4.8 heads compression ratio
05-02-2003, 06:34 AM
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4.8 heads compression ratio anyone know the cc's of the chambers on 2001 4.8 heads and what c/r it would make on a stock 01 short block with no milling?
05-02-2003, 08:38 AM
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Re: 4.8 heads compression ratio Chamber size for the 4.8l heads are usually around 62cc. It should up your compression to just under 11:1. The truck heads have a stock intake valve size of 1.89" but can be upgraded to the 5.7l's 2.00" valve size by most machine shops. I've got buckets full of new and used valves. Let me know if you need any.
Richard
Richard
05-05-2003, 04:38 PM
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Re: 4.8 heads compression ratio Richard
My heads are casting 862's. How much would it cost to have the port and bowl work done by your shop? I have a friend here who can do the valve work and porting but he doesnt have a flow bench and I would rather have someone do them who has LS1 experience, on the porting. I took a look at your website, good site. I would send them to you with the new seats cut, hot tanked and disassembled. Also, could you recommend a valve size and valve spring setup? I'm going to use an MTI C2 .224/.224 .581/.581 112 with a good spring would this be noisy and would I have to change the springs every year? What kind of power could I expect with your headwork on this setup? Sorry for all the questions, just trying to get my ducks in a row before I commit. Thanks again
My heads are casting 862's. How much would it cost to have the port and bowl work done by your shop? I have a friend here who can do the valve work and porting but he doesnt have a flow bench and I would rather have someone do them who has LS1 experience, on the porting. I took a look at your website, good site. I would send them to you with the new seats cut, hot tanked and disassembled. Also, could you recommend a valve size and valve spring setup? I'm going to use an MTI C2 .224/.224 .581/.581 112 with a good spring would this be noisy and would I have to change the springs every year? What kind of power could I expect with your headwork on this setup? Sorry for all the questions, just trying to get my ducks in a row before I commit. Thanks again
05-06-2003, 10:22 AM
#6
Re: 4.8 heads compression ratio I have both new and used valves I can sell you. The standard LS-1 valve sizes are 2.00" intake and 1.55" exhaust. The used valves are cleaned and faced on the seat surface. New valves cost $4.00ea and used valves cost $2.00ea. Stage 1 porting (valve bowl blend) costs $175.00 per pair and finished valve job costs $135.00. We see valve seat angles as being very important for proper airflow in LS-1 engines and we prefer to finish the valve seats along with our porting.
As far as springs go, I sell a dual spring kit using the REV springs. Our retainers and spring bases are CNC machined and the kit sells for $285.00. As far as noisy valve train goes, I've heard a variety of different cars with different valve train components including stock and I must say that there are some that are noisy under certain conditions and at certain times and quieter at other times. Some the the reported noise can come from improper lifter preload, but I've never heard of noisy springs. Strangely my brother in law's truck with 5.3l engine makes a lot of ticking noise that I thought was valve spring related, but ended up being noisy injectors.
One further note about the REV springs, the outer springs are the ones that have had breakage problems. Out of the 90 sets we have sold in the last year 6 springs have broken. It's my understanding that REV is currently working on a new outer spring design and will have those sets available this summer. No exact date has been given, but as soon as they are available I'll give them a try on my own car first.
The MTI cam is a great choice for road and track performance and isn't too harsh on valve springs, rockers, pushrods etc. Power output can vary wildly depending on other mods but rwhp between 350 and 400 can be expected with Stage 1 porting and stock valves.
Hope this helps,
Richard
As far as springs go, I sell a dual spring kit using the REV springs. Our retainers and spring bases are CNC machined and the kit sells for $285.00. As far as noisy valve train goes, I've heard a variety of different cars with different valve train components including stock and I must say that there are some that are noisy under certain conditions and at certain times and quieter at other times. Some the the reported noise can come from improper lifter preload, but I've never heard of noisy springs. Strangely my brother in law's truck with 5.3l engine makes a lot of ticking noise that I thought was valve spring related, but ended up being noisy injectors.
One further note about the REV springs, the outer springs are the ones that have had breakage problems. Out of the 90 sets we have sold in the last year 6 springs have broken. It's my understanding that REV is currently working on a new outer spring design and will have those sets available this summer. No exact date has been given, but as soon as they are available I'll give them a try on my own car first.The MTI cam is a great choice for road and track performance and isn't too harsh on valve springs, rockers, pushrods etc. Power output can vary wildly depending on other mods but rwhp between 350 and 400 can be expected with Stage 1 porting and stock valves.
Hope this helps,
Richard
05-06-2003, 04:06 PM
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Re: 4.8 heads compression ratio Richard,
how about a $$ for porting the intake and exhaust runners to flow at their maximum capacity, and would that capacity be near that of a ported LS1 head. How much for stainless 2.00 and stainless 1.55's?
thanks
jeff
how about a $$ for porting the intake and exhaust runners to flow at their maximum capacity, and would that capacity be near that of a ported LS1 head. How much for stainless 2.00 and stainless 1.55's?
thanks
jeff
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05-06-2003, 11:29 PM
#8
Re: 4.8 heads compression ratio Summer special on CNC ported Stage 2 heads starting last week, $1685.00 per pair exchanged. 
Cams cost $385.00 ea. Stainless valves cost $12.50ea. (all available REV sizes). (Sorry, web guy is a bit slow to update the site).
Our CNC Stage 2 heads are prepared with 2.02"/1.57" stainless valves. Customers are seeing 350-450rwhp NA depending on cam choice, intake, headers/exhaust and with proper tuning. We haven't tried finishing the heads with standard size valves (2.00"/1.55") so I have no data on flow or rwhp.
Richard
Cams cost $385.00 ea. Stainless valves cost $12.50ea. (all available REV sizes). (Sorry, web guy is a bit slow to update the site).Our CNC Stage 2 heads are prepared with 2.02"/1.57" stainless valves. Customers are seeing 350-450rwhp NA depending on cam choice, intake, headers/exhaust and with proper tuning. We haven't tried finishing the heads with standard size valves (2.00"/1.55") so I have no data on flow or rwhp.
Richard
