doing a head and cam swap on my 454.

i am putting on brodix race rite 115cc heads. it currently has 427 heads which have 98cc chambers so i know i am over the stock 8.5:1 ratio
i am trying to calculate my compression ratio using thes brodix heads but i need to know the specs on the stock 454 pistons.

stock compression with stock heads is supposed to be like 8.5:1 so with my current 98cc heads it should be a little higher.
i am going to assume that when i go to the 115cc brodix heads the comp will drop closer to the stock CR.

what is the best as well as easiest way to go up a point in compression? id like to be at 9.5-10:1

i am guessing i can have the racerite heads milled. plus i suppose that changing pistons with the engine still in the car is not going to work either.

i really dont want to pull the motor

 

Not knowing exactly what you have, working from an assumption that your original engine was apparently an LS4 from that low CR (which I've read as having been 8.25:1), I believe your stock heads (3999241's?) would have had 113cc chambers. IF this info is correct, your current CR with 98cc chambers would be on the order of ~9.25:1, and your new CR with 115cc chambers would drop to ~8.1:1, both of these depending on head gasket thickness.

So, FWIW, if you insist on leaving your short block alone (not the call I'd make, but it's your decision) you'd very likely be required to angle mill your brand new heads down to where they'd have on the order of ~90-95cc's to yield 9.5-10:1. That's a 20-25cc or greater than 20% combustion chamber volume reduction, and potentially a drastic enough alteration to have a detrimental affect on flow and possibly fit, btw. It's also going to reduce valve to piston clearance, which is another consideration if you're looking for much lift. I'd pull it and change the slugs, going thru the bottom end while you're at it, which is an especially good idea if it's tired and your looking for serious power gains, but you MIGHT get away with doing it with the block in the car if you have no appreciable cylinder wear (and no ridge). Certainly not the preferred route, tho. My $.02

 

damn,
well looks like it is time to look into other options.
it is supposed to be a LS5. however it is not the original motor plus it is a 4 bolt instead of a 2 bolt.
casting says it is a 72 454 though.
i am really trying to avoid pulling the motor out of the car to change the pistons.
8.5 is the published CR for a 72 454 with 113cc chamber heads so the slight larger chambers of the brodix heads when i did the math put it just under that.
i was considering a thinner head gasket than the .039 stock one to compensate slightly

i may just be better off keeping the 98cc chamber 427 heads that are on it now and just having them ported out.
or i could try these
http://www.jegs.com/i/Edelbrock/350/60499/10002/-1#

the performer hi compression from edelbrock
stock exhaust location and 100cc chambers

 

Now that you've shared more info, I'm fairly sure the '72 LS5 also had 8.25:1, tho the LS5 cam differs from the LS4, but the heads would still have had 113ccs, so those CR and cc projections should be valid.

If your deck height is zero, you need a .039" gasket, but if your pistons are ~.020" or more in the hole you could (read, "should") go thinner. However, this would likely net no more than .25:1 increase in CR. IMHO, those Edlebrock's appear a good option if you plan on leaving the bottom end alone, as they'd put your CR in the 9-9.5:1 neighborhood, again depending on gasket and deck ht.

FYI, your bottom end should be a 2-bolt main with a forged crank (IIRC), forged rods with 3/8" bolts, and cast pistons. Again, if it's tired it deserves being gone thru at this time, in which case installing main studs would be good insurance.

So, as heads, CR and cam are all relative, where are you on that latter decision now?

 

the only thing i worry about with the 100cc edelbrock heads is that it says that stock rocker arms wont work with .5 lift or higher. i am looking at two cams
the com HE 268H and the magum 270h
the 268 has a lift of .485 so they should be fine
the magnum has .51 so its too much.

i could always get the normal performer heads with the 110cc chambers
still smaller than stock chamber and no lift restrictions on the cam.

i definitely counted 4 bolts on each cap when i took off the oil pan

the car itself has less than 75K miles on it and i know its not the original engine so for now i am just going to do the top end.

 

As mentioned...a lot depends on what's actually in it for pistons and if block has been decked any.

The 100cc Edelbrocks are just regular ones that have been milled at the factory. They were first marketed as *truck* heads and later as the EFI heads. Check with Zwede here on the Forum....he has built exactly what you are planning.

Shouldn't be any difference on heads concerning rockers..but stock ones sure need to be checked closely in the .550 or so lift range. Anytime you change stuff around you need to verify pushrods, rockers etc.

You can get .015 gaskets from cometic that might help...but the Brodix heads are definitely going to be the HP winner between the Edelbrocks and the Brodix.

JIM

 

really
even with the drop in compression? the 115cc brodix heads will outperform the 100cc edelbrock heads?
thats interesting because using the compression ratios that have been mentioned here the cam quest has almost a 30hp loss projected in the brodix heads due to the lower compression

 

Airflow will out do compression anytime. The Brodix ovals can handle 500+" motor to the 700HP range easily. Those Edelbrocks are nice heads...but they will be wheezing long before that.


Just order the heads from Brodix milled to what you want. They will help you out. I'd hate to see you build anything in the 8-9.0 compression range...do whatever you can to get near 10.0 at least.

Might check with Mike Lewis at Lewis Racing. Tell him Jim sent you....he's been know to save folks some bucks on Brodix and AFR and is a very upstanding and honest guy to deal with. Run your head and cam choices by him and see what he thinks. It all depends on what your ultimate goals are...but the Brodix will be a much better head for you in the long run.

http://www.lewisracingengines.com/

Better heads beg for more cam...but the advantage is that the better the heads...the better the performance will be with any given cam you pick.


JIM

 

cool,
i am teetering on the edge of not exactly knowing what i am doing here so i appreciate the help

 

I hear you. Hey,,,we'll help you all we can. Please tell us a lot more about the car and what you plan to do with it. Those cams you're looking at are VERY mild...and will do well with great heads....but you won't be getting anywhere near the potential the heads have to offer.

Porting iron heads can make great power....but it all depends on the porter. It's easy to blow a lot of $$ on stock heads by the time you get valveguides and valves handled as well as any porting.

What trans, gears, converter (if auto) do you have? A/C, PS, PB etc? What do you like to do with it? Do you want to run 11's or 12's? Does it need to idle very smooth? Headers? Exhaust system?

All of these choices might add up to not really needing to change heads yet.

By the time you pull cam..and heads...you're about 30 minutes from having engine on a stand. Might be easier to just pull motor, do whatever you decide to do and clean it all up pretty and paint under hood etc. You'll be able to do a much nicer job with engine on a stand. Then you can think more about pistons...which actually are pretty easy to change on a Vette while motor is in the car..but you never really know about bore straightness etc unless you measure stuff closely.

JIM

 

if i thought i could get the engine out in my garage, id probably go ahead and do it.
my main goal is 350rwhp.
total setup on the car

it has a LS6 dual plane intake,
750 carb
hedman headers 2" primaries
th400 trans/2500 rpm stall
3.55:1 rear end
no air
power steering
power brakes

the current heads are closed chamber 98.4 cc heads
i chose the milder cams because beyond the 270 the recommended compression ratio just isnt there.


however i believe i found the perfect ones.
god i love the internet
its so easy to spend money
apparently you can order the race rite heads in 110cc combustion chambers
summit has them for special order.
http://store.summitracing.com/egnsea...115+4294889122

as long as they have the bung for a coolant sensor these are the ones i am going to go with.

 

This may not be what you want to hear, but if your engine is running good, leave it alone. Save up your pennies until you can build a combination of parts that work in concert to give you a motor that will make you happy and be worth the money you spent on it.

Since it is not the original block, look for a good block to build from, collect the pieces as you can, and when you get it done, spend a weekend and swap it out. You'll be happier in the end.

 

Are you SURE someone didn't change pistons during last rebuild? Maybe they have a small dome afterall? Have you done a compression test by any chance?

You've got decent gearing...so that helps and no A/C to deal with. Headers and a slightly better stall speed. Is the carb a Holley DP or vacuum? What about rest of the exhaust?

You're right where Marcus (Zwede) was at.....he made 375 or so RWHP I think with his using a relatively mild HR cam..but he had a stick trans. You need to be thinking 500+ flywheel HP for your automatic car.

That's really not a big deal for a 454 to do with the right parts. Are you willing to move to a roller cam? That will really help and open lots of possibilities. We can get there with the hyd flat tappet...but how about a solid flat tappet? Willing to check valves every year or so?

I'm assuming this is the flat LS-6 intake? Stock flat hood? No L-88 hood in the future?


JIM

 

absolutly not,
IMO that is the ugliest thing chevy ever stuck on a C3
i dont want to do a rebuild.
by the time you invest in the parts, the machine work,
the labor
you can just buy a 454 HO and be done with it.

 

Beauty is obviously in the eye of the beholder, and to many of us the form and function of the L88 style hood is quite appealing.



Just saying...

 

yeah yeah i know
i also like my luggage rack too but that l88 hood just doesnt look right.
i sat in a 75 once that had one and i couldnt even see over the hump

 

I reached your goal with some change to spare (358 RWHP and 411 RWT) using ported stock heads (same chamber size as your current set) on my 390 HP 427. The cam was a hydraulic flat tappet by Crower that peaked at 5900 RPM but stayed above 350 RWHP to over 6300 RPM. The heads also had been upgraded to 2.19 and 1.88 valves, which is a big factor IMO.

My combo was virtually identical in terms of gears, intake, headers, and trans/torque converter. My pistons were milled and chambers cc'ed to give me 9.5 comp. ratio and I was running a nicely modded DP Holley carb. The car ran low 12's like that and was a sweet driver on the street. I've since made a few changes but they aren't relevant to this discussion other than the fact that I'm running the Edelbrock heads you're looking at.

Those Brodix heads are sweet but might be wasted with the type of cam you're thinking of. You may want to port your current heads and have them fitted with the bigger valves if you have a good shop you can trust to do the work. That way you could stop worrying about the pistons and just go with a thin head gasket to bump your compression.

Hit me up if you want cam specs from the Crower I used to run.