Thread: Pontiac 400 Stroked to 407 Engine Spec Sheet (correct numbers) Input / Advice Wanted

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Ok so first I appologise for screwing up the first build sheet posted I was working on, so after noting to self not to have more than 1 engines notes written down in front of me at one time here is the correct spec sheet for a potential build up of a 77' Pontiac 400. Right now were in the initial stages of looking to take the ole gal and put a fire under the seat. I know pushing a 77' cast 500HP+ is not a good idea so no I don't want to go that far. However that being said I would like some input into potential tweaking of the numbers with maybe a slightly different setup. I punched these numbers in for the estimated HP/TQ which are estimates only. I do know paper is one thing dyno is another. So hopefully i didn't make any errors this time since I did make sure and only had one motors notes out at one time! Thanks in advance for any pointers or input. I would like to boost or maintain the HP/TQ estimates while bringing down the compression to around 9.5-9.7:1 if possible. It is also a goal to keep cost within reason so no im not even going to ask for the cheapo buildup ideas, cheap = more cost down the road.


Pontiac 400 (6.6 liter) 1967-1979
Cubic Inch Displacement 405.8ci +.030 Over Stock Bore W/ 10:1 Compression on Pump Gas. All balancing to within .1 Gram Tolerance

BLOCK: Cast Steel Crank W/ Performance Balance
Pistons H Series Premium Forged Flat Top
Bore 4.150 (+.030 Over)
Stroke 3.750
Main Journal 3.00
Rod Journal 2.250
Connecting Rods:
Forged 6.625 H-Beam W/ 3/8” Cap Screws
Piston to Deck .030 Head Gasket .039”
Piston Dished -5.00cc Flat Top Valve Relief Cut
HEADS: *note final number based on port & polish gasket matched job
Compression Ratio W/ 72 cc Combustion Chamber 10:1
Edelbrock D Port Performer (Bare)
72cc Combustion Chamber
Intake Runner Volume 204cc
Exhaust Runner Volume 145cc
Intake Valve 2.11
Exhaust Valve 1.66
Valve Spring Diameter 1.46” 120 lbs @ 1.800 Installed Height
Cam:
Cam #Magnum 51-240-4 292H
RPM Range 2500-6500
*Required 3000 Stall 9.5:1 Compression *minimum compression ratio
Advance Duration Degrees 292 Int 292 Exh
Lobe Separation 110 Degrees
Centerline 106 Degrees
Valve Lift .501 Int .501 Exh @.50 In Lift
Valve Timing @ .006 Lift
Exhaust Closes 32 ATDC Opens 80 BTDC
Intake Opens 40 BTDC Closes 72 ATDC
Gross Lift (1.65:1 Ratio Rockers) .411 Int .446 Exh
Gross Lift (1.50:1 Ratio Rockers) .374 Int .406 Exh
Intake Manifold
Edlebrock Performer RPM Series
1500-6500 RPM
Carburetion:
Holley 0-4779C 750 CFM Double Pumper
Estimated Numbers
405.8 ci Displacement
452.79 HP @ 6600 RPM 466.07 Ft Lbs Tq @ 4337 RPM(@ Flywheel)
Engine CFM 801
Volumetric Efficiency 103.07%
Compression Ratio 10.01:1
Estimated Wheel HP Based on Upgraded Transmission 369.94 HP
Octane Rating 90

many build use the bbc H beam rod 990 pin and 2200 rods size if you go with a crank. l would lose the stock crank its not realy a stroker till it gets some arm last one i built to 495 . i like to run roller cams most all builds as well

Yeah I know its not technically a stroker. Its how the rotating assembly is sold. I do like your idea though. I read a couple tech sheets about doing the bottom end like your post. All good stuff

not much about it realy scat crank PEP rods I beam rods 6800 and a icon pistons i made up stroker kits with parts i like to used . that is base off of past history with who i deal with . 4.500 crank drops right in the milodon road race pan fits nicely the windage tray may need to be trimed abit and use the mildon tray kit .most time making things fit was dealing with the dip stick guide tube that bolts on the main cap need some fab work to make sure it not bending the dip stick and not reading oil or hitting the counter weights on the crank . roller cam is the only way to go . my own numbers that Erson cams custome grind . Erson roller cam all cores it this time are 4/7 swap for the pontiac built many with and with out the 4/7 swap lower HP and Tq under 700hp and offer more then hp the fire order cuts down on crank flexs helps the engine run cooler .HP and TQ numbers you may not see the gain but still nice to get any ways the custom core cam and custom grind is not any more added to cost . if you go roller you will have to cut out baffle out of valley cover as it hits the roller cam lifter bodys and you will have to reroute your PCV to valve cover .it can not stay in valley pan if the baffler is cut out for the roller lifters

I don't think I have ever (or at least seldom) written, But I, like Pat, do a lot of this type stuff---and your choice of a 400 block ( with the smaller)(altho bigger than most engines) is the best choice Pontiac to use as The 455 block has even bigger main sizes---and with the stroker cranks with the Chev bearing sizes out there are good candidates for moveing up the cubes to the upper 4xx's-


Not only does the 455 have much bigger mains for the bearing size but that makes the distance fron main bore to cam bor shorter and easier to split------

yep well i would of did the 400 block ended up with the customers 455 that i made a 495 very very big mains but as now bigger in CID it may help him keep it under the 6500 + side of the rpms last time i talked to him he could not hook it in any gear on the road

Yeah the customer wants to keep the numbers matching aspect of the car but wants significant amount of gains in HP. I do think we can achieve what he wants through a good solid upgrade to the original spec but do more through the drive train. Right now I'm just spec'ng it out more for budget . Still gotta keep in mind machine shop costs and my labor on assembly. I've heard a lot of negative things about the #X heads so really thinking need to look at good options there. Course if it were me I'd just pickup a good crate motor to drop in and save the original #'s engine. But to each their own..I can do all the fab work for what's been mentioned so that's no issue either. Just looking at different setups to achieve a motor that will get him what he wants which is neck snapping torque and haul ass HP . I haven't done a whole lot of Pontiac build ups so appreciate the advice on their quirks. I'm working on my own 455 Buick engine right now for my 36' coupe so new quirks I'm learning on that motor too with its poor oiling issues in the bottom end. I may just post up what I've got so far . Its gunna be a real mover in that lil coupe all said n done compared to that inline 8 it had haha . I just didn't want to approach the 400 as I would with a Chevy since I've read a lot of subtle differences in the setup of the block

Originally Posted by pat mccarthy

many build use the bbc H beam rod 990 pin and 2200 rods size if you go with a crank. l would lose the stock crank its not realy a stroker till it gets some arm last one i built to 495 . i like to run roller cams most all builds as well

Yeah I've looked at that option and looks like with a trip to the machine shop its really no issues. Blocks gotta go there anyways.

well any stock iron pontiac head is going to roller cam is hard to get the set up on the valve springs that will not pass coil bind ..as for guys with number block s i done more then one and not just chevys every one wants more power out of there muscle car with pump gas .the only thing it can do is move up the cid of the engine move to a roller cam to get the power they want to see out of there car . most all the time the engine cam be put back to stock

I commonly suggest putting the original numbers matching STUFF on the shelf for safe keeping and built a replica to beat the hell out of---that way if you do have something split apart in a catiscrpic manner you haven't killed the value of your ORIGINAL package??????????


But also, in those deals I don't recommend an engine of another make/model because of all the accessories, exhaust, etc------you can still show your Poncho at a Pontiac DAY WITHOUT ALL THE SNUBBERS turning there backs on you---------


and probably valve seat, valve spring, rocker geometry are biggest concerns along with the roller cam /modern day oils issues




Also OSK, I didn't realize that you had recently opened a SHOP?

all good points on numbers stuff jerry. i do spend some time talking about this to the customer if they do want a block thats not numbers that fine .BUT some guys want there number engines and i do not spend more time on this as then needed or tell the guy thats wants the number engine built up not to do it. i see it no sense pissing a guy off and spending his money to the find the guy thats will build his number block has for the chevy in chevy . chevy in the pontiac deal well i have one and the next guy wants it back to stock has abit of work in front of him as the car was not pass warranty before the 389 pack it up then a 400 did not fair much better . so the l88 427 was not a option on the gto but did fit fine dad had it this way it s goning to stay this way till they throw dirt on me

I understand what your saying and where your coming from Pat-------------------


It just seems that here OSK got on here presenting some numbers and such, asking for drtails and opinions and in reality he was fishing for info to pass on to a propestive customer of his business he has formed but he doesn't have any machining equipment to do the work any way-nothing wrong with that, just a little questionable----------??

i hear you.... i will pass on what i was thinking has last time......well ...i had to sit in the corner till i learned how to play better with other s

Yes I did finally launch this last year mainly doing sheet metal fab & customizing. We also do old school speed equipment setups. As far as in house machining capabilities were just not there yet. I have been doing engine work on the side for many years but on the poncho motors I've read just so many different things I thought it best to get a real opinion not some blogger looking to get followers. Were just a small shop that's growing and are getting set to move into a larger facility. Which will allow me to finally bring in more equipment. I do understand where your coming from Jerry just understand I'm always looking to learn something new. I did post my setup though to begin with as how I want to build the motor based on what I know. If there is a better way I'm all ears

Originally Posted by jerry clayton

I commonly suggest putting the original numbers matching STUFF on the shelf for safe keeping and built a replica to beat the hell out of---that way if you do have something split apart in a catiscrpic manner you haven't killed the value of your ORIGINAL package??????????


But also, in those deals I don't recommend an engine of another make/model because of all the accessories, exhaust, etc------you can still show your Poncho at a Pontiac DAY WITHOUT ALL THE SNUBBERS turning there backs on you---------


and probably valve seat, valve spring, rocker geometry are biggest concerns along with the roller cam /modern day oils issues




Also OSK, I didn't realize that you had recently opened a SHOP?

Also yes I am pushing hard to get him to leave the original engine alone. I'd much rather go find another 400 to build and convince him to just store the numbers matching. I always try to side with what's best for the car first customer second. I decided awhile back I'm tired of working for others. Its much better working for myself!