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big block chevrolet head swap


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  #1  
Old 12-09-2018, 08:10:17 PM
Tracy T Tracy T is offline
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Question big block chevrolet head swap

i have a 1995 454, and i believe it is the gen v engine family. basically a boat anchor as far as performance. i have a set of 1965/1966 closed chamber heads that i think should wake this motor up! casting # 3856206. so here comes the questions, what length push rods to use? i am thinking use stock rockers, valve springs etc. i know i will have to use special head gaskets made just for this conversion and i may have to do some machine work to the valve covers. i haven't done my home work as far as intake manifold or exhaust manifolds yet. not looking for a drag racer just something that should pull like a 454 should and maybe a little bit better mpg. also thinking about ditching the dished out pistons for flat tops. i also may have a issue with coolant temp sensor, mine has two, one in the head and another in the intake. i am listening, what have i missed?
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Old 12-10-2018, 03:33:17 AM
Greg Mosley Greg Mosley is offline
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Default Re: big block chevrolet head swap

Greetings Tracy T. I would consider doing more research on your BBC cylinder head exchange. I don't believe your CC heads will successfully interchange to a Gen V block. GM made some significant water passage changes to the block deck with the Gen V. platform. The 702 castings which I believe you have, tend to shroud the valves. In the day they were designed for a .180 dome piston and higher octane. Your Gen V. heads are OC. and probably have a larger valve diameter. Better flow characteristics. My suggestion would be, install a set of flat tops, an appropriate cam for the application along with proper tuning. As the saying goes (KIS) Keep it Simple. Enuf Said.
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Old 12-10-2018, 09:18:44 AM
Tracy T Tracy T is offline
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Default Re: big block chevrolet head swap

supposedly the victor head gasket 4918 & 4923 takes care of the coolant passages. i could probably research this until the end of time and know nothing for sure until i tear it down. so far the only real difference i have found is push rod lengths are different, and i suppose that could be due to the older design having adjustable valves. it does get rather conflicting when looking up heads by application, because some bridge the gap. in other words they were used prior to the gen v and also on the gen v.
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Old 12-10-2018, 10:12:56 AM
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Default Re: big block chevrolet head swap

Don't think I'd open such a can of worms, too many Frankenstein creations laying around as it is. Always end up with more problems than success. I've never been a fan of mixing up a mish mash of parts to try to create a few extra ponies. Leave that to the race builders, they don't mind throwing away piles of cash. There are way more design changes over the years for those units than most suspect, EPA mandates in later years basically required an entirely different internal design.
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Old 12-10-2018, 10:30:27 AM
Tracy T Tracy T is offline
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Default Re: big block chevrolet head swap

IMHO the epa should have been castrated in 1972! remember air injection reactors? what a joke! basically pump fresh air into the exhaust manifold to get a better reading out the tail pipe.
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Old 12-10-2018, 12:04:28 PM
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Default Re: big block chevrolet head swap

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Originally Posted by Tracy T View Post
remember air injection reactors? what a joke! basically pump fresh air into the exhaust manifold to get a better reading out the tail pipe.
i had a new 1968 Camaro with the air pump. one day the highway patrol was checking emissions right by my driveway. when i came home, they checked my car before i could drive in, checked fine. i pulled the belt off and had them check it again, no difference. but they wouldn't let me run without the belt on
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Old 12-10-2018, 12:16:13 PM
Tracy T Tracy T is offline
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Default Re: big block chevrolet head swap

mary, i didnt realize the air pump was on vehicles in 68, so back up a few more years on how i feel about the epa! detuned, decompressioned, burn more fuel, less power is some how cleaner? blah!!!!
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Old 12-13-2018, 09:31:38 PM
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Default Re: big block chevrolet head swap

I have a 1994 c30 454. I was looking at mark V 366 heads. They are closed chamber. The original TBI is a problem blocking performance. The computer is not capable of working over about 4500 rpm. Vortec heads have a small chambers but no exhaust crossovers.
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Old 12-13-2018, 10:00:50 PM
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Default Re: big block chevrolet head swap

We have a mid 90s motor home on a GMC 3500 chassis. It has the Throttle Body 454 in it. Beautiful running engine and not bad on fuel, but like all later EPA engines, it's not the butt kicking horsepower beast of it predesessors. No slouch though, it will easily cruse at interstate speeds with the big coach 32 ft rv, no problems. Unless you are at the drag strip, no one ever needs any engine to reach those high RPMs, the torque curve on most big block engines are in the lower rev range where it's needed to do practical work. High rpm = high fuel consumption.
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Old 12-13-2018, 10:39:17 PM
pegasuspinto pegasuspinto is online now
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Default Re: big block chevrolet head swap

tracy, is your 454 throttle body or plenum with port injection?

The Vortec engine is supposed to be an improvement, I have a 1996 vortec 454 and it's OK but not a hot rod. 10mpg no matter what I do lol.

I have throught about what I could do to massage a bit better performance and fuel economy out of it...

Supposedly the 1995 was 230 horse, and the 1996 was 290 horse...
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Old 12-13-2018, 11:50:52 PM
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Default Re: big block chevrolet head swap

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Originally Posted by pegasuspinto View Post
tracy, is your 454 throttle body or plenum with port injection?

The Vortec engine is supposed to be an improvement, I have a 1996 vortec 454 and it's OK but not a hot rod. 10mpg no matter what I do lol.

I have throught about what I could do to massage a bit better performance and fuel economy out of it...

Supposedly the 1995 was 230 horse, and the 1996 was 290 horse...
mine is tbi. for what its worth from my research, in 1996 they went away from the dished pistons back to flat top pistons, this pushed the compression back up a bit. also the camshaft seems to run only a few years before a change. i was looking at camshafts for a 1988 they offer a stock replacement that the computer should accept, after all in 1988 they were injected. this camshaft under applications goes all the way back to 1970 and was listed for a corvette. i will see if i can dig that number up and post it, best i recall it was a common camshaft back in the early 70's. no dragster cam by any means. yes 230 hp sounds about right, its a slug for sure! as for the nay sayers just getting a few more ponies do your home work, it is perfectly possible to get another 100+ hp out of this engine using stock parts with no major modifications.

---------- Post added at 10:26:14 PM ---------- Previous post was at 10:15:08 PM ----------

camshaft, sealed power #cs774

---------- Post added at 10:50:52 PM ---------- Previous post was at 10:26:14 PM ----------

here are some interesting numbers, the heads i bought are casting #3856206. 1965/66 396 325 hp.

one other head casting #3872702. i forget the year but its close to the year range from above, 325- 390 hp depending on engine it was used on. 1cc difference in combustion chamber, same valves but larger intake runners. i have examined the intake runners and nothing a port and polish wont make up for. yeah, 230 hp out of 454 cubic inches anybody know what kind of cfm tbi was rated for?
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Old 12-14-2018, 02:20:19 AM
Tracy T Tracy T is offline
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Default Re: big block chevrolet head swap

Quote:
Originally Posted by Greg Mosley View Post
Greetings Tracy T. I would consider doing more research on your BBC cylinder head exchange. I don't believe your CC heads will successfully interchange to a Gen V block. GM made some significant water passage changes to the block deck with the Gen V. platform. The 702 castings which I believe you have, tend to shroud the valves. In the day they were designed for a .180 dome piston and higher octane. Your Gen V. heads are OC. and probably have a larger valve diameter. Better flow characteristics. My suggestion would be, install a set of flat tops, an appropriate cam for the application along with proper tuning. As the saying goes (KIS) Keep it Simple. Enuf Said.
good advice here, and i wont be able to check it out until i pull the heads. from what i have read the problem area is the 3 water jacket ports near the lifter valley. there are other changes as well but this seems to be the problem area. any way i dont think i have wasted any money at this point, period correct closed chamber heads arent worthless. from what i have learned with aftermarket heads the problem has been resolved. i wouldnt even bee attempting this if the motor wasnt comming out any way "time for a clutch". we will see where this winds up, may be flat tops with a different cam but it wont be what it was for sure.
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Old 12-14-2018, 05:54:57 AM
Glenn Ayers Glenn Ayers is offline
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Default Re: big block chevrolet head swap

I didn't see if you posted whether this 454 is in a truck or a car ???

You don't want Corvette big runner heads or a Racing style cam in a truck.
Intake air speed (small runners) is what you want for lower end torque.
Large runners & more air flow volume is what's needed for high RPM power.

Most good "Street" Engines are equipped with medium flow runners.

A good example of "Too Much" is no good for the "Street" .. is Ford Boss 429 "Hemi" ... They SUCKED for red light street racing. Built for mass air flow .. & they were terrible low to mid range performers.

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Old 12-14-2018, 08:42:18 AM
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Default Re: big block chevrolet head swap

If your application is for truck or rv, you might consider a Banks Power System. As mentioned before, max torque is in the lower rpm ranges. Reportedly this type of add on results in added hp and reduced fuel usage. I have seen them on 460 Fords used in rv application, max torque @ 2200 rpm.
JG
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Old 12-14-2018, 09:50:52 AM
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Default Re: big block chevrolet head swap

its in a 3/4 ton pickup with a 5 speed manual transmission, not sure of the gear ratio but it is low. this truck should be a stump puller but its not. the camshaft i looked up was for a 1988 1 ton, when i checked applications list a whole range of years came up including 1970 vette. yes looking for low rpm power and torque, this engine should never see above 4000 rpm, preferably never above 3000 rpm.
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Old 12-14-2018, 07:30:27 PM
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Default Re: big block chevrolet head swap

Then you do NOT want large intake runners.


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Old 12-29-2018, 01:56:03 PM
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Default Re: big block chevrolet head swap

ok so i got the engine out yesterday and the engine on the stand, so i pulled the driver side head and i see where the problem area is. second water jacket back from the front on the intake side of the head. i dont think there is enough material in the head to get a good seal, this is with a 702 head, my other heads that i am thinking about using are @ the machine shop being checked out. oh well if i cant use them their is more than one way to skin a cat.
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Old 12-30-2018, 03:32:04 PM
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Default Re: big block chevrolet head swap

Personally, I'd just add a good RV Camshaft for low end torque and dual exhaust if it doesn't already have it for better breathing on the top end.

And while you have the heads off anyway, treat them to a good 3 angle valve job.

No need to get crazy with a truck engine.

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Old 01-14-2019, 01:44:26 PM
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Default Re: big block chevrolet head swap

i spoke with a man that has extensive knowledge with this era engine, the problem with power is getting enough fuel to the engine. he experimented with fuel pressure on the tbi setup and unleashed a whole different side of this engine. the problem he ran into is the factory injectors cannot handle the needed pressure, his results were plenty of power with increased fuel pressure but when returned to a idle the injectors couldnt shut the fuel flow down causing a flooding condition at idle. he went with a aftermarket mpi setup and gained power and also improved fuel mileage. this was in a P30 step van loaded with tools, think tool truck like snap on mac etc where he is carring a pretty good load all the time.
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