[JimNut]

Hey everyone!

I'm currently finishing up a mild 400 sbc build and having some trouble deciding on which cam to go with. Specs on the engine are:

- 400 bored .060 over (412 ci)
- 10.5:1 compression
- World Product SR Torquer heads (76cc, 2.02 / 1.60's) (not the greatest heads I know but its what I have and money is kind of tight)
- Edelbrock Performer dual plane intake
- Holley 750cfm Vacuum Secondary's

I have a built TH350 trans that I will be using and the car has 3:23 (I believe but havent verified yet) gears. Currently don't have a stall but will purchase one that best matches the cam.

My car will be on the street 95% of the time with MAYBE one or two track visits a year so it has to be street friendly. Lately I have been looking at the Comp Camps XE274H and have heard some decent things but need to know if I should go bigger or smaller for my motor. Some people say I should jump up to the XE284 because I have enough cubic inches but I also don't want to have to rev this thing to the moon to make power

XE274 specs are here
http://www.compcams.com/Company/CC/c...x?csid=87&sb=2

Any help would be greatly appreciated! Thanks

[tuckpoint]

Compression a little high .Rear gears tall , World products good for the $. Go on the mild side.You won't need a lot of lift,You could use some duration.(shaves a little mechanical compression off).Call up the supplier (Jegs,Summit,Speedway) Those guys get paid to help.Don't overcam you'll have a boat anchor.

[ericnova72]

I do mostly just 400's and 383/385/388's strokers - go with the 284XE, it will act in the 400 just like the 274XE acts in a 350. The bigger cubic inches will suck up the added duration and make the cam seem smaller. Rpm range will drop from cam listing to 500-600 rpm smaller.

Remember that catalog rpm ranges and operating characteristics are based around the 350 cube engine in SBC cam listings, as it is the most common and used as the "standard" to measure to. You are 50 cubes bigger.

You must have a domed piston to have 10.5-1 comp with a 76cc head??

[JimNut]

Originally Posted by ericnova72

I do mostly just 400's and 383/385/388's strokers - go with the 284XE, it will act in the 400 just like the 274XE acts in a 350. The bigger cubic inches will suck up the added duration and make the cam seem smaller. Rpm range will drop from cam listing to 500-600 rpm smaller.

Remember that catalog rpm ranges and operating characteristics are based around the 350 cube engine in SBC cam listings, as it is the most common and used as the "standard" to measure to. You are 50 cubes bigger.

You must have a domed piston to have 10.5-1 comp with a 76cc head??

I haven't purchased the pistons yet but those numbers came from a online compression calculator.

numbers I used to get 10.5:1 (ish) were with a pure flat top piston. I decided that 10.68:1 was getting to high. Decided to go with a +5.0 cc piston to bring it down a little.

bore - 4.185
stroke - 3.75"
piston to deck height - 0.012
Gasket thickness - .040
flat top pistons (+5.0 cc)
Here is a link to them:
http://www.summitracing.net/parts/STL-H869CP60/

I decided to go with a piston that will get my closer to 10:1 (thats where the +5 cc comes in). I don't want to have to retard the timing to much to prevent spark knock. Calculators say it is good for 10.11:1 which sounds better to me anyways

[ericnova72]

Okay, I see how you worked it. Pure flat top is impossible to find for the SBC, they all have valve reliefs that add 5cc or more.

I got the same #'s with the parts you listed, 10.12-1.

You realize the piston you picked is going to require the use of the short stock 5.565" 400 connecting rod?? Not many folks use them anymore, with 5.7" rod pistons just as easily available. ZH816CP60 fits a 5.7" rod.

If you use the 400 rod, definately put ARP rod bolts in and have them resized.

Just some info, you can get a much better 5.7" cap screw type I-beam aftermarket rod for just slightly more $$ than it will take to recondition your stock weaker short 400 rods.

A great parts source I use a ton - www.competitionproducts.com in Oshkosh, Wisconsin. Good prices, good quality, good folks. Very good on valvetrain parts.