# Chamfering 350 block/ heads comparison



## Boomstick (Sep 13, 2021)

So im on a mission to build a badass 350 for my 69 le mans/gto clone just to beat a coworkers 06 gto who says "the 350 is junk, throw it away" among other things about our "old man" cars. its the original 69 xs code 350 block which leads me to believe the cylinders are not chamfered for the bigger 2.11/1.77 valves the 350 ho #48 heads had since mine was a 2bbl motor. im currently building a set of 1969 #46's which i picked up real cheap. sadly the car currently has 71 #94's on it. it came with 47's. anyway, on the 46's ive already ported the bowls to get those sharp corners out and smoothed out the walls and will be port matching them to a rav intake gasket. ive already lapped the valves, elongated the pushrod ports for 1.65 rockers, and ordered a 2801 cam. it already has an rpm intake and summit 600 duel feed, i have a 750 holley 3310 to put on it when its time. th400, 3:23 gears.

back to the original question. i'm 99% sure my cylinders are not chamfered for bigger valves since it was a small valve motor. to screw up my plans, a buddy of mine ordered a set of speedmaster heads for me for my bday/xmas (one week apart) that i will be putting on instead of the 46's... maybe... they might go on the 400 i just picked up 3 weeks ago... but thats a different conversation. im going to beat this guy with my original 350 under the hood just to prove a point, i dont care if i have to spray 350hp of giggle gas into it to beat him, i will beat that 6.0 with my "old man technology" even if i have to blow my engine up doing it (he's 20 something). im 47 in 2 weeks and my "old" ass can afford a new engine...

has anyone done their own cylinder chamfering on a 350? how much is too much/not enough? is it actually worth the work needed for the hp increase with the speedmasters vs the small valve ported 46's or am i just better off with the ported 46's?


----------



## O52 (Jan 27, 2019)

Some reading to do






notches at the top of the cylinders on Pontiac blocks - PY Online Forums - Bringing the Pontiac Hobby Together


notches at the top of the cylinders on Pontiac blocks Pontiac - Street



forums.maxperformanceinc.com










Big Valve Heads on a 350 - Some Questions - PY Online Forums - Bringing the Pontiac Hobby Together


Big Valve Heads on a 350 - Some Questions Pontiac - Street



forums.maxperformanceinc.com










068 cam.....in a 350 - PY Online Forums - Bringing the Pontiac Hobby Together


068 cam.....in a 350 Pontiac - Street



forums.maxperformanceinc.com


----------



## Boomstick (Sep 13, 2021)

O52 said:


> Some reading to do
> 
> 
> 
> ...


sooo is it safe to assume my block is chamfered? 

I guess ill find out when I pull the heads...

if they are chamfered, that changes every plan i have for this car...


----------



## PontiacJim (Dec 29, 2012)

I think you will find them chamfered.


----------



## Boomstick (Sep 13, 2021)

PontiacJim said:


> I think you will find them chamfered.


that would be awesome... then id put the aluminum heads on and send the 46's out to get 211/177 valves put in...


----------



## PontiacJim (Dec 29, 2012)

Boomstick said:


> that would be awesome... then id put the aluminum heads on and send the 46's out to get 211/177 valves put in...


You would also be wasting your money/time as the heads will flow more CFM's than the engine can handle. Save the aluminum heads for the 400CI.


----------



## Boomstick (Sep 13, 2021)

PontiacJim said:


> You would also be wasting your money/time as the heads will flow more CFM's than the engine can handle. Save the aluminum heads for the 400CI.


So it sounds like you're saying the 350 needs a blower to go with the speedmaster heads...


----------



## PontiacJim (Dec 29, 2012)

Boomstick said:


> So it sounds like you're saying the 350 needs a blower to go with the speedmaster heads...


Hmmm. I thought you had the car at the reputable shop and the engine was being pulled to fix that leaking rear main seal?

*Boomstick:* "Last monday i dropped it off to get the rear main replaced. The shop said they wouldn't have to pull the motor and it would be done in one day. They called me 4 hours later and told me they are pulling the motor (i knew that was going to happen) and the car wouldn't be done "until after thanksgiving" and now i have no idea when i'll get my new toy back... "

Then is seems you have #94 heads on the engine, #47 heads came with the car, you picked up a set of #46's which i picked up_ real cheap_ , and now you have Aluminum Heads on the way that a friend purchased.

You installed 1.65 rockers which you bought cheap and found the pushrods were too short. You also elongated the pushrod holes while the heads were on the block.

*Boomstick*: "so i got a set of comp 1.65s _cheap_. i installed them in the car by using the standard pontiac method. i.e., put the rockers in, balls in, nuts on and tighten till they stop. well every single valve wouldn't close. i called comp and they said i needed shorter push rods. yes i already cut the relief in the heads so the rods dont rub."

Then you got a 400CI engine which you bought "_real cheap._"

The 350CI had the SPS2 intake with Holley 750. Then you installed an RPM Performer and 600CFM. Put the SPS2 up for sale. Then you say "i have a 750 holley 3310 to put on it when its time" when you already had it on the engine and took it off.

Then you throw in"im trying to keep this 300+ hp 350 build under $1000, currently im at $750."


Honestly, I am not buying the tales you keep spinning. Why would anyone in their right minds have a shop pull their engine to fix an oil leak, yet you are capable of port blending the heads, and elongating pushrod holes (while still on the block no less), seem to find most all your parts "real cheap" but don't know if a 400 automatic engine code can work with a 4-speed set-up when you have an automatic in the car *yet the seller knew* the 6X-8 heads would not work on your 350?. Budget? 1K and you are at $750 and you don't want to spend more and then you take it to a shop to have the engine pulled to fix an oil leak? Then you are going to bring it back home and pull the heads with the engine in the car and then have to pull the front of the engine all apart again to get the cam out and rip the heads off?

Not even making any sense here. *Can you explain and clarify things for me?*


----------



## Boomstick (Sep 13, 2021)

1. It's still at the shop getting the rear main done. Adkins automotive in Hagerstown, right across the street from Mason Dixon speedway...

2.The car came with the 94 heads on it, sp2-2 intake and a Holley 3310-10. Ran like absolute crap. I put an rpm (used eBay $250 shipped) and 600 summit ($200 nib from dad) on and set the timing. I bought the 1.65's on eBay for 100. They didn't work because I didn't know you have to use the lock nuts provided and set the lash, I just put them in, tightened then up like stock and the valves wouldn't close. I called comp and was told I needed shorter pushrods which is not the case. I reinstalled the factory valves. Car runs great, leaks like a sieve.

With the wife complaining constantly about the huge oil stain, I took it to Adkins, the same shop the previous owner used. The very next day I paid $300 for the 1969 46's, which today I just finished cleaning and replacing 6 intake valves in with Manley valves I got on eBay for $36 for all 6.

i bought the 400 with the 6x-8 heads off friend of my dad, it's 2 hours away in Glen Burnie MD. I have heard it run. It has a cast intake and Holley dual feed. I'm keeping it for a spare or future project, undecided right now. $1000. I have a video of it running with my car next to it.

sorry i don't know if there was a difference in the pilot bearing size between the 4spd and 400th. I had a problem 25 years ago with putting a c4 to a 86 5.0 because of the pilot bushing being different. I guess I assumed this was a safe place to ask questions without a being treated... Well, like this... was I wrong?


----------



## Boomstick (Sep 13, 2021)

Here's more: the 400 Is next to my car, dad under the hood. At dads house. Can't post the video of it running, I guess you'll just have to not believe me on that... More pics of the 64's. Im sure these are before I started cleaning them... 750 on the car after I had to take the valley pan off to recover the pcv grommet I dropped in it. Ran like crap with the 750 so I put the 600 back on.


----------



## Boomstick (Sep 13, 2021)

Seams I missed answering a few of your doubts..

Port work with a Dremel, drill, and carbide cutter bits (harbor freight 69.99)

Cut the reliefs in the 94's with a Dremel and a shop vac next to the head to catch the shavings.

The guy who sold me the 400 said the big valves would hit on the 350... Apparently asking here if that was true was wrong?

"In my right mind" I haven't been there since the baseball bat attack, or do you not believe that either? I can take a picture off the scar in my head if you'd like...

Feel any better now?


----------



## PontiacJim (Dec 29, 2012)

Boomstick said:


> 1. It's still at the shop getting the rear main done. Adkins automotive in Hagerstown, right across the street from Mason Dixon speedway...
> 
> 2.The car came with the 94 heads on it, sp2-2 intake and a Holley 3310-10. Ran like absolute crap. I put an rpm (used eBay $150 shipped) and 600 summit ($200 nib from dad) on and set the timing. I bought the 1.65's on eBay for 100. They didn't work because I didn't know you have to use the lock nuts provided and set the lash, I just put them in, tightened then up like stock and the valves wouldn't close. I called comp and was told I needed shorter pushrods which is not the case. I reinstalled the factory valves. Car runs great, leaks like a sieve.
> 
> ...



Here is the deal. You are all over the place with what you are doing and your questions. First off, definitely NOT going to out run a late model GTO with a 350 and your car.

You seem to be on a "budget" and going for cheap. A Pontiac is not a Ford and they are not inexpensive.

You don't seem to have a build "plan." Appears to be a lack of knowledge of the Pontiac brand, which is fine, but there are several recommended books that would really help you, and us, in steering you where you want to go.

The* biggest mistake* with a Pontiac engine is when you do not match your parts so they work together as a unit. This can include the driveline. Pontiac engines are built for torque at lower RPM's, not high RPM's like a Ford or Chevy. So the engine build takes a different path. Throwing/adding parts willy-nilly can be a waste of your money and time and end in disappointment.

Many here are more than willing to help, but I personally, and in my opinion, see you doing what you want and will not get the results you seem to want. It does not matter that you are spending money on "bargain" parts, but if you don't know the ins & outs of the Pontiac engine, and are not familiar with building them, then sadly, you end up with some really poor results which could also include a broken engine.

You stated you purchased a 400CI and it has the 6X-8 heads. You did not say the year. Did you know the 1975 and up engines with the 6X-8 heads are the ones generally with the weaker blocks? Thinner castings, weaker main caps, and generally not good for any kind of a high-performance build and may hold up to a 400HP limit - but why chance investing in it and then exercising the HP/TQ only to have the bottom end blow out of the main caps? The casting number on the block to look for is 500557. Look at the photo. You can see how thinned down the main caps saddles are on the block and how they crack/break.

*This is the kind of thing many of us try to prevent for your sake*, not ours. _No one else but me_, will be hard on you when you are all over the place with your questions, don't seem to have a plan, don't seem to have a lot of experience with Pontiac builds, and are appearing to buy parts that are all over the board and not matching well - ie wasting your time & money when you seem to want to be on a cheap/inexpensive budget. I don't have a problem "getting real" with anyone if not to guide you and get to the bottom of what you actually want to do with your engine/car. Otherwise you are just "winging it" and its going to end poorly. So if things don't make sense to me after reading through all your posts, I am going to call you out on it and get a plan out of you that we can then help with. If you take offense, so be it, this is the adult forum.


----------



## Boomstick (Sep 13, 2021)

You're right, I don't have much experiance with Pontiac builds. I currently have 5 people telling me 5 different things to get this car where I want it. I already have 3.23 limited slip rear and the 400th. I know the 94's aren't worth their weight in dog poop, that everyone agrees on. I know the 46's will boost compression and power. How much? I don't know either answer. I've been told the 600 is perfect and been told it's too small and run the 750. I've been told trash then both and get a quadrajet. I've been told the rpm is perfect, been told it's too much, and been told go with a factory intake. Even one guy said I was better off with the sp2... I've been told to go with an 068, 2802, 2801, and something from comp that I can't recall right now. I've been told the big valves heads would be perfect, I've also been told there would be too much shrouding and even been told the valves will bend on the block ledge. 

What I know is, I smoothed out the sharp edges inside the ports at the valves in the 64's, they will breathe better, have more compression and therefore more power than the 94's. Once I get it back from Adkins, it's getting parked until spring at that point I'm putting the heads on, cam in and shift kit. That's my plan anyway and with my chaotic brain, subject to change at any moment. My birthday and Christmas are exactly one week apart, my best friend bought the speedmaster heads for my "Birthmas" gift during their sale. I think they still need to be built, I have no idea what I'm going to do with them yet, maybe I'll go hunting for a 455...

No I don't know what year the 400 block is and the guy I bought it from painted over the letter stamp by the head so I'll have to grind of the paint to read the code. Probably a later motor with my luck, I didn't know there was a difference when I bought it. I've also been told to "fill and sleeve the 350" because it's a stronger block, which I find hard to believe.

What I want is to be able to beat the 06 GTO and the 07 mustang another co-worker has but still be able to drive it to the beach without it overheating. I want the challenge of doing that with the "boat anchor" currently under the hood but if I need more cubes, I'll get more cubes...

Maybe I'll just just buy a Butler...


----------



## PontiacJim (Dec 29, 2012)

Boomstick said:


> You're right, I don't have much experiance with Pontiac builds. I currently have 5 people telling me 5 different things to get this car where I want it. I already have 3.23 limited slip rear and the 400th. I know the 94's aren't worth their weight in dog poop, that everyone agrees on. I know the 46's will boost compression and power. How much? I don't know either answer. I've been told the 600 is perfect and been told it's too small and run the 750. I've been told trash then both and get a quadrajet. I've been told the rpm is perfect, been told it's too much, and been told go with a factory intake. Even one guy said I was better off with the sp2... I've been told to go with an 068, 2802, 2801, and something from comp that I can't recall right now. I've been told the big valves heads would be perfect, I've also been told there would be too much shrouding and even been told the valves will bend on the block ledge.
> 
> What I know is, I smoothed out the sharp edges inside the ports at the valves in the 64's, they will breathe better, have more compression and therefore more power than the 94's. Once I get it back from Adkins, it's getting parked until spring at that point I'm putting the heads on, cam in and shift kit. That's my plan anyway and with my chaotic brain, subject to change at any moment. My birthday and Christmas are exactly one week apart, my best friend bought the speedmaster heads for my "Birthmas" gift during their sale. I think they still need to be built, I have no idea what I'm going to do with them yet, maybe I'll go hunting for a 455...
> 
> ...



Exactly, you are getting too many opinions, not enough facts. Since a stock 06 GTO can run in the low 13 second range and faster with mods, that 350 with your trans/gearing just won't ever match that without a lot of investment.

These are 1/4 mile times for a couple 1968 GTO's which are realistic numbers:

A '68 base 400 4bbl YS automatic no AC with 3.23 rear gears, ran the 1/4 in 15.93 @ 89 mph.

A 400 Ram Air 400CI, M21 4spd with 4.33 HD STT, PS, pwr disc brakes, console, rally gauges, rally II wheels, hood tach car ran a 14.45 sec 1/4 after its RA air cleaner was removed & Goodyear slicks on Ansen wheels. Before these easy mods, on G77x14's and original 14x6 RallyII's, the GTO ran a 14.80... 

So throw out the notion that your 350 is going to beat the 06 GTO. With Pontiac's, cubic inches is what moves them, and cubic inches means lots of torque and torque is what moves the car, not HP. Suppose you could add a 250HP Nitrous kit, but then you might put a factory cast rod through the block or bust a piston.

Again, look over the reading list and purchase a couple books on engine building, then you have facts and information to go on, rather than 5 opinions from 5 people that when added up aren't worth a wooden nickel. If the sources of your info have never owned, built, or raced a Pontiac, move on. But best is to learn what you need to know to put a plan in motion.









FAQ - General: GTO and Pontiac Reference Sources


Surprised this has not been brought up - a suggested reading list for us Pontiac enthusiasts. Let's list any books, journals, factory literature, CD's, or other printed materials tht may be of value. And, it does not have to necessarily be Pontiac specific if it can be applied to out hobby...




www.gtoforum.com





Begin with a good base 400 block, Butler stroker 400CI kit for 461 cubic inches, the Speedmaster heads, good cam, RPM Performer, 800 CFM Q-jet, good exhaust and then you will be on your way to beating the 06 GTO. But, not inexpensive.


----------



## Boomstick (Sep 13, 2021)

PontiacJim said:


> Exactly, you are getting too many opinions, not enough facts. Since a stock 06 GTO can run in the low 13 second range and faster with mods, that 350 with your trans/gearing just won't ever match that without a lot of investment.
> 
> These are 1/4 mile times for a couple 1968 GTO's which are realistic numbers:
> 
> ...


See, telling me it can't be done just makes me want to try even harder... I'd rather try and fail than not try at all...









Small-Bore Pontiac Performance Engine Build - Revenge Of The 350


Dust off Your Small-Bore Pontiac, Stroke it to 383 Cubes and Make 460+ HP




www.motortrend.com





I forgot to mention, the $1000 budget went out the window when that kid started running his mouth...


----------



## pontrc (Mar 18, 2020)

Boomstick said:


> See, telling me it can't be done just makes me want to try even harder... I'd rather try and fail than not try at all...
> 
> 
> 
> ...


Boom don’t let a punk get to ya , these cars get the thumbs up going down the road! I owned a 05 GTO years ago and yes it was a rocket. My 72 would not touch it either! But at least the 72 does not get confused like looking like a Camry like the 05 did👍


----------



## bigD (Jul 21, 2016)

Don't think anybody here is telling you that it absolutely CAN NOT be done. Adam Strang ran 10.80's with an NHRA Stock legal '68 350HO. And you just posted a link to a 350 stroker that made over 450hp. BUT, it would take LOTS of money to build either of those engines.

I'd say it will take a minimum of $10,000, nowadays, to build a Pontiac engine that will run high 12's in street trim. Guys who have most of the good parts already and can do most of the work themselves can shave some off that price. Then, after you get the engine built, you must get the trans & rear end set up correctly, & HD enuff to live AND produce the ET you want. Then, with that much Pontiac torque, you'll need to run soft compound tires & a good suspension set-up that will hook the power to the pavement.

YES, no problem at all building a 12 sec street Pontiac. All it takes is LOTS of money spent CORRECTLY !

If you can come up with enuff $$$$$, some of the guys here can tell you how to build a Pontiac that will easily run high 12's in street trim. 

It CAN be done with a 350. BUT, it's a lot easier with more cubes & torque. The bigger engine can also be a lot more street friendly. They can do it with torque. The 350 will need higher rpm, requiring lots rear gear & a higher stall speed converter.


----------



## Boomstick (Sep 13, 2021)

Well crap. The 400 I bought for a cool grand is a '77 557... 6x-8 heads. I don't know what cam it has but it's radical and much bigger than what my 350 has... My dad is going to fire it up Sunday and get a vacuum gauge on it to see if I need to swap the cam... 

So until I get my hands on a 68-74 400 this 400 will be dressed out with the speedmaster heads, a 2802 cam, rpm intake and 850 Holley unless I can get my hands on a good quadrajet... The XS code 350 that's in the car is getting the '69 #46's, 1.65s on the intake valves only, the same rpm intake and the 750 Holley I just rebuilt. I don't plan on swapping the motors until summer or fall... 

The kid with the 06 blew the rear and is probably selling the car since he can't afford to fix it. I offered to trade my 98 Camry for it but he didn't bite...lol...


----------

