I'm looking for some advice on my rebuild. My project started out innocent enough. I run a '77 460 and saw an ad for DOVE heads. They where nicely ported and I thought "why not", the better flow and little bump in compression would be great. That's when the adventure began.
I had the heads stripped and hot tanked, the first problem came to light. No cracks but the seats had been pounded out on some of the exhaust and a couple of the intakes. So hardened seats all around. Well the valves didn't look so good so stainless valves got ordered. No sense putting on heads without a little more lump in the cam so a Comp Xtreme (X4270H-11)was ordered, then their high energy lifters, matching springs, guide plates & studs with head machining. Ordered the pro magnum roller rockers and just about have the heads assembled. I then stepped up from the edelbrock performer to the performer RPM intake. Also sprung for a cam gear drive and stewart water pump and mildon head studs. Needless to say a long month of overtime. Now the questions.
- The ports on the heads have been opened up a lot, the edelbrock intake recommends port matching to the stock intake gasket size and no more. Should I use the CJ intake gasket or the stock size when doing the final install?
- For now I'm still using using stock exhaust manifolds with a 2.5" dual exhaust and 40 series flowmasters. When I can afford the headers the only ones that look will fit are L&L. Because the exhaust port is opened up do I use the stock size gasket to match the header or the CJ size to match the head? Since the headers are coated I can't really touch them.
- During the breakin of the cam I've read that you should hold it at 2000-2500rpm for 20 minutes to half and hour. But for valve springs they recommend low rpm for a while then a complete cool down and then another run to properly break them in. What would be the best compromise?
Sorry for the long winded post but getting in this deep I don't want to screw anything up. Any other suggestions are welcome. Thanks for your time.

 

You're gonna love that cam, but only if you break it in right.
As soon as the engine receives fire, bring the speed up to 2000 RPM, and keep it steady for 15-20 minutes. Then begin to cycle the engine speed from 1500-2500 RPM, to direct oil to different parts of the engine. Some say 20 minutes is enough, Comp Recommends 30 minutes, check your manual. If you have dual valve springs, only install the outer ones, you don't want too much spring pressure during break-in, it will really hurt the lobes. After your 30 minute break in, change the oil and the filter, and install the inner springs. Then drive it for 500 miles, without revving it over 4000 RPM, but not letting it get bogged down in too high of gear, usually around 2000 RPM. The Interstate is a great place to do this. Then change the oil/filter again. Then you will be ready to rock and roll.
Happy wrenching,
John F. Daly III
The TorqueKing

 

As for the port matching...you said the runners had already been opened up. are they bigger than the standard gasket now? if not, your best bet will be matching both intake and heads to the standard gasket. the larger cj one will require more work and will leave you with huge ports. you will want to blend back into the runners on both sides and doing so with such a big opening will probably cost you power down low. i could be wrong...you would think that the venturi effect would be more efficient, but ive heard unless you are running a high revving engine where bottom end isnt a concern, to leave them as close to standard as possibl and just smooth things out really. anyone else have experience with this?

 

Thanks TorgueKing, I finally got through on Comp's Cam line and you where bang on, install the outer spring only or risk wiping the lobes. That would have made an expensive mistake.
To 83f2504X4, when I picked up the heads they had been previously ported to what I believe are CJ specs. The heads are at the machine shop right now and the gaskets are here at home. I had an old exhaust gasket that I held up to the ports and it definitely was smaller so I'm assuming at this point the intakes are the same. The Edelbrock Performer RPM says its good for both stock and CJ applications but just not to open it up past the stock gasket size on the intake manifold. On both the intake and exhaust I was wondering which was best, use a gasket sized to the smaller port or the larger? My gut tells me the larger but I'm willing to listen to those with more experience on this. It gets expensive making all the mistakes yourself. Thanks.

 

on yer exhaust i would not use a gasket. i would just get some hi temp silicone. thats what my uncle runs on his 460. you need all you can get on the exhaust side, so dont go any smaller. on the intake side i wouldnt want my gasket sticking up into the port any what so ever. i would just stencil of the intake port on the head side. then put it on the intake side and match them up as close as you can. hope that helps ya out some.


-nathan