where i saw them. Some company had cast iron shorty type headers which gave the look of stock to the untrained eye. I've also seen New improved versions of the ram horns that had larger primaries and exhaust connection in the back of Chevy High Performance mag.

The side pipes are not for performance. You really need 2.5 to 3 inch

Simmo

The Holley can be modified for more airflow without hurting response infact you can improve it. Experts might be able to comment on this. New baseplate with bigger butterflies, slab mill throttle shafts, dome nuts. Remove choke assembly. Manifold can be improved upon too.
Strongly recommend you get David Vizzards book on intakes and carbs.

How thick are the head gaskets? What is your quench? if it has been increased you have lost horsepower. As you have put in a longer duration camshaft technically you need more compression to maintain torque output.

6T5RUSH

gskull,

I agree on the need for at least a true 2 1/2" pipe all the way back.

Simmo,

This Vizzard book on intakes/carbs sounds like a book I need to add to my library of tech articles on improving this 327.

I'm also going to check with Don, the engine assemblier/builder on how thick the Felpro gasket is.

Thanks for the suggestions guys. I'll post my results this Sunday on my real world experience at the strip.

Stay tuned!

Regards,

Jim

mike 1985

hey Jim

Someone here at work showed me your head flow sheets . The ex. port flowed really well. I would have not put a split lift cam in there. The cam you choose is 30 year old technology ( it may be good) but i believe there's better today. For instance, most HP , NA cams are on a much tighter LSA than a 116 ?? Did you measure the DCR with the new cam ? Pat Kelley from the Chevelle web site helped me with this, i believe there's guys here that know how to calculate this too.

Did you do a cranking compression test on the motor before and now ?

I know you like to have the stock look, but i think a performer RPM and a bigger carb would really help the motor, especially with your heads. If you want to see just how restrictive the ex. is uncap it for a run at the track ( if possible).

Good luck racing.


Mike

Evil_1979

Hey Jim,

Someone in the C3 classifieds section (parts for sale) has a pair of 2.5" Rams horns for sale. $130 for the pair (list is $130 each).

Just thought you may be interested.

Cheers!
~Kevin

SWCDuke

Typical pocket porting improves exhaust flow more than inlet, and the need for the early opening LT-1 cam exhaust lobe is not really necessary, but on the other hand it doesn't do any real harm. The early opening exists because in OE form the exhaust ports are quite restrictive relative to the inlet ports.

LSA is meaningless unless it's compared to a cam of equal duration. The effective duration at .050" above the lash point is about 229/237 (this is what should be compared to a hydraulic cam, not the 242/254 duration at .050" above the base circle) , which is about the limit for a reasonable high performance street cam, and the relatively wide lobe separation limits overlap to what is effective with exhaust manifolds while closing the inlet valve relatively late to improve top end power. The "116 LCA" is not actually the lobe center angle because the lobes are asymmertical. The 116 degrees is actually the cam angle between the points of maximum lift. The actual cam angle between the true centerlines is 114 degrees.

Most back yard hot rodders and cam grinders can't get beyond the simplistic "LCA" "centerlines" and "duration at .050", and don't even acknowdege the existance, much less the benefit of asymmetrical lobes. This is at best a view of valve timing from 100,000 feet. There's a whole other world of overlap and duration in square-inch-degrees and and how to achieve an optimum design utilizing available wave dynamics, while controlling valvetrain dynamics so the valvetrain will live forever.

There is not a cam on the market today that will provide the torque bandwidth and peak power of the LT-1 cam without compromising the bulletproof OE valvetrain reliability.

Duke

427Hotrod

First off, let me say I love threads like this. Lots of good info comes from folks giving lots of details and trying to keep testing accurate.

Looking at the two combos, there are some pretty distinct differences. That first hyd cam with 109 LSA had to provide more overlap than the 350hp one would have. While it was considered a decent cam in it's day, I'm betting the one you had in there was much better overall. As Duke said, there is no way to know without some serious Cam Doctor type work, but I'm guessing. The 1.6 rockers were also helping it some, so you were likely doing better than a basic 350hp would do.

The 180's are of course better, but it's not impossible to get pretty decent power out of a set of 461's on a 327. We recently had some geat runs using a set of 461's on a 327 and a roundy rounder type solid flat tappet. We just installed ported SR Torquers on it, but haven't had a chance to get new data. Scattered differential on it's first track run!

The LT-1 cam is a good street piece. I used in in a 350 a few years ago with 1.6 rockers on a heavily ported set of GM Bowtie aluminum heads (207cc- 302 CFM @ .650 lift) and it was killer. You can make great street power with it.

Is there any doubt the vacuum sec carb is not opening all the way? I often find on chassis dyno runs that they will only partially open. We picked up over 30 rwhp on a buddies 351 Mustang when I reached over and shoved the secondaries open on his 750 Holley under full power. We later installed a Double pumper and eliminated the issue....made it into a whole new car. The idea that vacuum secondaries are the best on the street is BS usually. A well tuned mechanical carb will kill it everytime. If it still has the stock spring in diaphragm, that could make a huge difference.

I think you can easily exceed 300 rwhp with rams horns and a real 2.5 " exhaust. If you have the factory type inserts in your sidepipes, you need to look at how small they really are. New mufflers under the covers can make a huge difference even at this HP level. But since you say it's hanging on better at high rpm, I'm not sure they are killiing it yet. I would expect it to start nosing over if they were the issue. But when you get it running to potential, it will quickly become an issue.

Any idea what true compression is? That LT-1 cam doesn't like 9.0-9.5 stuff. Does much better at a true 10.5 or so.



JIM

SWCDuke

A recently built '65 L-79 with a nicely reworked set of 461s and LT-1 cam made 360 HP SAE gross @6500 on a lab dyno and the power was still climbing, but 6500 was the observed redline. Engine Analyzer's peak power prediction for the configuratation was 357@6000. Eighty percent torque bandwidth was 1600 to 6500+, however it was basically flat to 2500 then began to climb nicely at 3000 to a peak of about 332 lb-ft in the range of 4-4500 - that classic SHP "coming on the cam" behavior.

Prior to getting good power runs a lot of ignition and carb sorting had to be carried out - including fixing the secondaries on the OE carb that were not opening all the way.

Worse case is the rule of thumb 80 percent conversion to SAE net and 15 percent driveline loss, which should yield .80(.85)(360) = 245 RWHP, but I think it will do a little better because the Corvette's clutch fan and 2.5" under the car exhaust with off-road repros mufflers will probably make more net HP than 80 percent of gross.

Back in 1963 Don Campbell of S&S Research who prepped Alan Green's SWC driven by Jerry Grant (and also co-drove at Sebring) told me a well tuned SCCA-prepped '63 FI engine would make about 250 RWHP. Back then with the exception of no mufflers these engines were really stock except for fuel and ignition system tuning. Headers were not allowed nor could you remove any metal from the cylinder head. They probably corrected observed readings to standard sea level conditions rather than current SAE J1349 conditions that are usually used for modern chassis dyno runs and OE SAE net ratings. J1349 conditions lower corrected output about 4.5 percent relative to standard sea level conditions.

Back to the '65 L-79 - with the heads improved the biggest impediment to power is now the inlet manifold. Substitution of the Z-28/LT-1 inlet manifold should yield at least 10 and maybe 20 more horsepower on the top end, but the owner wants to maintain original appearance, which is okay by me. Also, with the heads opened up a FI system will have a signficant advantage in top end power because of its big plenum and large nearly straight runners even though the FI air meter flows about the same as the Holley 2818. In production trim the FI system doesn't make significantly more power because the biggest restriction is the heads.

One other interesting data point was the effect of headers. Peak torque was significantly improved to about 358 lb-ft, but the top end only picked up three HP to 362@6500. The owner never intended to run headers, but it was nice that he tried them out so we can see the comparison!

Two days on the dyno - lots of good (no BS!) data!

Duke

mike 1985

LSA is meaningless unless it's compared to a cam of equal duration. The effective duration at .050" above the lash point is about 229/237 (this is what should be compared to a hydraulic cam, not the 242/254 duration at .050"


I did not know this.

mike 1985

actually as i read this

Most back yard hot rodders and cam grinders can't get beyond the simplistic "LCA" "centerlines" and "duration at .050", and don't even acknowdege the existance, much less the benefit of asymmetrical lobes. This is at best a view of valve timing from 100,000 feet. There's a whole other world of overlap and duration in square-inch-degrees and and how to achieve an optimum design utilizing available wave dynamics, while controlling valvetrain dynamics so the valvetrain will live forever.

There is not a cam on the market today that will provide the torque bandwidth and peak power of the LT-1 cam without compromising the bulletproof OE valvetrain reliability.

i don't know the difference , nor have i heard of this.

could you try to explain this to me in lamens terms ? As for this cam...it actually has 229-237 @ .050 and a 114 LSA ? How much over lap and what's the recommended RPM range ?

thanks

Mike

SWCDuke

I can't explain the low level details of cam lobe specifications and design considerations without writing a book to explain what I've learned in 20 years of study and research, and to understand the subject one needs to have a solid foundation in Dynamics, which is a core subject of Mechanical Engineering curriculums in universities.

The Engine Analyser program computes EFFECTIVE overlap in square-inch-degrees, which is what I use to compare actual overlap. The calculation is not perfect because the program will not accept complete lift-crank angle data, only basic timing points, so the effective overlap is an approximation, but it provides a reasonable comparison from cam to cam.

Hydraulic cams have very short (duration-wise) and shallow (height-wise above the base circle) constant acceleration clearance ramps, so .050" lifter rise yields effectively that much valve lift times rocker ratio. Mechanical lifter cams have long and high constant velocity ramps that end as much as .020" above the base circle, so the first .020" of lifter rise is just taking up lash with no valve movement. This is why mechanical lifter cam duration at .050" cannot be compared to hydraulic duration at .050", but a valid comparison would be .050" above the top of the clearance ramp, so for a mechnaical lifter cam with .020" tall ramps, the duration at .070" should be compared to a hydraulic cam at .050".

The only way to determine this is to take an accurate lift-crank angle diagram. In the case of the vintage SHP mechanical lifter cams I have the original GM drawings with all the lobe data and by keying the lobe profile data into a properly setup Excel spreadsheet I can compute the velocity, acceleration, and jerk profiles to completely "reverse engineer" the cam. I published the results for the L-72 lobe a couple of weeks ago on a thread on this board. The L-72 uses the same lobe on both sides, and it is also the inlet lobe on the LT-1 cam (the LT-1 exhaust lobe is the same as the 30-30 cam but phased four degrees earlier), though the SB cams have slightly smaller base circles and indexing is slightly different.

A good street high performance engine should have the 80 percent torque bandwidth begin not later than 2000 revs or the engine will feel pretty soggy in normal driving. In the example from my prior post it began at 1600 and the top end of the eighty percent bandwidth was beyond the recommended 6500 RPM redline, so the useable power band will extend to the range of 6800-7000, but will probably be a bit lower when installed in the chassis with a fan and exhaust system, so nothing will be given away and the 6500 redline should contain the full useable power bandwidth based on gear ratio spacing.

An engine with exhaust manifolds cannot handle as much overlap as an engine with headers, because manifolds cannot harness exhaust system wave dynamics to create negative pressure at the exhaust port during the overlap period to help initiate the inlet process. Chevrolet recognized this and optimized overlap for the OE manifolds. Though the OE cams will respond to headers, they are not optimzied for them. Headers would require different lobe designs to optimize torque bandwidth. By the same token, aftermarket cams on engines with OE manifolds can hurt torque bandwidth, particulary at the low end because they usually have too much overlap. Most are designed with the assumption that the engine has headers.

Given that I have all the OE lobe data and they are known by industry and they don't cause valvetrain problems, I embarked on a project to design the "perfect" vintage SB street mechanical lifter cam by mixing and matching the lobes and varying their phasing with the intent to have a new cam manufactured. I made hundreds of simulation runs and could not improve on the performance of the LT-1 cam enough to justify a new design with the primary criteria of maximizing average power in the range of 2000 to 6500.

Back in the sixties, Chevrolet engineers did not have anything close to the analysis tools that I have on my PC. They designed the lobes based on their intuitive understanding of valvetrain dynamics and flow characteristics of OE heads and trial and error on the dyno.

My conclusion is that they sure knew their stuff!!!

Duke

mike 1985

thanks for taking the time to type and explain all that to me.

Mike

6T5RUSH

Well All,

(I posted this @ the C1-C2 forum as well)

I came away impressed with the changes made to my 327...regardless of the dyno experience. For sure, that shop did a great job fine tuning this motor (enriching the air fuel ratio and adding a little more initial timing).

Here's the tale of the tape. Mind you I'm a little confused about which method for calculating the rear wheel horsepower reflects closer to the "real world" conditions 'cause I ran a best 13.826 @ 101.99 mph!!!!!

If you use the trap speed calculation, I end up with 272 rear wheel horsepower. If you use the e.t. method, it calculates to 245 rear wheel horsepower.

Either way the dyno used to determine my rear wheel horsepower had to be out of calibration as it calculated 225 horses at the rear wheels.

The event was GREAT!! Didn't come away a winner (was paired up with another Vette, same color also with a white top...a true 327/350 horse car). That car ran tight and the driver, Don, was able to consistently get out of the hole well. No excuses here except I did have to view a few runs to refresh my memory of which way the tree lights worked, up or down :eek

As I review my 10 runs over the 2 days, I see my consistency of leaving late !!!! Five of my 10 runs were over 1.++ for a Reaction Time. AND, the first race I lost I pulled a .945 Reaction Time AND had my fastest run of the 2 days @ 13.826 @ 101.99.... Man, that sleeping bag at the line sure was comfortable .

Seriously, my old habits die hard and as soon as I see that 3rd yellow, my foots to the floor...only I haven't let the clutch out....so when I do I'm just standing around not even breakin' the lights, burnin' up those radials. But, holy mackeral when she hooked it's like smakin' you in your lower backside!!!

Oh, my best 60 foot time was a 2.092 and my best 1/8 mile time was 9.004 @ 80.48.

So, I really am happy with this new setup and I honestly believe if I could relearn how to take off my times and speed would definetly improve (without changing exhaust, carb or tires).

I think what I'm seeing at the track is the result of the cam swap more than the head change. The improvement in head flow is just not going to be seen with my stock 2 1/2 side exhaust system (which when I look up inside the tips the straight pipe appears close to 2" in diameter). The just limit the head flow. But that LT1 cam sure made a believer out of me. At first I was reluctant to let her go to 6 grand but thought I'd just have to have confidence in my engine builder and the forum experience here from other guys with this setup. I never shifted below an indicated 6,100-6,200 through all the gears for every run.

SHE LIKES IT UP THERE!!! WOW!! Do you get the feeling I'm a happy camper. You betchum!!

You know, I never did check to see if my secondaries are opening.

A smiling Jim