Re: [Amc-list] 304 head swap

[Wrambler242@xxxxxxxxxxx]

My brother did a Ford build with new 80's era 5.0L heads on a 70 spec 351 Windosr.
You know small valves and all, he bought htem cheap from a shop that had installed GT40 heads on a customers new mustang.
   It ran similar to what you report.
Absolutely awesome bottmo end torque untill about 4-45--rpm. then it just flattened out and stopped pulling.
  Great gas mileage, great dirveability. The only time you knew something wasn't there was if you tried to rev it bast 4000 rpm.
   I had a 390 cfm holley on a 5.0L Mustang. It added the same atributes to it. Strong torque and bottom end, but it would not rev past about 3700rpm.

Bruce is right on the money on this.
I've seen the results of big valves in small motors. I knocks the crap out of your bottom end.
I doubt they are what you want in a torque motor for a Fullsize 80's Grand Cherokee.
   You might wan to consider finding the good 304 heads and have them worked with small valves and stems etc; It would keep the velocity up and help torque.

I don't remember what you said the heads were originally ported for, but seats and smaller valves may not be enough to do the trick.

--
Mark Price
Morgantown, WV
1969 AMC Rambler, 4.0L, EFI, T-5
2004 Grand Cherokee Laredo, 4.7L, Quadratrac II
" I realize that death is inevitable.
I just don't want to be around when it happens! "

 -------------- Original message ----------------------
From: "Bruce Hevner" <scramblr@xxxxxxxxxxx>
>  I have done the 290 head swap both ways.
> I had a Javelin which had the 343 in it. Since it was a daily driver I
> didn't want it out of commission while I modified the heads for "stock"
> class racing. I bought a set of new castings from the local AMC dealer and
> modified them in my spare time so I could just swap heads and keep the car
> on the road.
> I did a 3 angle valve job, a little "blending" in the bowls, cc'd and milled
> them to the minimum and a set of stouter valve springs. It definitely helped
> the performance but not by a lot.
>   Anyway that left me with the OE stock heads. A friend of mine had a 290
> AMX and wanted to see how much a "big valve" head swap would help. While the
> heads are a bolt on replacement I still needed to notch the cylinders AND
> the piston notches. I did this IN THE CAR by greasing the gap around the
> piston at TDC and then using a die grinder to notch the pistons and edge of
> the block till I had .060 (using clay) at all points. As you might imagine
> this took a LOT of time!! The results were mixed. It absolutely KILLED his
> bottom end power and response but did help power after about 3000 RPM. I
> couldn't say what the difference was since this was "back in the day" before
> gTechPro and dynos were so readily available. I would say it probably was
> faster overall, just can't say by how much.
>  Then later on I wanted to do some more work on the Javelin heads (which
> were on the car) so I decided to temporarily use the 290 heads. While it DID
> increase the mileage and low RPM response by a good bit. It KILLED power
> above 3000 and I was BARELY able to make it to the shift point of 4500 RPM
> (automatic with a shift kit).
>  So if I were giving advice to YOU (not knowing the rest of the specs on
> your build) I would STRONGLY advise you against the big valve heads UNLESS,,
> you have a 4 speed trans and a decent gear (3:70).
> I do NOT think you would be happy using that combination in a heavy car with
> an automatic and 2:70 rear end!!
> REMEMBER,,, it's the RIGHT COMBINATION that wins the race!!!
> 
> But HEY,,, that's just ME!!
> Bruce Hevner
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: 
> http://splatter.wps.com/pipermail/amc-list/attachments/20081016/04fc0060/attachm
> ent.htm 
> _______________________________________________
> Amc-list mailing list
> Amc-list@xxxxxxxxxxxx
> http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list

_______________________________________________
Amc-list mailing list
Amc-list@xxxxxxxxxxxx
http://splatter.wps.com/cgi-bin/mailman/listinfo/amc-list