Thread: Need help,suggestions with my 402 BB??

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I think this site went down today and my thread got erased.Anyway I'll repost it.I have a 69 camaro with a Muncie M-20 Trans(bad syncro in 4th Gear)
Forged pistons,Rods and crankshaft.I have stock but Ported oval iron Heads with 2.19 and 1.88 valve's,Torker 2 Manifold,Nitrous System.I have a rather big Cam which Duration at .050 is 248 Intake and 248 On Exhaust,595 Lift on both the Intake and exhaust,110 Lobe separation.Its a very Lopey cam and it is hard to get to Idle.It has a 780 Double Pumper carb which was rebuilt with a 4 corner Idling circuit a while ago(it fixed the constant fouling of my spark plugs)
I got some replies saying to ditch the Cam and Intake especially since this car will probably be used mainly on the street.I had 1 reply saying to get a 750 something??? because it is better for Cars on the street and is more responsive.i didn't get the whole message because the site went dead on me today.I do think the 4:11 Gear I am running now is too much Gear.I think a 3:73 gear would be much better.Is this to much Cam for the street(2500-6500 Power band) and does this Cam make my engine drink alot more gas because of the Cam?? Im charging the battery tonight and I going to see if i can get it Idling faster tommorow.The best way of doing that is running 16 degree's advance at Idle and either turn up the throttle linkage or wait 10 minutes until the Car warms up.I have an Edelbrock performer Manifold but I would have to change my Cam to get the benefits of the lower end torque and power.Im not sure exactly what to do.I certainly want to keep the car fast.Any suggestions would help. Thanks

I don't think if I kept the current Cam and swapped the 4:11's to 3:73's it would match the current set up.Im hoping to try to get the car to Idle faster today or tommorow.I have to turn the throttle linkage up a bit so it doesn't keep stalling out on me.

I sent you a rather long response yesterday, and now I find that it went away!!! Now I probably wont remember all of what I said. First of all, nitrous will work fine with any cam, not just big ones. Your cam is too big for the street, I know it sounds nasty and all that, but it is hurting your low end performance for sure, and it very well might be a big part of your idle problems. Something in the 234 to 244 or so will be much better. Lift should prob. come in at about .550 or so. I prefer a dual pattern cam, I think they do better with a longer exhaust duration for a BBC...they were never know to be very good on the exhaust side. Get it ground on a 108 if you want the nasty idle instead of a 110 LSA. I would dump the intake, use your Performer intake. A dual plane will be much better on the street. You will feel the difference, and it will be much better while warming up and at lower RPMs.. I'm the one who said that a 750 Holley vacuum secondary carb will do you fine. I have run many double pumpers on the street, and every single time I changed to a vacuum secondary carb, everything else being equal, the vacuum secondary was smoother and more responsive. And it took less messing with, idled better, etc. The Holley street avengers seem to be a good carb. I never used one myself, but have heard good reports about them. You can get the 770 CFM for your combo. Anyhow, I would go with the 3:73's, that's what I run. I actually wish I went a little more, maybe 3:42's or so...but the 4:11's on the street are bad news. On the timing, try 16 initial, make sure your vacuum advance is disabled and plugged. Big cams in big blocks like lots of initial. Just watch your total advance, no more than 36 or 38. Have it all in by about 3K. If you set your timing and idle, make sure the engine is completely warmed up first. Your idle problems are likely related to the big cam. You might have to either drill the primary butterflys, or crack open the back ones to give it enough air to idle right. But dont do that without checking how first! I dont know what cam you like, but if you want a name and number of the ones that have worked for me the best, along with the best service, I'll be glad to set you up with a phone number and contact names. You got a response on your other post about the carb sizes, saying they ran double pumpers on the street with no problems. I know others have also, but Im just relaying my experience with them, I have to say go with vacuum secondarys.

When I got the engine redone the engine builder put a Wolverine Cam in which was about 500 lift.It was a hydraulic Cam but that might be a bit small to work with a 3:73 Gear.It ran real good at low RPM on the street though.I decided to change the Cam to a Lunati 574/588 Lift.That Cam seemed to be Lopey but at least the engine Idled.Not quickly, but it didn't take 10 minutes like the 248/248 Competition Cams.I definately want 3:73's in there now especially with no overdrive.Im not sure if I could get some aftermarket Aluminum head's that would give me even more power from off Idle to 5500 RPM's.I heard of the Holley Oval port's which came out not to long ago.Those heads actually reduce Compression while adding power but I don't know by how much.

Im wondering what aftermarket Aluminum cylinder head's(oval ported) give a good increase in HorsePower over the stock oval ports?? I have read about the holley's with the Oval ports.i don't need a head that would bump up Compression because Im not sure what my compression is in my engine.

The advantage of aluminum would be less weight, which for the street, you really dont need to car about much. The other is that you can run a little more compression without fear of detonation, but as you said, you dont know what you have now, so what's the sense? You really need to know what you have in there, compression wise, heads and what have been done to them, all the details. You cant possible start changing things around without knowing for sure what you have. You'll just spend the rest of forever changing out parts and wasting more money. When you buy a cam, they ask you what your c/r is....what do you tell them? You cant just buy any cam that sounds good. You have to match it up to your engine combo. Same goes for the rear end gears, carb, intake, everything. If you have no idea, how can you even start? Im not trying to be negative, but it sounds like you're just pulling straws, and lets see what happens. Your iron heads are fine for the street, and will let you run much more HP than you'll ever need on the street. Many race only cars are running iron heads. GM made some fine flowing heads, so in my opinion, that would be a huge waste of money. Cant you find out more info from the guy who built this engine? You really need to know what you have for c/r, pistons, rods, etc.

I think he mentioned 9.1 Compressiom but the forged piston's were 10.5.1. I know the heads were the 360 HP Oval port stock heads ported and I know he used a thicker Head Gasket to reduce Compression.It seems hard for me to believe that it would take it down to a 9.1 Compression engine

The thicker gasket will not lower compression that much. You (or your builder) must have the numbers wrong, or not the whole story. Have you verified the numbers on the heads? If the number is 14092360, they are the truck "peanut port' heads, and you are not going to want them for a true performance build. They have small intake ports, and will not flow well at higher rpms. A great 'tow truck motor' head, though. Lots of torque, not a lot of HP. They have large combustion chambers, so the 9.1 compression is a possibility...and that's OK, you can make lots of power with 9/1....but I would not use those heads if I were building it. There are lots of GM iron heads that will flow much better. 781's are a very common one, and there are lots of them available. Your engine has a lot of potential, but it kind of sounds like no one really knows what is in there. And until you know what you're starting with, you cant make any changes that will help your performance. The parts of an engine MUST match and work with each other if you expect it to perform well. I have seen countless times where someone will throw a bunch of parts into and already unknown engine, and it wont get out of its own way. So, the car is sold, or just sits there, and someone loses interest in hot rods altogether. I know you want to run the car and have fun, but you need to either get some hard facts from whoever built that engine (like receipts or paperwork, not from 'memory'), or take some time, find a friend who knows their way around an engine, and pull it all apart and see exactly what you have. If you need more info on head choice, just ask. There are lots of combos that will work well. John

Originally Posted by 1JohnnyO

The thicker gasket will not lower compression that much. You (or your builder) must have the numbers wrong, or not the whole story. Have you verified the numbers on the heads? If the number is 14092360, they are the truck "peanut port' heads, and you are not going to want them for a true performance build. They have small intake ports, and will not flow well at higher rpms. A great 'tow truck motor' head, though. Lots of torque, not a lot of HP. They have large combustion chambers, so the 9.1 compression is a possibility...and that's OK, you can make lots of power with 9/1....but I would not use those heads if I were building it. There are lots of GM iron heads that will flow much better. 781's are a very common one, and there are lots of them available. Your engine has a lot of potential, but it kind of sounds like no one really knows what is in there. And until you know what you're starting with, you cant make any changes that will help your performance. The parts of an engine MUST match and work with each other if you expect it to perform well. I have seen countless times where someone will throw a bunch of parts into and already unknown engine, and it wont get out of its own way. So, the car is sold, or just sits there, and someone loses interest in hot rods altogether. I know you want to run the car and have fun, but you need to either get some hard facts from whoever built that engine (like receipts or paperwork, not from 'memory'), or take some time, find a friend who knows their way around an engine, and pull it all apart and see exactly what you have. If you need more info on head choice, just ask. There are lots of combos that will work well. John

Well A long time ago I brought them into a speed shop to get redone.The guy working there told me that those head's were the 360 HP Oval Port's which were a good head.The engine had enough power to send the ring gear bolts throgh the differential cover.It was not the heavy duty type of cover and bolts but still.I took it in 3rd gear on a nearby highway and then opened it up luckily I was able to coast the rest of the way home.These Heads are Ported.Im not sure about the Combustion Chamber but I know there open Chamber Heads.I have to check the number on the Heads to be sure.I don't think I would have wanted my engine at 10.1 Compression unless I was planning to race it.

14092360...86-90...oval...OPEN...454 Truck, "peanut" round ports

This is from Mortec.com. Check your numbers when you have the valve covers pulled. Im sure they make tons of power, but Im just saying they are not a performance head. I dont know where the HP came from in your description, that's not part of the number as far as I know. And 10/1 is ok for the street, depending on the cam you choose...but typically you dont want to more than that with today's crappy gas. John Oh, combustion chamber should be somewhere around 120cc's or so.

yes i can help here. buy my 402 all set and will run on pump gas

I have alway's used 93 Octane and the car has never overheated.It did have a problem shutting off but I think that was due to the MSD Ignition.I had to run a toggle switch to the Regulator because I needed the switch to turn on the Alternator.Now if I didn't have that switch to the Reulator the car wouldn't shut off if i turned the key in the off position.I don't know if I have a wiring problem or it was The MSD ignition but the only way I can shut my engine off is by the ignition toggle switch??

all you need to do is to keep the alt from backfeeding the power to the msd a diode will stop this or try a diffrent leg to pull 12 volts off of for the msd

Originally Posted by pat mccarthy

all you need to do is to keep the alt from backfeeding the power to the msd a diode will stop this or try a diffrent leg to pull 12 volts off of for the msd

I have a Diode in there.The problem is if the Diode is left in there without it attatched to a on and off Toggle switch inside the Car the Alternator will not charge or will destrot the alternator.So once the car is started I click the toggle switch to activate the Diode to the Regulator.This was done a long time ago but another reason was that I could not shut off my engine with the Diode in the on position for the whole time.Im unsure about that part but Im sure it affects the Alternator.I went through at least 7 alternator's until I put that Diode in with the Toggle switch on the Dash.

you do not need the diode if you have a power on and off switch .you have something screw up. if the diode is in line right it will not do any thing to the alt just stops back flow if you have a regulator you need to pull power off the restive wire coming out of the fire wall look like ss wire and has a cloth rap white in color and take this wire out and run standard wire for you 12 volts of the msd you are on the wrong leg of the switch sounds like you have it in line with the alt this will not work