sAFE COMPRESSIONRATIO FOR 454 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chris mc bride · 12-01-2023, 04:55 PM

I have 69 Panel with 454 and getting ready to do full rebuild. Boring .030, new pistons,rings with horizontal ported rings, new cam and some aluminum heads(still to be determined). Wonder how much compression I can get by with opn pump gas and good tuning? Have lot of engine building experience. Just heads up drag race stuff. Everything from alky injected bbc to top fuel. Street stuff is not my specialty.

Combo pretty simple deal.

454 plus .030 4 bolt block
454 steel crank 10 under
rods factory 3/8 with arp bolts, polished and balanced.
Gas ported rings on 10:1 piston
240 @.050 cam with lift around .600 give decent thump w/o killing TQ
Edlebrock RPM oval port with either 750 carb or EFI
2 1/4" headers with 3" SS exhaust and Borla mufflers
Heads are still up in air. Aluminum for sure just which ones?
Figure should make 425 to 450 hp Nothing Bad ass

I am thinking 10:1 about as high aas can get away with on street gas and then my need higher octane.

10:1 max or pushing it? Can get more with better ignition system? Will efi and tunning allow more?

Tom · 12-01-2023, 07:53 PM

EFI+ tuning will probably get you to 10.5 if you have access to 93. 91 like me and 10:1 might be it unless that cam has a large overlap to bleed compression.
As for heads, AFR all day. Brondix is always great as well.

Ziegelsteinfaust · 12-01-2023, 11:53 PM

My 1990's vintage LT1 5.7 runs 87 octane flawlessly on 10-1 with a stock cam, but over 10.5 becomes a pinging machine. Even with cams that should of bleed off enough pressure. No carb or tuning combo got rid of it.

I like 9.5 as a max if your going to run a carb.

10 is doable if your going to use fuel injection with knock sensors.

Depending on the swill you get for gas, but in my area. 91 is not as good as it used to be. So I prefer to keep ir safe to avoid swapping pistions or use a thicker head gasket.

b454rat · 12-02-2023, 07:39 AM

I ran 10:1 on a couple different 454s I had. One had 781s other had GM perf. aluminum heads. Ran both with 93, after getting timing down, they ran great. If EFI has timing control, should be fine.

chris mc bride · 12-02-2023, 08:52 AM

am has plenty of ovarlap. It is about as big as I want to go for street truck with regular gearing 3.73's here. I have self full of bigger cams but all way big for street and solid rollers.

Looking at AFR heads if can get what I want in oval port and not over valved. This is not race car.Heck if race car or truck 14:1 with alcohol in jection would be breeze. 1/4 mpg not good.LOL

12-01-2023, 04:55 PM	#1
chris mc bride Registered User Join Date: Aug 2008 Location: greensboro nc Posts: 673	sAFE COMPRESSIONRATIO FOR 454 I have 69 Panel with 454 and getting ready to do full rebuild. Boring .030, new pistons,rings with horizontal ported rings, new cam and some aluminum heads(still to be determined). Wonder how much compression I can get by with opn pump gas and good tuning? Have lot of engine building experience. Just heads up drag race stuff. Everything from alky injected bbc to top fuel. Street stuff is not my specialty. Combo pretty simple deal. 454 plus .030 4 bolt block 454 steel crank 10 under rods factory 3/8 with arp bolts, polished and balanced. Gas ported rings on 10:1 piston 240 @.050 cam with lift around .600 give decent thump w/o killing TQ Edlebrock RPM oval port with either 750 carb or EFI 2 1/4" headers with 3" SS exhaust and Borla mufflers Heads are still up in air. Aluminum for sure just which ones? Figure should make 425 to 450 hp Nothing Bad ass I am thinking 10:1 about as high aas can get away with on street gas and then my need higher octane. 10:1 max or pushing it? Can get more with better ignition system? Will efi and tunning allow more? __________________ Only the stupid know too much to learn something new. Last edited by chris mc bride; 12-01-2023 at 05:23 PM.

12-01-2023, 07:53 PM	#2
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,692	Re: sAFE COMPRESSIONRATIO FOR 454 EFI+ tuning will probably get you to 10.5 if you have access to 93. 91 like me and 10:1 might be it unless that cam has a large overlap to bleed compression. As for heads, AFR all day. Brondix is always great as well. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

12-01-2023, 11:53 PM	#3
Ziegelsteinfaust Registered User Join Date: Dec 2012 Location: Temple City Posts: 3,559	Re: sAFE COMPRESSIONRATIO FOR 454 My 1990's vintage LT1 5.7 runs 87 octane flawlessly on 10-1 with a stock cam, but over 10.5 becomes a pinging machine. Even with cams that should of bleed off enough pressure. No carb or tuning combo got rid of it. I like 9.5 as a max if your going to run a carb. 10 is doable if your going to use fuel injection with knock sensors. Depending on the swill you get for gas, but in my area. 91 is not as good as it used to be. So I prefer to keep ir safe to avoid swapping pistions or use a thicker head gasket.

12-02-2023, 07:39 AM	#4
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,453	Re: sAFE COMPRESSIONRATIO FOR 454 I ran 10:1 on a couple different 454s I had. One had 781s other had GM perf. aluminum heads. Ran both with 93, after getting timing down, they ran great. If EFI has timing control, should be fine. __________________ 2000 GMC CCSB 454/4L80 6” lift SAS 1999 Chevy CCSB 454/NV4500 6” lift 1999 GMC Yukon 350/4L60 4" SAS

12-02-2023, 08:52 AM	#5
chris mc bride Registered User Join Date: Aug 2008 Location: greensboro nc Posts: 673	Re: sAFE COMPRESSIONRATIO FOR 454 am has plenty of ovarlap. It is about as big as I want to go for street truck with regular gearing 3.73's here. I have self full of bigger cams but all way big for street and solid rollers. Looking at AFR heads if can get what I want in oval port and not over valved. This is not race car.Heck if race car or truck 14:1 with alcohol in jection would be breeze. 1/4 mpg not good.LOL __________________ Only the stupid know too much to learn something new.



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