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Author Topic:   400
posted January 05, 2004 06:03 PM
I have a couple questions concerning a 400. I have a chance to purchase one tha tI was told came out of a old caprice. My question is how can I tell its a real 400 and not something else? What 350 parts will interchange? (distributor, intake, etc.) Also in your opinion will it be worth the effort in a basically pure stock class with basically stock engine with 70 cc min head rule and a 410/420 lift cam rule, must run q-jet and stock cast intake, just curious if it worth it cause I just built my 350, 30 over, 336 heads shaved to 70 cc, speedpro hyper flat top w\ coated skirts, and mild under cover port work but if there is a deffinate advantage I will put new motor up for back up and build a 400 while I have chance. What type head numbers should I be looking for?

rico 08
posted January 05, 2004 07:15 PM
The older blocks have three freeze plugs down the side,later have a bump where the extra freeze plug would go,and the really late blocks just have a 509 cast there.Of course they will have the externally balanced balancer with the big scallop.They usually have 993 casting heads which should be ok with your rules.The 400 will be faster but you will have the extra expense.I'd buy the 400 and keep it for a backup unless you really get outrun(unlikely)then bring out the big dog.

dan ferry
posted January 05, 2004 07:24 PM
the 400 will be externally balanced the harmonic balancer and flywheel are diff. the flywheel has a weight welded on it and when you lookat the balancer youll notice that its not smooth the whole way around like the 305 350. as far as if its worth it or not its har to beat cubic inches no matter the cam or head rule there is still the cube difference. i cant imagine theyd give u the same rules for the 400 though usually in the stock class theyll give the spec motor option, or a weight difference.something. if they allow you to put the same stle of pistons heads cam intake and carb as the 350 and you got the money to do it the go for it. as for the head #s i dont know im not farmiliar with the cc has list of block head and intake casting listings could also use to find the 400 numbers on back of block. could just use the heads u have on 350 for the 400

[This message has been edited by dan ferry (edited January 05, 2004).]

posted January 05, 2004 07:50 PM
Whitelightning--run your hand across the side of your 350 block.It's flat. When you slide your hand across the side of a 400 block, you can feel the waterjackets around the cylinders. They are raised areas and are easy to feel.(It ain't like you gotta be some mojomamajamma--if it is a 400 you WILL FEEL THEM)
Everything off your 350 except the balancer will fit. You can even use the flywheel if you add a balance plate (about $14)
In your shoes, I'd go to and order a set of speedpro pistons some 5.7 re-con rods and a re ring set. You'll probably not have to have a small base circle camshaft with the small amount of lift you guys are running.You won't tie up a bunch on special "400" add on parts--but be sure that all the proper holes are drilled and tapped in the block. I had a block that had to have a starter bolt hole, a hole for the clutch ball and one down near the front of the block for the PS pump to mount onto. (That's an eazy job you can do yourself)
My saying is: The only thing that is better than cubic inches is cubic dollars!
Good luck!

[This message has been edited by Eljojo (edited January 05, 2004).]

posted January 05, 2004 09:24 PM
ok I have just got tru reading rules and yall where right. it states 400 must run dish pistons and 100 pounds more but does not say how deep a dish so i was thinking machine a small dish in flat tops but thats probly a whole lota money wasted I think I will buy the motor and keep around for later like above post recomended. The way I see it is unless some one is really running illegal than my 350 should be up to par but If not I will have the 400 laying around wating but I think there would be very small advantage if you have to run the dish pistons and the weight. thanks all

posted January 06, 2004 05:17 AM
Hey Whitelightning! I ran a both engines in my street stock camaro, but with a 17lb vac cam rule, etc. I ran a much bigger can in the 350 with bleed lifters, flat tops, stock heads, etc., and only had a 268 (RV) cam in the 400 with dish pistons. I put all the 350 parts I could, excluding the balancer and flywheel, on the 400 and man, what a difference. I could still turn the 400 in the same RPM range as the 350, but the 400 pulled like a freight train from corner to corner. Cubic inches is the way to go. I'd get the 400 and use the 350 as a backup. Just my 2 pennies. Good luck.

rico 08
posted January 06, 2004 05:04 PM
Do the rules say WHERE you have to put that 100 lbs?If it's anywhere then yes it'll be worth it BUT if they make you put the weight(lead)on the front(firewall)which is probably where they would want to to penalize you then i'd run the 350.

posted January 10, 2004 06:40 AM
400 all the way with the rules you said, cubes are hard to beat. the last 3 block #'s are 509 817 511 they are the only 3 block numbers i know, but could be wrong.

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