Great link Cheryl. :TU: I wonder what sort of power levels I can expect from a strong street 401? Who's got the strongest running Nailhead at the moment I wonder?
AWESOME THREAD This is a great thread. I've been doing some thinking about my up comming 425 rebuild and I truly didn't know where to start. I have not put much thought into "power matching" components. What order should things be decided and chosen for maximum power and torque Also what would you do without? I would like to hear anythoughts on this . It would seem head work is in order for sure. Then it seem the block is designed around the heads?What would you NOT do and for what reason? I will be lookin' for as much Nailhead power myself!! :TU: Since this is my first rebuild I want it done right. Still haven't found a guy locally. One person said he was in the buisness for 30 years. In the next breath asked "What's a Nailhead?":spank: So I'm coulting on your collective wisdom here :Smarty:
Jason, I would stay well away from any machine shop that doesn't know what a Nailhead is. That link that Cheryl posted to Crane Cams is a good place to start. It helps you determine your 'basic rpm' and 'cruise rpm at 60mph'. That's a good place to start as that will determine your application. I would say that the first thing to do is decide your application. I would say that it can probably be narrowed down to two choices. Strong Street or strictly drag racing. For "Strong Street" I'd be aiming for excellent mid range with 'respectable' top end. A mid range gear selection (3.23 or 3.42) would suit me nicely I'd say. A well prepared 800 Quadrajet or dual quad setup would be the intake of choice and good porting job with a fair amount of massaging of the heads without going overboard and a cam that works between 2,500 and 5,500 rpm. I'm not too concerned with low end power for the street as a stock Nailhead has heaps and some to spare. My advice would be to save up until you have the funds to do everything properly (even if it means sending your engine to someone who you trust) and then do it once, with thought and careful planning, calculation and lot's of communication with everyone involved as to your intended use. Drag Racing is easy. Just open everything up as much as it can take.
Hummm, now that we have a nice set of heads done. Who has had an intake manifold massaged? The Buick 2 X 4 could probably use a little help? Seems I remember someone doing some flow work on an Offy, yea I know there supposed to be junk, and had it flowing like the Quadrajet. Any thoughts??
Thanx Bill:beer . "Heavy" , my '66 Riv will probably be just a street cruiser and never see a track ( there are none locally). I do have a dual intake for the Nailhead and just purchased a set of 3.42's. I hope I purchase all of my parts in order so I'm not screwed later on. About cams; I've been told so much about not going to a "healthier" cam do to a lack of performance-even decreasing the power that I'm at my wits end trying to make heads-or tails of it all.o No:
Yeah the trick is in the rockers. Tom's Roller rockers should let us use all the ratio and therfore the roller rockers alone would add to the lift of even a stock cam. I'm saving like mad to buy a set.
I don't think you need to worry too much about losing low end torque in a 401 or 425. These engines have very small ports and flow in relationship to engine size. While it is best to discuss your complete combination with your head porter, in general a mild set of heads won't show any loss in low-end torque and even an all-out nailhead port job would probably be fine except in a very heavy car with no gear and low stall speed converter. The 401/425 ports are so small to begin with I wouldn't concern myself with them being to big in 95% of all cases. The Nailheads respond nicely to even mild porting. I have seen street cars pick up 4 MPH in the quarter with mild porting in a car using only a 2 speed trans.
Greg what improvements do you feel could be made on one of Buicks stock cast 2X4 intake? My motor is going to be 75% street but since I have a nice set of heads already done I'm looking to eliminate the weakest points. Thanks in Advance
Doug, I have not worked on a 2X4 425 intake yet, but i'm sure that after flowtesting one, I would find several runners that flow less that the others and would need more work to bring them up to speed. Alot would depend on how much your heads flow and intended application.
Hi Greg, thanks for joining in.... I am looking forward to rebuilding my motor in the near future. If you port a set of heads, are you generally able to make recommendations regarding cam grind? I have been doing a little too much thinking(my brain heats up and I get confused) about possible combinations, and it seems everything centers around cam choice. I'd like maximum porting with maximum streetable cam with headers and Qjet in a 4-spd. Where do you get the cam and custom pistons once you've opened up the heads? I'd like to go roller but don't know where to begin. I know some of the TR folks are modifying their lifter bores to use roller liters out of other motors.....All these questions and possibilities have kept me from pulling the motor so far, as it runs fine......Thanks, Dan
My blown 401 engine was built by Jim Burek (PAE). The heads have some mild porting work and these are the flow numbers (cfm) at 28 inches: Lift - Intake - Exhaust .100 - 74 - 51 .200 - 120 - 99 .300 - 169 - 123 .400 - 193 - 141 .500 - 201 - 150 This is my engine that is currently needing the heads rebuilt as I lost the oil feed to one of the rocker shafts and it ate the valve guides. So I do not have any numbers for performance. I bought the car from my friend and he reported that it ran very strong before it messed up. add on edit: I forgot to mention that my heads are stock valve sizes.
Greg if we don't get rained out for the Holmdel picnic are you planning to attend? If so I will bring the flow sheets from the heads and the manifold. Once you find out what it can do, carb choices are nexto No:
Doug, I can tell you this, I've had Greg Gessler do two sets of heads for me and you saw the work he did on my exhaust manifolds. The throttle response of my black GS is nothing short of incredible. I'm sure if you decide to have him do the porting for you, you'll be more than happy...:TU:
I won't be able to make the picnic. :ball: I have a family thing going on the same day. Hopefully I'll be able to make the next? one.
Off With Your Heads! Generally porting improves air flow throughout the RPM range, and in turn produces more horsepower and torque through the same RPM range while also extending the upper RPM range. The more air/fuel mix in at a given RPM, the more bang: cant loose that way! Case in point, a 455 (sorry, this is where a lot of my experience is transferred from) with a mild Stage-One port job in a full weight Skylark with 3500 stall converter and 3.55 rear gear. The car runs 11.70s at the track. Said vehicle has heads upgraded to competition port with no other changes and then runs 11.40s using the same shift points, and was capable of a little better time by shifting at a slightly higher RPM. Shifting at a higher RPM only slowed the times before the competition port. Three tenths quicker in an 11 second car from porting already ported heads is a big improvement. Although porting tends to be expensive, nothing will complement all other modifications or future modifications like porting. That is almost always the first thing I have done or look for when purchasing. Cheryl
