Cam shaft upgrade

68Runner · Post by **68Runner** » Wed Apr 13, 16 2:32 pm

Hi all

Has any body got any recommendations for a new cam in my 400ci
727 auto
Standard engine apart from
1 7/8" tubular headers with 3" system
Edelbrock performer inlet manifold
750cfnm Edelbrock

It's a street car but I would like something to liven it up a little

Cheers
Ralph

Pete · Post by **Pete** » Wed Apr 13, 16 5:49 pm

The problem you may face is that 400's (whilst being excellent and strong blocks) are pretty low compression from the factory and with poor single valve springs. I had float at 5300 rpm, everyone thought I was on the Rev limiter.

Putting a big cam in could hurt performance - losing you bottom end grunt but not making much more power as most bigger cams tend to favour higher compression.

Also I imagine it will have flat top pistons (or dished) and they will probably not have valve relief's in them, again limiting performance upgrades.

Sorry it is not better news, I am sure others will have their own opinions and feedback.

68Runner · Post by **68Runner** » Wed Apr 13, 16 6:14 pm

Looks like it may be just better to run this till the winter then build it into the motor I want. Looking for around 400-500bhp

Spoke to Dave Billedeau and he recommended building a 451 stroker.

I'll just have to wait I suppose

Blue · Post by **Blue** » Wed Apr 13, 16 6:15 pm

Have a look at the online catalog of Edelbrock or Comp Cams, follow their recommendations for something that will work with the stock convertor and low compression. You will need new lifters and matching valve springs and a quality billet timing set would be a sensible move. Quite a bit of work and money for a small return, you'd probably get more from a distributor recurve if you haven't already done that.

Pete · Post by **Pete** » Wed Apr 13, 16 6:24 pm

Also, the heads will have smaller valves if they are how they left the factory, so another thing not in their favour.

I think the key thing here is compatibility of parts - if you build a more powerful engine it will stall a stock convertor much earlier (as does advancing the initial timing on any motor to run on modern fuels) so the motor will bog at idle and you cannot tune it out.

I think the answer is "polycell" - do it once and do it right with all the right bits, including Convertor.

MilesnMiles · Post by **MilesnMiles** » Wed Apr 13, 16 6:55 pm

Good report so the Hughes Whiplash cams which are designed specifically for low compression motors. Even use stock valve springs. Make lots of torque but may lose some vacuum low down for power brakes if that applies.
Lots on US forums about them

Bozwell · Post by **Bozwell** » Wed Apr 13, 16 11:23 pm

anyone tried Rhoads bleed down lifters? seems to be 50/50 on whether they work or not.

i'm thinking of giving them a go but that'll be at a later date.

Blue · Post by **Blue** » Thu Apr 14, 16 6:44 am

Never used them myself. They were all the rage in the '90's but I've not heard of anyone useing or recommending them in donkeys years, can only assume they were a less than successful crutch.