73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: Funkatation on July 20, 2015, 02:30:15 PM
-
Hi,
I recently acquired a '74 GMC with stock 454. It's running rough and have decided to tear the engine down and rebuild it. What are some suggestions to get started on making a bit more power? This will not be a street racer or anything, but I figure if I can put some updated internals in to make it better/ more reliable I'd rather do it. Stroking it to a 496 seems like easy power, so thats on the list. Does anyone know what heads are likely to be on it from '74?
Thanks,
David
-
Get the casting numbers off the heads. That is a good place to start.
-
I'm in the process of rebuilding mine as well. You will need to know what heads are on the motor to determine what pistons you'll need and what compression you are shooting for.
-
My '73 454 had 353049 heads on it. Your '74 could have these or the 781s. Either set are what you want for a hot street runner. :)
-
Is it worth the expense to reuse/refresh the existing heads or just get a set of aluminum heads? I see some fully assembled ones for less than 1000 on eBay.
My truck came stock with this 454 and was curious if it matters if I keep the stock heads for value purposes. I don't need gobs of power but seeing as a reworking of stock heads may cost me just as much as these heads but newer technology should breathe much better.
-
Any thoughts on this cam and roller kit?
http://www.summitracing.com/parts/lun-20110120k/overview/make/chevrolet
I want a smooth idle and enough vacuum for brakes, etc. I do not plan on revving too high and want excellent street manners.
-
Checked my heads and they are 781 heads.
Anyone have a preference for pistons? I'm thinking Mahle Power Pak that come with the Scat rotating assembly.
-
Sealed Power/Speed Pro H426P pistons are what I am running. They will work great with your 781s. Should give a compression ratio in the low 9:1s. They are hyperutectic. A good, solid piston for the street and mild competition that isn't using radical shots of nitrous oxide.
Don't know anything about those eBay aluminum heads. What I have been reading about lately is the flood of cheap China made go fast parts. Do some research before buying anything that is not a traditional name brand. I know I wouldn't want to be a guinea pig on a $1,000.00 investment.
-
^Pay close attention to what Engineer says. He is right about the heads too. I would buy the heads bare and have them assembled with all good name brand parts. I would also go with someone that has been building heads for a while. Ask him what parts he prefers. You might ask in advance what aftermarket heads he recommends also.
-
I ended up ordering a Scat rotating assembly with mahle flat top pistons. Going to go with a lunati hydraulic roller cam and valve train components bill be taking the 781 heads to the machine shop for some minor work. I'm thinking a nice sleeper build. Definitely looking to stay in the 9-9.5 range. I'm sure some of the parts are overkill but wanted good quality stuff.
Anyone have suggestions on a good dual plane intake? It has a edelbrock 1406 carb but I think I might need a bit more than 600cfm.
-
Lunati voodoo 60210 would be a good choice with your compression.
http://www.lunatipower.com/Product.aspx?id=2154&gid=289
I think a good valve job with some quality springs matched for your cam and new valve guides with k- line valve guide liners on your 781's would be the way to go. You might want to shoot for at least 750 CFM carb.
Let us all know how it runs, sounds like it would be a stump puller.
-
Edelbrock performer rpm or rpm air gap would be my choice :)
-
I ended up going with the cam above that one, based on recommendations from Lunati. I also ordered the Intake from Chevrolet Performance that is CNC milled to match the heads. Looking forward to getting everything back together. Will post pics of the build.
-
I know you are trying not to go over board on the stock heads when there are affordable aftermarket alternatives but cutting the seats in those 781s for 2.19/1.88 valves will give you much better flow at low lift.
Of course you'll need to port the valve pockets to get the full advantage of the bigger valves and that adds cost.
And a fourth mod I did to my 049s (the third was gasket matching the ports to the intake) that is worth the time to do it is to polish the combustion chambers. Don't open them up and add volume just polish the rough grainy casting surface off.
There are tons of articles all over the interwebs on modified 781s/049s search and read away.
If you are not careful that 454 will run you into the poor house buying axle shafts, u-joints, differential gears, plastic surgery to remove the smile from your face, etc.
-
Does anyone know if I can use the stock oil pan with the bigger crank or do I need to buy a new pan? If so, what are everyone's suggestions.
-
You mean longer stroke? stock pan will be fine.
-
Another question... anyone have opinions on what kind of torque/stall converter I should use with my 489? I'm going to put in a 4L80E. Here are the specs of my cam: http://www.lunatipower.com/camspec.aspx?p=60211
I would like to keep the ability to tow, would a stock one work?
-
RPM range is 1800-5500 a stock converter should be fine.