283 feulie rebuild

[Duke W.]

Re: 283 feulie rebuild

The LT-1 cam is not "modern", but then "modern" cams don't work better. That's a myth. The inlet lobe is from the BB SHP cam that was designed in 1964. The exhaust lobe is from the 30-30 cam (and phased four degrees earlier), which was designed in 1963.

Idle characteritics are a function of overlap and since the LT-1 and Duntov cams have the same effectice overlap in sq-in-deg, their idle quality is the same.

When I designed my special cam, I followed the same course - the inlet lobe is from one OE cam and the exhaust lobe from another.

The OE lobes have very nice, mild dynamics (except the early base engine cam, which was replaced by the 3896929 in '67) and will support high revs with the modest force OE valve springs.

Duke

[Duke W.]

Re: no, really, what's your advice?

The later the inlet valve closes the more compression the engine can tolerate. Current data indicates 10.5:1 is okay for the LT-1 cam, but this is a maximum. Minimum should be no less than 10:1. Because the inlet valves close earlier on the L-79 and Duntov cams, I recommend no more than 10.25. Likewise the much earlier closing base cam CR dictates no more than 9.75. These are all true, MEASURED, CR, not some "spec", and in most cases, OE replacement pistons and proper gasket selection will achieve these values or somewhat less.

Compression ratio has to be MANAGED, which few do. This starts with measuring deck clearance on engine disassembly. If the block is bare, good machine shops have tooling that allows them to measure actual deck height. The nomimal is 9.025". Then you add the nominal crank throw radius, rod length, and piston compression height and subtract from deck height to get an estimate of deck clearance and pick some suitable head candidate gaskets. Head chamber nominal volumes are published, but should be measured. Most piston volume data are published and accurate.

Upon block assembly you measure actual final deck clearance, then pick a gasket to get your target CR.

I use the following online CR calculator.

http://www.csgnetwork.com/compcalc.html

There is no substitute for upfront system engineering and planning and attention to detail during assembly.

If you want to system engineer a configuration to a torque bandwidth specification (that's what I do) get the Engine Analyser simulation program, and simulate "as installed" performance with the front end accessories and an accurate exhaust system flow model.

Recently a L-76 was completed and tested - pocket ported heads, LT-1 cam, 10.5 true CR; 80 percent torque bandwidth is 2100-6700, 90 percent 2450-6100, with useable revs/power to 7200. The torque bandwidths are about the same as the current LS7 - not bad for a 50 year old architecture with a carburetor whose newest design part (the LT-1 cam) is nearly 40 years old, but good system engineering and attention to detail unleashes the hidden potential of these old engines, and the only non-OE equivalent parts you need are a good set of connecting rods.

Search threads started by me back in July for more info on this engine.

Keep in mind that FI uses a single plane manifold architecture, so low end torque is going to be weak and won't achieve 80 percent until well above 2000, but that was the nature of the original beast, so you'll need no less than a 3.70 gear. If you want to install a Richmond wide ratio Super T-10 (2.64, 1.75, 1.34, 1.00:1) then a 3.36 will work well. Highway cruising would be nicer and the overall first gear ratio would be about the same as the original CR T-10 with a 4.11.

Duke

[G B.]

Really, this is my advice.

Remember, you asked. I tend to go with what has worked well for me in the past.

Forget custom building a 265, 283, 302, or 307 for "more power" on the street. It's a waste of time and money. You will never, ever, get it to perform on the street like a larger displacement engine.

I suggest installing a 327, 350, 383, or 400 with 1/8" domed pistons; the Duntov 097, '64 - '65 30-30 (with lash at .030"/.030", oddly enough), or 1970 LT-1 (.024" / .030" lash) cam; a new 8" balancer and 2.02" / 64 cc aluminum heads; and Plain Jane everything else. Let the damn machine shop balance and assemble the long block. With composition head gaskets you can run pump premium and 12 degrees of initial advance with 36 total. Such an engine will make 13 - 15" of vacuum at 850 rpm. And, it'll outlive you on the street if you limit your felony speeding to an occasional 6,000 rpm blast through 3 gears.

In theory, bumblebees can't fly and the Federal Government is there to help us. Some things just don't work out in the real world like they do on paper. Yeah, yeah... I know... the '69 Z/28 302 was Superman. I owned four of them back in the seventies and eighties. They were turds below 5,000 rpm.

[Jack Alexander]

Re: Really, this is my advice.

Thanks guys for all of your time in letting me benefit from all of your expetise. I am no mechanic myself but from whatI am getting from all of this, in particular Jerry B(nice web page) and John D that I will not be able to get what I want from my 283 with the stock F.I unit. Again I am not a racer. I just want a good driver that performs well without any drastic modifications in the rebuild. Is the F.I. unit the problem? Should I just go with the 4 barrel and save the FI unit for the next owner? I really don't plan on ever selling it. Just want it to perform to it's maximum and be dependable.

REgard,

Jack Alexander

[Joe M.]

Re: no, really, what's your advice?

Jerry,
Your advice is sound and well taken. However, just like when you order a happy meal and refuse the fries even though they are free, for this car I want to use a period 283 and fuel injection. I have no delusion re high performance, just want to have an optimal running 283/FI combo. It is toward that end I seek advice and the rationale for doing what ever it is that needs to be done.
Basically I want to stay close to stock with exception of the 151' cam. If that cam is not synergistic in a 283 with FI then I'd reread the reams of discussion on the merits of the duntov, 30-30 and lt-1 cams. Compression ratio, pistons and cam selection seem to be points of tremendous speculation. I have spent much time reading the archives re engine building and cam selection. Most are not specific to a 283 but certainly applicable, but where does the relevance end? Duke's technical advice and other's practical advice surely provide an education for understanding the rationale for doing what you might do. Your advice is especially valued as the focus of this car is the 62 FI unit and I want to be sure it sits on a well thought out 283 engine. The couple of engine builders i've talked to just want to do their thing probably from a production and liability standpoint. Didn't seem to be interested in 'goals'. So I seek to at least be conversant and able to support what work and components I want.

Thanks,
joe

[Joseph T.]

Re: Really, this is my advice.

Jack

Until not too long ago..the 57 FI 283/283 was one of the fastest production cars tested by Road and Track and was in the top 10 for years and years.

If you build your engine to the original specifications..you will have more than enough street power to burn the tires in all 4 gears and still be able to drive the car at low rpm's. The FI will give you plenty of immediate throttle reaction...and no coughing in the turns.

My 283/245 HP 57 was not as high strung as the solid lifter 283/283 and was much more enjoyable to drive ..but thats me.

Joe

[G B.]

The 151 cam will work fine with FI.

It will idle at 800 rpm with 13 - 14" vacuum, even in a 283.

Do watch your compression though. Most 283 heads had 1.72" intake valves and 58 cc chambers. If you use later heads with 1.94" intakes and larger 64 cc chambers, you'll have to use domed pistons to get 10.5 to 1 compression.

[Michael H.]

Re: Really, this is my advice.

Jack,

Sounds like you and I, and a few others, are thinking along the same lines on this. My personal preference would be a completely correct/original 283 with all the correct components, right down to the 11.0 pistons. I would definitely choose the correct original "097" cam and all of the other components that make things right for the era. These engines work very well at 11.0 CR and there really isn't a pinging problem with todays fuel. I still have the original 11.25-1's in my 63 FI and I've never heard it ping in all the years I've owned it.

I definitely do agree with an upgrade for the connecting rods though. This is a reliability issue and has nothing to do with originality or performance.

I see no point, at all, in trying to make an old car pretend it's a new car as far as performance. It's just not going to happen. All the fancy cam and head work in the world isn't ever going to make an old Corvette as fast as some young kids C5 or C6. No point in even pretending.

You definitely won't have a screamer but it will run very well and be dependable. What more could we ask for?

One more thought. I recommend you ignore an engine builders recommendations to install new hardened valve seats for use with unleaded fuel. It's not at all necessary unless you plan on putting 100,000 miles on the car.

[James G.]

Re: 283 feulie rebuild

One of the best examples of fuel injection peformance was watching Joe Freitas prepare his old fuel injection racer in 2002 for the 50th anniversary celebration at the Monterey Historic Races.

Joe had a 30 over 283 motor, stock valve train, 14.1 compression race set up motor that put out an honest 488 hp on the dyno using the GM Performance intake and Holly Carb. Joe insisted on using the 62 injection he had on the car in 61-62 when he and Dave MacDonald raced it 'Back When'

After the 488 hp pull, we changed to the modified injector and re-tested the engine. 440hp is all we could get, but a much flatter torque curve with only a 6 lb drop from the carburated test.

The modified injector had its plenmum cut in half and raised 3/4 inch, then tumbled with it now looking factory NCRS correct. The air meter pizometer ring and butterfly were increased, high pressure pump shimmed, and the 'Z' nozzels used. CFM was now at 710 from about 625 of the original.

CAM PROFILE was a special Crower model similar to the original that concentrated on TORQUE........NOT HIGH HORSEPOWER. This resulted in great power off the corners, which in Road Race situations is what you need.

Due to a spinning car at turn 11, Joe had to dive under the car and 3 rd place Ken Epsman beat us all up the hill in the drag race finish. But that is another story. 2nd on the Podium was fine for us

[Duke W.]

Re: no, really, what's your advice?

The name of the game for power is HEADS, HEADS, HEADS.

You pick the cam to achieve your desired beginning of the 80 percent torque bandwidth and work the heads, inlet, and exhaust system to the limit of your budget to make top end power. Good torque is just a matter of cam choice. Top end power is a matter of budget.

Installing a big cam with OE machined heads will just kill the low end torque without making that much more top end power.

Good inlet and exhaust flow with a "moderate" cam is what makes broad torque bandwidth and good top end power.

Short stroke engines like 283s and 327s also need mechanical lifters, because with proper cam choice and head work they will make useable power to over 7000, which also dictates that you build a bulletproof bottom end.

The OE mechanical lifters cams with proper lash and attention to proper setup of the second design 3911068 springs will easily spin to about 7200.

Duke

[Jack Alexander]

Re: Really, this is my advice.

Hi Mike and Joe, all of the advice has been great. I love this board. I think your ideas are the closest thing to what I am looking for. Part of my problem is that I may not be appreciating the performance capabilities of the original car. My car was beat. The FI off and in a box. I think the bottom end had been blown and burns oil. Despite it all it is still very quick. Maybe sticking to a more original rebuild will suit my purposes better. I was warned about the compression many times as to the pinging. Was your motor that did not ping even with the 12 to 1 pistons a 283? I thought the vette went to the 327 in 62 or does that even make a diference?

[Michael H.]

Re: Really, this is my advice.

Jack,

Yes, the first model year for the 327 was 62. This motor had an advertised compression ratio of 11.25. Gm felt that was a tad high and dropped it to 11.0 for 64. You can get away with 11-1 with todays fuel if you have the original 097 cam. My 63 has the original everything and I don't believe I've ever heard it ping even with the 11.25 CR. Good luck with your project.

[Duke W.]

Re: Really, this is my advice.

Flint NEVER built an 11.25:1 CR engine in '63. It's achievable with nominal deck height and the OE shim gasket, but all SHP/FI engines were double gasketed in '63, which drops half a point right there. Add .010" to nominal deck height and the CR drops to about 10.5.

Advertised CRs are about as accurate as advertised SAE gross power ratings.

The following true CRs are okay maximums for current pump premium based on inlet valve closing point, which is determined by the camshaft.

30-30, LT-1, and Duke's special camshafts: 10.5
Duntov and L-79 camshafts: 10.25
Base engine camshafts: 9.75

These maximums are usually easily attainable with OE machined decks, OE or equivalent replacement pistons, and a head gasket with suitable compressed thickness. Head gasket availability starts at .015" and they can be used singly or doubled to attain just about any thickness in about .005" increments to well over .050".

Duke

[Jack Alexander]

Re: Really, this is my advice.

Thanks Duke. That's perfect just what I was looking for. Any opinions about what I am doing and using the Hydro lifters instead of the solids? My mechanic suggests the hydro. Says that if you use the solids there is a risk of damaging the cam upon startup unless you run it often.

Jack Alexander

[Duke W.]

Re: Really, this is my advice.

I always recommend that mechanical lifter cams be used to replace OE mechanical lifter cams, but not necessarily the SAME cam as OE. A mechanical lifter cam will maintain the engine's original visceral character and allow the engine to rev higher than a hydraulic lifter cam.

I think your mechanic's statement is a myth. There are increasing cam/lifter problems because modern SH oil is not suitable for vintage engines, but there will be no problems with CI-4 oil. (Search if you don't understand the oil issues. They have been extensively discussed.) New engines should have a bottle of GM EOS added to the crankcase and go through the normal "cam break-in procedure". OE cams and springs are the less likely to have problems than aftermarket cams and springs because the OE setup was better engineered for durability. The OE lobe dynamics and spring spring force are modest, and these combinations have been proven over 50 years of service in millions of engines.

Failure of an OE cam/lifter/spring combination is almost always a "people problem" - installation error or lack of adequate maintenance such as oil change interval.

To me it comes down to choosing either the Duntov or LT-1 cam. The Duntov cam was designed for the small port heads, but the 461 heads need a different valve timing scheme because of the larger inlet valves and ports. That's why the LT-1 cam works much better in 327s than the Duntov.

My biggest concern is that the LT-1 cam will lose low end torque relative to the Duntov and the 283/315 is already a torque shy configuration, but the LT-1 cam produces better low end torque than predictec by simulations, so maybe the LT-1 cam in a 283/461 head combination would be okay.

Any change in configuration carries risks, but if you want to e-mail me I can run some simulations with the two cams and get an idea of the performance differences. The Engine Analyzer program is fairly accurate on peak torque and power, but it's proved to be LOW on low end torque.

Either way I consider head work to be mandatory if you want to extract maximum performance with either cam. The single most effective improvement you can make to an OE engine is massaging the heads. It increases top end power and revs considerably with vitrually no impact on low end torque.

Duke