Head suggestion 1978

[joewithaboat]

Re: Head sugeston 1978

Re: Head sugeston 1978

I f your old lifters are ok you should keep them in order so they are matched to the lobe on the 305 marine cam, they should only be changed if there is a problem with them or if they have gotten mixed up.

Keeping lifters in order only works if your going back in the same block.
If you are changing blocks, new lifters give you the best shot at having a good break in "wear pattern".
Personally i think using a used flat tappet is a crap shoot.

 

[Bondo]

Re: Head sugeston 1978

Re: Head sugeston 1978

My obtained 350 1977
--the compression was 8.5:1, or 8:1.
--It is rated at horsepower 160-165 @ 3800 rpm,
--Torque 270 ft/lbs. @ 2400 rpm.

Ayuh,.... If ya run those numbers again, at a 4800rpm Wot, you'll find that motor builds well over 200hp....

After all,... Horsepower is a mathimagical number derived from torque, 'n time...'n rpms plays a Huge part in the equation....

 

[joewithaboat]

Re: Head sugeston 1978

Re: Head sugeston 1978

Ayuh,.... If ya run those numbers again, at a 4800rpm Wot, you'll find that motor builds well over 200hp....

After all,... Horsepower is a mathimagical number derived from torque, 'n time...'n rpms plays a Huge part in the equation....

stock cam is probably so small it falls on its face at 4,000 rpm

 

[Bondo]

Re: Head sugeston 1978

Re: Head sugeston 1978

stock cam is probably so small it falls on its face at 4,000 rpm

Ayuh,.... My Only point is,....
Mercruiser has been using pickup truck motors as their motors since dirt was invented, 'n the HP ratings have ALWAYS been higher in the boat motors...
Even though they're the same motors....

If the mathamagical equation is exploitated, I'm bettin' it comes out to where it oughta be....

 

[joewithaboat]

Re: Head sugeston 1978

Re: Head sugeston 1978

Ayuh,.... My Only point is,....
Mercruiser has been using pickup truck motors as their motors since dirt was invented, 'n the HP ratings have ALWAYS been higher in the boat motors...
Even though they're the same motors....

If the mathamagical equation is exploitated, I'm bettin' it comes out to where it oughta be....

I'm sure you are right about that.

Didn't they also typically use better intake manifolds on truck long blocks though?

I think they also had there own cams ground? Maybe not.

 

[Scott Danforth]

Re: Head sugeston 1978

Re: Head sugeston 1978

the boat motors used the same intakes as trucks until the mid 90's when the Marinizers started having their own intakes made.

the cams were slightly different

 

[John_S]

Re: Head sugeston 1978

Re: Head sugeston 1978

My obtained 350 1977
--the compression was 8.5:1, or 8:1.
--It is rated at horsepower 160-165 @ 3800 rpm,
--Torque 270 ft/lbs. @ 2400 rpm.

Heads 462624
1.94" / 1.50" valves
72cc chambers
people say the suck because the always crack but mine are currently OK.

I was planning using the stock 5.7 mercruser cam from the 305 with new lifters
They are both the same via #3 book about 260 on the intake 270 on exaust.
--will this alone get me back near the 200HP that the original 305 had,

The 350 1977 TLZ 350 has extreamly low CR 8:1.
I think this is my biggest problem?
What is CR on a 5.7 Mercruiser
--how would you get my 350 to the same CR as stock Mercruiser?

Mic the cam out of the 305. If good, get new lifters and keep the heads you have. A new cam is only $125. It will be over 200hp at prop. The heads are not heavy duty, so refrain from running wot for extended times. Make sure your cooling system is up to par.

 

[joewithaboat]

Re: Head sugeston 1978

Re: Head sugeston 1978

The Problem:
I have a low compression TYZ 350 rated @ 160 HP with a 4bl carb on it and 624 heads.
If it was yours how would you get it back to 200 HP like the original 305 mercruser.
I thought the main reason for the low 160 HP was low stock compression of the 350--much less than the boats 305.

If your engine is in usable shape, the C/R is not a deal beaker. There is a popular GM good wrench crate engine that was sold for years, not sure if it still is, that was 8 to 1 and made around 240hp even corked up with stock monifolds.
You could just swap in a decent cam, that will work with your stock springs, and use it. Again if you are trying that zero budget you mentioned earlier.

see part 1 http://www.rustpuppy.org/chp/

same general specs as yours 76cc heads, 8 to 1 c/r etc. makes 250hp

http://sdparts.reachlocal.com/?scid=1995374&kw=13659771&pub_cr_id=5873201138

 

[dollarten]

Re: Head sugeston 1978

Re: Head sugeston 1978

I'm sure you are right about that.

Didn't they also typically use better intake manifolds on truck long blocks though?

I think they also had there own cams ground? Maybe not.

They used the GM cams . For the 350 CI 260 HP engine they usesd the 350 CI 350 HP cam I did a number profile search crossing the Mecruiser cam specs crossed over to the GM 350 HP cam that was uses in the early seventies and found out that they were exact

 

[John_S]

Re: Head sugeston 1978

Re: Head sugeston 1978

They used the GM cams . For the 350 CI 260 HP engine they usesd the 350 CI 350 HP cam I did a number profile search crossing the Mecruiser cam specs crossed over to the GM 350 HP cam that was uses in the early seventies and found out that they were exact

Can you post those cam specs from a 1970's merc? If you are refering to the early '70's LT1 Hyd cam 350/350, I don't think that was used by merc. I also wouldn't recommend an old single pattern cam as a replacement.

 

[joewithaboat]

Re: Head sugeston 1978

Re: Head sugeston 1978

Can you post those cam specs from a 1970's merc? If you are refering to the early '70's LT1 Hyd cam 350/350, I don't think that was used by merc. I also wouldn't recommend an old single pattern cam as a replacement.

Cam technology has come a long way over the years. Anyone buying a new cam is missing out if they don't get a newer grind.

 

[John_S]

Re: Head sugeston 1978

Re: Head sugeston 1978

What I remember of that cam was a high lift, lumpy idle, and was designed to the 11:1 compression those engines had. Wouldn't think it would make a good boat cam.

 

[happyhitter]

Re: Head sugeston 1978

Re: Head sugeston 1978

What I remember of that cam was a high lift, lumpy idle, and was designed to the 11:1 compression those engines had. Wouldn't think it would make a good boat cam.

Hi guys! Just thought id chime in and give my 2 cents. My 1988 Four Winns has a Chevy 350 and I pulled it to rebuild it as it had some wear and water issues from PO. Had a reputable engine shop do the machining like .030 over on the bores with new standard pistons, a fresh valve job with a progressive angle on new valves and seats, milled heads and deck to bring C/R to around 8:6 or 8:7 to 1 and they sold me a new cam to keep my horsepower to within or just under 300. Old eng specs are 260hp. My combination also includes an Edlebrock alluminum intake w/Roch. Quad and updated dist. to include a new Pertronix electronic conversion. The machine shop guy is well versed in boat engines. Here are the cam specs... Duration @.050 lift is.....210in and .216ex....STOCK is .194 in and .202 ex. Lobe lift is .290 in and .303ex. STOCK is .269in and .276ex. My VALVE LIFT on new cam is .435in and .455ex which is very close to interference with valve giude binding (the limit for these crappy heads) My boat repair manual doesn't include VALVE LIFT. I hope this can help.

 

[joewithaboat]

Re: Head sugeston 1978

Re: Head sugeston 1978

What I remember of that cam was a high lift, lumpy idle, and was designed to the 11:1 compression those engines had. Wouldn't think it would make a good boat cam.

Don't for get the good fuel that went with it.

When talking HP of these old cams... i think the change in HP measurement procedures (SAE) was around 72 ??
The old 370 hp mechanical cam would really be around 300hp

Crane still had them last i knew "Blueprinted series"
Comp call them "muscle car" series I think

 

[dollarten]

Re: Head sugeston 1978

Re: Head sugeston 1978

I wish I had acess to the Mercruiser Manual .The more I thought about it I could have been the 300 HP cam I found the GM cam spec in an old Motors Repair Manual and it was the same as the Mercruiser cam specs found in the Mercuiser manual I will admit that the 350 350 HP cam was kind of a rachety sounding and was as big as you could go with hydrulic lifeters and probaly to big for a marine application .Like I said before , it's been awhile since I have been in the business and have forgot a few things but not all of them >>>>>>>>>>Quick note I did dind the lift fo a 350 CI 300HP engine has a cam lift spec of .3945 Intake and exhaust The 350 Hp engine has split pattern of .4500 intake and .4600 Intake and exhuast repectivley . I did remeber thet the Mercruiser 260 (350) and the 228 HP ( 305) with a four bbl. carb did have the same Mercruiser part number . Not sure about the Mercruiser 305 two bbl. had for a cam which used to be called the 190 HP ..Hope this helps

 

[John_S]

Re: Head sugeston 1978

Re: Head sugeston 1978

I wish I had acess to the Mercruiser Manual .The more I thought about it I could have been the 300 HP cam I found the GM cam spec in an old Motors Repair Manual and it was the same as the Mercruiser cam specs found in the Mercuiser manual I will admit that the 350 350 HP cam was kind of a rachety sounding and was as big as you could go with hydrulic lifeters and probaly to big for a marine application .Like I said before , it's been awhile since I have been in the business and have forgot a few things but not all of them >>>>>>>>>>Quick note I did dind the lift fo a 350 CI 300HP engine has a cam lift spec of .3945 Intake and exhaust The 350 Hp engine has split pattern of .4500 intake and .4600 Intake and exhuast repectivley . I did remeber thet the Mercruiser 260 (350) and the 228 HP ( 305) with a four bbl. carb did have the same Mercruiser part number . Not sure about the Mercruiser 305 two bbl. had for a cam which used to be called the 190 HP ..Hope this helps

I do think that GM changed to dual pattern after the initial single pattern cam was used.

The 350/300HP cam would make more sense to me.

3896929 Hyd. - 195/202 - .390/.410 - 112

 

[stevehendo34]

Re: Head sugeston 1978

Re: Head sugeston 1978

So I'll:
-Change the pistons to bump CR
-Do a little basic porting on my heads
-Move the cam--lifters in order
and hope for the original 200 HP of the 305 on the 350.

I did find some rebuilrt Vortec heads for $300 but it looks like I won't need them.
Additional cost of intake and square bolt catb kinda makes the cost too high for this old boat.
The adapter plate for my carb would raise it up too high for doghouse.
I may by some stock 260 mercruser heads from someone--I'll have to think about that,

Thanks guys for all the help.