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inline six upgrade suggestions?

7

79 blazer

1/2 ton status
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Dec 29, 2003
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FORT COLLINS,CO
hello, my best friend just bought a first gen blazer(71) with the 250 inline six it is rebuilt pretty well, has 32's and is stock. but we would like to see some more power out of it or at leaste some upgrades that when driving it will make it seem more powerful,haha. anyway neither of us have any experience or idea when it comes to upgrading theese engines. he has 1,000 dollars as the budget and we were thinking make some better exhaust and get a new carb. but wich carb and what size? and whatever else is a good mod for theese engines. so everyones opinion on what to do with 1,000 dollars on on inline six would be apreciated. thanks - mark
 
I assume that you still have the monojet carb on the motor and it has to go if you are looking for more power. With a grand to play with look for a 2bbl ( Holley 350cfm ) and an intake ( Clifford/Offy or just an adapter if budget does not permit an intake ). Also look for a H.E.I. set up from a 1975 on up in-line motor.
You will be surprised at what just a carb change will do for the 250 ! The 1bbl's were made for economy not throttle response so you will notice some real seat of the pants feel when you put some breathing and fuel to the motor. A header and cam shaft should be the next investment if money is still available.
There is way more that you could do to the motor but this will keep you in your budget and give you fairly good results for your dollars.
Good luck , Tom
 
Just take a look at Clifford Performance. Thier parts are expensive and they take a while to ship but they are all hand made and vary high quality. I got an intake and header set for my ford for $600 shipped for my Ford 300 and the headers are duals (front3 have thier own header and the back 3 thier own). As far what to expect, i have almost 500lb ft coming off the fly wheel of my ford. I have invested about $900 into it whith Clifford and it makes a mockery of 302s and 351s in identical trucks. And the best part, 19mpg on the highway :cool1:
 
For $1000.00 you can do a lot with an inline 6...

Look for a triple carb manifold setup and drop 3 1bbl carbs on top of it with chrome air filters... Summit sells a V8 version with manifold for like 2400, but the setup for your engine is only like $200.00 for the triple or double manifold, and $90.00 for each of the three carbs... If you don't want the triple setup, the other suggestions of a 2bbl carb and manifold would go a long way. A good Holley carb will add both horse power and torque to that already torquey 250... After you get the manifold and carb, you can find a set of small tube headers for your engine from summit for about $170.00 Black Painted, Ceramic Coated ones will run you about $300.00.

After reviewing the parts selection at Summit, from then you can either get a double or triple 1bbl setup, or a single 4bbl setup. I didn't find any 2bbl parts except the carb.... so if you wanted 2bbl stuff you'd have to get a converter/adaptor.

When I was driving my 73 Ford Maverick with the 250 "Iron Mike" Engine, I had many opportunities to do what you are thinking about doing, and I never actually put the time in... I had plenty of money when I was a kid, and I wish now that I had spent it on that car. It would be worth something today if it were in as good of condition as I kept it in. Yeah, they keep going, and going, and going... and on a 12 gallon fill-up, I could go like 2 weeks without filling up.
 
Yup Clifford performance is the place to go. I have built a few performance inlines. You will be very suprised how much power you can get out of a 6 banger. I buy parts mostly from clifford.
I recomend Headers, cam, and a 4 barrel intake. For a carb. I usually used Q-jets on my six bangers with a Q- jet adapter. I like q-jets because they are best for off road and they can be tuned for just about any CID engine.. If you go Holley just get a 390 CFM 4BBL that is plenty for a 250.
Webbers are also a VERY GOOD choice. A 36DGEV is a great all around on /offroad carb
If its cold where you live you will probabally need a heat plate to keep the carb from icing.
Call Clifford they will be glad to help you spend that $1K. They have good tech support And will guide you the parts that give the most bang for the buck. They know inlines inside and out that is all they do.
 
hey thanks alot you guys this will realy help im going to call them tomorrow morning, as for the tripple carb option that sounds like it would be sick for a street car how well would it work off-road? what do you guys think would be more functional a 350cfm range two barrle with a manifold/adapter and some headers or with a new cam?
 
79 blazer said:
hey thanks alot you guys this will realy help im going to call them tomorrow morning, as for the tripple carb option that sounds like it would be sick for a street car how well would it work off-road? what do you guys think would be more functional a 350cfm range two barrle with a manifold/adapter and some headers or with a new cam?
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I'd do what the guys up top said... After thinking about my own response, I realized you'd be wheeling, and a 3pack on a 6 is pretty much "Glow for Show" and straight up street power. If I were building a 6 for the dirt, I'd put a single carb manifold on it, and a holley 390 or 450 (depending on your other parts selection.) They also have those Lowrider carbs from Holley that are designed to not flood even when at a 45 degree angle... awesome for off roading and rock crawling, and I think they can be had in 470, 570 and 670 versions, just like the Truck Avenger series (minus the 470 on the Truck Avenger line.) Expect to pay more than $300.00 for a NEW Holley... I can't speak for the other brands of carbs, since I have no experience with them.
 
The newer 250 Chevys had a 2 barrel carb intake and dual exhaust manifolds. I would find one of those heads with the manifolds and swap the heads over. This would give you unleaded valves and seats also. Then you could go for a HEI and cam swap.
 
not true!

The newer "camelhumper" 250's did have a 2 bbl carb,but its a lousy ne--and the intake is cast into the cylinder head--its not removeable!--it does have a "split" exhaust manifold with a "y" pipe,but they were noted for running lean on the rear cylinders,many of them burnt valves or pistons!--my 79 C10's 250 died at 113.000 miles last summer when a chunk of the # 6 piston popped off,exposing the top rings--looked like a tire fire all the way home! :blush:

If you must build up a chevy 6,the old motors were much more rugged-( and had removable intakes and exhaust manifolds)-the way to go is with a new intake manifold from clifford,they are set up for a 4 bbl but a 2 bbl can be used with an adapter..they also sell headers for the six cylinders too,they each do 3 cylinders,so you get a true dual exhaust--the cam is the heart of the buildup--it will determine how much torque and power,and what rpm you get it at!

It will make a huge difference in power when its all said and done!-just adapting a 4 bbl to my C10 made a BIG difference!-but one thing to consider--for a thousand bucks you could likely find AND install a good running used big block!--or a brand new GM crate replacement motor for a bit more..gas mileage wont likely be as good as you might think with a hopped up six--they can be thirsty too....so its a toss up whether to invest thast kind of money in a six--resale might be difficult too,most people dont want a six,no matter how good it is... :crazy:
 
I dunno about that... many people will pay more for a truck with an original 6, just because it is original... yeah, after mods it won't be so much anymore, but the numbers will still match on the block to the VIN... that alone makes it worth more.
 
I agree with the guys who mentioned 3 and 6pack carb setups. I am not old enough to have much experience with anything besides V8's but if your looking for power the straight 6 can be built up. About ten years ago I had a guy with a 6cyl chevy cargo van from the 50's blow by me in a street race like I was standing still. I was in a worked 70 cutlass with a 455 and twin 4bbls and a nitrous blast. I could run easy 12's and sometimes mid 11's in the quater and that truck had me beat bad. I know it was a strait 6cyl but he did not tell me what else he did to it. He just laughed and mentioned good old fashioned redneck engine building. He did say he pulled close to 700Hp out of it. What ever he did I am still impressed by it.

If you can find him or someone like him your all set.
 
PhoenixZorn said:
I dunno about that... many people will pay more for a truck with an original 6, just because it is original... yeah, after mods it won't be so much anymore, but the numbers will still match on the block to the VIN... that alone makes it worth more.
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You should visit the classifieds at 67-72 chevy trucks.com sometime...people practically give away 250's and 292's. Small blocks are just cheaper to build for power (and sometimes) economy.

That being said, one of my friends has a '69 or '70 C/30 dumptruck rotting away in one of their pastures that has a 292 and a SM465. I wouldn't mind having it for the engine.
 
just make sure its not an integral head(intake and head 1 piece) junk.i have 1 on my 82 k10,looking for older head now
 
I felt bad..

I did feel kinda bad when my C10 lost the six--I like sixes,but in todays traffic conditions and all,I felt a V8 was better off in it..I did think about the fact the truck had fairly low miles for its age,and the body is decent too,I didnt really want to destroy its originality by replacing the six--but once you add a few patches to the floor pan,its not going to be sought after by collectors as much anyway--and all the guys who wanted to buy it balked at it when I told them it was a TWO fifty,not a 350!

I had the chance to buy a 292 at one yard from a 1 ton dump truck--but they have a motor mount different than the 250,I'd have to buy all the brackets,it had a one barrel carb,different linkage,etc--as much work as a V8 swap in the end--and since it was a dump truck,chances are the motor was beat...I passed on it--not many other straight sixes in ANY of the yards here now at all!!

I'm over my loss of a "matching numbers" truck!--it gets better mileage now,and lots more power!--I feel it was worth the aggravation to do the upgrade to a V8--but if the original motor was still running fine,I would have just drove it!--I actually enjoyed the six with its goofy looking 4 bbl adapter I made--got lots of long looks at the car shows!..

.And I have seen a few "screamers",like the slant six my friends Duster had--450hp,4 bbl,clifford headers and intake,full race cam--it beat many 340 Dusters at the track!
He said he loved it when he opened the hood in the pits,and saw their jaws drop to the ground when they saw it was only a slant six!--

Some old GMC's had 302 straight sixes--saw one of them with 5 one barrels,it went 132 mph in the 1/4 mile at a local track back in the 50's--the guy has it in an old ford coupe now,still drives it to the car shows! :crazy:
 
I don't know anyone that looks for "matching number" trucks. :confused: Especially when it comes to 6-banger versions. ;) It's not like GM trucks really compare to stuff like original Hemi 'cuda convertibles or some other ultra-rare vehicle. :cool1:

I'd rather have one that the 6 got tossed out in favor of a gnarly 502. :cool1: :cool1: :cool1:
 
And I have seen a few "screamers",like the slant six my friends Duster had--450hp,4 bbl,clifford headers and intake,full race cam--it beat many 340 Dusters at the track!
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you say "ONLY" a slant six like they were less beefy than the I6.... the slant 6 as I recall was designed with slightly less torque but hella more horsies than the I6's of the same makes.

450hp is not unheard of, in fact, it should be almost the norm for a slant 6 with any type of work put into it. =) j/k...

but, 300hp is the norm for slant 6 with only a few mods... if I were to put anything besides a 302 grabber or 250 "Iron Mike" in a 73 Maverick, it would have been the Ford Slant 6... but that's old news... that car is long gone.
 
HarryH3 said:
I don't know anyone that looks for "matching number" trucks. :confused: Especially when it comes to 6-banger versions. ;) It's not like GM trucks really compare to stuff like original Hemi 'cuda convertibles or some other ultra-rare vehicle. :cool1:

I'd rather have one that the 6 got tossed out in favor of a gnarly 502. :cool1: :cool1: :cool1:
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You show me a 32 Deuce Coupe that is worth more - to a collector - with a big block than with the original engine. Yeah, someone who wants a street rod is going to pay big bucks most of the time, but there's always that one guy who will pay you twice what the street rod guy would have if it were all original.

Case in point... the engine shop by my house is currently rebuilding the original 4 banger on a Model T Ford... it's worth a good $40,000+ as it is right now, because it's all original... If it were a 302, 351 or even a 460, it would be worth half that because the numbers wouldn't match.

Granted, we aren't talking about 80 year old cars and trucks here... but you get my drift.
 
Well then ya better be storing all those "numbers matching" 6-banger trucks so you can retire rich. ;) But I'm thinking that a 454 SS will be worth WAY more money. :cool1:
 
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