Old cam info

[mikeemon]

Hello all, I have a pontiac 400 that I put together about 15 years ago. I recently found the cam spec card, but cannot find any real info on it. The cam in question is an Erson Cams E311021. Grind #MP2.
Intake: .429 lift, 288*dur, .286 gross cam lift, 214*[email protected]".
Exhaust: .462 lift, 310*dur, .308 gross cam lift, 226*[email protected]".
Does anyone know what rpm range the powerband of this cam should be or anything?

The rest of the package includes .030" over bores, Edelbrock Performer intake and 600 cfm carb, comp cams 1.5 roller tip rockers, hooker super comp headers, compression is around 9.5-10:1 (I think, I cannot find piston head displacement, if anyone has any ideas or info on that it would be helpful too) with 6x heads and domed pistons.

I am finally getting to the point of fine tuning the engine any ideas would be appreciated.

[Morley]

Fair duration cam but low lift. I'd guess at 1500-4500 RPM is about it for its "useful" RPM range.

[mikeemon]

Thanks. I could improve the effective lift by using higher ratio rockers, but I'm concerned about valve/piston head clearance. I do not want to take it apart now to check it properly. It runs well now as it is, plenty of power.

[Morley]

I'm sure it has plenty of power, just don't expect it to keep pulling past 5k. I wouldn't bother with 1.6 rockers since you have domed pitons, you could end up in real trouble, real fast.

[mikeemon]

Thanks, You were pretty much right on. This is a reply I got from another forum. He had an old catalogue with the info.

RPM range 1500-5000, up to 9.50:1 compression, OK with stock converter and power brakes, Good idle, 114° LSA, 4° advance built in

[MrPbody]

You will be fine with 1.65:1 rockers, IF you have the springs to back it up. That's more a problem with Pontiac heads than valve-to-piston interference. Also, the holes for the pushrods must be enlarged toward the stud to get enough clearance for the higher ratio, or the pushrods will rub against the head.

Dump the Edelbrock carb and get a Q-Jet. You will thank me. Cliff's High Performance in Mt. Vernon, Ohio is the best place.

The Performer is okay, but if you still have a pre-'73 factory iron intake for the Q-Jet, it flows better than Performer. Remember, this is a Pontiac, NOT a Ford or Chevy. Not all the same sets of "rules" apply.

With a larger carb, this combo will be able to rev itself "to death". If you have stock connecting rods, 5,200 RPM is your practical limit. This is the biggest area of concern in the Pontiac. It's best to basically ignore cam grinders' "operating range" concerning Pontiacs, as the heads are so different than other, more "conventional" designs, providing a completely different power curve. This is why GTOs have the reputation they have, (it ain't from LOSING...) and still only revving to 5,200 RPM.

You also REALLY need to know what size "bump" the pistons have. Detonation will KILL a Pontiac. If your static compression is above 9.5:1, you need to mix race gas with pump gas. If it's above 11:1, you need to run "straight" race gas. If they're the old TRW L2277F, you have about 10:1. The chamber volume for the 6X is anywhere from 92 to 101 CCs. The only true way to be certain is to measure them. Published data is "nominal", and we've seen a great variance.

I highly recommend you buy Jim Hand's book "How to Build Max-performance Pontiac V8s", published in 2004 by SA Designs, this is the most current study of the ol' Injun, and is aimed strictly at street engines like yours.

Happy yakkin! (that'sd Ponti-yakkin!)

Jim

[mikeemon]

I do not have an old/orig intake manifold. The orig. mill was a 301 2bbl.
I do not have any paperwork on the pistons. I bought them off someone 15+yrs ago. I felt lucky to find the cam sheet.
Right now it runs really well. I have only been driving it for the past 3 seasons.
I run 93 octane. No detonation, even on hot days. Stock HEI. Base timing at 16*. Idles @900+- in D @700+-. (Good thump) Ported vac advance, it is an auto.
The EP1406 has worked well for me. It is basically out of the box and I have not really done any tuning to it. I had a Holley about the same size on before that. Not as much luck.

[MrPbody]

Base timning at 16??!! That's WAY high. Try it at 12 and see if the engine doesn't "like" it a bit better. 12 initial and 34 total is what most Pontiacs with 6Xs like.

Jim

[mikeemon]

I will give it a try for over the weekend. I was going by a haynes manual and picked a number that looked like it was in there the most to get some sort of baseline for me to work off of before I start tinkering.

[Morley]

Is that 16* at idle? If so, its a bit high. My 79 T/A with the 403 was 21* BTDC @ 1200 RPM in D. No idea what that was at idle because the timing marks didn't go low enough to check it.

[MrPbody]

Morley,

403 Olds and 400 Pontiac are completely different animals. The chamber in the Pontiac is a fully-machined "semi-hemi", while the Olds is cast "open" and not near as "efficient" (rate of burn). The less efficient a chamber is, the more timing it "likes".

FWIW

Jim

[Morley]

Originally Posted by MrPbody

Morley,

403 Olds and 400 Pontiac are completely different animals.
Jim

Uhhh, yeah, I think I know the difference. I was referring to the actual procedure he used/read for the timing. BPO liked to specify an RPM for the engine while setting timing.

[mikeemon]

Just to add... My idle speed varies with the amount of timing I set in. My idle speed screw on the carb is backed all the way out. If I back the timing down to where he is saying, I may actually be able to set the idle with the screw. The only problem I will run into trying to set it lower is the vac adv can hitting the heater hose/nipple in the rt rear head. I think the distributor might be in 180* off.

[Morley]

Originally Posted by mikeemon

Just to add... My idle speed varies with the amount of timing I set in. My idle speed screw on the carb is backed all the way out. If I back the timing down to where he is saying, I may actually be able to set the idle with the screw. The only problem I will run into trying to set it lower is the vac adv can hitting the heater hose/nipple in the rt rear head. I think the distributor might be in 180* off.

Naaa. If it were 180* out it would not run and it'd backfire through the carb. You are probably just "off a tooth" on it. Meaning that if you put the #1 on TDC and look at there the rotor is pointing (and mark it on the dist base), you'd take the distributor out, rotate the oil pump shaft by hand (long screw driver) a little in the direction you need the rotor to turn. then put the distributor back in so the rotor pointing to where you need it, not where it was.
The "best" advice I can give on setting the timing for an "un-known" engine would be to hook a vacuum gauge to the intake manifold and slowly start turning the distributor until you get 20" of vacuum (or as close to it as you can). Then set your idle mixture screw and check the vacuum gauge again and adjust timing to 20" vacuum again if needed.

I would agree that you should probably look into getting a Rochester Q-jet carb for it. With the small primaries you'll get better mileage (got 26 mpg at 80 mph in my 79) and with those massive secondaries...you'd better be holding onto the wheel when you mash the loud pedal.
The Q-jet does have a LOT more parts to it than a Holley type carb BUT, unlike the Holley, once it is set and set right, you'll never have to adjust it again. The Q's can be intimidating when it comes to a rebuild but most kits have very good instructions with them. I would not get a Jet remanufactured Q-jet. I've heard bad things about them from people that bought them.

[mikeemon]

I will give that a try. I never really messed with it because once it was running, I wanted it to stay that way and enjoy driving. I went about 15 yrs without driving it even after I built the motor. Removed everything from the firewall forward. It was hard to just hold onto the thing for so long. Also, there is no holley on it now, I used to have one, but it was on another 400 that was in the car prior to this one. I think I would need a different intake mainfold for the qjet than I have now and like I said I really don't want to start doing any unneccessary engine dissassembly. If I were building this engine today, there things I would have done differently, but when I did it there was no internet for info or access to the newer poncho motor parts.

What happened to the rest of the forum? Is the remodel underway?