chevy II 153 four cylinder

The 120 HP Mercruiser 153CI I just
pulled a head of also has a steel shim head gasket .
It had 4 eye brow flat tops that were about flush. Shame the block is cracked.
A few differant Mercruiser valve covers out there also .

 

Well my guy came through and I got 3 sets of manifolds.

There smaller port than the older (pre 91 or so ) 3.0 head. The intake will work on the early head it's just going to have a much smaller port feeding a bigger port that's got a much lower bottom. ( lumps or something maybe ) I'm sure it will run fine with a smaller port centered in a bigger port .

The exhaust ports are much smaller while they cover the earlier head ok there is going to be big step going out so not good . Maybe some porting on the manifold or a transition plate sandwiched in or both . There is a fair amount if material on bottom of the exhaust to allow for enlargement.

A later post 91 or so head would be the way to go I think that would be on the 1 piece rear seal engines.
I may have a line on one. ( MAYBE )
I'm not convinced the later head has more power potential however .
They claim it makes more but yet the later engine is onlyv rated at 135 not 140 in Mercrusiers literature and that's with electronic fuel injection.

I think a Rochester 2BBL carb bolt pattern can be drilled and tapped directly into the existing flange on the dual intake . If not a adapter spacer is simple . I laid a Rochester gasket on the intake and I think there is enough meat ti drill and tap and the butterflies align near perfect.
Might be better if there was a common plenum but the carbs are pretty high already .
Might be a bit tricky to get each barrel on two differant ports to have the same air fuel mixture needed to run a individual port manifold .


The exhaust is a poor fit for the 153" head the intake likely would work but it's two ports going into the common single 153 port . as long as it seals I guess It will run OK .
It might flow into a lump head pretty good .

I also got a Impco brand cast iron intake also in the deal.
It's got small ports while it will run its certainly not a performance piece. Will need a carb adapter or a one barrel or something .



The mock up looks good .
But I'm pretty sure some mods will be in order to use the rear exhaust to gain firewall clearance.

 

Looks good!

I’ve seen similar ford banger intakes with a small, 1”? Balance tube run between the two halves. Might be able to drill a hole and braze one in.

 

Great looking stuff. Enough to make re-thinking some things interesting.
What you said about ports and port matching. Massive ports and huge valves are most important at wide open throttle & high rpm. Street engines like a little restriction that creates velocity at lower rpm and builds torque at the bottom end. Remember these were derived from the Chevy six tradition. Low end power, long life & economy.

The first bolt in lumps were from PES they had a step at the bottom that matched a small port runner in their high velocity intake. These very likely out preform the later lumps from everyone else that are designed to work with everyone else's intakes with huge velocity killing runners. Good for racing? Not so much for street performance? If it isn't in a vintage midget where are you going to race one of these things.
I have pictures of my PES lumps somewhere with the instructions on removing the intake boss with a hammer!

 

I'd think the mercruiser and OMC engines would have heads for a engine that runs up to about 4000 RPM that's were most boats stop at .

How much say Mercruiser and other had as far as what GM gave them to work with I can't say .

I do find it odd the small port head makes the same or with in 5 HP as the giant port head on the 3.0 .
Both engines got a 140 HP on the valve cover . Both have around the same compression .

My gut is telling me the small port motor has more torque down low and there picking up the total HP with fuel injection and such.

So what would a big port head do with better air flow AND fuel injection??

The manifolds I have are pretty small intake runners . Might flow less than the boat intake even with two carbs . I do know a guy with a flow bench and it would be interesting to flow the heads with various intakes and exhaust manifolds .

I know the midget guys ran the 3.0 early head on there 2.5's and made a hell of a lot more power than were going to make on the street.
Then again they were likely 13-1 compression huge cams, injected on alcohol and likely spinning 8000 RPM or more .

If I can get a honest 140 I'd likely be happy . A cam is likely going to be required for much more to move the RPM'S UP.
Hard to pin down what the specs on the boat cam is .

That single carb IMPCO manifold looks like a nice shelf to sit a Eaton or 371 supercharger on.
First thing I thought when I set it on the engine .

 

My intakes I assume match the later heads on the 3.0 boat.
I don't know if the industrial head for forklifts and boom lifts and such have a differant head or valve size .
Specifications are hard to find.
If the industrial head and 3.0 boat head are the same then I should find a later head .
That said if I added a lump or filler to the bottom of the big port head the rest of my intake port matches the top and sides pretty well .

I'd like to see these PES ports and I take and how there retained.

I was thinking if I made a spacer between the intake and head I could add the lump to the spacer and it would just slide in the port floor.
How much would you gain filling a low spot in a runner when the intake Is smaller and above that dip ?? Likely not much at normal RPM .

 

This is the important. Manifold
They have the mount holes rotated from how a Ford or chevy bolt pattern a 1/4 turn so a one barrel won't bolt down and face the right way so a adapter of some sort is required.

It occurred to me I could mill the ends flush block off the middle and but two carbs on it.

There is some bolt holes on the end to likely make a adapter possable for 2 carbs.
Mocked it up just to see how it might look.

 

A lot of new- old info comes into play here. Way back when inline guys were building 216, 235, & 261 Chevys & 248, 270, & 302 GMCs Bill Fisher had a book about them. There is a story there about a guy that brought his family car in to have a "hot street engine" built. Fisher laid out the plan for a strong daily driver for the wife's car. He explained cam choice, port & valve size, compression......... and told th guy this was not a race engine. A short time later the guy cam back pissed because another Fisher build kicked his ass at the drags. So Fisher re-did the engine at much cost and the wife was pissed because it was a pain to drive in traffic. The difference was mostly in the head & cam plus the difference in a 248 and a 270.

The first lumps were welded/brazed in and then ground to shape. These were not something the average guy building in his garage wanted to tackle. When PES built their bolt in lumps they were built to match the port & runners of their manifold. Since the lumps raise the port floor it has a flat face on the bottom when used with other intakes. They might work better as a starting point with these intakes. I'll try to find my pictures. My computer is doing some funny stuff with my pictures.

 

PES Intake Manifold (12bolt.com)

PES Bolt In Lump Kit (12bolt.com)

I found the manifold and lumps . I see what you mean about the higher runner floor . That about what my manifolds are like except its a 8 port .

Since the 8 port has no head bolt to hole a lump in im thinking of adding to a spacer that goes between the head and intake . it could damn near be heavy sheet metal with a tab to act like a lump.

Time to look for a new style head to . If I can find a good 2.5 block im going to stick the 181 crank in it like you did . Sucks the second one I got was bad .

Lot of freeze cracked block in WI .

 

Look at Ford sheet metal gasket with tongue bent down into port for ideas
http://www.mpgheads.com/port_plates_a.php

 

I have another question...I'm sure it's been aksed before but I couldn't find it. Will the head, or at least the header from a 90's 2.5 Jeep engine fit my '70 2.5 Chevy II motor? I looked on Rock Auto and the part number is different for head gasket, so I'm thinking the head might be different also. But the header looks pretty neat, so I might go to a pick and pay yard to get one anyway. Thanks again, Gene.

 

1biggun, Yes, that is the PES set up. I had forgotten that Tom Lowe had gotten those patterns. I had also forgotten the 8 port didn't have the boss which is the whole point. I've never had an 8 port head. If I were you at this point I'd hurt down a good 181 block. Keep the extra few inches and possibly avoid the #2 rod and fuel pump lobe clearance issue. I milled the lobe off of my can and will have to run an electric fuel pump. I have heard that the #2 rod on the 181 is cut for that but none of my 181 rods were. I'm sure you can port match those manifolds to your head. This is fun new territory!

34Phil, That is interesting and would probably work on the siamiesed ports like a lump and might be a way to secure a divider like many have tried on the sixes. They have all tried to fit then in the port.

Soup, I don't think so. The 2.5 Jeep was using by the '90s was their own engine design. They used the GM 153 in the postal Jeep DJ for a while and the 151 Iron Duke up to the early '80s. I have a complete take out from a 80-81? YJ. No matter how many people claim the 151 is a totally different engine it shares much with the 153-181.

 

Ok...and yet another question. Just got a phone call from my machine shop guy, yep he works on Sunday too. I took my block, I thought to have it cleaned and honed. He thinks it's too loose to just hone. It's .030 now. What's a safe overbore on these?

 

kind of what I was thinking. Some thing to sandwich in between the manifold and head with a tongue bent in.
could mill a recess in to the face of the flange area of the head or the manfold to take a sort of L shaped deal that is held in by the head and manifold.
Likely a lot of work to gain very little.

Like mentioned by 6 ball nobody is racing this .

 

I see .060" over size pistons sold by many Marine suppliers .

If and when I get around to building a 153 I'm going to get he block sonic checked to see what could be done . I know .080" 283 piston's are still sold wonder if the 153 block will go that big and take them.

 

One way to find out…

 

0.060 is considered the max safe overbore in these and their 6 relatives. I have a 250 with pistons that have 0.080 on top. I have no idea how it ran but it is clear that it did. It has quite a bit of carbon so the rings may not have been sealing or maybe it ran a long time?

 

I was thinking, if he has to bore it I wouldn't want to go just .040. He said .060 pistons were listed. Damn...everything around here just Snowballs!!!

 

Look onto it and get the best 0.060 over pistons you can find. Remember the 153 uses the same pistons as a 283. There should be some good ones out there. Mine is 0.040 over. That leaves another rebuild if I live that long.
These? https://www.ebay.com/itm/1552106843...o8C2sdB2FOx2gKEEwvmsNTnH8=|tkp:Bk9SR4CP6bL8YA

 

There are .040" pistons listed for the Mercrusier as well as many 283 listed pistons.

CHEVROLET 2.5L/153 Pistons - Flat top, with four valve reliefs Piston Style - Free Shipping on Orders Over $99 at Summit Racing

clear up to .080 listed here . pretty sure these are the correct pistons .

I think there are hypereutectic from Keith black and others also .

 

Mr. Gun...thanks for the update. My guy was able to get me a decent price on pistons thru Liberty Supply.
He also was concerned that the 283 pistons might have more pin offset then the four banger needed?? Anyhow, stuff is ordered and by the end of the week, the little motor should be .060 bigger. Gene.

 

283s are the same. GM probably built the 153 & 230 to use them because they had them. The rods are the same too except the v8 has one one side ground off so they can sit next to each other on the crank.

Remember the larger the overbore the shorter the CH of the piston.

 

Working on this today.

This is a 2013 Clark forklift
3.0. .
That aluminum intake could easly be machined for 2 carbs and the center blocked . Could lower the plenum as well and weld in a carb plate .

Engine is dual fuel LP and gasoline
And the head has injectors for gasoline .

Electronic Direct port injection is not really a H.A.M.B thing but I think the ECM is stand alone on these and the boats . Meaning it could be done on a modern build .
Not seeing any mass air flow sensor just a MAP sensor in the intake so twin throttle bodies would be doable and the injectors are pretty hidden . out of tank fuel pump.

Same down ward exhaust I recently got .



This would be a later 1 piece seal block. Likely the small high port head .
Makes about 80 HP in a lift .
These engines do vibrate a bit.

 

Sure is a nice flowy looking exhaust manifold. Bet it would look great chromed.

are the raised areas on the side of that intake raised plenum space?

 

Man! You are coming up with some parts most of us didn't know were out there. I'd like to see more about that head. It sounds like a great candidate for boost.

 

I would assume it's space under it.
The manifold is aluminum so it would polish up nice.
No idea of the actual port size but I'd guess it's small like most the later stuff with the one piece crank seal. Block also appears to have a crank position sensor in the side of it near the rear .

 

I think the later boat motors are also fuel injected and if so then the computer would be pretty much just a stand alone ECM and could maybe be used.

Head has injectors right in the ports and has a fuel rail . I'll snap a picture of it before I finish serving it.

 

Cool!

 

Volvo Penta offered a fuel injected 3L in 2009-2010 before the engine was discontinued due to emissions costs. The runners ran over the valve cover for more midrange power so neat looking.

 

I think Latin America had an actual aftermarket for these motors but I haven’t had much luck hunting any info down. There are a couple videos on you tube and I believe a member from there replied to one of my posts confirming but that’s about it. My internet must need a passport
Lol