egnine rebuild questions?? whick one - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70GMC_BOB · 06-23-2005, 04:01 PM

I have a 72c20 cheyenne super. it has a 90's gm goodwrench crate engine that is smoking. My dad has his 350 engine from his 70gmc that was replaced by the dealer I think in 1971. Should I fix/rebuild the newer motor or the older block? Also if I were to rebuild the older block will I have less power if i just make it stock w/ rv cam? Can I use the newer heads on the old block? What are the advantages to each?

knsmodels · 06-24-2005, 12:34 AM

JMHO....but if you are going the rebuild route I would do the older motor. Chances are the crate motor is one of those Mexico motors compared to the quality casting of the older motor. The power you get out of the motor will be determined by what you put in (compression, cam, heads, etc.). The block will have nothing to do with more power. Chances are good to that the older motor is a 4bolt main block also since it is out of a truck. Crate motor is probably 2 bolt main block. Talk to a good builder and tell him what you want out of the motor. He should be able to steer you in the right direction.....Paul

70chevc10 · 06-24-2005, 01:10 AM

if you plan on paying soemone to rebuild it, i can refer you to the guy im having rebuild mine. he owns brynn racing, and ive worked with him for 2 years at a chevy dealership. he will be doing my engine next month. hes the best there is around here. if your serious about getting it done, let me know. i dont like to bug him with dead end jobs. hes a busy guy!

bowtieman4life · 06-24-2005, 02:11 AM

Unless the new heads are vortec style L31's they will flow nearly the same. Which GM motort did you get? Good Luck

70GMC_BOB · 06-24-2005, 11:57 AM

you are correct, the crate engine is a mexico motor. I think for now I will just pull the crate engine and see what I got. My spark plugs on #1 & 3 are tunring into a oil gumball. My dad thinks it is the rings. If that is the case I will just do that and get it back on the road.

but I do want to rebuild the original motor since it is better casting. the original motor has 1.65 heads setup for leaded gas. Maybe I can buy the older one and rebuild it over the winter. I wanted about 275hp.

Thanks for the info.

70GMC_BOB · 06-24-2005, 11:59 AM

Another quick question. If old engine is a 72 gm truck motor and I put it in my 72 truck does that give me matching numbers (i.e. stock catagory for a truck show) ?

06-24-2005, 12:34 AM	#2
knsmodels I make Models Join Date: May 2005 Location: Bucks, PA Posts: 626	JMHO....but if you are going the rebuild route I would do the older motor. Chances are the crate motor is one of those Mexico motors compared to the quality casting of the older motor. The power you get out of the motor will be determined by what you put in (compression, cam, heads, etc.). The block will have nothing to do with more power. Chances are good to that the older motor is a 4bolt main block also since it is out of a truck. Crate motor is probably 2 bolt main block. Talk to a good builder and tell him what you want out of the motor. He should be able to steer you in the right direction.....Paul __________________ Click to see what I do 1972 LWB K10 350/4 sp 1968 SS Chevelle 396/tremac5spd

06-24-2005, 02:11 AM	#4
bowtieman4life Registered User Join Date: Sep 2004 Location: Vacaville Ca Posts: 61	Unless the new heads are vortec style L31's they will flow nearly the same. Which GM motort did you get? Good Luck __________________ 72 SBFS 4X4. 385 stroker, Sportsman 2 Heads, RPM Air Gap, Hooker SC Headers, A3 33" tires.

06-24-2005, 11:57 AM	#5
70GMC_BOB Registered User Join Date: Jul 2001 Location: Lynnwood, washington Posts: 121	you are correct, the crate engine is a mexico motor. I think for now I will just pull the crate engine and see what I got. My spark plugs on #1 & 3 are tunring into a oil gumball. My dad thinks it is the rings. If that is the case I will just do that and get it back on the road. but I do want to rebuild the original motor since it is better casting. the original motor has 1.65 heads setup for leaded gas. Maybe I can buy the older one and rebuild it over the winter. I wanted about 275hp. Thanks for the info. __________________ 1972 chev c20 2wd lwb 350v8/th350. (dad's)1970 gmc longstep (9ft commercial bed), 1 ton, 2wd, 350/th400. Last edited by 70GMC_BOB; 06-24-2005 at 12:00 PM.

06-24-2005, 11:59 AM	#6
70GMC_BOB Registered User Join Date: Jul 2001 Location: Lynnwood, washington Posts: 121	Another quick question. If old engine is a 72 gm truck motor and I put it in my 72 truck does that give me matching numbers (i.e. stock catagory for a truck show) ? __________________ 1972 chev c20 2wd lwb 350v8/th350. (dad's)1970 gmc longstep (9ft commercial bed), 1 ton, 2wd, 350/th400.

06-23-2005, 04:01 PM	#1
70GMC_BOB Registered User Join Date: Jul 2001 Location: Lynnwood, washington Posts: 121	egnine rebuild questions?? whick one I have a 72c20 cheyenne super. it has a 90's gm goodwrench crate engine that is smoking. My dad has his 350 engine from his 70gmc that was replaced by the dealer I think in 1971. Should I fix/rebuild the newer motor or the older block? Also if I were to rebuild the older block will I have less power if i just make it stock w/ rv cam? Can I use the newer heads on the old block? What are the advantages to each? __________________ 1972 chev c20 2wd lwb 350v8/th350. (dad's)1970 gmc longstep (9ft commercial bed), 1 ton, 2wd, 350/th400.

06-24-2005, 01:10 AM	#3
70chevc10 Registered User Join Date: Jun 2004 Location: Puyallup, WA Posts: 535	if you plan on paying soemone to rebuild it, i can refer you to the guy im having rebuild mine. he owns brynn racing, and ive worked with him for 2 years at a chevy dealership. he will be doing my engine next month. hes the best there is around here. if your serious about getting it done, let me know. i dont like to bug him with dead end jobs. hes a busy guy!



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