I bought another big block for my 68 Nova project car. (Now the 402 is getting a blower and going in my dad's 65 SS Chevelle so fear not.) This is my setup so far:

1969 350hp 396 bored .040" over cast pistons
forged crank .020" under rods and mains
stock 69 rods resized w/ new bolts installed
'69 #3964290 heads 2.06/1.72 valves
280/280 Comp Magnum cam .520"/.520" lift
Weiand Action Plus intake
750cfm 3310 Holley
1-3/4" Hedman headers
2-1/2" Flowmaster exhaust w/ H pipe
3.73 posi rearend
TH350 with a TransGO programming kit
2400 stall converter

vehicle weight ~3200lb on the starting line


I am hoping for low 13 second performance given decent starting line traction(should be slicked by mid season). It seems I should be somewhere in the 10.4:1 static compression range. I think that will be a decent match to the cam/converter. What do you guys think? I also have a 68 L-88 intake with the cut out plenum, I have toyed with the idea of the L-88 intake and a 290 or so duration cam. But I fear the small valves will hold me back. Thoughts?

Sounds like a nice combo. What are the specs on that cam?

With good traction and with the exact combo you listed,you should be in the mid/high 12's..I don't see the smaller valves really holding you back for your ET goals..JMHO and experience.

The cam is a 280/280 advertised, 230/230 @.050", 110LSA installed on a 106 intake centerline, .520" lift intake and exhaust.

Whew! Mid to high 12s huh? That would sure be sweet.

Actually,a convertor that flashes to 3000 would really help the overall combo out in regards to mid/high 12 second ET..and make sure you run either a drag radial or a DOT slick

You might consider installing 2.19/1.88 valves in those heads if possible. See what the guys think about that idea.... graemlins/thumbsup.gif

Just went through the whole 2.19/1.88 deal on my own 290's. Already had the hardened exh seats in so wound up leaving the 1.72 exhaust alone and only doing the 2.19 intake. I plan to a general clean up of the bowls and blending the seats to the bowls, nothing too agressive, just a clean up. The exhaust port works best if you get a venturi effect through the valve port opening. There's not enough room to create this with a bigger valve. The opening has to be a cross section area of approx 85 -90% of the valves diameter that blends outward in the bowl area and into the exhaust port. A professonal head porter could recontour the bowl area, I doubt most home hobbiests could duplicate it. On top of it, on a 402 based engine you are limited to how much relief from shrouding you will have due to the smaller cylinder dia.

If a 540CI engine can expel through a 1.88, a 402 will work with a 1.72. Using the same ratio, a 1.72 will work up to a 458CI. The best bet is to use a split duration cam with the additional 10 degrees of exhaust timing. Everything I have been able to read indicates it is not the valve size that is the problem, the performance issue on the GM heads is the short side radius in relation to the top of the port. Hence the demand for raised ports and D-ports.

mr 4 speed- Why a drag radial or DOT slick only?

I don't think the big valves are really in the budget right now. Seems like I would be looking at $175 for valves, then some machine work and hardened seats, probably another $200 or so. Another $400 seems like a lot right now for what I want out of it. Right now, this car including everything listed except the slicks has only cost me $2200. I'm trying to be really critical of where I spend my money.

I had also considered a 2800 stall converter, but started to think it might be too high for my cruise RPM. I have read you should keep your stall speed well below your freeway cruise RPM. If I do get another converter, what are some recomendations for a manufacturer?

To answer your 1st question,forget about running street radials at the track if you want a good 60 ft. which = traction which = a good timeslip..again,forget about street tires if you're serious.Slicks are even better if you have them.If you ever decide to do the 2.19/1.88 vales,they're anywhere from $100-150 at either www.summitracing.com (http://www.summitracing.com) or www.competitionproducts.com (http://www.competitionproducts.com) and you do not need hardened exhaust seats so there is some money saved there.Next,a 3000 flash stall with 3.73's is fine,not an issue.As far as a convertor mfg. its all what you have for a budget..if you can afford an ATI or something at that level,go for it..as far "cheaper" off the shelf convertors,TCI or B&M comes to mind.And just an FYI,I run 2.73's with a convertor that flashes to 2800,and I have 10K miles on it with no problems.Hope this helps smile.gif

Amen on the hardened exhaust seats.
I had this done when I first took the heads in to get redone last summer. Now when I went back to do larger valves, the exh seat inserts are going to limit this. But, at least in my case, the 1.72's should be plenty on a 402 based engine. A 1.88 exh valve in a 4.155" bore will open very close to the cylinder wall with out providing a notch similiar to the notch for the intake valves. It would literally cut off flow along the oustide of the valve area where it parallels the cylinder wall in a closed chamber head. An open chamber head will compensate for this by providing an increased flow path in the other areas. On a 454/427 based .030 over bore, you have a good .060 - .070 in additional clearance when the valve is open. Doesn't seem like much, but it is.

Considering that small block based 406 motors get by real well with 1.6" exhausts, and a much smaller exh port, there is justification to stay with the stock valve size on the 396-402 based motors, at least the way I see it.

Don't bolt on that L88 open plenum intake either. There is a debate on whether they came that way ot not. Mine did not. ( 1972 crate L88), and I FOOLISHLY strapped it down to a Bridgeport and milled it out. That was 'trick" in the 70's. Recently had a chance to run that intake again, and ended up putting a Weiand divder plate back in. WHOA! more low speed and never pulled to 7000 so quick.

Dividerless dual plane is a bad idea IMHO, maybe its for 5000-8000, I don't know, but it SUCKS for street/strip. Sell that thing on Ebay to some collector or Vette guy. Its not a good intake unless it fitted with the Weiand divider as mine was. Dont waste any time on it. Plus its rect port.

BTW, you combo looks sweet OTHER than the lack of a splpt in your camshaft. Exhaust really should be bigger with those heads. Own the cam yet? If not, you might look at a 280/288 split. Chris will tell you about a great grind!

427L88,

A little off topic but since you are here. If I am correct, you are a big 427 fan. Have you considered maybe doing a long rod 427 based motor? Nothing too radical just use the standard 454 stroker piston comp ht of 1.520 - 1.525 to get a 1.699 rod ratio (ie - Buick) using the readily available 6.385" rods. I was looking into this as an option for the 402 based motor, along with stroking {which incidentally I was dead wrong on - the 402 based blocks will need major clearancing - read grinding - to clear a longer throw crank either 4" or 4.25" } but cost and limited allowable overbore on my block got in the way. If I could have went to a 4.310" bore, I was on my way to a 439" long rod motor. As I understand it, the real advantage of the longer rods is the increased power with less flowing heads. Seemed a natural for a bigger inch engine on basic closed chamber ovals. Not to mention I would bet that would be a smooooooth running engine.

Sorry, didn't want to steal your thread. Just thought I would throw this in.

I haven't bought the cam yet. That is the only part I have left to get for the engine. I went looking at some cams on Lunati's website. Nice to see Harold's grinds up. I have looked at the 276/286 and the 280/288 hydraulic grinds. I brielfy contemplated a solid, but don't want to futz with the valves. Maybe when I get real serious I will go solid. Which cam do you think would be better? How much split do I need? 8 degrees or is 10 better? I kind of like the 280/288 since it lowers my dynamic compression just a bit and should have a good lope in a 404 cubic inch motor. I don't have power brakes so they are not an issue. Thanks for the help guys.

280/88 would be a good choice, I wouldnt go much smaller due to the dynamic comp.

You are aware, of course, that you can potentially gain 5-10% more power with a solid. Especially an agreesive one. I'm making more power than my buddy's 510 with a mild solid roller.

GRN69, I can see the advantages of the longer rod, but "too small" is not a problem with my heads. In fact its quite the contrary. Although the motor doesnt know they're too big, it seems to be making exceptional power for a 439.

No sir, the only other project in the works, and its a very long term one, is a 496 using small heads. I'd like to use the longer rods unless a set of stockers falls in my lap for cheap.

By too small, i was referring to where I was heading before I said to heck with it and decided to stay with what I had and that was a long rod 439CI w/ closed chamber ovals. The 496 begs for long rods. I would like a truck based 496 with the 6.5" rod. I just have this thing about smoother engines.

I changed a little. I got a Performer intake instead of the Weiand. Should be really close though. Bad thing, is I can't find springs for the 280/288 UD cam that will fit in my stock spring pockets. And since i can't afford machining, I'm gonna have to go with the 280/280 Magnum. But, I think I can still make the low 13's maybe even the high high 12's with it. Thanks for all of your help everyone.

BTW I really like long rod motors too. My 383 in my 68SS Nova has 6" rods in it and I love it. I have an extra 396 steel crank that I got with my last 396. Maybe one day I will track down a 454 block to put it in and some long rods too.....

Originally posted by Rad Racer:
I changed a little. I got a Performer intake instead of the Weiand. Should be really close though. Bad thing, is I can't find springs for the 280/288 UD cam that will fit in my stock spring pocketsCRN-13308-1 (Crane) spring/retainer kit worked fine for me with my UD 280/288..springs are good to .580 lift and fit my #215 heads with NO machine work.

:mad: Those aren't listed on Crane's icky new website. But, the PN still shows up. graemlins/sad.gif

Thanks mr 4 speed. The 280/288 is still on!!