[ponyakr]

Originally Posted by Jay S

Out of curiosity, what are the NHRA S/SS factors for the 350 4 bbl and HO engines? Seems like those are good references for what hp potential was versus some of the factory ratings...

NHRA hp factors:

'68 350HO Stock = 305 / SS = 320

http://www.classracerinfo.com/Engine...8&MAKE=Pontiac

'69 350HO Stock = 325 / SS = 350

http://www.classracerinfo.com/Engine...8&MAKE=Pontiac

'74 350 4-barrel Stock Lemans = 273 / SS Lemans = 254
-------------------- Stock Ventura = 277 / SS Ventura = 250
-------------------- GT SS = 250

Although these are the same engine, NHRA factors 'em different, usually because of the performance of one really quick car, using a certain engine. In this case, lots of guys have raced a '74 GTO, but few, if any, have raced a 350 powered '74 Lemans. Bill Rink may have been responsible for the hp factor increase for the '74 Ventura Stocker. His GTO was probably the quickest ever, at that time.

http://www.classracerinfo.com/Engine...8&MAKE=Pontiac

Next to the '74, the '77 350 may be the next most competitive, under the current NHRA hp factors. All models except Birds are factored at 250hp across the board. In Birds Stock = 254hp SS = 246hp

http://www.classracerinfo.com/Engine...3&MAKE=Pontiac

The '69 350HO is probably the least competitive, because of it's high hp factor. Don't know of anybody running that engine in Stock or SS. The '69 350hp GTO engine is factored at 325 for Stock & only 306 for SS. So, that would be a much more competitive combo.

http://www.classracerinfo.com/Engine...4&MAKE=Pontiac

No 4-barrel 350's were available in several year models. 2-barrel equipped 350's are not known to be competitive. Don't know of anybody racing one.

NOTE: I have no way of knowing how accurate/current this info is. Just going by what's posted.

[Jay S]

That is interesting the 69 350HO had such a high rating. It would be difficult to compete with that, pretty big handicap. Overall looking at those NHRA numbers the 350s do not seem to need much of a handicap, in fact it appears some had to be factored the other way to slow them down.

I had the sbc 350 engine option numbers wrong, it was a L-82 that had the good sized cam in a mid 70s Corvette.

Save your $$$, use that cam you have and get a nice 9.5” street converter. That shorter exhaust profile will tame the cam down some compared that Ultradyne I listed. IMO, a well chosen converter is probably the best chance a 13s with the 3.08s. Doubt it will matter much which mild cam is used with a well built converter.

[ponyakr]

"...Doubt it will matter much which mild cam is used with a well built converter."


I dare say there are LOTS of guys on this site who will disagree with that statement. I'm among those.

For 1/4 mile ET, the converter will mostly just affect the launch. Once the engine gets past the converter's stall speed, the rest of the 1/4 mile is mostly all engine. Obviously, a small, lightweight converter will require less power to turn it.

Overall gearing makes a big difference. This includes the rear gear ratio & tire diameter, as well as the trans gearing. Some racers using a TH350 will opt for a lower 2.75 1st gear ratio, to get a harder launch. Some of the really quick cars use a TH200 trans, rather than a TH350. They have a lighter rotating assembly.

But, the cam can also make a BIG difference. I suppose it would depend on how "mild" the cam is or maybe how narrow a range you set for what you consider "mild" cams.

For example: Most here probably consider the 068 a "very mild" cam. But, I dare say, an 068, in a well built 350 would probably run a lot quicker than an 066. Likewise, most here would consider the small 256/262 Voodoo cam "mild". But, it would probably be quite a bit quicker than an 068.

As has been said here many times, it's the whole package. The converter needs to be correct for the engine, with whatever cam it has. The shift points need to be correct for the engine's power specs. As mentioned, for street driven vehicles, the converter, cam, and rear gear are all a compromise, rather than what will produce the lowest ET.

A converter that will produce the lowest ET, will have too much stall for low rpm street driving. A cam that will produce the lowest ET, when using a high stall racing converter, will not be very streetable, at all. And the rear gear ratio that would produce the lowest ET would be way too much gear for normal street driving.

So, I suppose it boils down too exactly how much ET a car owner is willing to sacrifice, in order to make the car streetable. And, some have a vastly different idea of what is streetable, & what's not.

[Jay S]

Converters have changed a lot in the last 20 years. The time you can take off the short time (60ft) generally you can knock 2X that number off your 1/4 mile e.t.

Pretty good example would be my Chevelle I have which is my first car. It started out with a 1600 stall with 4.10s. With slicks it would run 13.60s @100 with a 2.10 60 ft. It had a 214/224 cam in it with 1.6 rockers. We later put a tight 11” 4000 stall in it and dropped the 60ft to 1.78 with an E.T. in high 12s. That is were I am coming from when I say the cam will not effect the 1/4 e.t. like a converter does. Would that Chevelle have been faster with a bigger cam and that stall, absolutely. FWIW, We pulled the 4.10s out and ran 3.23s with the 11” 4000 stall and drove it on some pretty long trips. It knocked the mpg down to about 11 from 14 with the stock stall. That converter was junk compared to the 9.5 converters we run on the street now. Just saying, find out for yourself. That is our experience here.

[ponyakr]

"... a tight 11” 4000 stall..."

WOW, a TIGHT 11" that will stall to 4000 rpm ! If that is true, I suppose converter technology HAS changed a lot.

Back in '75, our Stocker had a 9" racing converter that would only flash to about 3000 or maybe a little over, with the high 12 sec 400 engine. Good enuff to win lots of local races, back then. But, about 2 seconds slower than today's '68 330hp Birds run.

A LOT has changed in 45 years !

[Jay S]

One other engine combo we did in the past might be more relevant to the 350 Pontiac econo projects. We built a low compression 360 dodge many years ago, it was a stock cast piston low compression engine with a 204/214 cam and a performer intake. Started out in our 73 Road Runner with 2.73 gears and exh manifolds. It ran ok, pretty boring though next to our big blocks we had at the time.

My younger brother built a 70 challenger and needed an engine so we let him pull the 360 and use it. So now it goes from a 2.73 gear, 1600 stall to a 3 speed manual with 3.23s and headers. He clocks a 14.8 with it. Not all that happy with 3 speed he switch’s to a 4 speed, car slows down to a 15.2. The 3 speed had a 3.09 first gear versus the 2.54 in the 4 speed. All e/t lost in the first 60 feet.

Move a couple years later, the very same 360 with headers ends up in a 76 Dodge Dart sport with 3.90 gears, same basic weight as the challenger, but this time goes together as an auto with fairly tight 10”3000 stall. Night and day how it runs with the last combo. It is a blast, hard to believe it was the same boring engine we started with in our Road Runner. That tiny cam puts the max torque right at the converters flash rpm. Another example of why I will fork over cash for a nice well built converter. Seem some big smiles after going for rides in that car.

[Burningbird]

I'm currently building 2 Pontiac 350's with Mopar 318-pistons. The piston is 3.94" (0.065" over/366ci) and have 1.741" comp height, no valve reliefs. The rods will be honed for 0.984" pins. The first engine will be built with #46 heads, Summit 2800-cam and a 389 4-bbl intake with a 600cfm Edelbrock. SCR calculates to 8.2:1 and DCR to 6.6:1. The second engine will be built with #92 heads, Melling SPC-3/Melling SPC-7 or Lunati Factory Performance 10511004 cam, 389 4-bbl intake with 625cfm AFB carb. SCR calculates to 10.35:1 and DCR to 6.96:1/7.36:1/7.41:1. I'm leaning towards the Lunati cam, specs are: 301/313 adv. duration, 220/228@.050, 110LSA, 106IC, 424"/424" lift. What do you guys think? Melling SPC-3 to bleed of more compression? This is budget builds with around 1800$ invested total in both engines.

[ponyakr]

Originally Posted by Burningbird

I'm currently building 2 Pontiac 350's with Mopar 318-pistons. The piston is 3.94" (0.065" over/366ci) and have 1.741" comp height, no valve reliefs. The rods will be honed for 0.984" pins. The first engine will be built with #46 heads, Summit 2800-cam and a 389 4-bbl intake with a 600cfm Edelbrock. SCR calculates to 8.2:1 and DCR to 6.6:1. The second engine will be built with #92 heads, Melling SPC-3/Melling SPC-7 or Lunati Factory Performance 10511004 cam, 389 4-bbl intake with 625cfm AFB carb. SCR calculates to 10.35:1 and DCR to 6.96:1/7.36:1/7.41:1. I'm leaning towards the Lunati cam, specs are: 301/313 adv. duration, 220/228@.050, 110LSA, 106IC, 424"/424" lift. What do you guys think? Melling SPC-3 to bleed of more compression? This is budget builds with around 1800$ invested total in both engines.

WOW, $900 bucks a piece, for 2 complete 350 Pontiac engines. Just guessing there are LOTS of guys here who would be happy to pay that for a fresh rebuilt 350.

https://www.summitracing.com/parts/u...iew/make/dodge

Question: With a 1.741 pin height, do you expect the top of the pistons to be above the deck ?

Question: Why the small E-carbs ? Most here usually agree that a correctly built Q-jet will get good mileage, while still providing adequate fuel for any size Pontiac V8 engine, from a 301 to a 455. The '77 low CR 350 came with an 800cfm Q-jet. So, I assume there is some particular reason for the E-carbs.

IF, & ONLY if, you want good performance from BOTH engines, that 1st, low CR engine will benefit from a small Voodoo cam. IF low cost is the primary goal, then that Summit cam is obviously better than a Voodoo.

About that bleeding off compression deal, many have bragged about how they have run well over 10:1 CR, for years, on pump gas with no detonation at all. No problem. They say you just have to maintain a good tune & not use too much ignition advance. Others claim detonation with much less than 10:1 CR.

I think I remember reading here where Paul Carter sited higher CR builds in which he used a Voodoo cam, with no detonation. So, I don't know that anybody here can say, with certainty, exactly which cam would bleed off enuff compression, for your particular build.

With the 301/313 SPC-3, if that isn't enuff, I'm not sure there is a shelf cam that would have more adv dur, and still be streetable in a 350. If more power is a goal, the Summit 2802 cam is sort of a higher lift version of the SPC-3. Just guessing that the 2802 will produce more power, and is cheaper.

I'll add this. A friend, who is also a member here, ran an 041 clone cam in his 350 dirt track engine. Ran good. Won races. But, it was NOT a street engine. And, some here have cited instances where guys were not happy with the 041 cam in their street 400. If used in a 350, it would definitely need Rhoads lifters. With the #92 heads, I don't know how much cam could be used with no valve reliefs ???

[Jay S]

Good economical builds.

It appears you used some different ratings for calculating dcr’s. I think you will be pretty happy with the 2800 on the first engine. Looked like an advertised (262/272) was used on the summit for the calculated dcr. 278/288 is the SAE rating on the 2800 to compare too the mellings (.006 lift at the valve). The Lunati advertised rating seems to match an old gm rating. More than likely that Lunati (110lsa) has much less seat timing than what they list, and has a much higher dcr than what was calculated. They can be ground like that though, but I would want to know more about that cam before I tried it with that 10.35 scr on a 110lsa. My guess is that combo will not work on pump gas. Depends some on your region and altitude though.

The lunati 276/286, 221/230, 455/.455, 112 lsa would be another possible cam choice. But I am uneasy about recommending that cam with that older style 92 head. IRC, it has the early style guides and pressed in studs. I have a stock set of 092s, I would have to look and see what max lift would work. SPC-3 is the safest of the cams listed for that compression. I would not go much higher than mid 230s on the exhaust duration at .050 if you need to go bigger to work around the 10.35 compression. FWIW, On that combo I would do a single pattern cam in the upper 220s lower 230s on a 112 lsa.

[ponyakr]

"...I would do a single pattern cam in the upper 220s lower 230s on a 112 lsa..."

Not what I'd use. But here are a few possibilities in that range.

How much lift is too much ?

https://www.summitracing.com/parts/s...w/make/pontiac

If you need a low lift, high duration cam, but don't wanna use the SPC-3 for some reason, a custom is in order. Here are lots of lobes that will get what you want. They'll grind it on the LSA you want.

http://www.bulletcams.com/Masters/Hlobes.htm

CC has a few lobes that fit the duration range, and have mid .400's lift. They're Magnum lobes, listed on page 11. There are 224°, 226°, & 230° @ .050 lobes.

https://www.compcams.com/lobe-catalog

Both CC & Bullet grind Stocker cams that have even less than .400 lift, but all the duration you want. So, just about anything is possible, for those who can afford it.

[Jay S]

A custom cam becomes more affordable when it does not require valve terrain changes, versus an off the self cam that will. The Summit 228/228 cam with .48/.48 lift would require mods. Were as a similar custom cam with .410 lift would not. Bullets custom hydrualic cams are not usually to much more money (at least for me) but by the time you add shipping they are more than an off the self cam from summit. Depends on the cost cam core too. With the price, specs ect, that melling spc-3 I bet will be hard to beat.

Bigger engines can need the exhaust valve opened earlier to keep the exhaust gasses from diluting the engine. Add in the high compression and the smaller intake valve and I think a bunch of extra exhaust duration is not all that necessary on a 350. If the compression was lower compression then I would start adding exhaust duration back on. IMO, the lower compression 350 needs the extra exhaust timing, the high compression likely doesn’t.

[Jay S]

Another way to look at spreading the cylinder pressure out with the big exhaust and intake duration split would be consider what a ram air 4 spec-8 cam does in a 455. It has 240 degrees (244-245 with 1.65 rockers) of duration on the exhaust and has enough duration to keep a 455 humming pretty good to 5500 rpm. Put that same profile in a 350 and your adding more than a 1000 rpm on to the power band. I am suggesting with the limited head flow to keeping the exhaust duration reasonable (around 230 at .050) for the street, and use the intake profile for spreading the cylinder pressure out. The cam like the 744 with the extra duration on the exhaust will make the power band smooth and broad, but If you have the compression to run it you could add intake duration, less exhaust duration, and pull the lsa in some and get more mid range, peak power, and likely a little better fuel economy. It likely would not hold on to the power on the top end like a 744, but that is not necessarily a good thing. My opinion, it would make for a better running street engine than the 744.

We used a big single pattern roller cam in a 350 stock car racing engine to come of the corners harder. For a long straight away I would have put more duration on the exhaust to extend power band. It may not make more power but it would hold on the the power longer. On the street spreading the power out with extra exhaust duration is not always the thing too do.

[Burningbird]

Originally Posted by ponyakr

WOW, $900 bucks a piece, for 2 complete 350 Pontiac engines. Just guessing there are LOTS of guys here who would be happy to pay that for a fresh rebuilt 350.

https://www.summitracing.com/parts/u...iew/make/dodge

Question: With a 1.741 pin height, do you expect the top of the pistons to be above the deck ?

Question: Why the small E-carbs ? Most here usually agree that a correctly built Q-jet will get good mileage, while still providing adequate fuel for any size Pontiac V8 engine, from a 301 to a 455. The '77 low CR 350 came with an 800cfm Q-jet. So, I assume there is some particular reason for the E-carbs.

IF, & ONLY if, you want good performance from BOTH engines, that 1st, low CR engine will benefit from a small Voodoo cam. IF low cost is the primary goal, then that Summit cam is obviously better than a Voodoo.

About that bleeding off compression deal, many have bragged about how they have run well over 10:1 CR, for years, on pump gas with no detonation at all. No problem. They say you just have to maintain a good tune & not use too much ignition advance. Others claim detonation with much less than 10:1 CR.

I think I remember reading here where Paul Carter sited higher CR builds in which he used a Voodoo cam, with no detonation. So, I don't know that anybody here can say, with certainty, exactly which cam would bleed off enuff compression, for your particular build.

With the 301/313 SPC-3, if that isn't enuff, I'm not sure there is a shelf cam that would have more adv dur, and still be streetable in a 350. If more power is a goal, the Summit 2802 cam is sort of a higher lift version of the SPC-3. Just guessing that the 2802 will produce more power, and is cheaper.

I'll add this. A friend, who is also a member here, ran an 041 clone cam in his 350 dirt track engine. Ran good. Won races. But, it was NOT a street engine. And, some here have cited instances where guys were not happy with the 041 cam in their street 400. If used in a 350, it would definitely need Rhoads lifters. With the #92 heads, I don't know how much cam could be used with no valve reliefs ???

I bought 2 complete engines, except intakes and carbs, for 300$. One of the engines had 6X-4 heads that I wanted to use for another build so the 350's was almost for free. The 389 intakes and E-carbs are leftovers from other builds but I'm sure that a Q-jet intake and carb would give more horsepower. I think the pistons will be around 0.008" above the deck. A Voodoo 256 and Summit 2802 cam would be my first choise but I'm a little worried with the piston to valve clearance with pistons popping out of the block and not having any valve reliefs. I have run several Pontiac engines with over 10:1 SCR on the pump gas we have here in Sweden with zero issues. Most of them with Melling SPC-7 or Summit 2801 cams and all with stock distriburators and slow timing curves. I hope the SPC-3 or Lunati cam will bleed of enuff compression without detonation. /Eric

[Burningbird]

Originally Posted by Jay S

Good economical builds.

It appears you used some different ratings for calculating dcr’s. I think you will be pretty happy with the 2800 on the first engine. Looked like an advertised (262/272) was used on the summit for the calculated dcr. 278/288 is the SAE rating on the 2800 to compare too the mellings (.006 lift at the valve). The Lunati advertised rating seems to match an old gm rating. More than likely that Lunati (110lsa) has much less seat timing than what they list, and has a much higher dcr than what was calculated. They can be ground like that though, but I would want to know more about that cam before I tried it with that 10.35 scr on a 110lsa. My guess is that combo will not work on pump gas. Depends some on your region and altitude though.

The lunati 276/286, 221/230, 455/.455, 112 lsa would be another possible cam choice. But I am uneasy about recommending that cam with that older style 92 head. IRC, it has the early style guides and pressed in studs. I have a stock set of 092s, I would have to look and see what max lift would work. SPC-3 is the safest of the cams listed for that compression. I would not go much higher than mid 230s on the exhaust duration at .050 if you need to go bigger to work around the 10.35 compression. FWIW, On that combo I would do a single pattern cam in the upper 220s lower 230s on a 112 lsa.

You are correct, the DCR with the Summit 2800 would be 6.45:1 and not 6.6:1. But I think the 2800 will work fine for a budget low comp. 350 build. I built a very similar 350 engine with the 2801 cam for my Firebird with 4.10 gears and posi, that car ran great and smoked the tires in both first and second gear with a stock converter. After giving it some thought I think I will go with the SPC-3 cam for the high comp. engine. It is the cheapest and safest choice. Thanks for the advice!